Patent Application
20200041178
The present invention relates to an air-conditioning apparatus, and more specifically to the structure of a heat exchanger including a distribution header.
In existing air-conditioning apparatuses, liquid refrigerant condensed in a heat exchanger equipped to an indoor unit and functioning as a condenser is reduced in pressure by an expansion valve, and thus turns into two-phase gas-liquid refrigerant containing both gas refrigerant and liquid refrigerant. The two-phase gas-liquid refrigerant then flows into a heat exchanger equipped to an outdoor unit and functioning as an evaporator.
When refrigerant flows in a two-phase gas-liquid state into the heat exchanger serving as an evaporator, the distribution of refrigerant to the heat exchange unit of the heat exchanger deteriorates. Accordingly, to improve the distribution performance of refrigerant, in some air-conditioning apparatuses, a header is used as a distribution unit for the heat exchanger equipped to the outdoor unit, and a partition plate, an eject port, or other such structural object is provided inside the header.
However, providing an additional structural object inside the header manifold as described above yields only a limited improvement in distribution despite a significant associated increase in cost. Accordingly, another method has been proposed in which the insertion length of branch tubes into the header manifold is adjusted (see, for example, Patent Literature 1). The method according to the invention described in Patent Literature 1 includes inserting a plurality of branch tubes at equal lengths, and optimizing the flow velocity of refrigerant in the flow space of the header manifold to thereby ensure uniform distribution of refrigerant to the heat exchanger.
Patent Literature 1: Japanese Patent No. 5626254
In general, the flow of air through the heat exchanger is unevenly distributed relative to the vertical direction of the heat exchanger. For instance, in the case of a heat exchanger in a top-flow arrangement with a fan installed over the top of the outdoor unit or the top of the heat exchanger of the outdoor unit, there is a large amount of airflow in areas of the heat exchanger closer to the fan, and the amount of airflow decreases progressively with increasing distance from the fan. This means that, even if refrigerant is uniformly distributed to the heat exchanger, this refrigerant distribution is not optimal relative to the airflow. In some cases, this can lead to deterioration of heat exchanger performance and, consequently, a decrease in the energy efficiency of the air-conditioning apparatus.
The present invention has been made to address the above-mentioned problem, and accordingly, an object thereof is to provide an air-conditioning apparatus that, although having a simple structure, allows refrigerant to be distributed in a manner optimal for the airflow through the heat exchanger.
An air-conditioning apparatus according to an embodiment of the present invention includes a heat exchanger, an axial fan, and a refrigerant circuit. The heat exchanger includes a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in the vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction. The axial fan includes a blade disposed around a boss that rotates, the blade having a rotational plane that faces the plurality of heat transfer tubes in the horizontal direction. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger. The refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at the center of the header manifold and liquid-phase refrigerant collects on the wall surface of the header manifold. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, among the plurality of branch tubes located within a height range that allows the blade to rotate, the majority of the branch tubes located at or below the height of the boss are inserted into the header manifold such that the distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and the majority of the branch tubes located above the height of the boss are connected to the header manifold such that the distal ends of the branch tubes are positioned at more than 50% of the distance from the center.
An air-conditioning apparatus according to another embodiment of the present invention includes a heat exchanger, a fan, and a refrigerant circuit. The heat exchanger includes a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in the vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction. The fan is located above the plurality of heat transfer tubes. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger. The refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at the center of the header manifold and liquid-phase refrigerant collects on the wall surface of the header manifold. The header manifold includes a plurality of header manifolds disposed at different heights in the vertical direction. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, the majority of the branch tubes connected to the header manifold located closest to the fan are inserted such that the distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and the majority of the branch tubes connected to the header manifold disposed below the header manifold located closest to the fan are connected such that the distal ends of the branch tubes are positioned at more than 50% of the distance from the center.
An air-conditioning apparatus according to another embodiment of the present invention includes a heat exchanger, a fan, and a refrigerant circuit. The heat exchanger includes a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in the vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction. The fan is located above the plurality of heat transfer tubes. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger. The refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at the center of the header manifold and liquid-phase refrigerant collects on the wall surface of the header manifold. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, the majority of the branch tubes connected to the header manifold are inserted into the header manifold such that the distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and at least the uppermost branch tube of the branch tubes connected to the header manifold is connected to the header manifold such that the distal end of the branch tube is positioned at more than 50% of the distance from the center.
In the air-conditioning apparatus according to an embodiment of the present invention, the branch tubes are inserted into the header manifold at lengths that are varied relative to the vertical direction of the heat exchanger depending on the positional relationship between the heat exchanger and the fan or between the heat exchanger and the axial fan. When the flow pattern of refrigerant entering the liquid header manifold is annular or churn, in an area of the header where the branch tubes are inserted so as to penetrate the liquid layer, the flow of liquid refrigerant is concentrated in an upper part of the area, and in an area of the header where the branch tubes are connected so as to be covered in the liquid layer, the flow of liquid refrigerant is concentrated in a lower part of the area. By suitably combining such areas in the vertical direction, refrigerant can be distributed in a manner suited for the distribution of air velocity in the heat exchanger. This helps enhance the performance of the heat exchanger.
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Embodiments of the present invention will be described below with reference to the drawings. Elements designated by the same reference signs in the drawings represent the same or corresponding elements throughout the specification. Further, the specific forms and arrangements of components described throughout the specification are illustrative only and not intended to limit the invention to the specific forms and arrangements described.
A heat exchanger 1 will be described below with reference to
In Embodiment 1, the heat exchanger 1 includes components such as a liquid header 10, a gas header 40, a heat exchange unit 20, and a plurality of branch tubes 12 that connect the liquid header 10 or the gas header 40 to the heat exchange unit 20. A single axial fan 30 is disposed over the side of the heat exchanger 1. The heat exchanger 1 constitutes a portion of the refrigeration cycle of an air-conditioning apparatus.
The liquid header 10 is formed by connecting the branch tubes 12 to a liquid header main tube 11. Hereinafter, one or more liquid header main tubes 11 constituting the liquid header 10 will be sometimes collectively referred to as a header manifold. The liquid header main tube 11 has a flow space defined therein that extends in the vertical direction (arrow Z direction). The liquid header main tube 11 is in the form of a circular tube. A lower portion of the liquid header main tube 11 is connected to an inlet pipe 52 whose upstream portion is connected to a pipe of a refrigerant circuit. Liquid-phase refrigerant Rb and gas-phase refrigerant Ra are distributed in the flow space. The liquid-phase refrigerant Rb collects along the wall surface of the liquid header main tube 11 to form a liquid layer in the flow space.
The gas header 40 is formed by connecting the branch tubes 12 to a gas header main tube 41, which defines a flow space therein and is in the form of a circular tube. A lower portion of the gas header 40 is connected with an outlet pipe 51 through which refrigerant exits.
Although
The axial fan 30 includes a boss 31, and blades 32 disposed around the boss 31. The axial fan 30 supplies air to the heat exchanger 1. As the boss 31 is rotated by a motor or other device, air is suctioned from one side of the axial fan 30 relative to the direction of the arrow Y, and blown out from the other side. In Embodiment 1, the axial fan 30 is disposed such that the rotational plane of the blades 32 faces the heat transfer tubes 22 of the heat exchanger 1 in the horizontal direction. Hereinafter, the height of the center of the boss 31 in the vertical direction (arrow Z direction) will be represented by a boss centerline Ob.
The branch tubes 12 are arranged so as to be spaced apart from each other in the vertical direction (arrow Z direction) to connect the liquid header 10 or the gas header 40 to the heat transfer tubes 22. Refrigerant flows inside each branch tube 12. The branch tubes 12 include branch tubes 12a located below the boss centerline Ob, and branch tubes 12b located above the boss centerline Ob, of which the branch tubes 12a are connected to the liquid header 10 such that the distal ends of the branch tubes 12a penetrate the liquid layer, and the branch tubes 12b are connected to the liquid header 10 such that the distal ends of the branch tubes 12b are covered in the liquid-phase refrigerant Rb. That is, the insertion length of the branch tubes 12a located below the boss centerline Ob into the liquid header main tube 11 is greater than the insertion length of the branch tubes 12b located above the boss centerline Ob.
