Patent Application
20240418448
The present invention relates to a parallel-flow-type heat exchanger and to an air conditioner.
Air conditioners incorporate a condenser for condensing a coolant. A so-called parallel-flow-type heat exchanger comprising a core, which is constituted by alternately stacking flat, multi-hole pipes and corrugated fins, and headers, which are disposed at both end portions of the flat, multi-hole pipes of the core in the longitudinal direction, is widely used as the condenser.
As an example of this type of heat exchanger, a coolant condenser is described in Patent Document 1 and comprises: a plurality of tubes; corrugated fins, which are disposed between adjacent tubes; and tanks, which are connected to end portions of the tubes; wherein the plurality of tubes is divided into a plurality of tube groups by separators provided within the tanks, and a coolant flows through the plurality of tube groups.
In the past, this type of heat exchanger was configured such that the number of tubes belonging to the tube group located most upstream of the coolant flow was the greatest, and the number of tubes belonging to each of the tube groups was fewer the more downstream. The reason for this is as follows. It is known that the heat transfer coefficient and the pressure drop during a typical in-pipe condensation heat transfer is greatly affected by the mass velocity of the coolant and the quality (i.e., the degree of condensation) of the coolant. Specifically, there is a tendency that the lower the mass velocity of the coolant, the smaller the heat transfer coefficient and the lower the pressure drop during in-pipe condensation heat transfer. In addition, there is a tendency that the more that coolant condensation progresses and the lower the quality becomes, the smaller the heat transfer coefficient and the lower the pressure drop during in-pipe condensation heat transfer.
In the tube group located most upstream of the coolant condenser, coolant in the gas-phase state flows in and, while condensing within the tubes, flows out to the tube group on the downstream side. Consequently, in the tube group located most upstream of the coolant condenser, there is a tendency for the pressure drop also to become high even though the heat transfer coefficient becomes high. Accordingly, in a preexisting coolant condenser, by making the number of tubes belonging to the tube group located most upstream the greatest, a high heat transfer coefficient is achieved while curtailing an increase in the pressure drop due to the high-quality coolant.
On the other hand, in the tube groups more downstream than the tube group located most upstream, because condensation of the coolant is progressing, the heat transfer coefficient and the pressure drop are lower than in the tube group located most upstream. Consequently, in the preexisting coolant condenser, by making the number of tubes belonging to the tube groups smaller as the quality of the coolant becomes lower, optimization of the heat transfer coefficient and the pressure drop is achieved.
However, there is strong demand for a heat exchanger in which the amount of heat exchanged is even greater than that of the coolant condenser according to Patent Document 1.
The present invention was conceived considering this background, and an object of the present invention is to provide a parallel-flow-type heat exchanger, in which the amount of heat exchanged can be increased while curtailing an increase in the pressure drop, and an air conditioner comprising this heat exchanger.
One aspect of the present invention is a parallel-flow-type heat exchanger comprising:
Another aspect of the present invention is an air conditioner comprising: the parallel-flow-type heat exchanger according to the above-mentioned aspect; and the coolant, which exists in the interior of the parallel-flow-type heat exchanger.
The core of the above-mentioned parallel-flow-type heat exchanger (hereinbelow, called a “heat exchanger”) comprises the plurality of flat, multi-hole pipes, and the plurality of flat, multi-hole pipes is divided into the plurality of flat, multi-hole pipe groups, including the first flat, multi-hole pipe group, which is disposed most upward, and the second flat, multi-hole pipe group, which is disposed downward of and adjacent to the first flat, multi-hole pipe group. Furthermore, the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group is 14 or more, and the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group is less than the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group.
As described above, pre-existing heat exchangers have been configured such that the number of tubes in upstream tube groups, through which high-quality coolant circulates, is greater than that of downstream tube groups, through which coolant of a quality that is lower to a certain degree circulates. However, as a result of diligent investigation by the present inventors, it was found that flat, multi-hole pipes have a characteristic heat-transfer property, in which, as condensation of the coolant progresses to a certain degree, the heat transfer coefficient no longer tends to affect the mass velocity of the coolant and the quality of the coolant. Utilizing this heat-transfer property, by making the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group less than the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group, it becomes possible to increase the effect of enlarging the heat-exchanging surface area more than the effect of decreasing the heat transfer coefficient in the second flat, multi-hole pipe group, thereby increasing the amount of heat exchanged by the second flat, multi-hole pipe group.
Furthermore, the above-mentioned heat exchanger is configured such that the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group is less than the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group. For this reason, the above-mentioned heat exchanger can increase the amount of heat exchanged by the second flat, multi-hole pipe group while curtailing an increase in the pressure drop. As result, the amount of heat exchanged by the entire heat exchanger can be increased.
As described above, according to the heat exchanger of the above-mentioned aspect, the amount of heat exchanged can be increased while curtailing an increase in the pressure drop.
In addition, because the above-mentioned air conditioner comprises the heat exchanger according to the above-mentioned aspect, the amount of heat exchanged can be increased while curtailing an increase in the pressure drop of the heat exchanger.
A core of the above-mentioned heat exchanger comprises a plurality of flat, multi-hole pipes. The total number of the flat, multi-hole pipes of the heat exchanger can be set as appropriate in accordance with the dimensions of the heat exchanger, the required rated capacity, the pressure drop, and the like. The total number of flat, multi-hole pipes may be, for example, 28 or more and 168 or less.
