Patent Application
20210310672
The present invention relates to a header in which refrigerant is distributed from a header manifold to a plurality of branch tubes, and also relates to a heat exchanger and an air-conditioning apparatus.
In a known air-conditioning apparatus, liquid refrigerant that is condensed by a heat exchanger serving as a condenser included in an indoor unit is depressurized by an expansion valve and falls into a gas-liquid two-phase state, which is a mixture of gas refrigerant and liquid refrigerant. The gas-liquid two-phase refrigerant flows into a heat exchanger serving as an evaporator included in an outdoor unit.
When the gas-liquid two-phase refrigerant flows into the heat exchanger serving as an evaporator, the performance of refrigerant distribution to that heat exchanger is deteriorated. Hence, as a method for improving the performance of refrigerant distribution, a header is employed as a distributor for the heat exchanger included in the outdoor unit, and the header is provided thereinside with a structural element, such as a partition, an ejection port, or the like.
However, in the header including any additional structural element provided as described above, the degree of improvement in the distribution performance is low, despite a significant cost increase. Moreover, the pressure loss in the header significantly increases, causing a reduction in energy efficiency. Furthermore, in an outdoor unit of an air-conditioning apparatus, a greater volume of air flows in an area that is nearer to a fan. Therefore, if a larger amount of refrigerant is distributed to a lower part of the header, which is farther from the fan than an upper part of the header is to the header, the performance of refrigerant distribution and the performance of the heat exchanger are deteriorated further, causing a further reduction in energy efficiency.
To overcome the above problems, there is a proposal of a technique in which a heat exchanger of an outdoor unit is divided into upper and lower parts, and the diameter of a header manifold connected to one of the heat exchangers that is nearer to a fan and receives a greater volume of air is made smaller than the diameter of a header manifold connected to the other heat exchanger that is farther from the fan and receives a smaller volume of air (see Patent Literature 1, for example). In the technique according to Patent Literature 1, a larger amount of liquid refrigerant can be distributed to the upper part of the header.
There is another proposal of a technique in which the length of insertion of branch tubes into a header manifold is adjusted (see Patent Literature 2, for example). In the technique according to Patent Literature 2, the performance of refrigerant distribution is improved by changing the flow resistance in the header manifold.
Patent Literature 1: International Publication No. 2015/178097
Patent Literature 2: Japanese Patent No. 5626254
The known techniques according to Patent Literature 1 and Patent Literature 2 depend on the refrigerant flow rate or the refrigerant speed. Therefore, the improvement in the performance of refrigerant distribution by using the header cannot be realized unless the range of the refrigerant flow rate or the refrigerant speed is limited and narrow. Hence, in a practical case where the air-conditioning apparatus is operated at a refrigerant flow rate that varies with the environmental load, there is a problem in that the improvement in the performance of refrigerant distribution by using the header cannot be realized depending on operating conditions.
The present invention is to overcome the above problem and provides a header that costs less with a simplified configuration and exhibits improved performance of refrigerant distribution from a header manifold to a plurality of branch tubes over a wide operating range, thereby improving the energy efficiency, and also provides a heat exchanger and an air-conditioning apparatus.
A header of an embodiment of the present invention includes a plurality of branch tubes, and a header manifold having a flow space that communicates with the plurality of branch tubes and in which gas-liquid two-phase refrigerant flows upward and is discharged into the plurality of branch tubes. If the refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold pass through a liquid-phase portion having a thickness δ [m] and reach a gas-phase portion.
The thickness δ [m] of the liquid-phase portion is defined as δ=G×(1−x)×D/(4ρL×ULS), where G is a flow speed [kg/(m2s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ρL is a liquid density [kg/m3] of the refrigerant, ULS is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into the flow space of the header manifold, the reference apparent liquid speed ULS [m/s] being defined as G(1−x)/ρL.
A heat exchanger of another embodiment of the present invention includes a plurality of heat-transfer tubes arranged side by side in a vertical direction in such a manner as to project therefrom on both sides, a first header connected to one end of each of the plurality of heat-transfer tubes, a second header connected to an other end of each of the plurality of heat-transfer tubes, and a plurality of fins joined to each of the plurality of heat-transfer tubes. The heat exchanger forms part of a refrigeration cycle circuit through which refrigerant circulates. The second header is the above header. The header manifold of the second header has a flow space that communicates with the plurality of branch tubes connected to the plurality of heat-transfer tubes, respectively. When the heat exchanger serves as an evaporator, gas-liquid two-phase refrigerant flows upward in the flow space and is discharged into the plurality of branch tubes.
An air-conditioning apparatus of yet another embodiment of the present invention includes a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger that form a refrigeration cycle circuit through which refrigerant circulates. The outdoor heat exchanger is the above heat exchanger. The air-conditioning apparatus includes a controller configured to control the compressor or the expansion device such that the quality x of the refrigerant flowing into the second header falls within the range 0.05≤x≤0.30 in the rated heating operation.
In each of the header, the heat exchanger, and the air-conditioning apparatus according to the above embodiments of the present invention, if the refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, the tips of the branch tubes inserted into the header manifold pass through the liquid-phase portion having a thickness δ [m] and reach the gas-phase portion. Thus, with a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the header manifold to the plurality of branch tubes can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
Embodiments of the present invention will now be described with reference to the drawings.
In the drawings, like reference numerals denote like or equivalent elements, which applies throughout this specification.
Modes of the elements disclosed in this specification are only exemplary and are not limited thereto.
As illustrated in
The second header manifold 11 extends vertically, with a section thereof along a horizontal plane being in a round tubular shape. A lower part of the second header manifold 11 is connected to a refrigerant pipe of a refrigeration cycle circuit.
The plurality of branch tubes 12 each extends horizontally, with a vertical section thereof that faces the second header manifold 11 being in a round tubular shape. The plurality of branch tubes 12 are arranged side by side in the vertical direction at a regular pitch. The plurality of branch tubes 12 are each connected to a corresponding one of heat-transfer tubes included in an outdoor heat exchanger forming part of the refrigeration cycle circuit.
The tips of the plurality of branch tubes 12 each communicate with the second header manifold 11 while projecting thereinto in such a manner as to reach the inside-diameter center of the second header manifold 11.
Now, the flow of gas-liquid two-phase refrigerant flowing through the second header 10 will be described.
The gas-liquid two-phase refrigerant enters the second header manifold 11 from the lower part thereof and forms an ascending current flowing against the gravity. The gas-liquid two-phase refrigerant thus entering the second header manifold 11 is distributed to the branch tubes 12 sequentially from the lower part of the second header manifold 11.
In this step, if the gas-liquid two-phase refrigerant flowing into the second header 10 forms a pattern of annular flow or churn flow, as illustrated in
As illustrated in
Since such a distribution of liquid flow rate is obtained, the header-specific problem, in which, for example, liquid refrigerant does not reach the upper part of the second header manifold 11 because of gravity, can be overcome. Thus, the performance of refrigerant distribution can be improved. Accordingly, the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
The most preferable position of the tip of each branch tube 12 in the second header manifold 11 is substantially the center. However, according to the result of an experiment conducted by the present inventers, if the refrigerant flowing into the second header manifold 11 forms a pattern of annular flow or churn flow, the tip of each branch tube 12 only needs to pass through the liquid-phase portion of the refrigerant flowing in the second header manifold 11, that is, the tip may be positioned within an area spreading around the center.
Herein, the area spreading around the center is regarded as follows. As illustrated in
Reference character A provided in each of
According to the experiment and analysis made by the present inventors, in the case of an annular flow or a churn flow, a thickness δ [m] of the liquid-phase portion is expressed as follows relatively matches well: δ=G×(1−x)×D/(4ρLULS), where G is the flow speed [kg/(m2s)] of the refrigerant, x is the quality of the refrigerant, D is the inside diameter [m] of the second header manifold 11, ρL is the liquid density [kg/m3] of the refrigerant, and ULS is the reference apparent liquid speed [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the second header manifold 11. Therefore, the tip of each of the plurality of branch tubes 12 connected to the second header manifold 11 projects at least from the liquid-phase portion having the thickness δ calculated in accordance with the above equation but does not project from another liquid-phase portion having the thickness δ and that is present on the other side of the second header manifold 11 toward which the branch tube 12 projects. That is, configurations are applicable as long as the tip of the branch tube 12 passes through the liquid-phase portion having the thickness δ and reach the gas-phase portion in such a manner as to be positioned in the gas-phase portion.