In the case of the heat exchanger 1 of a side-flow type with a single axial fan 30 disposed over the side of the heat exchanger 1 as in Embodiment 1, the velocity of airflow is greatest at the position of the height of the boss 31 of the axial fan 30. The velocity of airflow decreases as it is brought closer to the lower end or upper end of the heat exchanger 1. By contrast, the distribution of liquid refrigerant flow rate in the liquid header 10 is such that in the area from the lower end of the heat exchanger 1 to the boss centerline Ob, the flow rate of liquid refrigerant increases as it is brought closer to the boss 31, and in the area from the boss centerline Ob to the upper end of the heat exchanger 1, the flow rate of liquid refrigerant decreases as the distance from the boss 31 increases.
The above-mentioned distribution of liquid refrigerant flow rate in the liquid header 10 is obtained as a result of the difference in the amount of insertion between the branch tubes 12a and 12b. In the area of the liquid header 10 located below the boss centerline Ob, the branch tubes 12a penetrate the liquid layer of refrigerant flowing in the liquid header 10, resulting in reduced distribution of liquid refrigerant toward a lower part of the area, that is, toward a lower portion of the heat exchanger 1. By contrast, in the area of the liquid header 10 located above the boss centerline Ob, the branch tubes 12b fall within the liquid layer of refrigerant flowing in the liquid header 10, resulting in increased distribution of liquid refrigerant in a lower part of the area, that is, at the position of the height of the boss centerline Ob. The above-mentioned configuration allows refrigerant to be distributed in the heat exchanger 1 in a manner suited for the distribution of air velocity, leading to enhanced performance of the heat exchanger 1.
The following describes the connection between the liquid header 10, and the branch tubes 12a located below the boss centerline Ob. In
The expression “near the center” as used herein means that, as illustrated in
When the quality x=0.30, the performance of the heat exchanger 1 deteriorates sharply if the distal end portion of the branch tube 12a is located outside ±75%. When the quality x=0.05, the quality is lower and hence the liquid layer is thicker than when the quality x=0.30. Consequently, the performance of the heat exchanger 1 deteriorates sharply if the distal end portion of the branch tube 12a is located outside ±50%. By contrast, if the distal end portion of the branch tube 12a is located within ±50%, the deterioration in the performance of the heat exchanger 1 is slight.
Accordingly, assuming that the quality x=0.05 and hence the liquid layer is thick, improved distribution performance can be obtained by positioning the distal end portion of the branch tube 12 within ±50%. If the distal end portion of each branch tube 12a located below the boss centerline Ob is positioned within ±50%, this ensures that, in the area of the liquid header 10 from the lower end to the boss centerline Ob, a large amount of liquid refrigerant can be distributed in an upper part of the area, that is, near the position of the height of the boss centerline Ob. More desirably, if the distal end portion of the branch tube 12a is positioned at the center of the inside diameter of the liquid header main tube 11, that is, at the 0% position. This configuration allows more liquid refrigerant to be directed upward over a wider range of refrigerant flow rate conditions.
If the distal end portion of each branch tube 12b located above the boss centerline Ob lies within the range of greater than or equal to −100% and less than −50%, or within the range of greater than 50% and less than or equal to 100%, such a configuration is more desirable as this allows more liquid refrigerant to be directed downward in the area of the liquid header 10 from the boss centerline Ob to the upper end.
According to the results of an experiment and analysis conducted by the inventors, when the quality of refrigerant entering the liquid header 10 is 0.05≤x≤0.30, the thickness δ [m] of the liquid layer approximates relatively well to δ=G×(1−x)×D/(4 ρL×ULS), where G is refrigerant flow velocity [kg/(m2s)], x is refrigerant quality, D is the inside diameter [m] of the liquid header 10, ρL is refrigerant liquid density [kg/m3], and ULS is reference liquid apparent velocity [m/s], which is the maximum value within the variation range of the gas apparent velocity of refrigerant flowing into the flow space of the liquid header 10. Accordingly, the distal end portion of each branch tube 12a connected to the liquid header 10 at a position below the boss centerline Ob may be positioned anywhere as long as the distal end portion protrudes beyond the thickness δ of the liquid layer determined by the above-mentioned equation, and reaches the gas-phase refrigerant Ra in the flow space of the liquid header 10. The reference liquid apparent velocity ULS [m/s] is defined as G(1−x)/ρL.
A flow pattern is determined from the flow pattern chart for vertical upward flow, and set based on the reference gas apparent velocity UGS [m/s] of refrigerant at the maximum value within the variation range of the flow velocity of refrigerant entering the flow space of the liquid header main tube 11. Desirably, the reference gas apparent velocity UGS [m/s] of refrigerant entering the liquid header main tube 11 satisfies the following condition: UGS≥α×L× (g×D)0.5/(40.6×D)−0.22α×(g×D)0.5. Further desirably, the reference gas apparent velocity UGS [m/s] satisfies the following condition: UGS≥3.1/(ρG0.5)×[σ×g×(ρL−ρG)]0.25.
Now, α is defined as refrigerant void fraction α=x/[x+(ρG/ρL)×(1−x)], L is defined as entrance length [m], g is defined as acceleration due to gravity [m/s2], D is defined as the inside diameter [m] of the liquid header 10, x is defined as refrigerant quality, ρG is defined as refrigerant gas density [kg/m3], ρL is defined as refrigerant liquid density [kg/m3], and σ is defined as refrigerant surface tension [N/m]. The refrigerant void fraction α can be measured by, for example, a method such as measurement using electrical resistance or observation based on visualization. The entrance length L2 [m] at the inlet portion of the liquid header 10 is defined as the distance between the position of the inlet portion of the liquid header 10 where refrigerant enters, and the position of the central axis of the branch tube 12 located closest to the inlet portion.
The reference gas apparent velocity USG, which is calculated by measuring the flow velocity G of refrigerant entering the liquid header 10, refrigerant quality x, and refrigerant gas density ρG, is defined as USG=(G×x)/ρG.
As illustrated in
If, for instance, the liquid header 10 is equipped to an air-conditioning apparatus, at the maximum value within the variation range of the flow velocity of refrigerant entering the flow space of the liquid header 10, during rated heating operation, two-phase gas-liquid refrigerant flows through the flow space of the liquid header 10 as an upward flow.
When the quality of refrigerant entering the liquid header 10 falls within the range of 0.05≤x≤0.30, the refrigerant flows in the liquid header main tube 11 in such a flow pattern that a large amount of liquid-phase refrigerant Rb is distributed near the wall surface. This is desirable from the viewpoint of achieving a particularly large improvement in distribution performance and consequently in heat exchanger performance due to the protrusion of the branch tubes 12.
In the foregoing description, for the branch tubes 12a located below the boss centerline Ob, the central axis of each branch tube 12a that extends in the horizontal direction (arrow X direction) and the central axis of the liquid header main tube 11 that extends in the vertical direction (arrow Z direction) intersect each other. However, for example, the horizontally-extending central axis of the branch tube 12a may be shifted from the vertically-extending central axis of the liquid header main tube 11.
In this case, the center position in the horizontal plane of the flow space of the liquid header main tube 11 is defined as 0%. The wall surface position in the flow space of the liquid header main tube 11 in the horizontal plane is defined as ±100%. The direction of insertion of the branch tubes 12 in the horizontal plane is defined as X-direction, and the direction of width of the branch tubes 12 in the horizontal plane is defined as Y-direction.
A case is considered in which, as illustrated in
As illustrated in
Preferably, all the branch tubes 12a located below the boss centerline Ob are inserted by the same amount. However, the branch tubes 12a may not necessarily be inserted by the same amount as long as the distal end portion of each branch tube 12a or the central axis of each branch tube 12a lies within ±50%.
The improvement in the performance of the heat exchanger 1 due to improved distribution can be increased by using a refrigerant mixture of two or more refrigerants with different boiling points selected from the group consisting of, but not limited to, an olefin-based refrigerant such as R1234yf or R1234ze(E), a HFC refrigerant such as R32, a hydrocarbon refrigerant such as propane or isobutane, CO2, and dimethyl ether (DME).
The present invention is dependent on the flow pattern of refrigerant flowing in the liquid header 10 in a two-phase gas-liquid state. For this reason, it is desirable for the flow of two-phase gas-liquid refrigerant to be in a sufficiently developed state. According to an experiment conducted by the inventors, as for the entrance length L required for sufficient development of two-phase gas-liquid refrigerant, if the condition L≥5D is satisfied, where D is the inside diameter [m] of the liquid header main tube 11, the improvement in distribution performance can be increased. More desirably, the entrance length L satisfies the condition L≥10D.
