JP2022042066A - Parallel flow-type heat exchanger and air conditioner - Google Patents

Abstract

To provide a parallel flow type heat exchanger capable of increasing a heat exchange amount while suppressing increase of pressure loss, and an air conditioner including the heat exchanger.SOLUTION: A parallel flow type heat exchanger 1 has: a core 11 in which a plurality of flat porous tubes 2 are arranged in parallel with each other through fins 3, and the flat porous tubes 2 and fins 3 are alternately laminated in a vertical direction; a first header 4 disposed at one end of the core 11 in a longitudinal direction of the flat porous tubes 2; and a second header 5 disposed at the other end of the core 11 in the longitudinal direction. The plurality of flat porous tubes 2 are divided into a plurality of flat porous tube groups including a first flat porous tube group 21 positioned at an uppermost part of the core 11, and a second flat porous tube group 22 adjacent to a lower part of the first flat porous tube group 21. The number of flat porous tubes 2 belonging to the second flat porous tube group 22 is 14 or more, and the number of the flat porous tubes 2 belonging to the first flat porous tube group 21 is the number of the flat porous tubes 2 belonging to the second flat porous tube group 22, or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a parallel flow type heat exchanger and an air conditioner.

The air conditioner incorporates a condenser for condensing the refrigerant. The condenser is of a so-called parallel flow type, which includes a core in which flat multi-hole tubes and corrugated fins are alternately laminated, and headers arranged at both ends of the flat multi-hole tube in the longitudinal direction in the core. Heat exchangers are often used.

As an example of this type of heat exchanger, Patent Document 1 comprises a plurality of tubes, corrugated fins arranged between adjacent tubes, and a tank connected to the end of the tubes. Described is a refrigerant condenser in which the plurality of tubes are divided into a plurality of tube groups by a separator provided in the tank, and the refrigerant flows through the plurality of tube groups.

Conventionally, this type of heat exchanger is configured so that the number of tubes belonging to the tube group located at the uppermost stream of the refrigerant flow is the largest, and the number of tubes belonging to each tube group decreases toward the downstream. There is. The reason for this is as follows. It is known that the heat transfer coefficient and pressure loss in general in-pipe condensation heat transfer are greatly affected by the mass velocity of the refrigerant and the quality of the refrigerant (that is, the degree of condensation). Specifically, the heat transfer coefficient and pressure loss in the heat transfer of condensation in the pipe tend to decrease as the mass velocity of the refrigerant decreases. Further, the heat transfer coefficient and the pressure loss in the heat transfer for condensation in the pipe tend to decrease as the condensation of the refrigerant progresses and the quality becomes lower.

The refrigerant in the gas phase state flows into the tube group located at the uppermost stream of the refrigerant condenser, and flows out to the tube group on the downstream side while condensing in the tube. Therefore, in the tube group located at the uppermost stream of the refrigerant condenser, the heat transfer coefficient tends to be high, but the pressure loss tends to be high. Therefore, in the conventional refrigerant condenser, by increasing the number of tubes belonging to the tube group located at the uppermost stream, a high heat transfer coefficient is realized while suppressing an increase in pressure loss due to a high quality refrigerant. I am trying to do it.

On the other hand, in the tube group downstream from the tube group located in the uppermost stream, the heat transfer coefficient and the pressure loss are lower than those in the tube group located in the uppermost stream because the condensation of the refrigerant is progressing. Therefore, in the conventional refrigerant condenser, the heat transfer coefficient and the pressure loss are optimized by reducing the number of tubes belonging to each tube group as the quality of the refrigerant decreases.

Japanese Unexamined Patent Publication No. 3-59364

However, a heat exchanger having a larger heat exchange amount than the refrigerant condenser of Patent Document 1 is strongly desired.

The present invention has been made in view of this background, and provides a parallel flow type heat exchanger capable of increasing the amount of heat exchange while suppressing an increase in pressure loss, and an air conditioner equipped with this heat exchanger. It is what we are trying to provide.

In one aspect of the present invention, a plurality of flat multi-hole pipes configured to allow flow of a refrigerant are arranged in parallel via fins, and the flat multi-hole pipes and the fins are alternately laminated in the vertical direction. When,
A first header arranged at one end of the core in the longitudinal direction of the flat multi-hole tube and connected to the flat multi-hole tube.
It has a second header located at the other end of the core in the longitudinal direction and connected to the flat multi-hole tube.
The plurality of the flat multi-hole tubes include a first flat multi-hole tube group located at the uppermost part of the core and a second flat multi-hole tube group adjacent to the lower side of the first flat multi-hole tube group. It is divided into the flat multi-hole tube group of
The first header and the second header are configured so that the refrigerant can sequentially pass through the plurality of flat multi-hole pipe groups from the upper side to the lower side.
The number of the flat multi-hole tubes belonging to the second flat multi-hole tube group is 14 or more.
The number of the flat multi-hole tubes belonging to the first flat multi-hole tube group is less than or equal to the number of the flat multi-hole tubes belonging to the second flat multi-hole tube group in the parallel flow type heat exchanger.

Another aspect of the present invention is an air conditioner having the parallel flow type heat exchanger of the above aspect and the refrigerant existing inside the parallel flow type heat exchanger.

The core of the parallel flow type heat exchanger (hereinafter referred to as "heat exchanger") has a plurality of flat multi-hole tubes, and the plurality of flat multi-hole tubes are the first arranged at the uppermost position. It is divided into a plurality of flat multi-hole tube groups including a flat multi-hole tube group and a second flat multi-hole tube group arranged adjacent to the lower side of the first flat multi-hole tube group. The number of flat multi-hole tubes belonging to the second flat multi-hole tube group is 14 or more, and the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is flat belonging to the second flat multi-hole tube group. It is less than the number of multi-hole pipes.

As described above, the conventional heat exchanger is configured so that the number of tubes in the upstream tube group through which the high quality refrigerant flows is larger than that in the downstream tube group in which the quality of the refrigerant is deteriorated to some extent. .. However, as a result of diligent studies by the present inventors, the flat multi-hole tube has a peculiar heat transfer characteristic that the heat transfer coefficient is less affected by the mass velocity of the refrigerant and the quality of the refrigerant when the condensation of the refrigerant progresses to some extent. It was found that it was doing. By utilizing such heat transfer characteristics, the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is set to be equal to or less than the number of flat multi-hole tubes belonging to the second flat multi-hole tube group. It is possible to increase the effect of increasing the heat exchange area rather than the effect of lowering the heat transfer rate in the hole tube group, and increase the heat exchange amount in the second flat multi-hole tube group.

The heat exchanger is configured such that the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is equal to or less than the number of flat multi-hole tubes belonging to the second flat multi-hole tube group. Therefore, the heat exchanger can increase the amount of heat exchange in the second flat multi-hole tube group while suppressing the increase in pressure loss. As a result, the amount of heat exchange can be increased for the heat exchanger as a whole.

As described above, according to the heat exchanger of the above-described aspect, it is possible to increase the amount of heat exchange while suppressing the increase in pressure loss.

Further, since the air conditioner has the heat exchanger of the above-described embodiment, it is possible to increase the heat exchange amount while suppressing the increase in the pressure loss in the heat exchanger.

FIG. 1 is a cross-sectional view showing a main part of the parallel flow type heat exchanger in the first embodiment. FIG. 2 is a cross-sectional view of the flat multi-hole tube in Example 1. FIG. 3 is an explanatory diagram schematically showing the relationship between the position of the refrigerant in the flow direction and the amount of heat exchange in each test piece of Example 2. FIG. 4 is an explanatory diagram of an analysis model used for the numerical analysis in the second embodiment. FIG. 5 is an explanatory diagram schematically showing the calculation performed in each cell in the second embodiment. FIG. 6 is a graph showing the optimum value of the number of flat multi-hole tubes belonging to the first flat multi-hole tube group in Example 3.

