JP2017116152A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger capable of unifying flow of a refrigerant without using a complicated structure, in a structure where the refrigerant circulates in a lifting core part and a lowering core part.SOLUTION: A form of a heat exchanger in which the flow of a refrigerant is unified by factors specifying the shape of the heat exchanger is determined, owing to that there are put into a prescribed range: in a lifting core part or a lowering core part, the minimal value and maximum value of a shape coefficient of a lifting core part, obtained by prescribed mathematical formula comprising the relationship among the number of tubes 20, a total channel cross sectional area of the tube 20, a header axial length of a refrigerant circulation space of a header 10, a header radial direction maximum cross sectional area of the refrigerant circulation space 10a of the header 10, and a header radial direction minimum cross sectional area of the refrigerant circulation space 10a of the header 10; and the minimal value and maximum value of a shape coefficient of the lowering core part obtained by the prescribed mathematical formula.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a heat exchanger used as, for example, an evaporator of a heat pump hot water supply apparatus.

  Conventionally, as this type of heat exchanger, a pair of cylindrical headers are arranged vertically above each other in the radial direction, and are arranged at intervals in the axial direction of the headers. , Each header is connected to both ends, and has a plurality of flat tubes extending in the vertical direction and heat transfer fins provided between the tubes, and the heat medium is circulated between the headers via the tubes By doing so, there is known one in which heat is exchanged between the air flowing outside each tube and the refrigerant in each tube.

  Further, as the heat exchanger, by dividing the inside of the header at a predetermined position in the refrigerant distribution direction, at least one rising core portion including a refrigerant distribution path through which the refrigerant flows from the lower header toward the upper header; It is known that at least one descending core part consisting of a coolant circulation path through which the coolant flows from the upper header to the lower header is formed, and the coolant is alternately circulated through the ascending core part and the descending core part. (For example, refer to Patent Document 1).

  In this heat exchanger, the refrigerant circulates in a meandering manner by alternately circulating the rising core portion and the falling core portion, so that the refrigerant flow path can be lengthened and the amount of heat exchange is increased. be able to. Moreover, when this heat exchanger is used as an evaporator, each tube is arranged so as to extend in the vertical direction, so that dew condensation does not accumulate on the surface of each tube, and drainage can be improved.

JP2008-292022

  However, in the heat exchanger, since the refrigerant flows through each tube in the vertical direction, the flow of the refrigerant becomes uneven in the rising core portion and the lowering core portion due to the influence of gravity, and the heat exchange efficiency is lowered. there were.

  Therefore, conventionally, the flow rate of the refrigerant in the header is adjusted so that the refrigerant flow in each tube is uniform by arranging a contracted plate in the header or changing the amount of insertion of the tube into the header. I am doing so.

  However, in the case of using the reduced flow plate, the structure of the header becomes complicated, so that the manufacture becomes difficult and the cost becomes high. Furthermore, since the structure becomes complicated, there is a problem that the pressure loss in the refrigerant flow path is increased and the heat exchange performance is lowered. Moreover, when changing the amount of insertion of a tube, the tube insertion operation | work in a manufacturing process becomes complicated and there exists a problem that productivity falls.

  The present invention has been made in view of the above problems, and the object of the present invention is to evenly distribute the flow of the refrigerant without using a complicated structure even in the configuration in which the refrigerant flows through the rising core portion and the falling core portion. An object of the present invention is to provide a heat exchanger that can be converted into a heat exchanger.

In order to achieve the above-mentioned object, the present invention has a pair of cylindrical headers that are vertically spaced apart from each other and extend in the horizontal direction, and are spaced apart from each other in the axial direction of the header. A plurality of flat tubes each connected at both ends to each header and extending in the vertical direction; at least one rising core portion comprising a refrigerant circulation path through which refrigerant flows from the lower header toward the upper header; And at least one descending core portion comprising a coolant circulation path through which the coolant flows from the header to the lower header, and the coolant is alternately circulated through the ascending core portion and the descending core portion, and is circulated outside each tube. In the heat exchanger for exchanging heat between the air to be circulated and the refrigerant flowing through the flow path in each tube, The number of tubes is N, the total channel cross-sectional area of N tubes is St [mm ² ], the header axial direction length of the refrigerant circulation space of the header is L [mm], and the header radial direction maximum of the header refrigerant circulation space Assuming that the cross-sectional area is Sh1 [mm ² ] and the header radial direction minimum cross-sectional area of the header refrigerant distribution space is Sh2 [mm ² ], the minimum value of the shape factor εu1 of the rising core portion obtained by the following equation (1) is 0.06 × 10 ⁶ , the maximum value is 429.33 × 10 ⁶ , the minimum value of the shape factor εd1 of the descending core portion obtained by the following equation (2) is 3.73 × 10 ⁶ , and the maximum value is 230. .67 × 10 ⁶ .