It is to be noted that the foregoing description of the branch tube 12 made regarding the location of its end portion does not apply to, for example, a branch tube such as the end branch tube 18b that is connected from the upper or lower end of the liquid header main tube 11.
The foregoing description is directed to the bifurcated tubes 13 each having two inlets for each inlet. However, the configuration of the branch tubes 12 is not limited thereto. Any branch tube 12 having a larger number of outlets than inlets may be employed.
The branch tube 12 has been described above as a component of the liquid header 10. However, for example, the branch tube 12 may be formed of a portion of a heat transfer tube by extending a portion of the circular heat transfer tube 22 of the heat exchanger 1. Since the branch tube 12 may be substituted for by a portion of the heat transfer tube 22 in some cases, its inner surface may be machined to have a heat transfer-facilitating feature such as a groove.
Although the inlet pipe 52 is connected to the lower end of the liquid header main tube 11 in
As described above, in Embodiment 1, the air-conditioning apparatus includes the heat exchanger 1, the axial fan 30, and the refrigerant circuit. The heat exchanger 1 includes the heat transfer tubes 22 in which refrigerant flows, the heat transfer tubes 22 being arranged so as to be spaced apart from each other in the vertical direction, and the header manifold (liquid header main tube 11) that has a flow space defined inside the header manifold and extending in the vertical direction (arrow Z direction), the header manifold allowing refrigerant to flow into the heat transfer tubes 22 from the branch tubes 12 arranged so as to be spaced apart from each other in the vertical direction. The axial fan 30 includes the blades 32 disposed around the boss 31 that rotates. The blades 32 have a rotational plane that faces the heat transfer tubes 22 in the horizontal direction. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger 1. The refrigerant flows in the header manifold in an annular or churn flow pattern in which the gas-phase refrigerant Ra collects at the center of the header manifold and the liquid-phase refrigerant Rb collects on the wall surface of the header manifold. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, among the branch tubes 12 located within a height range that allows the blades 32 to rotate, the majority of the branch tubes 12a located at or below the height of the boss 31 are connected to the header manifold such that their distal ends are positioned at 0 to 50% of the distance from the center, and the majority of the branch tubes 12b located above the height of the boss 31 are connected to the header manifold such that their distal ends are positioned at more than 50% of the distance from the center.
Due to the above configuration, in the air-conditioning apparatus, the branch tubes 12 are connected to the liquid header main tube 11 such that, at positions above the boss 31, the branch tubes are covered in the liquid layer, and at positions below the boss 31, the branch tubes penetrate the liquid layer. Consequently, for a case in which a large amount of liquid-phase refrigerant Rb is distributed along the wall surface inside the liquid header 10, in the area above the boss 31, a large amount of liquid refrigerant is directed toward a lower portion of the area, whereas in the area below the boss 31, a large amount of liquid refrigerant is directed toward an upper portion of the area. Therefore, in the case of the heat exchanger 1 in a side-flow arrangement, the above-mentioned configuration makes it possible to obtain a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. As a result, in the air-conditioning apparatus, the performance of the heat exchanger 1 can be enhanced, leading to enhanced energy efficiency.
Among the branch tubes 12a located at a position at or below the height of the boss 31, the branch tube whose distal end position is at 0 to 50% of the distance from the center and which is located most upstream has a distal end that penetrates the liquid layer of the thickness δ [m], which is formed as the liquid-phase refrigerant Rb collects on the wall surface, and reaches the gas-phase refrigerant Ra. Among the branch tubes 12b located above the height of the boss 31, the branch tube whose distal end position is at more than 50% of the distance from the center and which is located most upstream has a distal end that falls within the liquid layer. The thickness δ [m] of the liquid layer is defined as δ=G×(1−x)×D/(4ρL×ULS), where G is refrigerant flow velocity [kg/(m2s)], x is refrigerant quality, D is the inside diameter [m] of the header manifold, ρL is refrigerant liquid density [kg/m3], and ULS is reference liquid apparent velocity [m/s], which is the maximum value within the variation range of gas apparent velocity of refrigerant entering the flow space of the header manifold. The reference liquid apparent velocity ULS [m/s] is defined as G(1−x)/ρL.
Accordingly, the branch tubes 12a connected below the height of the boss 31 may be inserted at any length into the liquid header 10 as long as the branch tubes 12a penetrate at least the liquid layer having the thickness δ [m] determined by the above-mentioned equation based on the experimental results. Consequently, the adjustable range of insertion length into the liquid header 10 can be increased.
In the heat exchanger 1, the refrigerant entering the header manifold (liquid header main tube 11) has a quality x in the range of 0.05≤x≤0.30. This ensures that the flow of refrigerant in the liquid header 10 readily follows a flow pattern in which a large amount of liquid-phase refrigerant Rb is distributed along the wall surface of the liquid header 10. Such a configuration, when combined with the method of connecting the branch tubes 12 mentioned above, helps provide improved distribution.
It is to be noted that the foregoing description of the branch tube 12 made regarding the location of its distal end portion does not apply to, for example, a branch tube such as the end branch tube 18a that is connected from the upper or lower end of the corresponding liquid header main tube.
Although
In connecting the branch tubes 12a to the first liquid header main tube 11a, the features described above with reference to Embodiment 1, such as the equation of the thickness δ [m] of the liquid layer, the range of locations of the distal end portions of the branch tubes 12a, the refrigerant quality range, and the characteristics of flow patterns, can be employed to thereby achieve improved distribution performance by utilizing the characteristics of an annular or churn flow pattern.
As for the second liquid header main tube 11b, the branch tubes 12b may be connected to the second liquid header main tube 11b in any manner as long as their insertion length is less than the thickness δ [m] of the liquid layer.
The following describes, with reference to
The center position in the horizontal plane of the flow space of the branch tubes 12b connected to the second liquid header main tube 11b is defined as 0%, and the position of the wall surface in the horizontal plane of the flow space of the second liquid header main tube 11b is defined as ±100%. In
As described above, in the air-conditioning apparatus according to Embodiment 2, the branch tubes 12b are connected to the second liquid header main tube 11b located above the boss 31 such that the distal ends of the branch tubes 12b are covered in the liquid layer, and the branch tubes 12a are inserted into the first liquid header main tube 11a located below the boss 31 such that the distal ends of the branch tube 12a penetrate the liquid layer.
As in Embodiment 1, this configuration makes it possible to obtain, for the heat exchanger 1 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
According to Embodiment 2, in the header manifold (liquid header main tube 11), the flow space connected to the branch tubes 12 located within a height range that allows the blades 32 to rotate is divided into a plurality of parts in the vertical direction.
This configuration allows the branch tube insertion length to be controlled for each individual flow space, leading to enhanced ease of manufacture. Further, as compared with when the liquid header 10 includes a single flow space, the distribution of refrigerant in the heat exchanger 1 can be easily controlled to suit the distribution of air velocity by means of suitable combination of upper and lower flow spaces.
The first flow control mechanism 53 allows the flow rate of refrigerant into each of the first liquid header main tube 11a and the second liquid header main tube 11b to be controlled by, for example, adjusting the opening degree of the first flow control mechanism 53. By adjusting the opening degree of the first flow control mechanism 53, the flow resistance can be varied, thus allowing the performance of the heat exchanger 1 to be enhanced over a wide operating range. If the flow resistance is increased by means of the first flow control mechanism 53, a pressure difference can be created between the upstream and downstream sides of the first flow control mechanism 53. As a result, over a wide operating range of the heat exchanger 1, the quality x of refrigerant entering the first liquid header main tube 11a can be controlled to be in the range of 0.05≤x≤0.30, thus allowing for enhanced performance of the heat exchanger 1.
Although
In the case of an arrangement provided with the outlet temperature sensor 43 as illustrated in
As described above, as in Embodiment 1, the configuration according to Embodiment 3 makes it possible to obtain, for the heat exchanger 1 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
In the first liquid header main tube 11a, which is the lower-positioned liquid header main tube, each branch tube 12 is inserted so as to penetrate the liquid layer. The channel area blocked by the branch tube 12 is thus greater in the first liquid header main tube 11a than in the second liquid header main tube 11b. Accordingly, the liquid header 10 is designed to satisfy the condition D1>D2, where D1 is the inside diameter [m] of the first liquid header main tube 11a and D2 is the inside diameter [m] of the second liquid header main tube 11b. That is, the inside diameter D1 of the first liquid header main tube 11a, which is located in the lower part of the liquid header 10, is made greater than the inside diameter D2 of the second liquid header main tube 11b, which is located in the upper part of the liquid header 10. This configuration minimizes an increase in flow resistance due to the branch tubes 12.