The core of the heat exchanger has a plurality of flat multi-hole tubes. The total number of flat multi-hole tubes included in the heat exchanger can be appropriately set according to the dimensions of the heat exchanger, the required rated capacity, the pressure loss, and the like. The total number of flat multi-hole tubes may be, for example, 28 or more and 168 or less.

The plurality of flat multi-hole tubes are divided into a plurality of flat multi-hole tube groups including a first flat multi-hole tube group and a second flat multi-hole tube group. For example, the plurality of flat multi-hole tubes in the heat exchanger are the first flat multi-hole tube group located at the uppermost position and the second flat multi-hole tube group arranged adjacent to the lower side of the first flat multi-hole tube group. The tube group, the third flat multi-hole tube group arranged adjacent to the lower side of the second flat multi-hole tube group, and the fourth flat multi-hole tube group arranged adjacent to the lower side of the third flat multi-hole tube group. It may be divided into four flat multi-hole tube groups with a tube group.

The first header and the second header are configured so that the refrigerant can sequentially pass through a plurality of flat multi-hole pipe groups from the upper side to the lower side. For example, when the heat exchanger has four flat multi-hole pipe groups, in the first header and the second header, the refrigerant is the first flat multi-hole pipe group, the second flat multi-hole pipe group, and the second header. It suffices if it is configured to sequentially pass through the 3 flat multi-hole tube group and the 4th flat multi-hole tube group.

In order to realize such an embodiment, for example, the internal space of the first header is connected to the end portion of the first flat multi-hole tube group, the second flat multi-hole tube group, and the third flat. The inside of the second header is divided into three spaces, a second turn portion connected to both ends of the multi-hole tube group and an outlet portion connected to the end of the fourth flat multi-hole tube group. Both the first turn portion connecting the space to the ends of both the first flat multi-hole tube group and the second flat multi-hole tube group, and the third flat multi-hole tube group and the fourth flat multi-hole tube group. It suffices to divide into two spaces of the third turn part connected to the end part of. In this case, by supplying the refrigerant to the inlet portion of the first header, the refrigerant is the first flat multi-hole tube group, the first turn portion, the second flat multi-hole tube group, the second turn portion, and the third flat multi-hole tube group. It passes through the tube group, the third turn portion, and the fourth flat multi-hole tube group in sequence. Then, by discharging the refrigerant from the outlet of the first header to the outside of the heat exchanger, the refrigerant can be circulated in the heat exchanger.

The number of flat multi-hole tubes belonging to the second flat multi-hole tube group is 14 or more, and is less than or equal to the number of flat multi-hole tubes belonging to the first flat multi-hole tube group. As a result, the amount of heat exchange when the refrigerant passes through the second flat multi-hole tube group can be increased, and eventually the amount of heat exchange in the entire heat exchanger can be increased. From the viewpoint of the balance between the pressure loss of the heat exchanger and the amount of heat exchange, the number of flat multi-hole tubes belonging to the second flat multi-hole tube group is the number of each flat multi-hole tube group other than the second flat multi-hole tube group. It is preferable that the number is equal to or greater than the number of flat multi-hole tubes belonging to.

Specifically, for example, when the heat exchanger has four flat multi-hole tubes, the number of flat multi-hole tubes belonging to the second flat multi-hole tube group is the total number of flat multi-hole tubes of the heat exchanger. It can be 35% or more and 79% or less, preferably 35% or more and 75% or less, and more preferably 35% or more and 60% or less.

The number of flat multi-hole tubes belonging to the first flat multi-hole tube group is less than or equal to the number of flat multi-hole tubes belonging to the second flat multi-hole tube group. Since the refrigerant flowing into the first flat multi-hole tube group is in a gas phase state, that is, a refrigerant having high quality, the heat transfer coefficient when the refrigerant passes through the first flat multi-hole tube group tends to be relatively high. .. Further, when the number of flat multi-hole pipes belonging to the first flat multi-hole pipe group is reduced, the heat exchange area is reduced and the mass velocity of the refrigerant is increased. Therefore, even if the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is less than the number of flat multi-hole tubes belonging to the second flat multi-hole tube group, the amount of heat exchange in the first flat multi-hole tube group Can be suppressed. As a result, the amount of heat exchange in the entire heat exchanger can be increased.

When the heat exchanger has three or more flat multi-hole tube groups, the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is the third flat multi-hole tube group and the third flat multi-hole tube group. It is preferable that the number is larger than the number of flat multi-hole tubes belonging to the flat multi-hole tube group located below the hole tube group. In this case, the pressure loss when the refrigerant passes through the first flat multi-hole tube group can be further reduced, and the heat exchange amount can be further increased. As a result, the pressure loss in the entire heat exchanger can be further reduced and the amount of heat exchange can be increased.

Further, the heat exchanger may be designed to exhibit excellent heat exchange performance when a specific refrigerant is used. In such a case, it is more preferable that the number N ₁ [lines] of the flat multi-hole tubes belonging to the first flat multi-hole tube group satisfies the relationship of the following formula (1).
N ₁ > N x 0.0014 x ΔP _TP ^0.48737 -2 ... (1)

However, N [book] in the above formula (1) is the total number of flat multi-hole tubes possessed by the heat exchanger. The value of ΔP _TP is the pressure loss of the heat exchanger. For the values of ΔP _TP , the mass flow rate of the refrigerant flowing inside the parallel flow heat exchanger is _mref [kg / s], the flow path cross-sectional area of the flat multi-hole pipe is A _tube [m ² ], and the above. The hydraulic diameter of the flat multi-hole tube is D _h [m], the length of the flat multi-hole tube is L _tube [m], the viscosity of the refrigerant in the liquid phase is μ _L [Pa · s], and the refrigerant in the gas phase. The viscosity of the refrigerant is μ _V [Pa · s], the density of the refrigerant in the liquid phase is ρ _L [kg / m ³ ], and the density of the refrigerant in the gas phase is ρ _V [kg / m ³ ]. It is calculated by the formulas (2) to (4).
ΔP _TP = 0.0661 × C ₁ × Γ ^-1.841 ... (2)
C ₁ = m _ref ^1.75 x A _tube ^-1.75 x D _h ^-0.75 x μ _L ^0.25 x ρ _L ^-1 x 4 x L _tube ... (3)
Γ = (ρ _V / ρ _L ) ^0.5 × (μ _L / μ _V ) ^0.125 ... (4)

In this way, by keeping the number of flat multi-hole pipes belonging to the first flat multi-hole pipe group within the range in consideration of the physical characteristics of the refrigerant, the balance between the amount of heat exchange and the pressure loss in the first flat multi-hole pipe group is achieved. Can be optimized. As a result, the pressure loss in the entire heat exchanger can be further reduced and the amount of heat exchange can be increased.

The equations (1) to (4) are determined based on the following ideas. That is, as a result of trial and error studies by the inventors using numerical analysis, the optimum number N ₁ of the flat multi-hole tubes belonging to the first flat multi-hole tube group is the pressure loss ΔP of the heat exchanger. It was found that it varies greatly depending on the size of _TP . The pressure loss ΔP _TP of the heat exchanger is considered to occur mainly when the refrigerant passes through the flat multi-hole tube.

Assuming that the flow of the refrigerant in the flat multi-hole pipe is turbulent, the pressure loss ΔP _SP when the refrigerant passes through the flat multi-hole pipe is expressed by Darcy-Weisbach's equation (see equation (5) below). Will be done.