Note that the reference apparent liquid speed ULS [m/s] is defined as G(1−x)/ρL.
The flow pattern is identified with reference to the flow pattern diagram of a vertically ascending current and is set in accordance with a reference apparent gas speed UGS [m/s] of the refrigerant at the maximum value within the range of variation in the flow speed of the refrigerant flowing into the flow space of the second header manifold 11.
It is preferable that the reference apparent gas speed UGS [m/s] of the refrigerant flowing into the second header manifold 11 satisfy a condition UGS≥α×L×(g×D)0.5/(40.6×D)−0.22α×(g×D)0.5. It is more preferable that the reference apparent gas speed UGS [m/s] satisfy a condition UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25.
As illustrated in
Note that α is the void fraction of the refrigerant and is expressed as α=x/[x+(ρG/ρL)×(1−x)], L is the entrance length [m], g is the gravitational acceleration [m/s2], D is the inside diameter [m] of the second header manifold 11, x is the quality of the refrigerant, ρG is the gas density [kg/m3] of the refrigerant, ρL is the liquid density [kg/m3] of the refrigerant, and σ is the surface tension [N/m] of the refrigerant. The void fraction α of the refrigerant is measured by, for example, utilizing electrical resistance, or by visual observation. The entrance length L [m] at an inlet of the second header manifold 11 is defined as a distance between a position of the inlet of the second header manifold 11 and a position of the center axis of one of the branch tubes 12 that is nearest to the position of the inlet.
The reference apparent gas speed USG is calculated by measuring the flow speed G, the quality x, and the gas density ρG of the refrigerant flowing into the second header manifold 11 and is defined as USG=(G×x)/ρG.
As illustrated in
For example, in an air-conditioning apparatus including the second header 10, if the flow speed of the refrigerant flowing into the flow space of the second header manifold 11 is the maximum value within the range of variation and in a rated heating operation of the second header manifold 11, gas-liquid two-phase refrigerant forming an ascending current flows through the flow space of the second header manifold 11.
It is preferable that the quality x of the refrigerant in the second header manifold 11 flowing into the second header 10 fall within a range 0.05≤x≤0.30, because such a condition particularly increases the degree of improvement in the distribution performance and in the performance of the heat exchanger that is brought by the branch tubes 12 projecting into the second header manifold 11.
In the drawing, the position of the tip of the branch tube 12 is based on the definition that the center position of the flow space of the second header manifold 11 in the horizontal plane corresponds to 0%, and the position of the wall surface of the flow space of the second header manifold 11 in the horizontal plane corresponds to 100% on either side, as illustrated in
If the quality x is 0.30 and if the tip of the branch tube 12 is positioned on the outer side with respect to 75% on either side, the performance of the heat exchanger sharply drops.
If the quality x is 0.05, since the quality x is lower than 0.30, the liquid-phase portion has a greater thickness. Accordingly, the performance of the heat exchanger sharply drops if the tip of the branch tube 12 is positioned on the outer side with respect to 50% on either side. In contrast, if the tip of the branch tube 12 is positioned on the inner side with respect to 50% on either side, the drop of the performance of the heat exchanger is gentle.
Hence, assuming that the quality x is 0.05 with which the liquid-phase portion has a large thickness, the distribution performance can be improved by positioning the tip of the branch tube 12 in the area within 50% on either side.
If the tip of the branch tube 12 is positioned in the area within 50% on either side, a larger amount of liquid refrigerant can be distributed to the upper part of the second header 10. It is more preferable that the tip of the branch tube 12 be positioned at the inside-diameter center of the second header manifold 11, that is, at 0%, because the liquid refrigerant at a flow rate ranging more widely can be distributed to the upper part of the second header manifold 11.
The above description concerns a case where the center axis of the branch tube 12 that extends horizontally and the center axis of the second header manifold 11 that extends vertically cross each other. Alternatively, for example, the center axis of the branch tube 12 that extends horizontally may be displaced from the center axis of the second header manifold 11 that extends vertically.
Here, the center position of the flow space of the second header manifold 11 in a horizontal plane is defined as 0%, the position of the wall surface of the flow space of the second header manifold 11 in the horizontal plane is defined as 100% on either side, the direction of insertion of each of the plurality of branch tubes 12 in the horizontal plane is defined as the X direction, and the width direction of each of the plurality of branch tubes 12 that is orthogonal to the X direction in the horizontal plane is defined as the Y direction.
As illustrated in
However, as long as the center axis of the branch tube 12 is positioned in an area within 50% on either side in the Y direction, the distribution performance can be improved by utilizing characteristics of the pattern of annular or churn flow.
As illustrated in
In such a case, if the center axis of the branch tube 12 is positioned in an area within 25% on either side in the Y direction and the tip of the branch tube 12 is positioned in an area within 25% on either side, the distribution performance can be improved stably even with a low quality of the refrigerant.
The lengths of insertion of the plurality of branch tubes 12 into the second header manifold 11 are preferably the same but may be different as long as the tips of the branch tubes 12 or the center axes of the branch tubes 12 are each positioned in the area within 50% on either side.
The branch tubes 12 are each described as a component of the second header 10. Alternatively, for example, the branch tube 12 may be provided as part of a round heat-transfer tube of the heat exchanger, that is, as an extension of the heat-transfer tube.
Since the branch tube 12 may be used as a substitution for part of the heat-transfer tube, the inner surface of the branch tube 12 may be processed to have a shape that promotes heat transfer, with grooves or the like.
The kind of refrigerant that flows through the second header 10 is not specifically limited. However, using any of refrigerants each having a high refrigerant gas density, namely, R32, R410A, and CO2, is preferable. Originally, liquid refrigerant is characterized in being less likely to reach the upper part of the second header 10. Therefore, the use of any of the above refrigerant greatly improves the performance of the heat exchanger.
Also preferable is a mixture of two or more kinds of refrigerant having different boiling point differences that are selected from olefin-based refrigerant such as R1234yf and R1234ze(E); HFC refrigerant such as R32; hydrocarbon refrigerant such as propane and isobutane; CO2; DME (dimethyl ether); and the like. The use of such refrigerant also greatly improves the performance of the heat exchanger with an improvement in the distribution performance.
The present invention depends on the flow pattern of the gas-liquid two-phase refrigerant that flows through the second header manifold 11. Therefore, it is more preferable that the flow of the gas-liquid two-phase refrigerant be fully developed. According to the experiment conducted by the present inventors, the entrance length L required for the gas-liquid two-phase refrigerant to develop needs to satisfy a condition L≥5D, where D is the inside diameter [m] of the second header manifold 11: as long as L≥5D is satisfied, the distribution performance can be improved. The improvement becomes greater if the entrance length L satisfies a condition L≥10D.
The gas-liquid two-phase refrigerant enters the second header manifold 11 from the lower part thereof as a vertically ascending current. The liquid-phase portion is thick at the inlet. As the flow develops, droplets start to be generated. Therefore, the liquid-phase portion gradually becomes thinner. In an area above an area defined by a length Li where a fully developed annular flow is formed, the liquid-phase portion has a uniform thickness.
When the pitch between adjacent ones of the plurality of branch tubes 12 is Lp, and the length of a stagnation area in the upper part of the second header manifold 11 is Lt, a relationship Lt≥2×Lp is established.
In such a case, the influence of collision of the gas-liquid two-phase refrigerant in the upper part of the second header manifold 11 is reduced. Therefore, the flow pattern is stabilized, whereby the improvement in the distribution performance becomes greater.
The above description concerns a case where the branch tubes 12 extend from a lateral side of the second header manifold 11. The present invention is not limited to such a case.
As illustrated in
Such a configuration is preferable because the variation in the dynamic pressure that is caused by the collision of the refrigerant in the upper part of the second header manifold 11 is small. Accordingly, the flow pattern of the refrigerant flowing through the flow space of the second header manifold 11 is stabilized. Consequently, the efficiency of the heat exchanger is improved.
If the branch tube 12 is connected to the lower part of the second header manifold 11 such that a head difference is produced, the head difference makes it difficult for the liquid refrigerant to flow to the lower part of the second header manifold 11. Such a configuration is more preferable because a larger amount of liquid refrigerant can be distributed to the upper part of the second header manifold 11.