As described above, as in Embodiment 1, the configuration according to Embodiment 4 makes it possible to obtain, for the heat exchanger 1 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
In Embodiment 3, the header manifold (liquid header main tube 11) includes a plurality of header manifolds (the first liquid header main tube 11a and the second liquid header main tube 11b) disposed at different heights in the vertical direction (arrow Z direction). The header manifolds include a lower header manifold (first liquid header main tube 11a) and an upper header manifold (second liquid header main tube 11b). The lower header manifold is a header manifold that is connected with the branch tubes 12a located below the height of the boss 31 among the branch tubes 12 located within the height range that allows the blades 32 to rotate. The upper header manifold is a header manifold that is connected with the branch tubes 12b located above the height of the boss among the branch tubes 12 located within the height range that allows the blades 32 to rotate. The flow space of the lower header manifold has the inside diameter D1 greater than the inside diameter D2 of the flow space of the upper header manifold.
As described above, the inside diameter D1 of the first liquid header main tube 11a is made greater than the inside diameter D2 of the second liquid header main tube 11b. Consequently, an increase in the flow resistance of the first liquid header main tube 11a due to the branch tubes 12a can be minimized. This helps minimize the difference in flow resistance resulting from the difference in the amount of insertion of the branch tubes 12 between the upper and lower parts of the liquid header 10, thus allowing for nearly uniform distribution of refrigerant flow into the upper and lower parts of the liquid header 10.
Although
As illustrated in
The distal end portions of the branch tubes 12a located below the boss centerline Ob of the axial fan 30 are inserted into the liquid header 10 so as to penetrate the liquid layer, and are connected to the first liquid header passage 13a. The distal end portions of the branch tubes 12b located above the boss centerline Ob are inserted into the liquid header 10 so as to be covered in the liquid layer, and are connected to the second liquid header passage 13b. By using the liquid header 10 having a plurality of flow passages with different amounts of tube insertion as described above, refrigerant can be distributed in the heat exchanger 1 in a manner suited for the distribution of air velocity in a side-flow arrangement as illustrated in
The liquid header 10 is preferably designed to have flow passages that satisfy the condition D1>D2, where D1 is the inside diameter [m] of the first liquid header passage 13a and D2 is the inside diameter [m] of the second liquid header passage 13b. This configuration helps minimize the difference in flow resistance between flow passages resulting from the difference in the amount of insertion of the branch tubes 12. This ensures nearly uniform distribution of refrigerant into individual flow passages.
With the heat exchanger 1 of a side-flow type configured as described above, a single header tube defines a plurality of flow passages. This facilitates positioning in inserting the branch tubes 12 into the header tube, thus enhancing the ease of manufacture. Further, the presence of the partition wall 14 to separate flow passages enhances the pressure resistance of the liquid header 10. Such a configuration proves advantageous for the ability to separate flow passages to achieve enhanced pressure resistance, particularly for cases in which the liquid header 10 has, for example, an elliptical shape, a rectangular shape, a D-shape, or a semi-circular shape rather than a circular shape in horizontal cross-section.
As described above, the quality x of refrigerant entering the liquid header 10 is controlled to fall within the range of 0.05≤x≤0.30. This configuration results in a flow pattern in which a large amount of liquid-phase refrigerant Rb is distributed along the wall surface of the first liquid header passage 13a, thus realizing improved distribution.
As described above, as in Embodiment 1, the configuration according to Embodiment 5 makes it possible to obtain, for the heat exchanger 1 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
According to Embodiment 5, in the header manifold (liquid header main tube 11), the flow space connected to the branch tubes 12 located within a height range that allows the blades to rotate is divided into a plurality of parts in the vertical direction. As a result, the insertion length of branch tubes can be controlled for each individual flow space, leading to enhanced ease of manufacture. Further, as compared with a case when the liquid header 10 includes a single flow space, the distribution of refrigerant in the heat exchanger 1 can be easily controlled to suit the distribution of air velocity by means of suitable combination of upper and lower flow spaces.
The two axial fans 30a and 30b are disposed such that the respective rotational planes of blades 32a and 32b face the heat transfer tubes 22 in the horizontal direction. Within the height range corresponding to the rotational plane of the axial fan 30a, which is the lower-positioned one of the two axial fans, the liquid header 110 is divided into a first liquid header main tube 111a and a second liquid header main tube 111b respectively located below and above the boss centerline Ob1, and within the height range corresponding to the rotational plane of the axial fan 30b, which is the upper-positioned one of the two axial fans, the liquid header 110 is divided into a third liquid header main tube 111c and a fourth liquid header main tube 111d respectively located below and above the boss centerline Ob2.
A distributor 54 is disposed upstream of the liquid header 110 to uniformly distribute refrigerant to the first liquid header main tube 111a, the second liquid header main tube 111b, the third liquid header main tube 111c, and the fourth liquid header main tube 111d. The distributor 54 and each liquid header main tube are connected by the corresponding one of first, second, third, and fourth inlet pipes 52a, 52b, 52c, and 52d through which refrigerant flows.
In
In Embodiment 6, of the two liquid header main tubes located above and below the boss centerline Ob1 of the axial fan 30a, which is the lower axial fan, the lower liquid header main tube, that is, the first liquid header main tube 111a, is connected with a plurality of branch tubes 112a. Each branch tube 112a is inserted up to a point near the center of the inside diameter of the first liquid header main tube 111a such that its distal end portion penetrates the liquid layer. The second liquid header main tube 111b, which is located above the boss centerline Ob1, is connected with a plurality of branch tubes 112b. Each branch tube 112b is connected such that its distal end portion is covered in the liquid-phase refrigerant Rb.
Similarly, of the two liquid header main tubes located above and below the boss centerline Ob2 of the axial fan 30b, which is the upper axial fan, the lower liquid header main tube, that is, the third liquid header main tube 111c, is connected with a plurality of branch tubes 112c. Each branch tube 112c is inserted up to a point near the center of the inside diameter of the third liquid header main tube 111c such that its distal end portion penetrates the liquid layer. The fourth liquid header main tube 111d, which is located above the boss centerline Ob2, is connected with a plurality of branch tubes 112d. Each branch tube 112d is connected such that its distal end portion is covered in the liquid-phase refrigerant Rb.
In this case, by controlling the quality x of refrigerant entering the liquid header 110 to be in the range of 0.05≤x≤0.30, a flow pattern is obtained in which a large amount of liquid-phase refrigerant Rb is distributed near the wall of each liquid header main tube. This makes it possible to obtain, for the heat exchanger 101, a distribution of refrigerant suited for the distribution of airflow in the case of a side-flow arrangement in which the two axial fans 30a and 30b are disposed above and below each other.
As described above, the liquid header 110 of the heat exchanger 101 is divided into upper and lower parts relative to each of the boss centerlines Ob1 and Ob2, and the amount of insertion of the branch tubes 12 is made to differ between the upper and lower parts. This configuration makes it possible to obtain a distribution of refrigerant as illustrated in
Now, let D1 be the inside diameter [m] of the first liquid header main tube 111a, D2 be the inside diameter [m] of the second liquid header main tube 111b, D3 be the inside diameter [m] of the third liquid header main tube 111c, and D4 be the inside diameter [m] of the fourth liquid header main tube 111d. In this case, if D1>D2 and D3>D4, such a configuration is more desirable from the viewpoint of reducing the difference in flow resistance between liquid header main tubes resulting from the difference in the amount of insertion of the branch tubes 12.
As described above, as in Embodiment 1, the configuration according to Embodiment 6 makes it possible to obtain, for the heat exchanger 101 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of each of the boss centerlines Ob1 and Ob2. This leads to enhanced performance of the heat exchanger 101.