In the above formula (5), the following formula (6) can be derived by using the Bradius pipe friction coefficient for the pipe friction coefficient f.

Since G in the formula (6) can be expressed as _mref / A _tube , the relationship of the following formula (3') can be derived by rearranging the formula (6).
ΔP _SP ^∝m _ref ^1.75 × A _tube -1.75 × D _h ^−0.75 × μ _L ^0.25 × ρ _L ^-1 × 4 × L _tube・ ・ ・ (3')

From the above, in expressing the pressure loss ΔP _TP of the heat exchanger, the parameter C ₁ (the above equation (3)) related to the pressure loss ΔP _SP when the refrigerant passes through the flat multi-hole pipe may be used. Recognize.

Further, the refrigerant flowing in the heat exchanger is a gas-liquid two-phase flow. Therefore, in calculating the magnitude of the pressure loss ΔP _TP of the heat exchanger, not only the parameter C1 described above but also the parameter Γ for considering the influence of the gas-liquid two- _phase flow (the above equation (4). )) Need to be introduced.

Summarizing the results of the numerical analysis performed by the inventors based on the above, the optimum number N 1'of the flat multi-hole tubes belonging to the first flat multi-hole tube group can be approximated by the following equation ( ₁ '), and It was found that the pressure loss ΔP _TP of the heat exchanger can be approximated by the above equation (2).
N ₁ '= N x 0.0014 x ΔP _TP ^0.48737 ... (1')

Then, as described in Examples described later, the optimum number N 1'of flat multi-hole tubes predicted by the above equation ( ₁ ') is the optimum number N of flat multi-hole tubes derived by numerical analysis. Up to 2 more than ₁ . Therefore, the equation ( ₁ ) can be derived by subtracting 2 from both sides of the equation (1') and setting the left side as N1.

When the heat exchanger has three or more flat multi-hole tube groups, the flats belonging to the flat multi-hole tube group located below the third flat multi-hole tube group and the third flat multi-hole tube group. The number of multi-hole tubes is not particularly limited. However, the quality of the refrigerant flowing through the flat multi-hole tube group located below is usually equal to or lower than the quality of the refrigerant flowing through the flat multi-hole tube group located above. Therefore, by setting the number of flat multi-hole tubes belonging to the flat multi-hole tube group located below to be less than the number of flat multi-hole tubes belonging to the flat multi-hole tube group located above, the heat exchanger as a whole can be used. The pressure loss can be further reduced and the amount of heat exchange can be further increased.

For example, when the heat exchanger has four flat multi-hole tubes, the number of flat multi-hole tubes belonging to the third flat multi-hole tube group is 5 of the total number of flat multi-hole tubes of the heat exchanger. It can be% or more and 21% or less. From the viewpoint of the balance between the pressure loss and the amount of heat exchange, the number of flat multi-hole tubes belonging to the third flat multi-hole tube group is preferably 7% or more and 17% or less, and 9% or more and 14% or less. It is more preferable to do so.

Similarly, the number of flat multi-hole tubes belonging to the fourth flat multi-hole tube group can be, for example, 4% or more and 14% or less of the total number of flat multi-hole tubes possessed by the heat exchanger. From the viewpoint of the balance between the pressure loss and the amount of heat exchange, the number of flat multi-hole tubes belonging to the 4th flat multi-hole tube group is preferably 6% or more and 12% or less, and 6% or more and 10% or less. It is more preferable to do so.

The flat multi-hole tube in the heat exchanger includes a pair of flat wall portions arranged so as to face each other at intervals, a connecting wall portion connecting both ends in the width direction of the flat wall portion, and a flat wall portion. It has a partition wall portion that divides the internal space surrounded by the connection wall portion into a plurality of refrigerant flow paths. The shape of each refrigerant flow path in a cross section perpendicular to the longitudinal direction of a flat multi-hole tube is, for example, circular, elliptical, oval, semi-circular, triangular, quadrangular in a cross section perpendicular to the longitudinal direction of the flat multi-hole tube. It can take various aspects such as. The number of refrigerant flow paths in the flat multi-hole pipe can be appropriately set from, for example, a range of 4 or more and 20 or less.

The refrigerant flow path of the flat multi-hole pipe is preferably non-circular, that is, has a shape having one or more corners in a cross section perpendicular to the longitudinal direction. By incorporating the flat multi-hole pipe provided with the refrigerant flow path into the second flat multi-hole pipe group, it is possible to further suppress the decrease in the heat transfer coefficient in the second flat multi-hole pipe group. As a result, the effect of increasing the heat exchange amount in the second flat multi-hole tube group can be further enhanced, and by extension, the heat exchange amount of the entire heat exchanger can be further increased. The non-circular cross-sectional shape described above includes, for example, a semicircular shape, a triangular shape, a quadrangular shape, or the like. From the viewpoint of further enhancing the above-mentioned effects, it is more preferable that the refrigerant flow path of the flat multi-hole pipe has a shape in which the contour in the cross section perpendicular to the longitudinal direction is composed only of straight lines. Such a cross-sectional shape includes, for example, a shape such as a triangle or a quadrangle.

The hydraulic diameter D _h of the flat multi-hole pipe can be appropriately set from the range of, for example, 0.00032 m or more and 0.001 m or less. In this case, the heat transfer efficiency in each flat multi-hole tube can be further improved. The hydraulic diameter D _h of the above-mentioned flat multi-hole pipe is described below using the channel cross-sectional area A _tube [m ² ] of the flat multi-hole pipe and the flow path wet edge length S _tube [m] of the flat multi-hole pipe. It is represented by the equation (7).
D _h = 4 × A _tube / _Tube ... (7)

Further, the length L _tube of the flat multi-hole tube can be appropriately set from a range of 0.4 m or more and 0.9 m or less. In this case, the heat transfer efficiency in each flat multi-hole tube can be further improved.

When the heat exchanger is configured to use R32 (that is, difluoromethane) as a refrigerant, the hydraulic diameter D _h of the flat multi-hole pipe is 0.00032 m or more and 0.001 m or less, and the length L. _{The tube} is preferably 0.4 m or more and 0.9 m or less. The flat multi-hole tube having the hydraulic diameter D _h and the length L _tube in the specific range can realize particularly excellent heat exchange efficiency when R32 is used as the refrigerant. Therefore, a flat multi-hole tube with a hydraulic diameter D _h and a length L _tube in the particular range is suitable for heat exchangers configured to use R32 as the refrigerant.

The heat exchanger may have a rated capacity of, for example, 2 kW or more and 12 kW or less. The rated capacity of the heat exchanger described above is the value of the rated cooling capacity obtained by the cooling capacity test specified in JIS B8615-1: 2013.

The use of the heat exchanger is not particularly limited, and may be configured to be used for an outdoor unit in a stationary air conditioner, for example, for home use or commercial use. Further, the heat exchanger may be configured to be used in a condenser of an air conditioner for a vehicle, for example.

By connecting the heat exchanger to components of an air conditioner such as a compressor, an expansion valve, a pump, and a heat exchanger different from the heat exchanger via a refrigerant pipe, and filling the inside with a refrigerant. , Air conditioners can be configured.

The refrigerant used in the air conditioner is not particularly limited, and for example, a hydrofluorocarbon refrigerant such as R410A and R32, a hydrofluoroolefin refrigerant such as R1234yf and R1123, and the like can be used. The refrigerant used in the air conditioner is preferably R32. Since R32 has a relatively large latent heat of condensation and a high thermal conductivity, it is possible to more easily reduce the size and increase the efficiency of the air conditioner.