The plurality of flat, multi-hole pipes may be divided into a plurality of flat, multi-hole pipe groups, which include a first flat, multi-hole pipe group and a second flat, multi-hole pipe group. For example, the plurality of flat, multi-hole pipes in the above-mentioned heat exchanger may be divided into four flat, multi-hole pipe groups: a first flat, multi-hole pipe group, which is located most upward; a second flat, multi-hole pipe group, which is disposed downward of and proximate to the first flat, multi-hole pipe group; a third flat, multi-hole pipe group, which is disposed downward of and proximate to the second flat, multi-hole pipe group; and a fourth flat, multi-hole pipe group, which is disposed downward of and proximate to the third flat, multi-hole pipe group.
A first header and a second header are configured such that a coolant can be sequentially passed through, from above to below, the plurality of flat, multi-hole pipe groups. For example, in the situation in which the above-mentioned heat exchanger comprises four of the flat, multi-hole pipe groups, the first header and the second header may be configured such that the coolant can be sequentially passed through the first flat, multi-hole pipe group, the second flat, multi-hole pipe group, the third flat, multi-hole pipe group, and the fourth flat, multi-hole pipe group.
To implement such an aspect, for example, the interior space of the first header may be partitioned into three spaces: an inlet portion, which is connected to an end portion of the first flat, multi-hole pipe group; a second turn portion, which is connected to an end portion of the second flat, multi-hole pipe group and an end portion of the third flat, multi-hole pipe group; and an outlet portion, which is a connected to an end portion of the fourth flat, multi-hole pipe group; in addition, the interior space of the second header may be partitioned into two spaces: a first turn portion, which is connected to an end portion of the first flat, multi-hole pipe group and an end portion of the second flat, multi-hole pipe group; and a third turn portion, which is connected to an end portion of the third flat, multi-hole pipe group and an end portion of the fourth flat, multi-hole pipe group. In this situation, by supplying the coolant to the inlet portion of the first header, the coolant sequentially passes through the first flat, multi-hole pipe group, the first turn portion, the second flat, multi-hole pipe group, the second turn portion, the third flat, multi-hole pipe group, the third turn portion, and the fourth flat, multi-hole pipe group. Furthermore, by discharging the coolant via the outlet portion of the first header to the exterior of the heat exchanger, the coolant can be caused to circulate through the interior of the heat exchanger.
The number of flat, multi-hole pipes belonging to the second flat, multi-hole pipe group is 14 or more and is greater than or equal to the number of flat, multi-hole pipes belonging to the first flat, multi-hole pipe group. Thereby, the amount of heat exchanged when the coolant passes through the second flat, multi-hole pipe group can be increased and, in turn, the amount of heat exchanged by the entire heat exchanger can be increased. From the viewpoint of balancing the pressure drop of the heat exchanger and the amount of heat exchanged, the number of flat, multi-hole pipes belonging to the second flat, multi-hole pipe group preferably is greater than or equal to the number of flat, multi-hole pipes belonging to each of the flat, multi-hole pipe groups, other than the second flat, multi-hole pipe group.
Specifically, in the situation in which, for example, the heat exchanger comprises four of the flat, multi-hole pipe groups, the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group can be made to be 35% or more and 79% or less of the total number of the flat, multi-hole pipes of the heat exchanger, preferably can be made to be 35% or more and 75% or less, and more preferably can be made to be 35% or more and 60% or less.
The number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group is less than the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group. Because the coolant that flows into the first flat, multi-hole pipe group is in the gas-phase state, i.e., a coolant having high quality, the heat transfer coefficient when the coolant passes through the first flat, multi-hole pipe group tends to become relatively high. In addition, in the situation in which the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group is made small, the mass velocity of the coolant increases as the heat-exchanging surface area decreases. For this reason, even if the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group is made to be less than the number of the flat, multi-hole pipes belonging to the second flat, multi-hole pipe group, a decrease in the amount of heat exchanged in the first flat, multi-hole pipe group can be curtailed. As a result, the amount of heat exchanged by the entire heat exchanger can be increased.
In the situation in which the above-mentioned heat exchanger comprises three or more of the flat, multi-hole pipe groups, the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group preferably is greater than the number of the flat, multi-hole pipes belonging to the third flat, multi-hole pipe group and to the flat, multi-hole pipe groups located more downward than the third flat, multi-hole pipe group. In this situation, the pressure drop when the coolant passes through the first flat, multi-hole pipe group can be further reduced, and the amount of heat exchanged can be further increased. As a result, the pressure drop of the entire heat exchanger can be further reduced, and the amount of heat exchanged by the entire heat exchanger can be further increased.
In addition, the above-mentioned heat exchanger is sometimes designed to exhibit heat-exchanging performance that excels when using a specific coolant. In such a situation, number N1 [number] of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group more preferably satisfies the relation in equation (1) below.
Therein, N [number] in the above-mentioned equation (1) is the total number of the flat, multi-hole pipes of the heat exchanger. In addition, the value of ΔPTP is the pressure drop of the heat exchanger. The value of ΔPTP is calculated by equations (2)-(4) below, wherein the mass-flow rate of the above-mentioned coolant that flows through the interior of the above-mentioned parallel-flow-type heat exchanger is expressed as mref [kg/s], the passageway, cross-sectional area of the above-mentioned flat, multi-hole pipe is expressed as Atube [m2], the hydraulic diameter of the above-mentioned flat, multi-hole pipe is expressed as Dh [m], the length of the above-mentioned flat, multi-hole pipe is expressed as Ltube [m], the viscosity of the above-mentioned coolant in the liquid phase is expressed as μL [Pa·s], the viscosity of the above-mentioned coolant in the gas phase is expressed as μV [Pa·s], the density of the above-mentioned coolant in the liquid phase is expressed as ρL [kg/m3], and the density of the above-mentioned coolant in the gas phase is expressed as ρV [kg/m3].