With the two-way tube 13 employed as the branch tube, the variation in the dynamic pressure that is caused by the branch tubes projecting into the second header manifold 11 can be reduced. Such a configuration is preferable because the variation in the flow pattern can be reduced, and the efficiency of the heat exchanger can be improved.
The above description concerns the two-way tube 13 having two outflow ports for one inflow port. The present invention is not limited to such a case. Other configurations are applicable as long as the branch tube has more outflow ports than inflow ports.
According to Embodiment 1, the second header 10 includes the plurality of branch tubes 12. The second header 10 includes the second header manifold 11 having a flow space that communicates with the plurality of branch tubes 12 and in which gas-liquid two-phase refrigerant flows upward and is discharged into the branch tubes 12. The second header 10 is configured such that if the refrigerant flowing into the second header manifold 11 forms a pattern of annular flow or churn flow, the tips of the branch tubes 12 inserted into the second header manifold 11 pass through the liquid-phase portion having the thickness δ [m] and reach the gas-phase portion. The thickness δ [m] of the liquid-phase portion is defined as δ=G×(1−x)×D/(4ρL×ULS), where G is the flow speed [kg/(m2s)] of the refrigerant, x is the quality of the refrigerant, D is the inside diameter [m] of the header manifold, ρL is the liquid density [kg/m3] of the refrigerant, ULS is the reference apparent liquid speed [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the header manifold. The reference apparent liquid speed ULS [m/s] is defined as G(1−x)/ρL.
In such a configuration, an annular flow or a churn flow is formed in the second header manifold 11 in which gas-liquid two-phase refrigerant flows upward. In the annular flow or the churn flow, more gas refrigerant is present around the center axis of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Since the tips of the branch tubes 12 inserted into the second header manifold 11 pass through the liquid-phase portion having the thickness δ and reach the gas-phase portion, more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, the efficiency of the heat exchanger can be improved, and the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
That is, the gas-liquid two-phase refrigerant flowing upward in the second header manifold 11 can have a pattern of annular flow or churn flow. Accordingly, gas refrigerant gathers in a central part of the second header manifold 11, whereas liquid refrigerant gathers on the periphery of the second header manifold 11. Therefore, the gas refrigerant can be selectively distributed more to those branch tubes 12 provided in the lower part of the second header 10 than to those branch tubes 12 provided in the upper part of the second header 10. Thus, the ratio of distribution of the liquid refrigerant gradually increases from the bottom toward the top of the second header 10. That is, the refrigerant can be distributed in conformity with the distribution of the volume of airflow generated by a top-flow fan. Therefore, the performance of the outdoor heat exchanger can be improved. On the other hand, the flow rate of the refrigerant varies greatly with operating conditions of the outdoor heat exchanger or the load imposed on the outdoor heat exchanger to which the second header 10 is attached. However, the quality of the refrigerant is adjustable by changing the opening degree of an expansion device provided on the upstream side of the outdoor heat exchanger in the direction of refrigerant flow. Therefore, the performance of refrigerant distribution can be improved suitably for the top-flow fan under widely varying operating conditions. Accordingly, the energy efficiency can be improved over a wide operating range. Such an advantageous effect is pronounced particularly in an outdoor heat exchanger employing a top-flow fan. An outdoor heat exchanger employing a side-flow fan also has the problem that liquid refrigerant is less likely to reach the upper part of the second header manifold 11. However, with the use of the second header 10, the liquid refrigerant becomes more likely to reach the upper side of the second header manifold 11. Thus, the distribution performance can be improved, and the energy efficiency can be improved.
According to Embodiment 1, in the second header 10, the reference apparent gas speed UGS [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the second header manifold 11 satisfies the condition UGS≥α×L×(g×D)0.5/(40.6×D)−0.22α×(g×D)0.5, where α is the void fraction of the refrigerant, L is the entrance length [m], g is the gravitational acceleration [m/s2], and D is the inside diameter [m] of the second header manifold 11. Here, the void fraction α of the refrigerant is defined as x/[x+(ρG/ρL)×(1−x)], where xis the quality of the refrigerant, ρG is the gas density [kg/m3] of the refrigerant, and ρL is the liquid density [kg/m3] of the refrigerant.
In such a configuration, an annular flow or a churn flow is formed in the second header manifold 11 in which gas-liquid two-phase refrigerant flows upward. In the annular flow or the churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Since the condition UGS≥α×L×(g×D)0.5/(40.6×D)−0.22α×(g×D)0.5 is satisfied, more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, the efficiency of the heat exchanger can be improved, and the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
According to Embodiment 1, in the second header 10, the reference apparent gas speed UGS [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the second header manifold 11 satisfies the condition UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25, where ρG is the gas density [kg/m3] of the refrigerant, σ is the surface tension [N/m] of the refrigerant, g is the gravitational acceleration [m/s2], and ρL is the liquid density [kg/m3] of the refrigerant.
In such a configuration, an annular flow or a churn flow is formed in the second header manifold 11 in which gas-liquid two-phase refrigerant flows upward. In the annular flow or the churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Since the condition UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25 is satisfied, much more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it much easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, the efficiency of the heat exchanger can be improved, and the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the second header 10 includes the plurality of branch tubes 12. The second header 10 includes the second header manifold 11 having the flow space that communicates with the plurality of branch tubes 12 and in which gas-liquid two-phase refrigerant flows upward and is discharged into the plurality of branch tubes 12. The center position of the flow space of the second header manifold 11 in a horizontal plane is defined as 0%. The position of the wall surface of the flow space of the second header manifold 11 in the horizontal plane is defined as 100% on either side. Under such definitions, the tip of each of the branch tubes 12 inserted into the second header manifold 11 is positioned in the area within 50% on either side. The reference apparent gas speed UGS [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the second header manifold 11 satisfies the condition UGS≥α×L×(g×D)0.5/(40.6×D)−0.22α×(g×D)0.5, where α is the void fraction of the refrigerant, L is the entrance length [m], g is the gravitational acceleration [m/s2], and D is the inside diameter [m] of the second header manifold 11. Here, the void fraction α of the refrigerant is defined as x/[x+(ρG/ρL)×(1−x)], where x is the quality of the refrigerant, ρG is the gas density [kg/m3] of the refrigerant, and ρL is the liquid density [kg/m3] of the refrigerant.
In such a configuration, an annular flow or a churn flow is formed in the second header manifold 11 in which gas-liquid two-phase refrigerant flows upward. In the annular flow or the churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Since the tip of each of the branch tubes 12 is positioned in the area within 50% on either side and the condition UGS≥α×L×(g×D)0.5/(40.6×D)−0.22α×(g×D)0.5 is satisfied, more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, the efficiency of the heat exchanger can be improved, and the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the reference apparent gas speed UGS [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the second header manifold 11 satisfies the condition UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25 , where ρG is the gas density [kg/m3] of the refrigerant, σ is the surface tension [N/m] of the refrigerant, g is the gravitational acceleration [m/s2], and ρL is the liquid density [kg/m3] of the refrigerant.
In such a configuration, an annular flow or a churn flow is formed in the second header manifold 11 in which gas-liquid two-phase refrigerant flows upward. In the annular flow or the churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Since the tip of each of the branch tubes 12 is positioned in the area within 50% on either side and the condition UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25 is satisfied, much more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it much easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, the efficiency of the heat exchanger can be improved, and the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the center position of the flow space of the second header manifold 11 in a horizontal plane is defined as 0%, the position of the wall surface of the flow space of the second header manifold 11 in the horizontal plane is defined as 100% on either side, the direction of insertion of each of the plurality of branch tubes 12 in the horizontal plane is defined as the X direction, and the width direction of each of the plurality of branch tubes 12 that is orthogonal to the X direction in the horizontal plane is defined as the Y direction. Under such definitions, the tips of all of the plurality of branch tubes 12 are positioned in the area within 50% on either side in the X direction, and the center axes of all of the plurality of branch tubes 12 are positioned in the area within 50% on either side in the Y direction.
In such a configuration, in an annular flow or a churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery of the second header manifold 11. Under such circumstances, the tips of all of the plurality of branch tubes 12 are positioned in the area within 50% on either side in the X direction, and the center axes of all of the plurality of branch tubes 12 are positioned in the area within 50% on either side in the Y direction. Therefore, more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the distribution performance of the second header 10 can be improved, and the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the tips of all of the plurality of branch tubes 12 are positioned in the area within 25% on either side in the X direction, and the center axes of all of the plurality of branch tubes 12 are positioned in the area within 25% on either side in the Y direction.