In the air conditioner, the total number of flat multi-hole tubes N [lines] and the number of flat multi-hole tubes belonging to the first flat multi-hole tube group N ₁ [lines] satisfy the relationship of the above formula (1). It is preferable to have a parallel flow type heat exchanger.
N ₁ > N x 0.0014 x ΔP _TP ^0.48737 -2 ... (1)

As described above, by keeping the number of flat multi-hole pipes belonging to the first flat multi-hole pipe group within the range considering the physical characteristics of the refrigerant, the increase in pressure loss in the entire heat exchanger is more effectively suppressed. At the same time, the amount of heat exchange can be increased. As a result, the energy consumption of the air conditioner can be further reduced.

The air conditioner is configured so that the mass flow rate _mref of the refrigerant inside the heat exchanger can be set, for example, from a range of 0.01 kg / s or more and 0.03333 kg / s or less. May be good. In this case, it is possible to more effectively suppress the increase in pressure loss in the heat exchanger and further increase the amount of heat exchange. As a result, the energy consumption of the air conditioner can be further reduced.

In particular, when the refrigerant of the air conditioner is R32, the mass flow rate _mref of the refrigerant inside the heat exchanger is set within the range of 0.01 kg / s or more and 0.03333 kg / s or less. The action and effect can be achieved more reliably.

From the same viewpoint, when the refrigerant of the air conditioner is R32, the hydraulic diameter D _h of the flat multi-hole pipe in the heat exchanger is 0.00032 m or more and 0.001 m or less, and the length L _tube is 0.4 m. It is particularly preferable that the diameter is 0.9 m or less and the mass flow rate _mref of the refrigerant is within the range of 0.01 kg / s or more and 0.03333 kg / s or less.

An embodiment of the parallel flow heat exchanger will be described.

(Example 1)
As shown in FIG. 1, in the parallel flow type heat exchanger 1 of this example, a plurality of flat multi-hole pipes 2 for flowing a refrigerant are arranged in parallel via fins 3, and the flat multi-hole pipes 2 and fins 3 are arranged. The core 11 is alternately laminated in the vertical direction, the first header 4 is arranged at one end of the core 11 in the longitudinal direction of the flat multi-hole tube 2, and the second header 4 is arranged at the other end of the core 11 in the longitudinal direction. It has a header 5 and. The plurality of flat multi-hole tubes 2 include a first flat multi-hole tube group 21 located at the uppermost part of the core 11 and a second flat multi-hole tube group 22 adjacent to the lower part of the first flat multi-hole tube group 21. It is divided into a plurality of flat multi-hole tube groups 21 to 24 including.

The number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 is 14 or more. Further, the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 is less than the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22. Hereinafter, the configuration of the heat exchanger 1 of this example will be described in more detail.

Each component constituting the heat exchanger 1 may be made of an aluminum material (including aluminum and an aluminum alloy). For example, the flat multi-hole tube 2 may be made of 1000 series aluminum or 3000 series alloy. By using a 3000 series alloy as the material of the flat multi-hole pipe 2, a refrigerant having a higher pressure can be used. The fin 3 may be made of, for example, 1000 series aluminum or 3000 series alloy. Further, the fin 3 may be composed of a brazing sheet in which a brazing material made of a 4000 series alloy is laminated on both sides of a core material made of 1000 series aluminum or a 3000 series alloy.

The first header 4 and the second header 5 may be made of 1000 series aluminum or 3000 series alloy. Further, the first header 4 and the second header 5 may be composed of a brazing sheet in which a brazing material made of a 4000 series alloy is laminated on both sides of a core material made of 1000 series aluminum or a 3000 series alloy.

As shown in FIG. 1, the core 11 of the heat exchanger 1 includes a plurality of flat multi-hole pipes 2 arranged at intervals in the vertical direction, and fins 3 interposed between the flat multi-hole pipes 2. have. The flat multi-hole tube 2 and the fin 3 are joined by brazing. The core 11 of this example further has a side sheet 111 made of an aluminum material. The side sheet 111 is joined to the flat multi-hole pipe 2a arranged at the upper end and the flat multi-hole pipe 2b arranged at the lower end of the plurality of flat multi-hole pipes 2 via fins 3.

The dimensions of the core 11 can be appropriately set according to a desired heat exchange amount, an arrangement space allowed in the air conditioner, and the like. Specifically, the outer dimensions of the core 11 in the vertical direction, that is, in the stacking direction of the core 11, may be appropriately set from a range of 250 mm or more and 1500 mm or less. Further, the outer dimension in the depth direction of the core 11, that is, the outer dimension in the width direction of the flat multi-hole tube 2 may be appropriately set from a range of 6 mm or more and 20 mm or less.

The outer dimension in the width direction of the core may be set according to the desired effective length of the flat multi-hole tube 2, that is, the distance from the first header 4 to the second header 5 in the longitudinal direction of the flat multi-hole tube 2. .. The effective length of the flat multi-hole tube 2 can be appropriately set from, for example, a range of 400 mm or more and 1000 mm or less.

The total number of flat multi-hole tubes 2 included in the core 11 can be appropriately set from a range of 28 or more and 168 or less. For example, in this example, the total number of flat multi-hole tubes 2 possessed by the core 11 can be 52.

The flat multi-hole tube 2 in the heat exchanger 1 of this example is divided into four flat multi-hole tube groups of a first flat multi-hole tube group 21 to a fourth flat multi-hole tube group 24. The first flat multi-hole tube group 21 is arranged at the uppermost position in the core 11. The second flat multi-hole tube group 22 is arranged adjacent to the lower side of the first flat multi-hole tube group 21. The third flat multi-hole tube group 23 is arranged adjacent to the lower side of the second flat multi-hole tube group 22. The fourth flat multi-hole tube group 24 is arranged adjacent to the lower side of the third flat multi-hole tube group 23, and is located at the lowermost position in the core 11.

The internal space of the first header 4 is the entrance portion 41 connected to the end of the first flat multi-hole tube group 21, and both the second flat multi-hole tube group 22 and the third flat multi-hole tube group 23. It is divided into three spaces, a second turn portion 42 connected to the end portion and an outlet portion 43 connected to the end portion of the fourth flat multi-hole tube group 24. First partition plates 44, 45 for partitioning these spaces are provided between the entrance portion 41 and the second turn portion 42, and between the second turn portion 42 and the exit portion 43.

The internal space of the second header 5 includes a first turn portion 51 connected to both ends of the first flat multi-hole tube group 21 and the second flat multi-hole tube group 22, and a third flat multi-hole tube group. It is divided into two spaces, a third turn portion 52 connected to both ends of the 23 and the fourth flat multi-hole tube group 24. A second partition plate 53 for partitioning the first turn portion 51 and the third turn portion 52 is provided.

Further, a refrigerant supply pipe 6 configured to be able to supply a refrigerant in the heat exchanger 1 is connected to the inlet portion 41 of the first header 4, and the refrigerant in the heat exchanger 1 is connected to the outlet portion 43. A refrigerant discharge pipe 7 configured to be able to discharge the air to the outside is connected.

Therefore, the flow of the refrigerant in the heat exchanger 1 of this example is as follows. That is, the refrigerant flowing into the inlet portion 41 from the refrigerant supply pipe 6 is distributed to each flat multi-hole pipe 2 belonging to the first flat multi-hole pipe group 21 at the inlet portion 41. The refrigerant that has passed through the first flat multi-hole tube group 21 flows into the first turn portion 51 in the second header 5. The refrigerant merged in the first turn portion 51 is distributed to each flat multi-hole pipe 2 belonging to the second flat multi-hole pipe group 22. The refrigerant that has passed through the second flat multi-hole tube group 22 is subsequently the second turn portion 42 in the first header 4, the third flat multi-hole tube group 23, the third turn portion 52 in the second header 5, and the fourth flat portion. It sequentially passes through the multi-hole tube group 24 and flows into the outlet portion 43 of the first header 4. Then, the refrigerant merged at the outlet portion 43 is discharged to the outside of the heat exchanger 1 from the refrigerant discharge pipe 7.