In Embodiment 6, the axial fan 30 includes the axial fans 30a and 30b disposed at different heights in the vertical direction (arrow Z direction). Among a plurality of branch tubes 112 located within a height range that allows the blades 32a or 32b of each axial fan to rotate, the majority of the branch tubes 112a or 112c located below the height of the boss 31a or 31b of the axial fan are inserted into the header manifold (the first liquid header main tube 111a or the third liquid header main tube 111c) such that the distal ends of these branch tubes are positioned at 0 to 50% of the distance from the center of the header manifold, and the majority of the branch tubes 112b or 112d located above the height of the boss 31a or 31b of the axial fan are connected to the header manifold such that the distal ends of these branch tubes are positioned at more than 50% of the distance from the center of the header manifold.
As a result of the above-mentioned configuration, for each of the axial fans 30a and 30b, the insertion length of the branch tubes 12 is made to differ between the portion of the liquid header 110 located above the height of the boss 31a or 31b and the portion of the liquid header 110 located below the height of the boss 31a or 31b. Consequently, even in the case of the heat exchanger 101 of a side-flow type with the axial fans 30a and 30b disposed above and below each other, refrigerant can be distributed in a manner suited for the velocity distribution of air passing through the heat exchanger 101. This leads to enhanced performance of the heat exchanger 101.
Embodiment 7 of the present invention will be described below. In the following, a description will not be given of features overlapping those of Embodiments 1 to 6, and features identical or corresponding to those of Embodiments 1 to 6 will be designated by the same reference signs. In Embodiment 7, the liquid header main tube 11 of the liquid header 10 has a flow passage that is non-circular in horizontal cross-section.
First, a case in which the liquid header main tube 11 is rectangular in horizontal cross-section will be described with reference to
Further, as illustrated in
In the case of the liquid header 10 that is rectangular in horizontal cross-section, the respective joint surfaces of the liquid header main tube 11 and branch tube 12 are at right angles to each other. Joining of these two metal components is generally performed by brazing. Therefore, if the liquid header 10 is rectangular in horizontal cross-section, this facilitates brazing of the respective joint surfaces of the two metal components during the brazing process. This leads to enhanced quality of the resulting joint.
In Embodiments 1 to 6 mentioned above, the center position in the horizontal plane of the flow space needs to be defined to indicate where the distal end of each branch tube 12 is located within the liquid header 10. In this regard, if the flow passage in the liquid header 10 is a rectangular passage, the center position in the horizontal plane of the flow space of the liquid header 10 is defined as the intersection of the diagonals of the rectangular passage as illustrated in
As for the working fluid in the heat exchanger 1, a low pressure fluorocarbon refrigerant such as R134a, an HFO refrigerant such as R1234yf or R1234ze(E), dimethyl ether (DME), or a hydrocarbon-based refrigerant such as propane, or other such refrigerant may be used as a pure refrigerant or as a component of a refrigerant mixture. From the viewpoint of pressure resistance, using a refrigerant mixture is more desirable as this allows pressure to be minimized.
The following describes, with reference to
If the flow passage in the liquid header 10 is an elliptical passage, the center position in the horizontal plane of the flow space of the liquid header 10 is defined as the intersection of the long and short axes of the ellipse as illustrated in
As illustrated in
The liquid header 10 may not necessarily be circular, rectangular, or elliptical in horizontal cross-section.
If the liquid header 10 has a semi-circular passage, the center position in the horizontal plane of the flow space of the liquid header 10 is defined as the intersection of lines joining the three closest positions to the center with the three farthest positions from the center. The flow pattern shall be determined in this case by using the diameter of the equivalent circle corresponding to the channel cross-sectional area A of the semi-circular passage.
In the case of the liquid header 10 having such a semi-circular passage, the channel cross-sectional area A can be increased while minimizing an increase in volume in the widthwise direction (arrow X direction). This proves advantageous from the viewpoint of space saving, and results in reduced pressure loss. Further, the above-mentioned configuration of the liquid header 10 allows its joint surface with the branch tube 12 to be made flat, thus facilitating brazing.
If the liquid header 10 has a triangular passage, the center position in the horizontal plane of the flow space of the liquid header 10 is defined as the intersection of lines joining the three midpoints of the sides of the triangle, which are the points located closest to the center, with the vertices located farthest therefrom. The flow pattern shall be determined in this case by using the diameter of the equivalent circle corresponding to the channel cross-sectional area A of the triangular passage.
In the case of the liquid header 10 having such a triangular passage, the channel cross-sectional area A can be increased while minimizing an increase in volume in the widthwise direction (arrow Y direction). This configuration proves to be advantageous from the viewpoint of space saving, and results in reduced pressure loss. Further, the above-mentioned configuration of the liquid header 10 allows its joint surface with the branch tube 12 to be made flat, thus facilitating brazing.
For the liquid header 10 having a rectangular passage, an elliptical passage, a semi-circular passage, or a triangular passage as described above, refrigerant is preferably made to flow into the liquid header 10 in an annular or churn flow pattern. This makes it possible to achieve improved distribution performance for the liquid header 10 with various shapes in horizontal cross-section. Further, if the quality x of refrigerant entering the liquid header 10 is in the range of 0.05≤x≤0.30, a further improvement in distribution performance can be obtained.
As described above, as in Embodiment 1, the configuration according to Embodiment 7 makes it possible to obtain, for the heat exchanger 1, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
Embodiment 8 of the present invention will be described below. In Embodiment 8, the branch tubes 12 have a flat shape. In the following, a description will not be given of features overlapping those of Embodiments 1 to 7, and features identical or corresponding to those of Embodiments 1 to 7 will be designated by the same reference signs.
As for the position of the center axis of each branch tube 12 in the Y-direction defined as described above, the equivalent diameter of a circular tube corresponding to the effective channel cross-sectional area of such a flat flow passage is considered, and it is considered that the center axis is located within ±50%. The branch tube 12 having a flat shape may be a portion of the heat exchanger 1. That is, a portion of a flat heat transfer tube constituting the heat exchanger 1 may be extended to form the branch tube 12 having a flat shape. Since the branch tube 12 having a flat shape is substituted for a portion of the heat transfer tube 22 in some cases, its inner surface may be machined to have a heat transfer-facilitating feature such as a groove.
As illustrated in
As described above, as in Embodiment 1, the configuration according to Embodiment 8 makes it possible to obtain, for the heat exchanger 1, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
In Embodiment 8, the branch tubes 12 are formed by the end portions of the corresponding heat transfer tubes 22. This configuration makes it possible to substitute the heat transfer tubes 22 of the heat exchange unit 20 for the branch tubes 12, thus reducing the number of components of the heat exchanger 1.
As illustrated in
The joint tube 23 may be a tube connected to the heat transfer tube 22 at one end and connected to the branch tube 12 at the other end. Alternatively, the joint tube 23 may be a tube integrated with the branch tube 12 and connected at one end to the heat transfer tube 22.
The joint tube 23 may not necessarily be used only for the liquid header 10 but may be also used for connection between the gas header 40 and the heat exchange unit 20. As compared with connecting the heat transfer tube 22 to the gas header main tube 41, this configuration reduces pressure loss in the gas header 40 resulting from the insertion of the branch tube 12.
As described above, as in Embodiment 1, the configuration according to Embodiment 9 makes it possible to obtain, for the heat exchanger 1 of a side-flow type, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak near the height of the boss centerline Ob. This leads to enhanced performance of the heat exchanger 1.
Further, in Embodiment 9, each branch tube 12 is the joint tube 23 attached to the end portion of the corresponding heat transfer tube 22. Consequently, the branch tube 12 having a smaller width than the heat transfer tube 22 is connected to the liquid header 10. This configuration makes it possible to reduce pressure loss in the liquid header 10 resulting from the protrusion of the branch tube 12 into the flow passage of the liquid header 10.
As illustrated in
The fan 35 includes a boss 36, and blades 37 disposed around the boss 36. The fan 35 supplies air to the heat exchanger 201 as the fan 35 rotates. With the fan 35, for example, air is allowed to pass from the side of the heat exchanger 201, and sent upward in the vertical direction (arrow Z direction). In the heat exchanger 201 of a top-flow type described above, the velocity of air is greatest near the fan 35, that is, in an upper portion of the heat exchanger 201 as illustrated in
As in Embodiment 1, if the quality x of refrigerant entering the liquid header 210 is in the range of 0.05≤x≤0.30, the resulting refrigerant distribution is optimal for the distribution of airflow in the heat exchanger 201 of a top-flow type, leading to enhanced heat exchanger performance.