Thus, by making the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group to be within a range that considers the physical properties of the coolant, the balance between the amount of heat exchanged and the pressure drop of the first flat, multi-hole pipe group can be optimized. As a result, the pressure drop of the entire heat exchanger can be further reduced, and the amount of heat exchanged by the entire heat exchanger can be further increased.
It is noted that the above-mentioned equation (1) to equation (4) are determined based on the following approach. That is, as a result of the inventors investigating by trial and error using numerical analysis, it was found that the optimal number N1 of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group varies greatly with the size of pressure drop ΔPTP of the heat exchanger. Pressure drop ΔPTP of the heat exchanger is considered to arise principally when the coolant passes through the flat, multi-hole pipes.
Assuming that the flow of the coolant within the flat, multi-hole pipes is a turbulent flow, pressure drop ΔPSP when the coolant passes through the flat, multi-hole pipes is expressed by the Darcy-Weisbach equation (refer to equation (5) below).
In the above-mentioned equation (5), equation (6) below can be derived by using the Blasius pipe coefficient of friction as the pipe coefficient of friction f.
Because G in the above-mentioned equation (6) can be expressed as mref/Atube, the relation in equation (3′) below can be derived by rearranging the above-mentioned equation (6).
Based on the above, in expressing pressure drop ΔPTP of the heat exchanger, it is understood that parameter C1 (above-mentioned equation (3)), which is related to pressure drop ΔPSP when the coolant passes through the flat, multi-hole pipes, should be used.
In addition, the flow of the coolant through the interior of the heat exchanger is a gas-liquid, two-phase flow. For this reason, in calculating the size of pressure drop ΔPTP of the heat exchanger, it is necessary to introduce not only the above-described parameter C1 but also Γ (above-mentioned equation (4)), which is a parameter for taking the effects of the gas-liquid, two-phase flow into consideration.
When the results of the numerical analysis performed by the inventors based on the above were rearranged, it was found that the optimal number N1′ of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group can be approximated by equation (1′) below, and pressure drop ΔPTP of the heat exchanger can be approximated by the above-mentioned equation (2).
Furthermore, as will be explained in the working examples described below, the optimal number N1′ of the flat, multi-hole pipes estimated by the above-mentioned equation (1′) is greater by two at the maximum relative to the optimal number N1 of the flat, multi-hole pipes derived by numerical analysis. Accordingly, the above-mentioned equation (1) can be derived by subtracting two from both sides of the above-mentioned equation (1′) and leaving the left side as N1.
In the situation in which the above-mentioned heat exchanger comprises three or more of the flat, multi-hole pipe groups, the number of the flat, multi-hole pipes belonging to the third flat, multi-hole pipe group and to the flat, multi-hole pipe groups located more downward than the third flat, multi-hole pipe group is not particularly limited. However, normally, the quality of the coolant that flows through the flat, multi-hole pipe groups located downward is less than or equal to the quality of the coolant that flows through the flat, multi-hole pipe groups located upward. For this reason, by making the number of the flat, multi-hole pipes belonging to the flat, multi-hole pipe groups located downward less than the number of the flat, multi-hole pipes belonging to the flat, multi-hole pipe groups located upward, the pressure drop of the entire heat exchanger can be further reduced, and the amount of heat exchanged by the entire heat exchanger can be further increased.
For example, in the situation in which the heat exchanger comprises four of the flat, multi-hole pipe groups, the number of the flat, multi-hole pipes belonging to the third flat, multi-hole pipe group can be made to be 5% or more and 21% or less of the total number of the flat, multi-hole pipes of the heat exchanger. From the viewpoint of balancing the pressure drop and the amount of heat exchanged, the number of the flat, multi-hole pipes belonging to the third flat, multi-hole pipe group preferably is made to be 7% or more and 17% or less of the total number of the flat, multi-hole pipes of the heat exchanger, and more preferably is made to be 9% or more and 14% or less.
Likewise, the number of the flat, multi-hole pipes belonging to the fourth flat, multi-hole pipe group can be made to be, for example, 4% or more and 14% or less of the total number of the flat, multi-hole pipes of the heat exchanger. From the viewpoint of balancing the pressure drop and the amount of heat exchanged, the number of the flat, multi-hole pipes belonging to the fourth flat, multi-hole pipe group preferably is made to be 6% or more and 12% or less of the total number of the flat, multi-hole pipes of the heat exchanger, and more preferably is made to be 6% or more and 10% or less.
Each of the flat, multi-hole pipes of the above-mentioned heat exchanger has: a pair of flat-wall portions, the flat-wall portions being disposed spaced apart and opposing each other; connecting-wall portions, which connect both ends of the flat-wall portions in the width direction to each other; and partition portions, which partition the interior space surrounded by the flat-wall portions and the connecting-wall portions into a plurality of coolant passageways. The shape of each of the coolant passageways in a cross section perpendicular to the longitudinal direction of the flat, multi-hole pipes can take on various forms, for example, circular, elliptical, oblong, semicircular, triangular, quadrangular, and the like, in a cross section perpendicular to the longitudinal direction of the flat, multi-hole pipe. The number of the coolant passageways in each of the flat, multi-hole pipes can be set as appropriate within the range of, for example, 4 or more and 20 or less.