In the heat exchanger 1 of this example, the number of flat multi-hole tubes 2 belonging to each flat multi-hole tube group 21 to 24 is 14 or more as the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22. And the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 may be set to be less than or equal to the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22.

For example, in this example, as shown in FIG. 1, the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 is 19, and the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 is 19. The number of flat multi-hole tubes 2 belonging to the third flat multi-hole tube group 23 is four, and the number of flat multi-hole tubes 2 belonging to the fourth flat multi-hole tube group 24 is four. Can be done.

As shown in FIG. 2, the flat multi-hole tube 2 of this example has a rectangular shape in a cross section perpendicular to the longitudinal direction. The outer dimensions of the flat multi-hole tube 2 can be appropriately set from a range of, for example, a thickness of 1.1 mm or more and 3.0 mm or less and a width of 6 mm or more and 20 mm or less. For example, in this example, the thickness of the flat multi-hole tube 2 can be 1.15 mm and the width can be 13.85 mm.

The flat multi-hole pipe 2 includes a pair of flat wall portions 211 arranged so as to face each other at intervals, a connecting wall portion 212 connecting both ends of the flat wall portion 211 in the width direction, and a flat wall portion 211. It has a partition wall portion 214 that divides the internal space surrounded by the connection wall portion 212 into a plurality of refrigerant flow paths 213. The flat multi-hole tube 2 may have a rectangular shape as shown in FIG. 2 or an oval shape as shown in FIG. 2 in a cross section perpendicular to the longitudinal direction. As shown in FIG. 1, fins 3 are joined to the flat wall portion 211 of the flat multi-hole pipe 2.

The number of refrigerant flow paths 213 in the flat multi-hole pipe 2 can be appropriately set from, for example, 4 or more and 20 or less. For example, in this example, as shown in FIG. 2, the number of the refrigerant flow paths 213 in the flat multi-hole pipe 2 can be 15. Further, the refrigerant flow path 213 in the flat multi-hole pipe 2 of this example has a rectangular shape in a cross section perpendicular to the longitudinal direction.

As shown in FIG. 1, corrugated fins can be used as the fins 3. The plate thickness of the fin 3 can be, for example, 0.06 to 0.12 mm. Further, the height of the fin 3 in the vertical direction can be 6 to 8 mm.

A louver protruding in the thickness direction of the fin 3 may be provided in the flat portion 31 (see FIG. 1) of the fin 3, that is, the portion between the bent portions 32 joined to the flat multi-hole pipe 2. The number of louvers can be 6 to 16 per flat portion 31 in one place. Further, the louver can be extended in a direction inclined by 20 to 60 degrees with respect to the width direction of the fin 3. In FIG. 1, the description of the louver is omitted for convenience.

The first header 4 has a header main body 46 having a tubular shape extending in the vertical direction, that is, in the stacking direction of the core 11, and caps 47 and 48 that close the upper ends and the lower ends of the header main body 46.

As the header main body 46, for example, a cylindrical tube having an outer diameter of 15 to 25 mm and a wall thickness of 1.0 to 2.5 mm can be used, but the shape is not limited to this. Further, the caps 47 and 48 and the first partition plates 44 and 45 are joined to the header main body 46 by brazing.

The internal space of the first header 4 surrounded by the header body 46 and the caps 47 and 48 is divided into three spaces by two first partition plates 44 and 45. The portion from the upper end 411 of the first header 4 to the first partition plate 44 arranged above constitutes the inlet portion 41 of the first header 4. The end of the flat multi-hole tube 2 belonging to the first flat multi-hole tube group 21 is inserted into the inlet portion 41.

Further, a refrigerant supply pipe 6 for supplying a refrigerant into the heat exchanger 1 is connected to the inlet portion 41. The end of the refrigerant supply pipe 6 is inserted into the inlet portion 41, and the refrigerant supply pipe 6 and each of 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. There is. As a result, the inlet portion 41 is configured so that the refrigerant supplied from the refrigerant supply pipe 6 can be distributed to each flat multi-hole pipe 2 belonging to the first flat multi-hole pipe group 21.

The portion of the first header 4 from the first partition plate 44 arranged above to the first partition plate 45 arranged below constitutes the second turn portion 42. The end of the flat multi-hole tube 2 belonging to the second flat multi-hole tube group 22 and the third flat multi-hole tube group 23 is inserted into the second turn portion 42. As a result, the second turn portion 42 merges the refrigerant that has passed through the flat multi-hole pipes 2 belonging to the second flat multi-hole pipe group 22, and the flat multi-hole pipes belonging to the third flat multi-hole pipe group 23. It is configured so that the refrigerant can be distributed to 2.

The portion from the lower end 412 of the first header 4 to the first partition plate 45 arranged below constitutes the outlet portion 43. The end of the flat multi-hole tube 2 belonging to the fourth flat multi-hole tube group 24 is inserted into the outlet portion 43.

Further, a refrigerant discharge pipe 7 for discharging the refrigerant in the heat exchanger 1 to the outside is connected to the outlet portion 43. The end of the refrigerant discharge pipe 7 is inserted into the outlet portion 43, and the refrigerant discharge pipe 7 and each flat multi-hole pipe 2 belonging to the fourth flat multi-hole pipe group 24 communicate with each other via the outlet portion 43. There is. As a result, the outlet portion 43 merges the refrigerant discharged from each of the flat multi-hole pipes 2 belonging to the fourth flat multi-hole pipe group 24, and discharges the refrigerant to the outside of the heat exchanger 1 via the refrigerant discharge pipe 7. It is configured to be able to.

The flat multi-hole pipe 2, the refrigerant supply pipe 6, and the refrigerant discharge pipe 7 inserted into the first header 4 are joined to the header body 46 of the first header 4 by brazing.

The second header 5 has a header body 56 having a tubular shape extending in the vertical direction, that is, in the stacking direction of the core 11, and caps 57 and 58 that close the upper ends and the lower ends of the header body 56. Further, the internal space of the second header 5 surrounded by the header body 56 and the caps 57 and 58 is divided into two spaces by one second partition plate 53.

As the header main body 56, for example, a cylindrical tube having an outer diameter of 15 to 25 mm and a wall thickness of 1.0 to 2.5 mm can be used as in the header main body 46 of the first header 4, but the shape is limited to this. It is not something that is done. Further, the caps 57, 58 and the second partition plate 53 are joined to the header main body 56 by brazing.

The portion from the upper end 511 of the second header 5 to the second partition plate 53 constitutes the first turn portion 51. The end of the flat multi-hole tube 2 belonging to the first flat multi-hole tube group 21 and the second flat multi-hole tube group 22 is inserted into the first turn portion 51. As a result, the second turn portion 42 merges the refrigerant that has passed through the flat multi-hole pipes 2 belonging to the first flat multi-hole pipe group 21, and the flat multi-hole pipes belonging to the second flat multi-hole pipe group 22. It is configured so that the refrigerant can be distributed to 2.

The portion from the lower end 512 of the second header 5 to the second partition plate 53 constitutes the third turn portion 52. The end of the flat multi-hole tube 2 belonging to the third flat multi-hole tube group 23 and the fourth flat multi-hole tube group 24 is inserted into the third turn portion 52. As a result, the third turn portion 52 merges the refrigerant that has passed through each of the flat multi-hole pipes 2 belonging to the third flat multi-hole pipe group 23, and at the same time, each flat multi-hole pipe belonging to the fourth flat multi-hole pipe group 24. It is configured so that the refrigerant can be distributed to 2.