In such a configuration, in an annular flow or a churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery of the second header manifold 11. Under such circumstances, the tips of all of the plurality of branch tubes 12 are positioned in the area within 25% on either side in the X direction, and the center axes of all of the plurality of branch tubes 12 are positioned in the area within 25% on either side in the Y direction. Therefore, the distribution performance can be improved stably even with a low quality. Accordingly, the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the tips of all of the plurality of branch tubes 12 are positioned at 0% in the X direction, and the center axes of all of the plurality of branch tubes 12 are positioned at 0% in the Y direction.
In such a configuration, a particularly great improvement in the distribution performance can be realized. Accordingly, the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the branch tubes 12 are each obtained by extending part of a heat-transfer tube included in a heat exchanger.
In such a configuration, since part of the heat-transfer tubes is used as each of the plurality of branch tubes 12, no joint for connecting the branch tube 12 and the heat-transfer tube to each other is necessary. Consequently, the space can be saved, and the pressure loss can be reduced.
According to Embodiment 1, when the pitch between adjacent ones of the plurality of branch tubes 12 is Lp and the length of a stagnation area in the upper part of the second header manifold 11 is Lt, the relationship Lt≥2×Lp is established.
In such a configuration, the influence of the collision of the gas-liquid two-phase refrigerant in the upper part of the second header manifold 11 is reduced. Therefore, the flow pattern is stabilized, whereby the improvement in the distribution performance that is brought by the projecting branch tube becomes greater. Accordingly, the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the uppermost one of the plurality of branch tubes 12 is connected to the upper end of the second header manifold 11 from the upper side.
In such a configuration, the reduction in the dynamic pressure that is caused by the collision of the refrigerant in the upper part of the second header manifold 11 becomes small. Therefore, the flow pattern is stabilized, whereby the improvement in the distribution performance becomes greater. Accordingly, the efficiency of the heat exchanger can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 1, the refrigerant employed is R32, R410A, or CO2.
In such a case, since the refrigerants listed above each have a high gas density, the improvement in the distribution performance that is brought by the projecting branch tubes 12 becomes greater.
According to Embodiment 1, the refrigerant employed is a mixture of at least two or more kinds of refrigerant having different boiling point differences that are selected from olefin-based refrigerant, HFC refrigerant, hydrocarbon refrigerant, CO2, and DME. In such a case, the variation in the density distribution that is caused by poor refrigerant distribution can be reduced by the use of the mixed refrigerant. Therefore, the distribution performance is improved, whereby the improvement in the efficiency of the heat exchanger becomes greater. Consequently, the energy efficiency can be improved.
Embodiment 2 of the present invention will now be described. Description that has been given in Embodiment 1 is omitted. Elements that are the same as or equivalent to those described in Embodiment 1 are denoted by corresponding ones of the reference numerals.
In Embodiment 2, the second header manifold 11 forms a passage whose horizontal section does not have a round tubular shape. The horizontal section of the second header manifold 11 has a non-round tubular shape.
As illustrated in
As illustrated in
In the second header manifold 11 having a rectangular tubular horizontal section, the surface joined to the branch tube 12 is orthogonal thereto. In general, such metal members are joined to each other by brazing. In the brazing, if the joining surfaces are orthogonal to each other, the ease of brazing is increased, leading to high joining quality.
If the second header manifold 11 has a rectangular passage, the center position of the passage is defined as the point of intersection of the diagonals of the rectangular passage. In such a case, the flow pattern is identified on the basis of the diameter of an equivalent circle having the same area as the section of the rectangular passage.
As illustrated in
The center of the elliptical passage is defined as the point of intersection of the center lines, that is, the major axis and the minor axis.
With the second header manifold having an elliptical passage, the increase in the pressure loss of the refrigerant flowing through the second header manifold 11 having the elliptical shape that is caused by the branch tube 12 projecting up to a position near the center can be suppressed. Such a configuration is preferable for stabilizing the flow pattern.
If the branch tube 12 is inserted toward the major axis of the elliptical passage, the surface of the second header manifold 11 that is brazed to the branch tube 12 has a smaller curvature than in the case where the second header manifold has a round tubular horizontal section. Therefore, the ease of brazing is increased.
The flow pattern formed in the elliptical passage is identified on the basis of the diameter of an equivalent circle having the same area as the section of the elliptical passage.
As illustrated in
The center of the second header manifold 11 having a half-round passage is defined as the point of intersection of lines each connecting a corresponding one of three positions nearest to the center and a corresponding one of three positions farthest from the center.
The flow pattern is identified on the basis of the diameter of an equivalent circle having the same area as the section of the half-round passage.
With the second header manifold 11 having a half-round passage, the increase in the capacity thereof in the width direction is suppressed, whereas the sectional area of the passage can be increased. Such a configuration is preferable because the space can be saved, and the pressure loss is small. Furthermore, since the surface to be joined to the branch tube 12 is flat, the ease of brazing is increased.
As illustrated in
The center of the second header manifold 11 having a triangular passage is defined as the point of intersection of lines each connecting a corresponding one of the centers of the three sides, the centers being nearest to one another, and a corresponding one of the three corners that are farthest therefrom.
The flow pattern is identified on the basis of the diameter of an equivalent circle having the same area as the section of the triangular passage.
With the second header manifold 11 having a triangular passage, the increase in the capacity thereof in the width direction is suppressed, whereas the sectional area of the passage can be increased. Such a configuration is preferable because the space can be saved, and the pressure loss is small. Furthermore, since the surface to be joined to the branch tube 12 is flat, the ease of brazing is increased.
In the second header manifold 11 having any of the rectangular passage, the elliptical passage, the half-round passage, and the triangular passage described above, the branch tube 12 is made to project into the second header manifold 11, as with the case of Embodiment 1. Furthermore, the refrigerant flowing into the second header manifold 11 is controlled to form a pattern of annular flow or churn flow. Thus, the distribution performance can be improved. Furthermore, it is preferable that the quality x be within the range 0.05≤x≤0.30, because a great improvement in the distribution performance can be realized.
Embodiment 3 of the present invention will now be described. Description that has been given in Embodiment 1 or 2 is omitted. Elements that are the same as or equivalent to those described in Embodiment 1 or 2 are denoted by corresponding ones of the reference numerals.
In Embodiment 3, the plurality of branch tubes 12 each have a flat tubular shape.
As illustrated in
With the flat tubular branch tubes 12, the influence of the surface tension at the branching points is increased. Accordingly, the liquid refrigerant flows uniformly in each of the branch tubes 12. Such a configuration is preferable because a great improvement in the efficiency of the heat exchanger is realized.
In such a configuration, the Y-direction position of the center axis of each branch tube 12 that is defined above is assumed to be in the area within 50% on either side with respect to an equivalent diameter of a circular tube calculated from the effective passage-section area of the flat passage.
The branch tube 12 having the flat tubular shape may be part of an air-heat exchanger. That is, part of a flat heat-transfer tube included in an air-heat exchanger may be extended to form a flat tubular shape.
Occasionally, the branch tube 12 having the flat tubular shape is used as a substitution for part of the heat-transfer tube. Therefore, the inner surface of the branch tube 12 may be processed to have a shape that promotes heat transfer, with grooves or the like.
A configuration illustrated in
According to Embodiment 3, the plurality of branch tubes 12 each have a flat tubular shape.
In such a configuration, since the flat tubular branch tubes 12 are employed, the influence of the surface tension at the branching points is increased. Accordingly, the liquid refrigerant flows uniformly in each of the branch tubes 12. Consequently, a great improvement in the efficiency of the heat exchanger is realized.
Furthermore, since the flat tubular branch tube 12 is inserted directly into the second header manifold 11, the number of components can be reduced, leading to a cost reduction.
Embodiment 4 of the present invention will now be described. Description that has been given in any of Embodiments 1 to 3 is omitted. Elements that are the same as or equivalent to those described in any of Embodiments 1 to 3 are denoted by corresponding ones of the reference numerals.
In the drawings, solid-line arrows represent the flow of refrigerant and broken-line arrows represent the flow of air in the outdoor unit 100 of the air-conditioning apparatus in a heating operation.