In a cross section perpendicular to the longitudinal direction, each of the coolant passageways in the flat, multi-hole pipes preferably is noncircular, i.e., a shape that has an angled portion at one or more locations. By incorporating the flat, multi-hole pipes, each of which has such coolant passageways, in the second flat, multi-hole pipe group, a decrease in the heat transfer coefficient of the second flat, multi-hole pipe group can be further curtailed. As a result, the effect of increasing the amount of heat exchanged by the second flat, multi-hole pipe group can be further enhanced and, in turn, the amount of heat exchanged by the entire heat exchanger can be further increased. It is note that, for example, the noncircular cross-sectional shape described above includes shapes such as a semicircle, a triangle, a quadrilateral, and the like. From the viewpoint of further enhancing the functions and effects described above, each of the coolant passageways in the flat, multi-hole pipes more preferably is a shape in which the contour in a cross section perpendicular to the longitudinal direction is composed of only straight lines. Such a cross-sectional shape includes shapes such as, for example, a triangle, a quadrilateral, and the like.
Hydraulic diameter Dh of the flat, multi-hole pipe can be set as appropriate within a range of, for example, 0.00032 m or more and 0.001 m or less. In this situation, the heat-transfer efficiency of each of the flat, multi-hole pipes can be further increased. It is noted that hydraulic diameter Dh of the flat, multi-hole pipe described above is expressed by equation (7) below using passageway, cross-sectional area Atube [m2] of the flat, multi-hole pipe and passageway, wet-edge length Stube [m] of the flat, multi-hole pipe.
In addition, length Ltube of the flat, multi-hole pipe can be set as appropriate within a range of 0.4 m or more and 0.9 m or less. In this situation, the heat-transfer efficiency of each of the flat, multi-hole pipes can be further increased.
In the situation in which the above-mentioned heat exchanger is configured to use R32 (i.e., difluoromethane) as the coolant, hydraulic diameter Dh of the flat, multi-hole pipe preferably is 0.00032 m or more and 0.001 m or less, and length Ltube preferably is 0.4 m or more and 0.9 m or less. The flat, multi-hole pipe having hydraulic diameter Dh and length Ltube within the above-mentioned specific ranges can achieve a heat-exchanging efficiency that excels in particular when R32 is used as the coolant. For this reason, flat, multi-hole pipes having hydraulic diameter Dh and length Ltube within the above-mentioned specific ranges are suited to a heat exchanger configured to use R32 as the coolant.
The above-mentioned heat exchanger may have a rated capacity of, for example, 2 KW or more and 12 kW or less. It is noted that the rated capacity of the heat exchanger described above is assigned the value of the rated cooling capacity obtained by the cooling-capacity test stipulated in JIS B8615-1:2013.
Applications of the above-mentioned heat exchanger are not particularly limited, and the above-mentioned heat exchanger may be configured to be used in an outdoor unit of a stationary-type air conditioner, for example, for home use, for business use, or the like. In addition, the above-mentioned heat exchanger may be configured to be used in, for example, a condenser of a vehicle air conditioner.
An air conditioner can be constituted by connecting the above-mentioned heat exchanger to the component parts of an air conditioner, such as a compressor, an expansion valve, a pump, a heat exchanger other than the above-mentioned heat exchanger, and the like, via coolant piping and filling the interior thereof with the coolant.
The coolant used in the air conditioner is not particularly limited; for example, hydrofluorocarbon coolants such as R410A and R32, hydrofluoroolefin coolants, such as R1234yf and R1123, or the like can be used. The coolant used in the air conditioner preferably is R32. Because R32 has a comparatively large latent heat of condensation as well as high thermal conductivity, it is even easier to make the air conditioner compact and highly efficient.
The above-mentioned air conditioner preferably has a parallel-flow-type heat exchanger in which total number N [number] of the flat, multi-hole pipes and number N1 [number] of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group satisfy the relation in the above-mentioned equation (1).
As described above, by making the number of the flat, multi-hole pipes belonging to the first flat, multi-hole pipe group within a range that takes the physical properties of the coolant into consideration, an increase in the pressure drop of the entire heat exchanger can be more effectively curtailed, and the amount of heat exchanged can be further increased. As a result, the energy consumption of the air conditioner can be further reduced.
The above-mentioned air conditioner may be configured such that mass-flow rate mref of the above-mentioned coolant in the interior of the heat exchanger can be set within a range of, for example, 0.01 kg/s or more and 0.03333 kg/s or less. In this situation, an increase in the pressure drop of the above-mentioned heat exchanger can be more effectively curtailed, and the amount of heat exchanged by the above-mentioned heat exchanger can be further increased. As a result, the energy consumption of the air conditioner can be further reduced.
In particular, in the situation in which the coolant of the above-mentioned air conditioner is R32, by making mass-flow rate mref of the above-mentioned coolant in the interior of the heat exchanger to be within a range of 0.01 kg/s or more and 0.03333 kg/s or less, the functions and effects described above can be more reliably exhibited.
From the same viewpoint, in the situation in which the coolant of the above-mentioned air conditioner is R32, it is particularly preferable for hydraulic diameter Dh of the flat, multi-hole pipe in the heat exchanger to be within a range of 0.00032 m or more and 0.001 m or less, length Ltube to be within a range of 0.4 m or more and 0.9 m or less, and mass-flow rate mref of the coolant to be within a range of 0.01 kg/s or more and 0.03333 kg/s or less.