The flat multi-hole tube 2 inserted into the second header 5 is joined to the header body 56 of the second header 5 by brazing.

The core 11 of the heat exchanger 1 of this example has a plurality of flat multi-hole tube groups 21 to 24, the first flat multi-hole tube group 21, the second flat multi-hole tube group 22, and the third flat multi-hole tube group 21. The hole tube group 23 and the fourth flat multi-hole tube group 24 are configured so that the refrigerant flows in this order. Further, the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 is 14 or more, and the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 is the second flat multi-hole tube. It is less than or equal to the number of flat multi-hole tubes 2 belonging to group 22. Therefore, the heat exchanger 1 can increase the amount of heat exchange in the second flat multi-hole tube group 22 while suppressing the increase in pressure loss. As a result, the amount of heat exchange can be increased for the heat exchanger 1 as a whole.

As a result of the above, according to the heat exchanger 1 of this example, it is possible to increase the amount of heat exchange while suppressing the increase in pressure loss.

(Example 2)
In this example, two types of heat exchangers 1 (test body A and test body B) in which the number of flat multi-hole tubes 2 belonging to each flat multi-hole tube group 21 to 24 are changed are prepared, and heat exchange thereof is performed. Evaluate the amount of heat exchange in the vessel 1. The specific configuration of each test piece will be described below. In addition, among the codes used in the examples after this example, the same codes as those used in the above-mentioned examples represent the same components and the like as the components and the like in the above-mentioned examples unless otherwise specified.

<Test body A>
The basic shape of the test body A is the same as that of the heat exchanger 1 of the first embodiment. The specific dimensions and the like of each part of the test body A are as follows.
-Effective width: 664 mm
・ External dimensions in the depth direction: 13.85 mm
-Dimensions of flat multi-hole tube 2: width 13.85 mm, thickness 1.15 mm
・ Number of refrigerant flow paths in the flat multi-hole pipe 2: 15 ・ Hydraulic diameter of the flat multi-hole pipe 2 D _h : 0.530 mm
・ Channel cross-sectional area of flat multi-hole pipe 2 A _tube : 5.433 mm ²

-Total number of flat multi-hole pipes 2: 52-Number of flat multi-hole pipes 2 belonging to the first flat multi-hole pipe group 21: 19-Number of flat multi-hole pipes 2 belonging to the second flat multi-hole pipe group 22 : 25 / Number of flat multi-hole tubes 2 belonging to the 3rd flat multi-hole tube group 23: 4 / Number of flat multi-hole tubes 2 belonging to the 4th flat multi-hole tube group 24: 4

-Height of fin 3: 7.61 mm
・ Pitch of fin 3: 1.1 mm

The above-mentioned effective width is the distance from the first header 4 to the second header 5 in the longitudinal direction of the flat multi-hole tube 2, that is, heat exchange between the flat multi-hole tube 2 and the outside air is substantially performed. The length of the part. Further, the pitch of the fins 3 means the length of the period of the bent portion 32 in the fins 3.

<Test body B>
The test body B has the same configuration as the test body A except that the number of the flat multi-hole tubes 2 belonging to the flat multi-hole tube groups 21 to 24 is changed as follows.

-Number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21: 22-Number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22: 15-Third flat multi-hole tube group Number of flat multi-hole tubes 2 belonging to 23: 10 ・ Number of flat multi-hole tubes 2 belonging to the 4th flat multi-hole tube group 24: 5

Next, a method for measuring the amount of heat exchange between the test body A and the test body B will be described. First, the test body A or the test body B is installed in a wind tunnel device provided in a constant temperature and humidity test chamber. Next, the air temperature in the test chamber is set to a dry-bulb temperature: 35 ° C. and a wet-bulb temperature: 24 ° C., and air is blown from the wind tunnel device to the heat exchanger at any of the wind speeds shown in Table 1. After that, R32 is supplied as a refrigerant from the refrigerant supply pipe 6 of each test piece. The condensation temperature of R32 is 45 ° C.

Then, the refrigerant is circulated so that the temperature of the refrigerant in the refrigerant supply pipe 6 is 65 ° C. (that is, the degree of superheating: 20K) and the temperature of the refrigerant in the refrigerant discharge pipe 7 is 40 ° C. (that is, the degree of supercooling: 5K). At the same time, the heat balance between the air and the refrigerant is measured. The "heat exchange amount" column of Table 1 shows the heat exchange amount when the heat balance between the air and the refrigerant reaches a steady state. Further, in the "ratio" column of Table 1, the ratio of the heat exchange amount of the test body A to the heat exchange amount of the test body B at each wind speed is shown as a percentage (%).

As shown in Table 1, the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 is set to be equal to or greater than the number of flat multi-hole tubes 2 belonging to the other flat multi-hole tube groups 21, 23, 24. The test piece A has a smaller number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 than the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 as compared with the test body B. The amount of heat exchange can be increased at any wind velocity.

FIG. 3 is a diagram schematically showing the relationship between the position of the refrigerant in the flow direction and the amount of heat exchange in each test piece. The vertical axis of FIG. 3 shows the heat transfer coefficient α _ref between the flat multi-hole pipe 2 and the refrigerant, and the heat exchange areas Ai and _cell between the flat multi-hole pipe 2 and the refrigerant in each of the flat multi-hole pipe groups 21 to 24. Is the product of. Further, the horizontal axis of FIG. 3 is a position in the flow direction of the refrigerant when the refrigerant supply pipe 6 is used as a reference. The product of α _ref and _{Ai, cell} is a value that is an index of the heat exchange amount, and the larger the product of α _ref and _{Ai, cell} , the larger the heat exchange amount can be.

As shown in FIG. 3, when the refrigerant flows into the test piece A, first, the amount of heat is exchanged between the high quality refrigerant and the air. Therefore, at the inlet of the first flat multi-hole tube group 21, the product of α _ref and _{Ai, cell} rises sharply because of the high heat transfer coefficient α _ref derived from the high quality refrigerant. Then, the quality of the refrigerant gradually decreases as it advances in the first flat multi-hole tube group 21. Along with this, the product of α _ref and _{Ai, cell} gradually attenuates as it advances in the first flat multi-hole tube group 21.

On the other hand, in the second flat multi-hole tube group 22, the heat exchange area Ai _{and cell} with the refrigerant increase as the number of flat multi-hole tubes 2 increases. As a result, the product of α _ref and _{Ai, cell} can be increased. Further, the flat multi-hole tube 2 can suppress a decrease in the heat transfer coefficient α _ref when the refrigerant having been condensed to some extent passes through the flat multi-hole tube 2 due to the above-mentioned unique heat transfer characteristics. Therefore, by increasing the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22, the amount of heat exchange in the second flat multi-hole tube group 22 can be further increased, and as a result, as shown in FIG. The amount of heat exchange in the entire heat exchanger can be increased.

(Example 3)
In this example, the number of flat multi-hole pipes 2 belonging to the first flat multi-hole pipe group 21 will be examined. In this example, in order to examine the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21, numerical analysis is performed using the following analysis model.