In the following description, terms representing directions (such as “top”, “bottom”, “right”, “left”, “front”, and “rear”) are used for easy understanding. Such terms are only explanatory and do not limit the present invention. In Embodiment 4, the terms “top”, “bottom”, “right”, “left”, “front”, and “rear” are used on the premise that the outdoor unit 100 is seen from the front, which also applies to the subsequent embodiments.
The outdoor unit 100 of the air-conditioning apparatus according to Embodiment 4 illustrated in
The outdoor unit 100 includes a box-like casing 101. The outdoor unit 100 has an air inlet 102 in the form of an opening provided in a side face of the casing 101. The outdoor unit 100 includes the outdoor heat exchanger 20, illustrated in
The outdoor heat exchanger 20 included in the outdoor unit 100 of the air-conditioning apparatus causes the outdoor air taken in from the air inlet 102 by the fan 30 and the refrigerant to exchange heat therebetween. As illustrated in
The plurality of heat-transfer tubes 22 are each connected at one end thereof to a first header 40. The plurality of heat-transfer tubes 22 are each connected at the other end thereof to the second header 10.
An outflow pipe 51 is connected to the bottom of the first header 40. An inflow pipe 52 is connected to the bottom of the second header 10.
In Embodiment 4, as illustrated in
The heat-transfer tubes 22 of the outdoor heat exchanger 20 according to Embodiment 4 may each be a flat tube having a flat sectional shape as illustrated in
Now, the flow of the refrigerant in the outdoor unit 100 of the air-conditioning apparatus according to Embodiment 4 in a heating operation will be described with reference to
In the heating operation, gas-liquid two-phase refrigerant flows into the second header 10 of the outdoor unit 100 from the inflow pipe 52. In the second header 10, the refrigerant flows toward the upper of the second header manifold 11 and is distributed to the plurality of heat-transfer tubes 22 that are orthogonal to the second header manifold 11. The refrigerant thus distributed to the plurality of heat-transfer tubes 22 receive heat from ambient air in the outdoor heat exchanger 20 and evaporates into gas refrigerant or refrigerant containing a large amount of gas. The refrigerant that has undergone heat exchange in the outdoor heat exchanger 20 is collected in the first header 40, flows through the outflow pipe 51, and is discharged.
As described in Embodiments 1 to 3, the quality x of the refrigerant flowing through the inflow pipe 52 satisfies the condition 0.05≤x≤0.30. The second header 10 is the header according to any of Embodiments 1 to 3.
As illustrated in
The refrigerant distribution that conforms to the distribution of the volume of airflow generated by the top-flow fan 30 significantly depends on the liquid-phase thickness as a parameter. According to the experiment conducted by the present inventors, if the outdoor heat exchanger 20 employs the top-flow fan 30, the parameter (MR×x)/(31.6×A) concerning the thickness of a liquid film formed of the refrigerant (the liquid-phase thickness) falls within a range 0.004×106≤(MR×x)/(31.6×A)≤0.120×106, where MR is the maximum flow rate [kg/h] of the refrigerant flowing into the second header 10, x is the quality of the refrigerant, and A is the effective passage-section area [m2] of the second header manifold 11.
It is more preferable that the parameter (MR×x)/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant (the liquid-phase thickness) be within a range 0.010×106≤(MR×x)/(31.6)≤0.120×106. Such a case is more preferable because the distribution performance can be improved over a wide range of operating conditions.
If the parameter (MR×x)/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant (the liquid-phase thickness) is within the range indicated in
As illustrated in
As illustrated in
As illustrated in
The apparent gas speed USG [m/s] is defined as USG=(G×x)/ρG, where G is the flow speed [kg/(m2s)] of the refrigerant flowing into the second header manifold 11, x is the quality of the refrigerant, and ρG is the gas density [kg/m3] of the refrigerant.
Furthermore, the flow speed G [kg/(m2s)] of the refrigerant is defined as G=MR/(3600×A), where MR is the maximum flow rate [kg/h] of the refrigerant flowing into the second header 10, and A is the effective passage-section area [m2] of the second header manifold 11.
In Embodiment 4, the outflow pipe 51 is connected to the bottom of the first header 40. However, the present invention is not limited to such a case.
As illustrated in
As illustrated in
In the above case, as illustrated in
The shape or orientation, that is, the attaching angle, of the inflow pipe 52 may be such that the inflow pipe is inclined, for example, as illustrated in
In such a case, letting the combined length of a portion of the entrance portion of the second header 10 and a straight portion of the inflow pipe 52 be L2 and the inclined portion of the inflow pipe 52 be L3, it is preferable that a condition (L2+L3)≥6D be satisfied, because the flow pattern develops well.
According to Embodiment 4, letting the flow rate [kg/h] of the refrigerant be MR; the quality of the refrigerant flowing into the header manifold in the rated heating operation be x; and the effective passage-section area [m2] of the header manifold be A, the quality x of the refrigerant flowing into the second header manifold 11 satisfies the condition 0.05≤x≤0.30, and the parameter (MR×x)/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant falls within the range 0.004×106≤(MR×x)/(31.6×A)≤0.120×106.
In such a configuration, more liquid refrigerant can be distributed to those heat-transfer tubes 22 nearer to the top-flow fan 30 where there is more airflow.
Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 4, letting the flow rate [kg/h] of the refrigerant be MR, the quality of the refrigerant flowing into the header manifold in the rated heating operation be x, and the effective passage-section area [m2] of the second header manifold 11 be A, the quality x of the refrigerant flowing into the second header manifold 11 satisfies the condition 0.05≤x≤0.30, and the parameter (MR×x)/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant falls within the range 0.010×106≤(MR×x)/(31.6×A)≤0.120×106.
In such a configuration, much more liquid refrigerant can be distributed to those heat-transfer tubes 22 nearer to the top-flow fan 30 where there is more airflow. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved further. Consequently, the energy efficiency can be improved further.
According to Embodiment 4, letting the flow rate [kg/h] of the refrigerant be MR and the quality of the refrigerant flowing into the second header manifold 11 in the rated heating operation be x, the quality x of the refrigerant flowing into the second header manifold 11 satisfies the condition 0.05≤x≤0.30, the inside diameter D [m] of the second header manifold 11 falls within the range 0.010≤D≤0.018, and the parameter (MR×x)/31.6 concerning the thickness of the liquid film formed of the refrigerant falls within the range 0.427≤(MR×x)/31.6≤5.700.
In such a configuration, a refrigerant distribution that is most suitable for the distribution of the volume of airflow generated by the top-flow fan 30 can be obtained. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 4, letting the quality of the refrigerant flowing into the second header manifold 11 in the rated heating operation be x and the effective passage-section area [m2] of the second header manifold 11 be A, the quality x of the refrigerant flowing into the second header manifold 11 satisfies the condition 0.05≤x≤0.30, the inside diameter D [m] of the second header manifold 11 falls within the range 0.010≤D≤0.018, and the parameter x/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant falls within the range 1.4×10≤x/(31.6×A)≤8.7×10.
In such a configuration, a refrigerant distribution that is most suitable for the distribution of the volume of airflow generated by the top-flow fan 30 can be obtained. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 4, letting the quality of the refrigerant flowing into the second header manifold 11 in the rated heating operation be x, the quality x of the refrigerant flowing into the second header manifold 11 satisfies the condition 0.05≤x≤0.30, and the apparent gas speed USG [m/s] of the refrigerant flowing into the second header manifold 11 falls within the range 1≤UGS≤10.
The apparent gas speed USG [m/s] is defined as USG=(G×x)/ρG, where G is the flow speed [kg/(m2s)] of the refrigerant flowing into the second header manifold 11, x is the quality of the refrigerant, and ρG is the gas density [kg/(m3)] of the refrigerant. Furthermore, the flow speed [kg/(m2s)] of the refrigerant is defined as G=MR/(3600×A), where MR is the flow rate [kg/h] of the refrigerant flowing into the second header manifold 11 in the rated heating operation, and A is the effective passage-section area [m2] of the second header manifold 11.