Working examples of the above-mentioned parallel-flow-type heat exchanger will now be explained.
As shown in
The number of flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 is 14 or more. In addition, the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 is less than the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22. The configuration of the heat exchanger 1 of the present example will be explained in greater detail below.
Each component that constitutes the heat exchanger 1 may be composed of an aluminum material (including aluminum and aluminum alloys). For example, the flat, multi-hole pipes 2 may be composed of a 1000-series aluminum or a 3000-series alloy. By using a 3000-series alloy as the material of the flat, multi-hole pipes 2, the coolant can be used at a higher pressure. The fins 3 may be composed of, for example, a 1000-series aluminum, a 3000-series alloy, or the like. In addition, the fins 3 may be constituted from a brazing sheet, in which a filler material composed of a 4000-series alloy is layered on both surfaces of a core material composed of a 1000-series aluminum, a 3000-series alloy, or the like.
The first header 4 and the second header 5 may be composed of a 1000-series aluminum, a 3000-series alloy, or the like. In addition, the first header 4 and the second header 5 may be constituted from a brazing sheet, in which a filler material composed of a 4000-series alloy is layered on both surfaces of a core material composed of a 1000-series aluminum, a 3000-series alloy, or the like.
As shown in
The dimensions of the core 11 can be set as appropriate in accordance with the layout space or the like allowed in the desired heat exchanger, the air conditioner, or the like. Specifically, the outer dimension of the core 11 in the up-down direction, i.e., the outer dimension of the core 11 in the stacked direction, should be set as appropriate within a range of 250 mm or more and 1,500 mm or less. In addition, the outer dimension of the core 11 in the depth direction, i.e., the outer dimension of the flat, multi-hole pipe 2 in the width direction, should be set as appropriate within a range of 6 mm or more and 20 mm or less.
The outer dimension of the core in the width direction should be set in accordance with the desired effective length of each of the flat, multi-hole pipes 2, i.e., in accordance with the distance from the first header 4 to the second header 5 in the longitudinal direction of the flat, multi-hole pipes 2. The effective length of each of the flat, multi-hole pipes 2 can be set as appropriate within a range of, for example, 400 mm or more and 1,000 mm or less.
The total number of flat, multi-hole pipes 2 of the core 11 can be set as appropriate within a range of 28 or more and 168 or less. For example, in the present example, the total number of the flat, multi-hole pipes 2 of the core 11 can be made to be 52.
The flat, multi-hole pipes 2 in the heat exchanger 1 of the present example are divided into four flat, multi-hole pipe groups: the first flat, multi-hole pipe group 21 to the fourth flat, multi-hole pipe group 24. The first flat, multi-hole pipe group 21 is disposed most upward of the core 11. The second flat, multi-hole pipe group 22 is disposed downward of and adjacent to the first flat, multi-hole pipe group 21. The third flat, multi-hole pipe group 23 is disposed downward of and adjacent to the second flat, multi-hole pipe group 22. The fourth flat, multi-hole pipe group 24 is disposed downward of and adjacent to the third flat, multi-hole pipe group 23 and is located most downward in the core 11.
The interior space of the first header 4 is partitioned into three spaces: an inlet portion 41, which is connected to an end portion of the first flat, multi-hole pipe group 21; a second turn portion 42, which is connected to an end portion of the second flat, multi-hole pipe group 22 and an end portion of the third flat, multi-hole pipe group 23; and an outlet portion 43, which is connected to an end portion of the fourth flat, multi-hole pipe group 24. First partition sheets 44, 45, which partition these spaces, are provided between the inlet portion 41 and the second turn portion 42 and between the second turn portion 42 and the outlet portion 43.
The interior space of the second header 5 is partitioned into two spaces: a first turn portion 51, which is connected to an end portion of the first flat, multi-hole pipe group 21 and an end portion of the second flat, multi-hole pipe group 22; and a third turn portion 52, which is connected to an end portion of the third flat, multi-hole pipe group 23 and an end portion of the fourth flat, multi-hole pipe group 24. A second partition sheet 53, which partitions the two, is provided between the first turn portion 51 and the third turn portion 52.
In addition, a coolant supply pipe 6, which is configured to be capable of supplying the coolant into the heat exchanger 1, is connected to the inlet portion 41 of the first header 4, and a coolant exhaust pipe 7, which is configured to be capable of discharging the coolant inside the heat exchanger 1 to the exterior, is connected to the outlet portion 43.
Therefore, the flow of the coolant in the heat exchanger 1 of the present example is as follows. That is, the coolant that flows from the coolant supply pipe 6 into the inlet portion 41 is distributed, in the inlet portion 41, to each of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21. The coolant that has passed through the first flat, multi-hole pipe group 21 flows into the first turn portion 51 in the second header 5. The coolant that has merged in the first turn portion 51 is distributed to each of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22. The coolant that has passed through the second flat, multi-hole pipe group 22 subsequently passes sequentially through the second turn portion 42 in the first header 4, the third flat, multi-hole pipe group 23, the third turn portion 52 in the second header 5, and the fourth flat, multi-hole pipe group 24, and then flows into the outlet portion 43 of the first header 4. Furthermore, the coolant that has merged in the outlet portion 43 is exhausted from the coolant exhaust pipe 7 to the exterior of the heat exchanger 1.