4 and 5 show an outline of the analysis model. As schematically shown in FIG. 4, the analysis model has four refrigerant paths P1 to P4 corresponding to the first flat multi-hole tube group 21 to the fourth flat multi-hole tube group 24. These refrigerant paths P1 to P4 are divided into a plurality of calculation cells C in the longitudinal direction of the flat multi-hole pipe 2. Then, as schematically shown in FIG. 5, the state quantities of the refrigerant at the inlet of the cell (temperature _{ref, in} [K], pressure _{Ref, in} [Pa] and specific enthalpy h _{ref, in} [kJ / kg]. ) And the state quantity of the refrigerant at the outlet (temperature T _{ref, out} [K], pressure _{Ref, out} [Pa] and specific enthalpy h _{ref, out} based on the state quantity of air (temperature T _{air, in} [K]). By sequentially performing the operations of calculating [kJ / kg]) and the state amount of air (temperature _{Tair, out} [K]) along the flow direction of the refrigerant, the heat exchange amount and pressure loss of the entire heat exchanger, etc. Can be calculated.

The state amount of the refrigerant at the outlet of each cell can be calculated by repeatedly solving the energy conservation formula and the momentum conservation formula in the cell. Specifically, the energy conservation formula between the air and the flat multi-hole pipe 2 is used to calculate the refrigerant temperature Tref _{, out} and the specific enthalpy href _{, out} at the outlet of the cell (see the following formula (8)). And the energy conservation formula between the flat multi-hole pipe 2 and the refrigerant (see the following formula (10)) may be used.

The energy conservation formula on the air side in each cell can be expressed by the following formula (8).
α _air・ LMTD ・ A _{o, cell} = V _air・ A _{front, cell}・ ρ _air・ C _p (T _{air, out} -T _{air, in} ) ・ ・ ・ (8)

The meanings of the symbols in the above formula (8) are as follows.
α _air : Heat transfer coefficient between air and the flat multi-hole tube 2 and fin 3 [W / (m ² · K)]
A _{o, cell} : Heat exchange area between the flat multi-hole tube 2 and fin 3 per cell and air [m ² ]
V _air : Wind speed of air flowing into the air inlet of each cell [m / s]
A _{front, cell} : Area of air inlet in each cell [m ² ]
ρ _air : Density of air [kg / m ³ ]
C _p : Constant pressure specific heat of air [J / (kg · K)]
T _{air, out} : Air temperature at the air outlet of each cell [K]
T _{air, in} : Air temperature at the air inlet of each cell [K]

For the wind speed _Vair of the air flowing into the air inlet of each cell, the volumetric flow rate [m ³ / s] of the air flowing into the cell is divided by the area A _{front, cell} [m ² ] of the air inlet of the cell. It is the value that was set.

Further, the symbol LMTD in the above formula (8) is a logarithmic mean temperature difference between the temperature of the inlet / outlet of the refrigerant in each cell and the temperature of the inlet / outlet of air. Specifically, the value of LMTD can be calculated by the following formula (9) using the wall surface temperature T _wall [K] of the flat multi-hole tube 2.
LMTD = (T _{air, out} -T _{air, in} ) / log {(T _{air, out} -T _wall ) / (T _{air, in} -T _wall )} ... (9)

The energy conservation formula on the refrigerant side in each cell can be expressed by the following formula (10).
α _ref・ (T _ref -T _wall ) ・ Ai _{, cell} = M _ref・ (h _{ref, in} -h _{ref, out} ) ・ ・ ・ (10)

The meanings of the symbols in the above formula (10) are as follows.
α _ref : Heat transfer coefficient between the refrigerant and the flat multi-hole tube 2 [W / (m ² · K)]
T _ref : Refrigerant temperature [K]
A _{i, cell} : Heat exchange area between the refrigerant and the flat multi-hole pipe 2 per cell [m ² ]
M _ref : Mass flow rate of refrigerant [kg / s]
h _{ref, in} : Refrigerant ratio enthalpy at the refrigerant inlet of each cell h _{ref, out} : Refrigerant ratio enthalpy at the refrigerant outlet of each cell

Since the amount of heat exchange between the air and the flat multi-hole tube 2 and the amount of heat exchange between the flat multi-hole tube 2 and the refrigerant are equal, the right side of the equation (8) and the right side of the equation (10) are equal numbers. Can be tied with. As a result, the following equation (11) can be obtained.
V _air · A _{front, cell} · ρ _air · C _p (T _{air, out} -T _{air, in} ) = M _ref · (h _{ref, in} -h _{ref, out} ) ... (11)

The heat transfer coefficient α _air between the air and the flat multi-hole pipe 2 in the formula (8) and the heat transfer coefficient α _ref between the refrigerant and the flat multi-hole pipe 2 in the formula (10) are determined separately. can do. In addition, for the state quantity of the refrigerant at the inlet of each cell, if the cell does not exist upstream of the cell to be calculated, an appropriately set initial value is used, and when the cell exists upstream of the cell to be calculated. The state quantity at the exit of the upstream cell may be used for. Further, an appropriately set initial value may be used for the amount of air condition at the inlet of each cell.

Therefore, in the above equations (8), (10) and (11), the temperature of the air at the outlet of the air in the cell is _{Air, out} , the wall temperature of the flat multi-hole pipe 2 T _wall , and the refrigerant at the outlet of the refrigerant. There are three unknown state quantities of the specific enthalpy h _{ref and out} . On the other hand, since the equations (8), (10) and (11) are conservative equations, these unknown state quantities can be determined by using the iterative method. Specifically, these unknown state quantities may be determined using the dichotomy method.

Further, the following equation (12) may be used for the refrigerant pressures _{Ref and out} at the outlet of the refrigerant in the cell.
P _{ref, out} = P _{ref, in} -ΔP _f -ΔP _m ... (12)

The symbol ΔP _f in the above equation (12) is the value of the friction loss in the pipe based on the underground-small mountain equation, and ΔP _m is the pressure change accompanying the phase change of the refrigerant. The value of the pressure change ΔP _m accompanying the phase change of the refrigerant can be expressed by the following equation (13).
ΔP _m = G ² · (1 / ρ _V -1 / ρ _L ) · (x _{ref, in} -x _{ref, out} ) ... (13)

The meanings of the symbols in the formula (13) are as follows.
G: Mass velocity of refrigerant [kg / (m ² s)]
x _{ref, in} : Refrigerant quality at the inlet of the cell refrigerant [-]
x _{ref, out} : Refrigerant quality at the outlet of the cell refrigerant [-]

The validity of the above-mentioned analysis model can be confirmed, for example, by comparing the calculation results of the models simulating the test body A and the test body B in Example 1 with the experimental results. Table 2 shows the calculation results of the model simulating the test body A and the test body B.

As shown in Table 2, the heat exchange amount of the test body A calculated by the numerical analysis was larger than the heat exchange amount of the test body B at any wind speed. Further, the heat exchange amount of the test piece A increased as the wind speed increased. As described above, the heat exchange amount calculated by the above analysis model shows the same tendency as the experimental result. From these results, it can be understood that the above analysis model is valid.

Next, using the above analysis model, a method for distributing the flat multi-hole tube 2 having the largest heat exchange amount under each of the analysis conditions A to J shown in Table 3 is searched for. The configuration of the analysis model other than the values shown in Table 3 is as follows.

・ Effective width: 700 mm
・ External dimensions in the depth direction: 13.85 mm
・ Total number of flat multi-hole pipes 2: 52 ・ Height of fins 3: 7.61 mm
・ Pitch of fin 3: 1.1 mm

-Refrigerant: R32
・ Dry-bulb temperature of air: 35 ℃
・ Wet-bulb temperature of air: 24 ℃

・ Flat multi-hole tube A
Dimensions: width 13.85mm, thickness 1.15mm
Number of refrigerant flow paths: 15 Hydraulic diameter D _h : 0.530 mm
Channel cross-sectional area A _tube : 5.433 mm ²

・ Flat multi-hole tube B
Dimensions: width 13.85mm, thickness 1.93mm
Number of refrigerant flow paths: 13 Hydraulic diameter D _h : 0.740 mm
Channel cross-sectional area A _tube : 12.23 mm ²

Table 3 shows the optimum value of the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 under each of the analysis conditions A to J. Although not shown in the table, the optimum value of the number of flat multi-hole tubes 2 belonging to the second flat multi-hole tube group 22 is set to the first flat multi-hole tube group 21 under any of the analysis conditions A to J. It is equal to or more than the optimum value of the number of flat multi-hole tubes 2 to which it belongs.