In such a configuration, a refrigerant distribution that is most suitable for the distribution of the volume of airflow generated by the top-flow fan 30 can be obtained. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
According to Embodiment 4, the outdoor heat exchanger 20 includes the plurality of heat-transfer tubes 22 arranged in such a manner as to project therefrom on both sides. The outdoor heat exchanger 20 includes the first header 40 connected to one end of each of the plurality of heat-transfer tubes 22. The outdoor heat exchanger 20 includes the second header 10 connected to the other end of each of the plurality of heat-transfer tubes 22. The outdoor heat exchanger 20 includes the plurality of fins 21 joined to each of the plurality of heat-transfer tubes 22. The outdoor heat exchanger 20 forms part of the refrigeration cycle circuit through which refrigerant circulates. The second header 10 is the header according to any of Embodiments 1 to 4. The second header manifold 11 of the second header 10 has the flow space that communicates with the plurality of branch tubes 12 connected to the plurality of heat-transfer tubes 22, respectively. When the outdoor heat exchanger serves as an evaporator, gas-liquid two-phase refrigerant flows upward in the flow space and is discharged into the plurality of branch tubes 12.
In such a configuration, the gas-liquid two-phase refrigerant flows upward in the second header manifold 11 of the second header 10 and forms an annular flow or a churn flow. Hence, in the annular flow or the churn flow, more gas refrigerant is present around the center of the second header manifold 11, whereas more liquid refrigerant is present on the periphery. Therefore, more gas refrigerant is selectively distributed in the lower part of the second header manifold 11, making it easier for the liquid refrigerant to reach the upper part of the second header manifold 11. Accordingly, the performance of refrigerant distribution in the second header 10 is improved, and the efficiency of the outdoor heat exchanger 20 is improved. Consequently, the energy efficiency can be improved. Thus, with the second header 10 having a simplified configuration, a cost reduction is realized, and the performance of refrigerant distribution from the second header manifold 11 to the plurality of branch tubes 12 can be improved over a wide operating range. Consequently, the energy efficiency can be improved.
Embodiment 5 of the present invention will now be described. Description that has been given in any of Embodiments 1 to 4 is omitted. Elements that are the same as or equivalent to those described in any of Embodiments 1 to 4 are denoted by corresponding ones of the reference numerals.
Embodiment 5 employs tube-shape-converting joints 23 provided to the plurality of branch tubes 12, respectively, of the second header 10. The tube-shape-converting joints 23 each convert the tip of a corresponding one of the branch tubes 12 inserted into the second header manifold 11 from the flat tubular shape for the connection to a corresponding one of the flat heat-transfer tubes 22 included in the heat exchanger into the round tubular shape.
In Embodiment 5, the tube-shape-converting joints 23 are provided. The tube-shape-converting joints 23 connect the round tubular branch tubes 12 connected to the second header 10 and the flat tubular heat-transfer tubes 22 included in the outdoor heat exchanger 20 to each other, respectively, while changing the shape thereof. Furthermore, tube-shape-converting joints 24 are provided. The tube-shape-converting joints 24 connect round tubular branch tubes 42 connected to the first header 40 and the flat tubular heat-transfer tubes 22 included in the outdoor heat exchanger 20 to each other, respectively, while changing the shape thereof.
The tube-shape-converting joints 23 and 24 convert the shape of the branch tubes 12 and 42 inserted into the second header 10 and the first header 40 from the flat tubular shape for the heat-transfer tubes 22 into the round tubular shape.
Since the shape of the branch tubes 12 and 42 inserted into the second header 10 and the first header 40 is converted from the flat tubular shape into the round tubular shape, the effective passage-section area of each of the second header 10 and the first header 40 can be increased. Therefore, the increase in the pressure loss that is caused by the projecting portions of the branch tubes 12 and 42 can be suppressed, whereby the reduction in the performance of the outdoor heat exchanger 20 can be suppressed. Such an advantageous effect is pronounced particularly in the second header 10, in which the branch tubes 12 project into the second header manifold 11 in such a manner as to reach near the center.
Furthermore, the influence of the projecting portions of the branch tubes 12 upon the flow of the refrigerant in the second header manifold 11 can be reduced. Therefore, the flow pattern tends to be stabilized, whereby the improvement in the distribution performance that is brought by the projecting branch tubes 12 becomes greater.
Furthermore, with the tube-shape-converting joints 23 and 24, the diameters of the second header 10 and the first header 40 in a horizontal section can be reduced. Consequently, a distributor occupying a smaller space can be provided.
The configuration illustrated in
In such a case, it is effective that the tube-shape-converting joints 23 are provided to those branch tubes 12 that are near the inflow port of the header where the flow rate of the refrigerant is relatively high, because a greater reduction in the pressure loss can be realized.
The tube-shape-converting joint is not limited to those that convert the heat-transfer tube 22 having the flat tubular shape into a round tubular shape. For example, if the heat-transfer tube 22 is a round tube, the tube-shape-converting joint may be a converting joint that allows the diameter of the branch tube 12 to be smaller than the diameter of the heat-transfer tube 22. Other configurations are applicable as long as such a joint converts the heat-transfer tube 22 into the branch tube 12 such that the effective passage-section area of the second header manifold 11 becomes larger than in a hypothetical case where the heat-transfer tube 22 is made to project into the second header manifold 11.
According to Embodiment 5, the branch tubes 12 are provided with the tube-shape-converting joints 23 each convert the tip of a corresponding one of the branch tubes 12 inserted into the second header manifold 11 from the flat tubular shape for the connection to a corresponding one of the flat heat-transfer tubes 22 included in the heat exchanger into the round tubular shape.
In such a configuration, the reduction in the effective passage-section area of the second header manifold 11 that is caused by the insertion can be suppressed, whereby the disturbance of the flow pattern can be suppressed, realizing a greater improvement in the distribution performance. Accordingly, the efficiency of the outdoor heat exchanger 20 is improved. Consequently, the energy efficiency can be improved.
Embodiment 6 of the present invention will now be described. Description that has been given in any of Embodiments 1 to 5 is omitted. Elements that are the same as or equivalent to those described in any of Embodiments 1 to 5 are denoted by corresponding ones of the reference numerals.
In Embodiment 6, at least two second headers 10a and 10b that are separate from each other in the height direction are connected to each other on the upstream side in the direction in which the refrigerant flows into the outdoor heat exchanger 20 in the heating operation.
As illustrated in
Since the outdoor heat exchanger 20 is divided into the second headers 10a and 10b in the height direction, the influence of the head difference can be reduced. Accordingly, more liquid refrigerant can be distributed to the upper part of the outdoor heat exchanger 20 where there is more airflow generated by the top-flow fan 30. Therefore, a greater improvement in the efficiency of performance of the outdoor heat exchanger 20 and in the energy efficiency can be realized than in a case where the second header is not divided.
Embodiment 6 concerns a case where the second header is divided into two pieces. However, the number of pieces into which the second header is divided and the number of branch tubes provided to each of the pieces of the header are not limited.
According to Embodiment 6, at least two second headers 10a and 10b that are separate from each other in the height direction are connected to each other on the upstream side in the direction in which the refrigerant flows into the outdoor heat exchanger 20 in the heating operation.
In such a configuration, the influence of the head difference in the second headers 10a and 10b can be reduced. Consequently, a greater improvement in the distribution performance can be realized.
Embodiment 7 of the present invention will now be described. Description that has been given in any of Embodiments 1 to 6 is omitted. Elements that are the same as or equivalent to those described in any of Embodiments 1 to 6 are denoted by corresponding ones of the reference numerals.
In Embodiment 7, the outdoor heat exchanger 20 including the second header 10 according to any of Embodiments 1 to 6 is connected to a compressor 61, an expansion device 62, and an indoor heat exchanger 63 by refrigerant pipes in such a manner as to form a refrigeration cycle circuit, whereby an air-conditioning apparatus 200 capable of performing a heating operation is obtained.
In the air-conditioning apparatus 200 illustrated in
The expansion device 62, such as an expansion valve, is provided on the upstream side of the inflow pipe 52 of the outdoor heat exchanger 20. The expansion device 62 and the indoor unit 201 are connected to each other by a connecting pipe 64. The indoor unit 201 and the compressor 61 are connected to each other by a connecting pipe 65. The refrigerant discharged from the outdoor heat exchanger 20 flows into the compressor 61 through the outflow pipe 51.
A controller 70 is configured to control the compressor 61 or the expansion device 62 such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30 in the rated heating operation.
The controller 70 includes a microcomputer including a CPU, a ROM, a RAM, an I/O port, and so forth.
The controller 70 is provided with various sensors connected thereto wirelessly or by control signal lines so that the controller 70 can receive detected values therefrom. The controller 70 is connected in such a manner as to be capable of controlling the rotation speed of the compressor 61 or the opening degree of the expansion device 62 wirelessly or via the control signal lines.