In the heat exchanger 1 of the present example, the number of the flat, multi-hole pipes 2 belonging to the flat, multi-hole pipe groups 21-24 should be set such that the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 is 14 or more, and the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 is less than the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22.
For example, in the present example, as shown in
As shown in
Each of the flat, multi-hole pipes 2 has: a pair of flat-wall portions 211, the flat-wall portions 211 being disposed spaced apart and opposing each other; connecting-wall portions 212, which connect both ends of the flat-wall portions 211 in the width direction to each other; and partition portions 214, which partition the interior space surrounded by the flat-wall portions 211 and the connecting-wall portions 212 into a plurality of coolant passageways 213. Each of the flat, multi-hole pipes 2 may exhibit a rectangular shape, as shown in
The number of the coolant passageways 213 in each of the flat, multi-hole pipes 2 can be set as appropriate within a range of, for example, 4 or more and 20 or less. For example, in the present example, as shown in
As shown in
Louvers, which protrude from the fins 3 in the thickness direction, may be provided at flat portions 31 (refer to
The first header 4 comprises: a header main body 46, which exhibits a tube shape extending in the up-down direction, i.e., the stacked direction of the core 11; and caps 47, 48, which close up the upper end and the lower end of the header main body 46.
For example, although a circular-tube pipe having an outer diameter of 15-25 mm and a wall thickness of 1.0-2.5 mm can be used as the header main body 46, the header main body 46 is not limited to this shape. In addition, the caps 47, 48 and the first partition sheets 44, 45 are joined to the header main body 46 by brazing.
The interior space of the first header 4 surrounded by the header main body 46 and the caps 47, 48 is partitioned into three spaces by the two first partition sheets 44, 45. The portion from an upper end 411 of the first header 4 to the first partition sheet 44 disposed upward constitutes the inlet portion 41 of the first header 4. The end portions of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 are inserted into the inlet portion 41.
In addition, a coolant supply pipe 6, which is for supplying the coolant into the heat exchanger 1, is connected to the inlet portion 41. An end portion of the coolant supply pipe 6 is inserted into the inlet portion 41, and the coolant supply pipe 6 and the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 communicate with each other via the inlet portion 41. Thereby, the inlet portion 41 is configured such that the coolant supplied from the coolant supply pipe 6 can be distributed to each of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21.
In the first header 4, the portion from the first partition sheet 44, which is disposed upward, to the first partition sheet 45, which is disposed downward, constitutes the second turn portion 42. End portions of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 and the third flat, multi-hole pipe group 23 are inserted into the second turn portion 42. Thereby, the second turn portion 42 is configured to merge the coolant that has passed through the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 and to be capable of distributing the coolant to the flat, multi-hole pipes 2 belonging to the third flat, multi-hole pipe group 23.
The portion from a lower end 412 of the first header 4 to the first partition sheet 45 disposed downward constitutes the outlet portion 43. The end portions of the flat, multi-hole pipes 2 belonging to the fourth flat, multi-hole pipe group 24 are inserted into the outlet portion 43.
In addition, the coolant exhaust pipe 7, which is for discharging the coolant in the heat exchanger 1 to the exterior, is connected to the outlet portion 43. An end portion of the coolant exhaust pipe 7 is inserted into the outlet portion 43, and the coolant exhaust pipe 7 and the flat, multi-hole pipes 2 belonging to the fourth flat, multi-hole pipe group 24 communicate with each other via the outlet portion 43. Thereby, the outlet portion 43 is configured to merge the coolant discharged from the flat, multi-hole pipes 2 belonging to the fourth flat, multi-hole pipe group 24 and to be capable of discharging the coolant to the exterior of the heat exchanger 1 via the coolant exhaust pipe 7.
The flat, multi-hole pipes 2, the coolant supply pipe 6, and the coolant exhaust pipe 7 inserted into the first header 4 are joined to the header main body 46 of the first header 4 by brazing.
The second header 5 comprises: a header main body 56, which exhibits a tube shape extending in the up-down direction, i.e., the stacked direction of the core 11; and caps 57, 58, which close up the upper end and the lower end of the header main body 56. In addition, the interior space of the second header 5 surrounded by the header main body 56 and the caps 57, 58 is partitioned into two spaces by the one second partition sheet 53.
Like the header main body 46 of the first header 4, for example, a circular-tube pipe having an outer diameter of 15-25 mm and a wall thickness of 1.0-2.5 mm can be used as the header main body 56, but the header main body 56 is not limited to this shape. In addition, the caps 57, 58 and the second partition sheet 53 are joined to the header main body 56 by brazing.
The portion from an upper end 511 of the second header 5 to the second partition sheet 53 constitutes the first turn portion 51. End portions of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 and the second flat, multi-hole pipe group 22 are inserted into the first turn portion 51. Thereby, the first turn portion 51 is configured to merge the coolant that has passed through the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 and to be capable of distributing the coolant to the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22.
The portion from a lower end 512 of the second header 5 to the second partition sheet 53 constitutes the third turn portion 52. End portions of the flat, multi-hole pipes 2 belonging to the third flat, multi-hole pipe group 23 and the fourth flat, multi-hole pipe group 24 are inserted into the third turn portion 52. Thereby, the third turn portion 52 is configured to merge the coolant that has passed through the flat, multi-hole pipes 2 belonging to the third flat, multi-hole pipe group 23 and to be capable of distributing the coolant to the flat, multi-hole pipes 2 belonging to the fourth flat, multi-hole pipe group 24.