In
In
Although
The inlet pipe 52 may not necessarily be connected to the lower end of the liquid header 10. The inlet pipe 52 may be inserted at any position located within the space defined by the lower end of the liquid header 10 and the centerline of the branch tube 12 located closest to the lower end.
Although the foregoing description is directed to the case of using the branch tube 12, the heat transfer tube 22 of the heat exchange unit 20 may be extended and connected to the liquid header main tube 211. Alternatively, the joint tube 23 that transforms a tube shape may be used. The branch tube 12 may not necessarily be a circular tube but may be, for example, a flat tube.
As for the portion of the liquid header main tube 211 at the 0% to 75% height positions, the branch tubes 212a may be connected to the liquid header main tube 211 in any manner as long as the branch tubes 212a penetrate the liquid layer of refrigerant flowing in the liquid header main tube 211. That is, the distal end portions of the branch tubes 212a may be located within a certain range of area near the center of the liquid header main tube 211.
In connecting the branch tubes 212a to the liquid header main tube 211 at the 0% to 75% height positions, the features described above with reference to Embodiment 1, such as the range of locations of the distal end portions of the branch tubes 212a, the refrigerant quality range, and the characteristics of flow patterns, can be employed to thereby achieve improved distribution performance by utilizing, for example, the characteristics of an annular or churn flow pattern as illustrated in
In the following description, words indicating directions (e.g., “upper”, “lower”, “right”, “left, “front”, or “back”) are used to facilitate understanding. However, these words are for illustrative purposes only. These words are not intended to limit the scope of the present invention. In Embodiment 10, the words such as “upper”, “lower”, “right”, “left, “front”, and “back” are defined with reference to when an outdoor unit 100 is viewed from the front.
In the outdoor unit 100 illustrated in
The outdoor unit 100 includes a casing 102 formed in a box-like shape. The casing 102 has an air inlet 103 defined by an opening on the side of the casing 102, and an air outlet 104 defined by an opening on the top of the casing 102. The outdoor unit 100 includes the heat exchanger 201 disposed inside the casing 102 along the air inlet 103. The outdoor unit 100 is provided with a fan guard 105 disposed to cover the air outlet 104 in a manner that allows passage of air therethrough. The outdoor unit 100 is also provided with the fan 35 of a top-flow type disposed inside the fan guard 105 to suck in outside air from the air inlet 103 and discharge the outside air from the air outlet 104.
More preferably, the parameter (MR×x)/(31.6×A) related to the thickness of the liquid film (thickness of the liquid phase) of refrigerant is in the range of 0.010≤(MR×x)/(31.6×A)≤0.120×106. In this case, improved distribution performance can be obtained over a wide range of operating conditions.
If the parameter (MR×x)/(31.6×A) representing the thickness of the liquid film (thickness of the liquid phase) of refrigerant satisfies the range condition as illustrated in
As described above, in Embodiment 10, the air-conditioning apparatus includes the heat exchanger 201, the fan 35, and the refrigerant circuit. The heat exchanger 201 includes the heat transfer tubes 22 in which refrigerant flows, the heat transfer tubes 22 being arranged so as to be spaced apart from each other in the vertical direction (arrow Z direction), and the header manifold (liquid header main tube 211) that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the heat transfer tubes 22 from the branch tubes 212 arranged so as to be spaced apart from each other in the vertical direction. The fan 35 is located above the heat transfer tubes 22. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger 201. The refrigerant flows in the header manifold in an annular or churn flow pattern in which the gas-phase refrigerant Ra collects at the center of the header manifold and the liquid-phase refrigerant Rb collects on the wall surface of the header manifold. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, the majority (e.g., the branch tubes 212a) of the branch tubes 212 connected to the header manifold are inserted into the header manifold such that the distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and at least the uppermost one (e.g., the branch tube 212b) of the branch tubes connected to the header manifold is connected to the header manifold such that the distal end of the branch tube is positioned at more than 50% of the distance from the center.
Consequently, in the air-conditioning apparatus, the branch tubes 212a, which represent the majority of the branch tubes 212 connected to the liquid header main tube 211, are inserted such that the distal ends of the branch tubes 212a penetrate the liquid layer, and at least the uppermost branch tube 212b is inserted such that the distal end of the branch tube 212b is covered in the liquid layer. This ensures that, in the case of an arrangement with a large amount of liquid-phase refrigerant Rb distributed along the wall surface inside the liquid header 210, in an area of the liquid header 210 connected with the branch tubes 212a, which represent the majority of the branch tubes 212, a large amount of liquid refrigerant is distributed to an upper portion of the area, and in an area of the liquid header 210 connected with the uppermost branch tube 212b, pressure loss resulting from the protrusion of the branch tube 212b into the flow passage of the liquid header 210 is reduced. Therefore, in the case of the heat exchanger 201 of a top-flow type with the fan 35 disposed above the heat exchanger 201, the above-mentioned configuration makes it possible to obtain a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak at the location closest to the fan 35. This results in enhanced performance of the heat exchanger 1 in the air-conditioning apparatus, leading to enhanced energy efficiency.
The main tube of the liquid header 310 is divided into upper and lower parts. The liquid header 310 thus includes a first liquid header main tube 311a, which is the lower liquid header main tube, and a second liquid header main tube 311b, which is the upper liquid header main tube. That is, the second liquid header main tube 311b is disposed in the portion of the liquid header 310 located closest to the fan 35.
In Embodiment 11, a plurality of branch tubes 312b connected to the second liquid header main tube 311b, which is the upper liquid header main tube, are inserted so as to penetrate the liquid layer. By contrast, a plurality of branch tubes 312a connected to the first liquid header main tube 311a, which is the lower liquid header main tube, may be inserted such that the distal end portions of the branch tubes 312a penetrate the liquid layer, or may be connected such that the distal end portions of the branch tubes 312a are covered in the liquid layer. For a case in which the branch tubes 312a are connected so as to be covered in the liquid layer as illustrated in
As described above, the branch tubes 312b are connected to the second liquid header main tube 311b such that the distal end portions of the branch tubes 312b penetrate the liquid layer. As a result, in areas of the liquid header 310 close to the fan, a large amount of liquid refrigerant can be distributed to the upper portion of the liquid header 310.
The liquid header 310 may not necessarily be divided into a plurality of main tubes. For example, as with the arrangement illustrated in
As described above, in Embodiment 11, the air-conditioning apparatus includes the heat exchanger 301, the fan 35, and the refrigerant circuit. The heat exchanger 301 includes the heat transfer tubes 22 in which refrigerant flows, the heat transfer tubes 22 being arranged so as to be spaced apart from each other in the vertical direction (arrow Z direction), and the header manifold (the first liquid header main tube 311a and the second liquid header main tube 311b) that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the heat transfer tubes 22 from the branch tubes 312 arranged so as to be spaced apart from each other in the vertical direction. The fan 35 is located above the heat transfer tubes 22. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger 301. The refrigerant flows in the header manifold in an annular or churn flow pattern in which the gas-phase refrigerant Ra collects at the center of the header manifold and the liquid-phase refrigerant Rb collects on the wall surface of the header manifold. The header manifold includes a plurality of header manifolds (the first liquid header main tube 311a and the second liquid header main tube 311b) disposed at different heights in the vertical direction. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is the position of the wall surface of the header manifold, the majority of the branch tubes 312b connected to the header manifold (second liquid header main tube 311b) located closest to the fan 35 are inserted such that the distal ends of the branch tubes 312b are positioned at 0 to 50% of the distance from the center, and the majority of the branch tubes 312a connected to the header manifold (first liquid header main tube 311a) disposed below the header manifold located closest to the fan 35 are connected such that the distal ends of the branch tubes 312a are positioned at more than 50% of the distance from the center.
Consequently, in the air-conditioning apparatus, among the branch tubes 212 connected to the liquid header 310, the majority of the branch tubes 312b connected to the second liquid header main tube 311b located closest to the fan 35 are inserted such that their distal ends penetrate the liquid layer. This ensures that, if a large amount of liquid-phase refrigerant Rb is distributed along the wall surface inside the liquid header 310, in the second liquid header main tube 311b located closest to the fan 35, a large amount of liquid refrigerant can be distributed to the upper portion of the second liquid header main tube 311b. Therefore, in the case of the heat exchanger 301 of a top-flow type with the fan 35 disposed above the heat exchanger 301, the above-mentioned configuration makes it possible to obtain a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak at the position closest to the fan 35. This results in enhanced performance of the heat exchanger 301 in the air-conditioning apparatus, leading to enhanced energy efficiency.