Although the type or shape of the indoor unit 201 is not limited herein, the indoor unit 201 includes, in general, the indoor heat exchanger 63, a fan that is not illustrated, and the expansion device 62 such as an expansion valve. The indoor unit 201 is provided with indoor-unit headers connected to both sides, respectively, of the indoor heat exchanger 63, whereby refrigerant flows through the heat-transfer tubes of the indoor heat exchanger 63.
Now, the flow of the refrigerant in the air-conditioning apparatus 200 according to Embodiment 7 in the heating operation will be described with reference to
In the drawings, solid-line arrows represent the flow of refrigerant in the heating operation. Gas refrigerant compressed by the compressor 61 and thus having a high temperature and a high pressure flows through the connecting pipe 65 into the indoor unit 201. The refrigerant thus flowed into the indoor unit 201 flows into the header, is distributed to the plurality of heat-transfer tubes included in the indoor heat exchanger 63, and flows into the indoor heat exchanger 63. The refrigerant in the indoor heat exchanger 63 releases its heat to ambient air, turns into single-phase liquid refrigerant or gas-liquid two-phase refrigerant, and flows into and is collected in the header. The refrigerant thus collected in the header flows through the connecting pipe 64 into the expansion device 62. In the expansion device 62, the refrigerant turns into low-temperature, low-pressure, gas-liquid two-phase refrigerant or single-phase liquid refrigerant. Then, the refrigerant flows through the inflow pipe 52 into the second header 10.
The gas-liquid two-phase refrigerant reaches the bottom of the second header 10 and is distributed to the plurality of heat-transfer tubes 22 while flowing upward in the second header manifold 11. The refrigerant thus distributed receives heat from air flowing outside the heat-transfer tubes 22, whereby the phase of the refrigerant changes from the liquid phase to the gas phase. Then, the gas-phase refrigerant is discharged into the first header 40. In the first header 40, the refrigerant is collected from the heat-transfer tubes 22. The collected refrigerant is discharged from the bottom of the first header 40 and flows into the compressor 61 again.
The frequency of the compressor 61 changes with the capacity of the indoor heat exchanger 63 that is required for the indoor unit 201.
The opening degree of the expansion device 62 is controlled such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30 in the rated heating operation. The opening degree is controlled by, for example, storing a table summarizing optimum opening degrees of the expansion device 62 for rotation speeds of the compressor 61. In such a control method, an improvement in the distribution performance that is brought by the branch tubes 12 projecting into the second header 10 can be realized under widely varying operating conditions.
According to Embodiment 7, the air-conditioning apparatus 200 includes the compressor 61, the indoor heat exchanger 63, the expansion device 62, and the outdoor heat exchanger 20 that form a refrigeration cycle circuit through which refrigerant circulates. The outdoor heat exchanger 20 is the heat exchanger according to any of Embodiments 1 to 6. The air-conditioning apparatus 200 includes the controller 70 configured to control the compressor 61 or the expansion device 62 such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30 in the rated heating operation.
In such a configuration, the distribution performance of the second header 10 can be improved stably over a wide range of operating conditions. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
In Embodiment 8, the air-conditioning apparatus 200 according to Embodiment 7 includes a first temperature sensor 66 provided on the connecting pipe 64 and that detects the temperature at the outlet of the indoor unit. Furthermore, the air-conditioning apparatus 200 includes a second temperature sensor 67 provided on the indoor heat exchanger 63 and that detects the temperature of the refrigerant flowing through the heat-transfer tubes of the indoor heat exchanger 63.
In the heating operation, the controller 70 measures a condensation saturation temperature Tc of the refrigerant by using the second temperature sensor 67 and a condenser outlet temperature TRout of the refrigerant by using the first temperature sensor 66 provided at the outlet of the indoor unit. Thus, the controller 70 detects S.C. at the outlet of the condenser (=Tc−TRout, also referred to as outlet temperature difference) and controls the quality x flowing into the second header 10 to fall within the range 0.05≤x≤0.30.
The S.C. can be controlled by adjusting the opening degree of the expansion device 62 and by, for example, examining in advance the relationship among the frequency of the compressor 61, the S.C., and the quality. In such a control method, an improvement in the distribution performance that is brought by the branch tube 12 projecting into the second header 10 can be realized under widely varying operating conditions.
According to Embodiment 8, the air-conditioning apparatus 200 includes the compressor 61, the indoor heat exchanger 63, the expansion device 62, and the outdoor heat exchanger 20 that form a refrigeration cycle circuit through which refrigerant circulates. The outdoor heat exchanger 20 is the heat exchanger according to any of Embodiments 1 to 6. The air-conditioning apparatus 200 includes the first temperature sensor 66 provided on the downstream side, in the heating operation, of the indoor heat exchanger 63. The air-conditioning apparatus 200 includes the second temperature sensor 67 provided on the indoor heat exchanger. The air-conditioning apparatus 200 includes the controller 70 configured to calculate the outlet temperature difference S.C. (=Tc−TRout) of the indoor heat exchanger 63 from the temperature (the condenser outlet temperature TRout) detected by the first temperature sensor 66 and the temperature (the condensation saturation temperature Tc) detected by the second temperature sensor 67 in the heating operation, and to control the compressor 61 or the expansion device 62 such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30 in the rated heating operation.
In such a configuration, the distribution performance of the second header 10 can be improved stably over a wide range of operating conditions. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
In Embodiment 9, the air-conditioning apparatus 200 according to Embodiment 7 or 8 includes a gas-liquid separator 80 provided between the second header 10 and the expansion device 62. The expansion device 62 and the gas-liquid separator 80 are connected to each other by a connecting pipe 81. The gas-liquid separator 80 and the outflow pipe 51 are connected to each other by a gas bypass pipe 82. The gas bypass pipe 82 allows gas refrigerant obtained through the separation by the gas-liquid separator 80 to flow directly to the compressor 61. The gas bypass pipe 82 is provided at a halfway position thereof with a gas-bypass regulating valve 83. The opening degree of the gas-bypass regulating valve 83 is changeable by the controller 70.
The controller 70 adjusts the opening degree of the gas-bypass regulating valve 83 in accordance with operating conditions and thus controls the quality x of the refrigerant flowing into the second header 10 to fall within the range 0.05≤x≤0.30.
In such a control method, a greater improvement in the distribution performance of the second header 10 that is brought by the branch tubes 12 projecting thereinto can be realized under widely varying operating conditions.
In addition, since some of the gas refrigerant is made to flow into the gas bypass pipe 82 and thus bypass the outdoor heat exchanger 20, the pressure loss in the outdoor heat exchanger 20 can be reduced. Consequently, the efficiency of the outdoor heat exchanger 20 can be improved.
The gas-bypass regulating valve 83 whose opening degree is changeable may be an electronic expansion valve or the like whose opening degree is adjustable. Alternatively, for example, the gas-bypass regulating valve 83 may be substituted for by a combination of a solenoid valve and a capillary tube or a check valve and a flow resistor provided to the gas bypass pipe 82, but is not specifically limited.
In general, as illustrated in
For example, a simple gas-liquid separator 80 that utilizes the orientation of the refrigerant pipe may be employed, such as a T-shaped branching pipe 85 illustrated in
The controller 70 controls, for example, the quality x to fall within the range 0.05≤x≤0.30 in the rated heating operation. More preferably, the controller 70 controls the gas-bypass regulating valve 83 to be open in the rated heating operation but to be closed under the other conditions. The degree to which the gas-bypass regulating valve 83 is opened is determined by, for example, examining in advance the relationship between the rotation speed of the compressor 61 and the opening degree that is optimum therefor. Alternatively, the degree to which the gas-bypass regulating valve 83 is opened may be determined by examining the relationship between the number of operating indoor units 201 and the opening degree that is optimum therefor.
While
According to Embodiment 9, the air-conditioning apparatus 200 includes the compressor 61, the indoor heat exchanger 63, the expansion device 62, and the outdoor heat exchanger 20 that form a refrigeration cycle circuit through which refrigerant circulates. The outdoor heat exchanger 20 is the heat exchanger according to any of Embodiments 1 to 6. The air-conditioning apparatus 200 includes the gas-liquid separator 80 provided between the outdoor heat exchanger 20 and the expansion device 62. The air-conditioning apparatus 200 includes the gas bypass pipe 82 that allows the gas refrigerant obtained through the separation by the gas-liquid separator 80 to flow directly to the compressor 61. The air-conditioning apparatus 200 includes the gas-bypass regulating valve 83 provided on the gas bypass pipe 82. The air-conditioning apparatus 200 includes the controller 70 configured to control the gas-bypass regulating valve 83 in accordance with operating conditions such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30.