In FIG. 6, the ratio N ₁ / N of the number N ₁ [lines] of the number of flat multi-hole tubes belonging to the first flat multi-hole tube group to the total number N [lines] of flat multi-hole tubes possessed by the heat exchanger is expressed by the following equation ( The graph arranged by the value of ΔP _TP in 2) is shown. The vertical axis of FIG. 6 is the value of N ₁ / N, and the horizontal axis is the value of ΔP _TP in the following equation (2). The broken line in FIG. 6 is a curve represented by the following equation (1'). The scale on the horizontal axis in FIG. 6 is a logarithmic scale.

ΔP _TP = 0.0661 × C ₁ × Γ ^-1.841 ... (2)
N ₁ ^' = N x 0.0014 x ΔP _TP ^0.48737 ... (1')

However, the value of ΔP _TP in the formula (2) is the mass flow rate of the refrigerant flowing inside the parallel flow heat exchanger as _mref [kg / s], and the flow path cross-sectional area of the flat multi-hole pipe. A _tube [m ² ], the hydraulic diameter of the flat multi-hole tube is D _h [m], the length of the flat multi-hole tube is L _tube [m], and the viscosity of the refrigerant in the liquid phase is μ _L [Pa. s], the viscosity of the refrigerant in the gas phase is μ _V [Pa · s], the density of the refrigerant in the liquid phase is ρ _L [kg / m ³ ], and the density of the refrigerant in the gas phase is ρ _V [kg / m]. ³ ] is a value calculated by the following equations (3) to (4).
C ₁ = m _ref ^1.75 x A _tube ^-1.75 x D _h ^-0.75 x μ _L ^0.25 x ρ _L ^-1 x 4 x L _tube ... (3)
Γ = (ρ _V / ρ _L ) ^0.5 × (μ _L / μ _V ) ^0.125 ... (4)

According to the graph shown in FIG. 6, the curve represented by the above equation (1') often has the optimum value of the flat multi-hole tube 2 belonging to the first flat multi-hole tube group 21 under the analysis conditions A to J. It can be understood that they are similar. Therefore, by using the above formula (1'), the optimum value of the flat multi-hole tube 2 belonging to the first flat multi-hole tube group 21 can be easily predicted.

Further, in the "predicted value by the formula (1')" column of Table 3, the optimum value of the flat multi-hole pipe 2 belonging to the first flat multi-hole pipe group 21 calculated by the formula (1') is shown. According to these results, the value predicted by the above equation (1') is the maximum with respect to the optimum number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 derived by numerical analysis. It can be understood that there are two more.

Therefore, the lower limit of the number of flat multi-hole tubes 2 belonging to the first flat multi-hole tube group 21 is the optimum for the flat multi-hole tube 2 belonging to the first flat multi-hole tube group 21 predicted by the above equation (1'). By setting the number of pipes to two less than the value, the number of flat multi-hole pipes 2 belonging to the first flat multi-hole pipe group 21 can be easily optimized, and the heat exchange amount of the entire heat exchanger can be increased. ..

As described above, the configuration example of the parallel flow type heat exchanger according to the present invention has been described based on Examples 1 to 3, but the specific embodiment of the parallel flow type heat exchanger according to the present invention is described above. The present invention is not limited to the embodiments described in the above embodiment, and the configuration can be appropriately changed as long as the gist of the present invention is not impaired.

1 Parallel flow heat exchanger 11 core 2 Flat multi-hole tube 21 1st flat multi-hole tube group 22 2nd flat multi-hole tube group 3 Fin 4 1st header 5 2nd header

Claims (7)

A core in which a plurality of flat multi-hole pipes configured to allow the flow of a refrigerant are arranged in parallel via fins, and the flat multi-hole pipes and the fins are alternately laminated in the vertical direction.
A first header arranged at one end of the core in the longitudinal direction of the flat multi-hole tube and connected to the flat multi-hole tube.
It has a second header located at the other end of the core in the longitudinal direction and connected to the flat multi-hole tube.
The plurality of the flat multi-hole tubes include a first flat multi-hole tube group located at the uppermost part of the core and a second flat multi-hole tube group adjacent to the lower side of the first flat multi-hole tube group. It is divided into the flat multi-hole tube group of
The first header and the second header are configured so that the refrigerant can sequentially pass through the plurality of flat multi-hole pipe groups from the upper side to the lower side.
The number of the flat multi-hole tubes belonging to the second flat multi-hole tube group is 14 or more.
A parallel flow type heat exchanger in which the number of flat multi-hole tubes belonging to the first flat multi-hole tube group is less than or equal to the number of the flat multi-hole tubes belonging to the second flat multi-hole tube group. The parallel flow type heat exchanger is configured to use R32 as a refrigerant, the hydraulic diameter D _h of the flat multi-hole pipe is 0.00032 m or more and 0.001 m or less, and the flat multi-hole pipe is used. The parallel flow type heat exchanger according to claim 1, wherein the length L _tube is 0.4 m or more and 0.9 m or less. The parallel flow heat exchanger according to claim 1 or 2, wherein the rated capacity is 2 kW or more and 12 kW or less. An air conditioner comprising the parallel flow type heat exchanger according to any one of claims 1 to 3 and a refrigerant existing inside the parallel flow type heat exchanger. The total number N [lines] of the flat multi-hole tubes included in the parallel flow type heat exchanger and the number N ₁ [lines] of the flat multi-hole tubes belonging to the first flat multi-hole tube group are the following equations (1). ) Satisfying the relationship of the air conditioner according to claim 4.
N ₁ > N x 0.0014 x ΔP _TP ^0.48737 -2 ... (1)
(However, the value of ΔP _TP in the formula (1) is the mass flow rate of the refrigerant flowing inside the parallel flow type heat exchanger _mref [kg / s], and the flow path cross-sectional area of the flat multi-hole pipe. A _tube [m ² ], the hydraulic diameter of the flat multi-hole tube is D _h [m], the length of the flat multi-hole tube is L _tube [m], and the viscosity of the refrigerant in the liquid phase is μ _L [Pa]. S], the viscosity of the refrigerant in the gas phase is μ _V [Pa · s], the density of the refrigerant in the liquid phase is ρ _L [kg / m ³ ], and the density of the refrigerant in the gas phase is ρ _V [kg / m ³ ] is a value calculated by the following equations (2) to (4).
ΔP _TP = 0.0661 × C ₁ × Γ ^-1.841 ... (2)
C ₁ = m _ref ^1.75 x A _tube ^-1.75 x D _h ^-0.75 x μ _L ^0.25 x ρ _L ^-1 x 4 x L _tube ... (3)
Γ = (ρ _V / ρ _L ) ^0.5 × (μ _L / μ _V ) ^0.125 ... (4)) The air conditioner according to claim 4 or 5, wherein the refrigerant is R32. The air conditioner is configured so that the mass flow rate _mref of the refrigerant inside the parallel flow heat exchanger can be 0.01 kg / s or more and 0.03333 kg / s or less. The air conditioner according to any one of 4 to 6.

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