The flat, multi-hole pipes 2 inserted into the second header 5 are joined to the header main body 56 of the second header 5 by brazing.
The core 11 of the heat exchanger 1 of the present example comprises the plurality of flat, multi-hole pipe groups 21-24 and is configured such that the coolant flows sequentially to the first flat, multi-hole pipe group 21, the second flat, multi-hole pipe group 22, the third flat, multi-hole pipe group 23, and the fourth flat, multi-hole pipe group 24. In addition, the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 is 14 or more, and the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 is less than the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22. For this reason, the heat exchanger 1 can increase the amount of heat exchanged by the second flat, multi-hole pipe group 22 while curtailing an increase in the pressure drop. As a result, the amount of heat exchanged by the entire heat exchanger 1 can be increased.
As a result of the above, according to the heat exchanger 1 of the present example, the amount of heat exchanged can be increased while curtailing an increase in the pressure drop.
In the present example, two types of the heat exchangers 1 (Test Specimen A and Test Specimen B), in which the number of the flat, multi-hole pipes 2 belonging to each of the flat, multi-hole pipe groups 21-24 was modified, were prepared, and the amounts of heat exchanged by these heat exchangers 1 were evaluated. The specific configuration of each of the test specimens is explained below. It is noted that symbols used in examples subsequent to the present example that are identical to the symbols used in the previously discussed example indicate structural elements the same as the structural elements in the previously discussed example, unless otherwise described.
The basic shape of Test Specimen A was the same as that of the heat exchanger 1 of Working Example 1. The specific dimensions and the like of each part of Test Specimen A were as below.
It is noted that the effective width described above refers to the distance from the first header 4 to the second header 5 in the longitudinal direction of the flat, multi-hole pipes 2, i.e., substantially to the length of the portion at which heat exchange is performed between the flat, multi-hole pipes 2 and the outside air. In addition, the pitch of the fins 3 refers to the length of the period of the bent portions 32 of the fins 3.
Test Specimen B has the same configuration as Test Specimen A, except for the number of the flat, multi-hole pipes 2 belonging to each of the flat, multi-hole pipe groups 21-24 being modified as below.
Next, a method of measuring the amounts of heat exchanged by Test Specimen A and Test Specimen B will be explained. First, Test Specimen A and Test Specimen B were placed in a wind-tunnel apparatus, which was provided in a thermo-hygrostatic test chamber. Then, the air temperature inside the test chamber was set to a dry-bulb temperature of 35° C. and a wet-bulb temperature of 24° C., and air was blown from the wind-tunnel apparatus toward the heat exchangers at one of the wind velocities listed in Table 1. Subsequently, R32, which served as the coolant, was supplied from the coolant supply pipe 6 of each test specimen. It is noted that the condensation temperature of R32 is 45° C.
Then, the heat balance between the air and the coolant was measured while circulating the coolant such that the temperature of the coolant at the coolant supply pipe 6 became 65° C. (i.e., a degree of superheating of 20 K) and the temperature of the coolant at the coolant exhaust pipe 7 became 40° C. (i.e., a degree of supercooling of 5 K). The “Amount of Heat Exchanged” column in Table 1 lists the amount of heat exchanged at the point in time when the heat balance between the air and the coolant reached a steady state. In addition, the “Ratio” column in Table 1 lists, using a value expressed as a percentage (%), the ratio of the amount of heat exchanged by Test Specimen A relative to the amount of heat exchanged by Test Specimen B at each wind velocity.
As listed in Table 1, compared with Test Specimen B, in which the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 was less than the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21, Test Specimen A, in which the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 was greater than or equal to the number of the flat, multi-hole pipes 2 belonging to the other flat, multi-hole pipe groups 21, 23, 24, exhibited a greater amount of heat exchanged at every wind velocity.
As shown in
On the other hand, in the second flat, multi-hole pipe group 22, the heat-exchanging surface area Ai, cell with the coolant becomes large commensurate with the increase in the number of the flat, multi-hole pipes 2. Thereby, the product of αref and Ai, cell can be made large. In addition, owing to the characteristic heat-transfer property described above, the flat, multi-hole pipes 2 can curtail a decrease in the heat transfer coefficient αref when the coolant, for which condensation has progressed to a certain extent, passes through. Consequently, by making the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 large, as shown in
In the present example, the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 was investigated. In the present example, to investigate the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21, numerical analysis was performed using the analytical model below.
The state quantities of the coolant at the outlet of each cell can be calculated by solving an energy-conservation equation and a conservation of momentum equation within each cell by iterative calculations. Specifically, the energy-conservation equation (refer to equation (8) below) between the air and the flat, multi-hole pipes 2 and the energy-conservation equation (refer to equation (10) below) between the flat, multi-hole pipes 2 and the coolant should be used in the calculation of temperature Tref, out and specific enthalpy href, out of the coolant at the outlet of each cell.
The energy-conservation equation on the air side at each cell can be expressed by equation (8) below.
The meanings of the symbols in the above-mentioned equation (8) are as below.
It is noted that wind velocity Vair of the air that flows into the air inlet of each cell is a value calculated by dividing the volume-flow rate [m3/s] of the air that flows into each cell by surface area Afront, cell [m2] of the air inlet of the cell.
In addition, symbol LMTD in the above-mentioned equation (8) is the logarithmic mean-temperature difference between the temperature of the coolant inlet/outlet at each cell and the temperature of the air inlet/outlet at each cell. The value of LMTD specifically can be calculated by equation (9) below, using wall-surface temperature Twall [K] of the flat, multi-hole pipes 2.