In such a configuration, an improvement in the distribution performance of the second header 10 can be realized over a wide range of operating conditions. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
In Embodiment 10, a header-preceding regulating valve 90 is provided at a halfway position of the inflow pipe 52 between the gas-liquid separator 80 and the second header 10 according to Embodiment 9. Furthermore, an accumulator 91 is provided on the upstream side with respect to the compressor 61. The accumulator 91 is provided on the upstream side thereof with an accumulator inflow pipe 92. The compressor 61 is provided on the discharge side thereof with a compressor discharge pipe 93. Furthermore, a four-way valve 94 that switches the flow of the refrigerant between that for the cooling operation and that for the heating operation is provided.
The controller 70 controls the opening degree of the header-preceding regulating valve 90, whereby completely separated liquid refrigerant is obtained by the gas-liquid separator 80 even at a low flow rate of the refrigerant. Therefore, a situation where x<0.05 can be prevented. Accordingly, an improvement in the efficiency of the outdoor heat exchanger 20 is realized with a stable improvement in the distribution performance over a wide operating range. Consequently, the energy efficiency can be improved.
The accumulator 91 is provided on the upstream side with respect to the compressor 61 so that the entry of the liquid refrigerant into the compressor 61 is suppressed or excessive refrigerant is stored therein. In such a configuration, the controller 70 adjusts the opening degree of the expansion device 62 and the opening degree of the header-preceding regulating valve 90. Thus, the inflow pipe 52, the connecting pipe 81, and the gas-liquid separator 80 that are provided between the expansion device 62 and the header-preceding regulating valve 90 can be used as a liquid storage. It is preferable to use such a liquid storage because the capacity of the accumulator 91 can be reduced correspondingly.
In the cooling operation, the controller 70 fully opens the header-preceding regulating valve 90. Thus, the liquid refrigerant can be stored in the inflow pipe 52, a portion of the gas bypass pipe 82, the gas-liquid separator 80, and the connecting pipe 81. Therefore, the S.C. at the outlet of the outdoor heat exchanger 20 can be reduced. Such a configuration is preferable because, in the cooling operation as well, the efficiency of the outdoor heat exchanger 20 can be improved, and the energy efficiency can be improved.
Now, the flow of the refrigerant in the cooling operation will be described.
As illustrated in
Now, the reason why the efficiency of the outdoor heat exchanger 20 can be improved either in the heating operation or in the cooling operation by adjusting the header-preceding regulating valve 90, the expansion device 62, and the gas-bypass regulating valve 83 according to Embodiment 10 will be described.
In the heating operation, the controller 70 adjusts the opening degree of the expansion device 62, thereby turning the refrigerant into a gas-liquid two-phase state.
In this step, the controller 70 fully opens the header-preceding regulating valve 90 and opens the gas-bypass regulating valve 83, whereby the flow rate of the gas refrigerant flowing into the second header 10 can be reduced. Accordingly, the quality x of the refrigerant flowing into the second header 10 is controlled to fall within the range 0.05≤x≤0.30. Thus, an improvement in the distribution performance that is brought by the projecting branch tube 12 is realized, and the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
In the cooling operation, the controller 70 fully opens the gas-bypass regulating valve 83 under a condition where a large amount of refrigerant is necessary, thereby turning the refrigerant into a low-pressure, gas-liquid two-phase state at the header-preceding regulating valve 90. Thus, the two-phase gas-liquid area in the air-conditioning apparatus 200 is increased. In such a manner, the amount of refrigerant can be optimized. Consequently, the efficiency of the air-conditioning apparatus 200 can be improved. On the other hand, if there is an excessively large amount of refrigerant, the controller 70 fully opens the header-preceding regulating valve 90, thereby increasing the area filled with liquid refrigerant. Accordingly, the area of the outdoor heat exchanger 20 that is filled with liquid refrigerant can be reduced. Thus, the heat-transfer area filled with single-phase liquid refrigerant can be reduced. Therefore, the efficiency of the outdoor heat exchanger 20 can be improved.
The mechanism of improving the efficiency of the outdoor heat exchanger 20 by reducing the area filled with liquid refrigerant is as follows.
The S.C. is defined by the difference between the saturation temperature of the refrigerant and the temperature of the refrigerant at the outlet of the heat-transfer tube. The greater the S.C., the larger the area of the heat-transfer tube 22 that is filled with liquid refrigerant.
If the area filled with liquid refrigerant is large, the area of the heat-transfer tube 22 that is filled with single-phase liquid refrigerant is large. The heat-transfer coefficient of the single-phase liquid refrigerant in the tube is smaller than the heat-transfer coefficient of the gas-liquid two-phase refrigerant. Therefore, if the area of the heat-transfer tube 22 that is filled with single-phase liquid refrigerant becomes large, the efficiency of the outdoor heat exchanger 20 is reduced.
According to Embodiment 10, the air-conditioning apparatus 200 includes the compressor 61, the four-way valve 94, the indoor heat exchanger 63, the expansion device 62, and the outdoor heat exchanger 20 that form a refrigeration cycle circuit through which refrigerant circulates. The air-conditioning apparatus 200 is capable of performing the heating operation and the cooling operation by switching the flow of the refrigerant at the four-way valve 94. The outdoor heat exchanger 20 is the heat exchanger according to any of Embodiments 1 to 6. The air-conditioning apparatus 200 includes the gas-liquid separator 80 provided between the outdoor heat exchanger 20 and the expansion device 62. The air-conditioning apparatus 200 includes the gas bypass pipe 82 that allows the gas refrigerant obtained through the separation by the gas-liquid separator 80 to flow directly to the compressor 61. The air-conditioning apparatus 200 includes the gas-bypass regulating valve 83 provided on the gas bypass pipe 82. The air-conditioning apparatus 200 includes the header-preceding regulating valve 90 provided on the downstream side, in the heating operation, with respect to the gas-liquid separator 80. The air-conditioning apparatus 200 includes the controller 70 configured to control the expansion device 62, the gas-bypass regulating valve 83, and the header-preceding regulating valve 90 in the heating operation such that the quality x of the refrigerant flowing into the second header 10 falls within the range 0.05≤x≤0.30, and to control the header-preceding regulating valve 90 in the cooling operation such that the gas-liquid separator 80 is used as a liquid storage.
In such a configuration, the efficiency of the outdoor heat exchanger 20 can be improved either in the cooling operation or in the heating operation. Consequently, the energy efficiency can be improved.
As illustrated in
The outdoor heat exchanger 20 including the side-flow fan 30 also has a problem in that liquid refrigerant is less likely to reach the upper part of the second header manifold 11. Therefore, with the use of the second header 10, liquid refrigerant becomes more likely to flow toward the upper side of the second header manifold 11. Hence, the distribution performance can be improved. Accordingly, the efficiency of the outdoor heat exchanger 20 can be improved. Consequently, the energy efficiency can be improved.
10 second header 10a second header 10b second header 11 second header manifold 12 branch tube 12a partition 13 two-way tube 20 outdoor heat exchanger 21 fin 22 heat-transfer tube 23 tube-shape-converting joint 24 tube-shape-converting joint 30 fan 40 first header 42 branch tube 51 outflow pipe 52 inflow pipe 52a first inflow pipe 52b second inflow pipe 61 compressor 62 expansion device 63 indoor heat exchanger 64 connecting pipe 65 connecting pipe 66 first temperature sensor 67 second temperature sensor 70 controller 80 gas-liquid separator 81 connecting pipe 82 gas bypass pipe 83 gas-bypass regulating valve 84 gas-liquid-separating container 85 branching pipe 86 branching pipe 90 header-preceding regulating valve 91 accumulator 92 accumulator inflow pipe compressor discharge pipe 94 four-way valve 100 outdoor unit 101 casing 102 air inlet 103 air outlet 104 fan guard 200 air-conditioning apparatus 201 indoor unit
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16319721 | Jan 2019 | US |
| Child | 17353862 | US |