The flow space in the header manifold (second liquid header main tube 311b) located closest to the fan 35 has the inside diameter D12 greater than the inside diameter D11 of the flow space in the header manifold (first liquid header main tube 311a) disposed below the header manifold located closest to the fan 35.
Consequently, in the second liquid header main tube 311b, which is the liquid header main tube of the liquid header 310 located closest to the fan 35, an increase in flow resistance due to the branch tubes 12 can be minimized, thus facilitating entry of refrigerant. As a result, in the heat exchanger 301, a large amount of liquid refrigerant can be distributed to the upper portion of the liquid header 310. This allows refrigerant to be distributed in a manner suited for the distribution of air velocity in the heat exchanger 301 in a top-flow arrangement.
Embodiment 12 of the present invention will be described below.
The following description of Embodiment 12 will be directed to the air-conditioning apparatus 200 capable of heating operation and in which the heat exchanger 201 (to be referred to as outdoor heat exchanger hereinafter) including the liquid header 210 described above with reference to Embodiment 10 is connected to a compressor 61, a first expansion device 62, and an indoor heat exchanger 26 by refrigerant pipes to form a refrigeration cycle circuit. In the air-conditioning apparatus 200 illustrated in
The air-conditioning apparatus 200 includes a controller 70 configured to control operation. The controller 70 is implemented by a microcomputer including a CPU, a ROM, a RAM, and an I/O port. The controller 70 is connected with various sensors via wireless or wired control signal lines in a manner that allows the controller 70 to receive information detected by these sensors.
The controller 70 controls the quality of refrigerant entering the liquid header main tube 211 in accordance with the operating condition, for example. Specifically, the controller 70 controls the first expansion device 62 in accordance with the operation mode, the number of indoor units 25 being connected, the frequency of the compressor 61, outside air temperature, indoor temperature, and other operating conditions to thereby control the quality x of refrigerant entering the liquid header 210.
The following describes the flow of refrigerant in heating operation according to Embodiment 12. Refrigerant turns into a high-temperature, high-pressure gaseous state in the compressor 61. The resulting refrigerant is then routed through a compressor discharge pipe 93 into the indoor unit 25. In the indoor unit 25, the gas refrigerant is cooled in the indoor heat exchanger 26 through heat exchange with indoor air. The resulting liquid refrigerant, which has turned into a high-pressure, low-temperature state in the indoor heat exchanger 26, is then routed through an indoor-unit outlet pipe 17 toward the first expansion device 62. In the first expansion device 62, the refrigerant is reduced in pressure, causing the refrigerant to change to two-phase gas-liquid refrigerant or liquid refrigerant at low temperature and low pressure. The refrigerant is then routed through the inlet pipe 52 into the liquid header 210. In the liquid header 210, the refrigerant is distributed to the heat transfer tubes 22. After removing heat in the heat exchange unit 20, the refrigerant is routed through the gas header 40 and the outlet pipe 51 and returned to the compressor 61. The refrigerant returned to the compressor 61 is compressed again into high-temperature, high-pressure refrigerant, which then circulates in the refrigerant circuit.
The controller 70 varies the opening degree of the first expansion device 62 in accordance with the operating condition to control the degree of pressure reduction, thus making it possible to control the quality of refrigerant in the liquid header 210. At this time, desirably, the controller 70 controls the quality x of refrigerant such that, during rated heating operation (100% heating operation), the quality x falls within the range of 0.05≤x≤0.30. Such a control allows refrigerant to be distributed in a manner suited for the relative arrangement of the fan 35 and the heat exchanger 201, such as a top-flow arrangement or a side-flow arrangement. This helps enhance the performance of the heat exchanger 201, leading to enhanced energy efficiency of the air-conditioning apparatus 200.
The air-conditioning apparatus 200 may further include a plurality of sensors.
In the air-conditioning apparatus 200, the controller 70 estimates the quality x of refrigerant based on information detected by the above-mentioned temperature sensors. In the air-conditioning apparatus 200, the temperature and pressure of refrigerant entering the first expansion device 62 can be estimated by using the first temperature sensor 66 and the second temperature sensor 67, thus making it possible to estimate the enthalpy of refrigerant entering the first expansion device 62. Further, in the air-conditioning apparatus 200, a change in refrigerant before and after passage through the first expansion device 62 is considered to be an isenthalpic process, and the saturation temperature downstream of the first expansion device 62 is measured by the third temperature sensor 68 to thereby estimate the pressure of refrigerant. The enthalpy and pressure of refrigerant downstream of the first expansion device 62 are thus determined. This makes it possible for the air-conditioning apparatus 200 to estimate the quality of refrigerant.
As described above, due to the presence of temperature sensors in the air-conditioning apparatus 200, the opening degree of the first expansion device 62 can be adjusted such that the refrigerant quality x falls within the range of 0.05≤x≤0.30 under various operating conditions. This makes it possible to extend the optimization range of refrigerant distribution in the liquid header 210.
Although
Although the foregoing description is directed to heating operation, cooling operation and heating operation may be made switchable. In this case, the direction of refrigerant flow in cooling operation is reverse to that in heating operation. That is, refrigerant gas at high temperature and high pressure flows into the outdoor heat exchanger (heat exchanger 201) where the refrigerant gas is then cooled through heat exchange with outside air.
As described above, as in Embodiment 10, the configuration according to Embodiment 12 makes it possible to obtain, for the heat exchanger 201 of the air-conditioning apparatus 200, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak at the position closest to the fan 35. This results in enhanced performance of the heat exchanger 1, leading to enhanced energy efficiency of the air-conditioning apparatus 200.
In Embodiment 12, the air-conditioning apparatus 200 includes the above-mentioned air-conditioning apparatus, and the controller 70 that controls the quality x of refrigerant entering the header manifold (liquid header main tube 211) depending on the operating condition. In the refrigerant circuit, the first expansion device 62 is disposed at a position located upstream of the header manifold relative to the direction of refrigerant flow during heating operation. The controller 70 controls the first expansion device 62.
Consequently, in the air-conditioning apparatus 200, the quality x of refrigerant in the liquid header 210 can be controlled by controlling the first expansion device 62. Such a control allows refrigerant to be distributed in a manner suited for the relative arrangement of the fan 35 and the heat exchanger 201. This helps enhance the performance of the heat exchanger 201, leading to enhanced energy efficiency of the air-conditioning apparatus 200.
Further, the controller 70 controls, during heating operation, the quality x of refrigerant entering the liquid header manifold (liquid header main tube 211) such that the quality x falls within the range of 0.05≤x≤0.30. This makes it possible to extend the optimization range of refrigerant distribution in the liquid header 210 of the air-conditioning apparatus 200.
The gas-liquid separator vessel 84 is disposed between the liquid header 210 and the first expansion device 62. The first expansion device 62 and the gas-liquid separator vessel 84 are connected by a connecting pipe 47. The inlet pipe 52, which connects to the liquid header 210, is connected to a lower portion of the gas-liquid separator vessel 84. A bypass pipe 82, which connects to the outlet pipe 51, is connected to an upper portion of the gas-liquid separator vessel 84. A bypass control valve 83 is disposed on the bypass pipe 82. The bypass pipe 82 is used to bypass gas refrigerant separated by the gas-liquid separator vessel 84 to the compressor 61. The opening degree of the bypass control valve 83 can be changed by the controller 70.
Refrigerant in a two-phase gas-liquid state entering the connecting pipe 47 in the refrigerant circuit flows into the gas-liquid separator vessel 84 where the refrigerant is then separated into gas and liquid by gravity, of which gas refrigerant is directed to the bypass pipe 82 and liquid refrigerant is directed to the inlet pipe 52. At this time, the controller 70 controls the bypass control valve 83 toward the closed position if the quality x of refrigerant flowing in the inlet pipe 52 is x<0.05, and controls the bypass control valve 83 toward the open position if x>0.30. The quality x of refrigerant entering the liquid header 210 is thus controlled to be in the range of 0.05≤x≤0.30. The above-mentioned configuration of the air-conditioning apparatus 200a helps optimize the distribution of refrigerant to the liquid header 210, leading to enhanced efficiency of the heat exchanger 201 and consequently enhanced energy efficiency. Further, the air-conditioning apparatus 200a includes the gas-liquid separator vessel 84. This leads to an extended range of operating conditions over which distribution can be improved.