The energy-conservation equation on the coolant side of each cell can be expressed by equation (10) below.
The meanings of the symbols in the above-mentioned equation (10) are as below.
Because the amount of heat exchanged between the air and the flat, multi-hole pipes 2 and the amount of heat exchanged between the flat, multi-hole pipes 2 and the coolant are equal, the right side of the above-mentioned equation (8) and the right side of the above-mentioned equation (10) can be linked together by an equal sign. Thereby, equation (11) below can be obtained.
Heat transfer coefficient αair between the air and the flat, multi-hole pipes 2 in the above-mentioned equation (8) and heat transfer coefficient αref between the coolant and the flat, multi-hole pipes 2 in the above-mentioned equation (10) can be determined by separate calculations. In addition, in the situation in which a cell does not exist upstream of the cell that is the calculation object, properly set initial values should be used as the state quantities of the coolant at the inlet of each cell; and in the situation in which a cell does exist upstream of the cell that is the calculation object, the state quantities at the outlet of the upstream cell should be used. In addition, a properly set initial value should be used as the state quantity of the air at the inlet of each cell.
Accordingly, in the above-mentioned equation (8), equation (10), and equation (11), three unknown state quantities exist: temperature Tair, out of the air at the air outlet of each cell; wall-surface temperature Twall of the flat, multi-hole pipes 2; and specific enthalpy href, out of the coolant at the coolant outlet. On the other hand, because the above-mentioned equation (8), equation (10), and equation (11) are conservation equations, these unknown state quantities can be determined by using an iterative method. Specifically, these unknown state quantities should be determined using a bisection method.
In addition, equation (12) below should be used as pressure Pref, out of the coolant at the coolant outlet of each cell.
Symbol ΔPf in the above-mentioned equation (12) is the value of the pipe friction loss based on the Jige-Koyama equation, and ΔPm is the pressure change associated with the phase change in the coolant. The value of the pressure change ΔPm associated with the phase change in the coolant can be expressed by equation (13) below.
It is noted that the meanings of the symbols in the above-mentioned equation (13) are as below.
The validity of the above-mentioned analytical model can be confirmed by, for example, comparing the calculation results of the model that simulates Test Specimen A and Test Specimen B in Working Example 1 with the test results. Table 2 lists the calculation results of the model that simulates Test Specimen A and Test Specimen B.
As listed in Table 2, the amount of heat exchanged by Test Specimen A, calculated by numerical analysis, is greater than the amount of heat exchanged of Test Specimen B at every wind velocity. In addition, the higher the wind velocity, the greater the amount of heat exchanged by Test Specimen A. Thus, the amount of heat exchanged calculated by the above-mentioned analytical model exhibits the same tendency as the test results. Based on these results, it can be understood that the above-mentioned analytical model is valid.
Next, a method of distributing the flat, multi-hole pipes 2, in which the amount of heat exchanged is the greatest for each of analysis conditions A-J listed in Table 3, will be investigated using the above-mentioned analytical model. It is noted that the structure of the analytical model, other than the values listed in Table 3, is as below.
Table 3 lists, for each of the analysis conditions A-J, the optimal value of the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21. It is noted that, although not listed in the table, the optimal value of the number of the flat, multi-hole pipes 2 belonging to the second flat, multi-hole pipe group 22 for each of the analysis conditions A-J is greater than or equal to the optimal value of the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21.
In
Therein, the value of ΔPTP in the above-mentioned equation (2) is the value calculated by equations (3)-(4) below, wherein: the mass-flow rate of the above-mentioned coolant that flows through the interior of the above-mentioned parallel-flow-type heat exchanger is expressed as mref [kg/s]; the passageway, cross-sectional area of the above-mentioned flat, multi-hole pipe is expressed as Atube [m2]; the hydraulic diameter of the above-mentioned flat, multi-hole pipe is expressed as Dh [m]; the length of the above-mentioned flat, multi-hole pipe is expressed as Ltube [m]; the viscosity of the above-mentioned coolant in the liquid phase is expressed as μL [Pa·s]; the viscosity of the above-mentioned coolant in the gas phase is expressed as μV [Pa·s]; the density of the above-mentioned coolant in the liquid phase is expressed as ρL [kg/m3]; and the density of the above-mentioned coolant in the gas phase is expressed as ρV [kg/m3].
According to the graph shown in
In addition, the “Estimated Value According to Equation (1′)” column in Table 3 lists the optimal values of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 calculated by the above-mentioned equation (1′). According to these results, it can be understood that the value estimated by the above-mentioned equation (1′) is greater by two at the maximum relative to the optimal number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 derived by numerical analysis.
Accordingly, by setting the lower limit of the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 to a number that is two fewer than the optimal value of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 estimated by the above-mentioned equation (1′), the number of the flat, multi-hole pipes 2 belonging to the first flat, multi-hole pipe group 21 can be easily optimized, and the amount of heat exchanged by the entire heat exchanger can be further increased.
As described above, although a configuration example of the parallel-flow-type heat exchanger according to the present invention was explained based on Working Example 1 to Working Example 3, embodiments of the parallel-flow-type heat exchanger according to the present invention are not limited to the aspects recited in the working examples described above, and the configurations can be modified as appropriate within a scope that does not depart from the gist of the present invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/002855 | 1/26/2022 | WO |