The foregoing description of the gas-liquid separator vessel is specifically directed to an example of a collision-type gas-liquid separator vessel. Alternatively, for example, other types of gas-liquid separator vessels may be employed, such as another collision-type gas-liquid separator vessel, a gas-liquid separator vessel utilizing surface tension, or a gas-liquid separator vessel utilizing centrifugal force.
In the air-conditioning apparatus 200a, gas refrigerant is bypassed by using the gas-liquid separator vessel 84 as described above to thereby reduce the flow of gas refrigerant into the heat exchanger 201. This helps reduce pressure loss in the heat exchanger 201. This configuration of the air-conditioning apparatus 200a makes it possible to achieve, in addition to improved distribution of refrigerant, enhanced performance of the heat exchanger 201 due to reduced pressure loss.
As for the effect of incorporating the gas-liquid separator vessel 84, the improvement in distribution, and the reduction of pressure loss in the heat exchanger 201 are greatest in the case of rated heating operation (100% heating operation). For this reason, it is desirable for the controller 70 to, during operation under rated heating condition, control the bypass control valve 83 such that the quality x of refrigerant entering the liquid header 210 is in the range of 0.05≤x≤0.30.
Although the bypass control valve 83 has been described above as a valve whose opening degree can be adjusted, the bypass control valve 83 may be any component (bypass flow control mechanism) capable of controlling the flow rate of refrigerant through the bypass pipe 82.
Although the foregoing description is directed to the fan 35 in a top-flow arrangement, the above-mentioned configuration may be employed for any one of the heat exchangers described above with reference to Embodiments 1 to 12.
As described above, as in Embodiment 10, the configuration according to Embodiment 13 makes it possible to obtain, for the heat exchanger 201 of the air-conditioning apparatus 200a, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak at the position closest to the fan 35. This results in enhanced performance of the heat exchanger 201, leading to enhanced energy efficiency of the air-conditioning apparatus 200a.
The refrigerant circuit includes the gas-liquid separator vessel 84 (the gas-liquid separator vessel 84, the pipe 85, or the Y-shaped pipe 86) disposed between the first expansion device 62 and the header manifold (liquid header main tube 211), the bypass pipe 82 that connects the gas-liquid separator vessel 84 with an area located downstream of the heat exchanger 201 relative to the direction of refrigerant flow during heating operation, and the bypass flow control mechanism (e.g., the bypass control valve 83) disposed on the bypass pipe 82 to control the flow rate of refrigerant.
As a result, with the air-conditioning apparatus 200a, refrigerant in a two-phase gas-liquid state can be separated in the gas-liquid separator vessel 84, and also the quality x of refrigerant entering the liquid header 210 can be controlled by controlling the bypass control valve 83. Therefore, with the air-conditioning apparatus 200a, the distribution of refrigerant to the liquid header 210 can be optimized, leading to enhanced efficiency of the heat exchanger 201 and consequently enhanced energy efficiency.
In Embodiment 14, the air-conditioning apparatus 200b further includes a flow switching device 94, an accumulator 91, and a second expansion device 90. The flow switching device 94 is implemented by, for example, a four-way valve. The flow switching device 94 switches the direction of refrigerant flow between cooling operation and heating operation. The accumulator 91 is disposed on the suction side of the compressor 61. An accumulator inlet pipe 92 is disposed upstream of the accumulator 91. The second expansion device 90 is disposed at a position between the gas-liquid separator vessel 84 and the liquid header 10, that is, on the inlet pipe 52. The opening degree of the second expansion device 90 is adjusted by means of the controller 70.
During heating operation, the quality x of refrigerant entering the liquid header 10 preferably satisfies the condition 0.05≤x≤0.30 as this provides improved distribution. In this case, by increasing the pressure of the gas-liquid separator vessel 84 by means of the second expansion device 90, the gas density of refrigerant is increased, and the flow velocity of refrigerant entering the gas-liquid separator vessel 84 is reduced. This makes it possible to obtain high gas-liquid separation efficiency even with the gas-liquid separator vessel 84 that is small in size. When an excessive amount of gas refrigerant is being bypassed by the gas-liquid separator vessel 84 under low refrigerant flow rate conditions, the opening degree of the second expansion device 90 is controlled to a smaller value to increase the flow resistance of the second expansion device 90. This leads to an increased operating range over which the quality x of refrigerant entering the liquid header 10 can be controlled to be in the range of 0.05≤x≤0.30.
Although the foregoing description of
Although the heat exchanger 201 has been described above with reference to an exemplary arrangement related to the fan 35 of a top-flow type, any one of the heat exchangers described above with reference to Embodiments 1 to 13 may be employed.
As described above, as in Embodiment 10, the configuration according to Embodiment 14 makes it possible to obtain, for the heat exchanger 201 of the air-conditioning apparatus 200b, a distribution of liquid refrigerant flow rate suited for the distribution of air velocity that has a peak at the position closest to the fan 35. This results in enhanced performance of the heat exchanger 201, leading to enhanced energy efficiency of the air-conditioning apparatus 200b.
In Embodiment 14, the refrigerant circuit of the air-conditioning apparatus 200b further includes the flow switching device 94 that switches the direction of flow of refrigerant, and the second expansion device 90 disposed between the heat exchanger 201 and the first expansion device 62. The controller 70 controls the flow switching device 94, the first expansion device 62, and the second expansion device 90.
Consequently, during heating operation of the air-conditioning apparatus 200b, the second expansion device 90 is controlled to increase the efficiency of gas-liquid separation in the gas-liquid separator vessel 84, thus extending the operating range over which the quality x of refrigerant entering the liquid header 10 can be controlled. Further, the air-conditioning apparatus 200b includes the second expansion device 90 and the first expansion device 62. This facilitates the control of refrigerant flow rate also during cooling operation, leading to enhanced performance of the air-conditioning apparatus 200.
Embodiments of the present invention are not limited to the above-mentioned embodiments but may include various modifications. For example, although the foregoing description of embodiments is directed to the case in which there is a single indoor unit 25, this should not be construed restrictively. Alternatively, a plurality of indoor units 25 may be connected.
1, 101, 201, 301 heat exchanger 10, 110, 210, 310 liquid header 11, 211 liquid header main tube 11a first liquid header main tube 11b second liquid header main tube 12 (12a, 12b), 112 (112a, 112b, 112c, 112d), 212 (212a, 212b), 312 (312a, 312b) branch tube 13 bifurcated tube 13a first liquid header passage 13b second liquid header passage 14 partition wall 15a first inlet 15b second inlet 16 partition 17 indoor-unit outlet pipe 18a, 18b end branch tube 20 heat exchange unit 21 fin 22 heat transfer tube 22a flat perforated pipe 22b circular tube 23 joint tube 25 indoor unit 26 indoor heat exchanger 30, 30a, 30b axial fan 31, 31a, 31b boss 32, 32a, 32b blade 35 fan 36 boss 37 blade 40 gas header 41 gas header main tube 42 upper temperature sensor 43 outlet temperature sensor 47 connecting pipe outlet pipe 52 inlet pipe 52a first inlet pipe 52b second inlet pipe 52c third inlet pipe 52d fourth inlet pipe 53 first flow control mechanism 54 distributor 61 compressor 62 first expansion device 66 first temperature sensor 67 second temperature sensor 68 third temperature sensor 70 controller 82 bypass pipe 83 bypass control valve 84 gas-liquid separator vessel 85 pipe 86 Y-shaped pipe 90 second expansion device 91 accumulator 92 accumulator inlet pipe 93 compressor discharge pipe 94 flow switching device 100 outdoor unit 102 casing 103 air inlet 104 air outlet 105 fan guard 111a first liquid header main tube 111b second liquid header main tube 111c third liquid header main tube 111d fourth liquid header main tube 113a first liquid header passage 113b second liquid header passage 113c third liquid header passage 113d fourth liquid header passage 200, 200a, 200b air-conditioning apparatus 311a first liquid header main tube 311b second liquid header main tube Ob, Ob1, Ob2 boss centerline Ra gas-phase refrigerant Rb liquid-phase refrigerant x quality δ thickness of liquid layer
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/012014 | 3/24/2017 | WO | 00 |