  As a result, the factors specifying the shape of the heat exchanger, that is, the header axial length L, the header radial direction maximum cross-sectional area Sh1, the header radial direction minimum cross-sectional area Sh2, the total tube flow path cross-sectional area St, the number of tubes N, The shape of the heat exchanger that makes the flow of the refrigerant uniform can be determined.

In order to achieve the above-mentioned object, the present invention is arranged vertically above and below each other in the radial direction, and is arranged with a pair of cylindrical headers extending in the horizontal direction and spaced apart from each other in the axial direction of the header. And a plurality of flat tubes that are connected to each header at both ends and extend in the vertical direction, and at least one ascending core portion including a refrigerant flow path through which the refrigerant flows from the lower header toward the upper header, And at least one descending core portion consisting of a coolant circulation path through which the coolant flows from the upper header toward the lower header, and the coolant is alternately circulated through the ascending core portion and the descending core portion, and the outside of each tube. In the heat exchanger that exchanges heat between the air that flows through the refrigerant and the refrigerant that flows through the flow path in each tube, , The number of tubes N, the total flow path cross-sectional area of the N tubes St [mm ^2], the header axial length of the refrigerant circulation space of the header L [mm], the header radial refrigerant circulation space of the header The maximum cross-sectional area is Sh1 [mm ² ], the header radial minimum cross-sectional area of the header refrigerant distribution space is Sh2 [mm ² ], the refrigerant mass flux is Gr [kg / m ² s], and the refrigerant mass flow rate is Mr. [Kg / s], the dryness of the refrigerant at the core inlet x, the liquid phase velocity in the header v1 [m / s], the gas phase velocity in the header v2 [m / s], the slip ratio s, The liquid refrigerant density at the core inlet is ρ1 [kg / m ³ ], the gas refrigerant density at the core inlet is ρ2 [kg / m ³ ], the void fraction is α, the gravitational acceleration is g [m / s ² ], e Assuming 0.4, the void ratio α is the following formula (3), the liquid phase velocity v1 is the following formula (4), and the gas phase The velocity v2 is the following formula (5), the mass flux Gr is the following formula (6), and the slip ratio s is the following formula (7). The characteristic coefficient εu of the falling core is 0.02 or more, and the characteristic coefficient εd of the descending core obtained by the following equation (9) is 0.005 or more.

  As a result, the characteristic coefficient εu of the rising core portion is 0.02 or more and the characteristic coefficient εd of the descending core portion is 0.005 or more. The physical properties of the refrigerant can be determined.

  According to the present invention, since the shape of the heat exchanger in which the flow of the refrigerant becomes uniform can be determined by a factor that specifies the shape of the heat exchanger, in the configuration in which the refrigerant flows through the rising core portion and the falling core portion However, the flow of the refrigerant can be made uniform without using a complicated structure, and a heat exchanger with high heat exchange efficiency can be manufactured easily and at low cost.

The front view of the heat exchanger which shows one Embodiment of this invention Cross section of tube Partial cross-sectional perspective view of header and tube Front view of heat exchanger showing refrigerant flow path AA arrow direction sectional view of the header Front view of tube BB cross-sectional view of the header CC cross-sectional view of the header Diagram showing the relationship between εu and cooling capacity Diagram showing the relationship between εd and cooling capacity Schematic front view of heat exchanger with 2 refrigerant flow paths Schematic front view of heat exchanger with 2 refrigerant flow paths Schematic front view of heat exchanger with 3 refrigerant flow paths Schematic front view of heat exchanger with 3 refrigerant flow paths Schematic front view of heat exchanger with 4 refrigerant distribution channels Schematic front view of heat exchanger with 4 refrigerant distribution channels Schematic front view of heat exchanger with 5 refrigerant flow paths Schematic front view of heat exchanger with 5 refrigerant flow paths Schematic front view of heat exchanger with "6" refrigerant distribution channels Schematic front view of heat exchanger with "6" refrigerant distribution channels Schematic front view of heat exchanger with 7 refrigerant flow paths Schematic front view of heat exchanger with 7 refrigerant flow paths Schematic front view of heat exchanger with 8 refrigerant flow paths Schematic front view of heat exchanger with 8 refrigerant flow paths Schematic front view of heat exchanger with 9 refrigerant distribution channels Schematic front view of heat exchanger with 9 refrigerant distribution channels Schematic front view of heat exchanger with "10" refrigerant distribution channels Schematic front view of heat exchanger with "10" refrigerant distribution channels The figure which shows the shape factor in the heat exchanger with the number of refrigerant | coolant distribution paths of "2" The figure which shows the shape factor in the heat exchanger with the number of refrigerant | coolant distribution paths of "2" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "3" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "3" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "4" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "4" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "5" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "5" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "6" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "6" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "7" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "7" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "8" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "8" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "9" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "9" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "10" The figure which shows the shape factor in the heat exchanger whose refrigerant | coolant distribution channel number is "10"

  1 to 46 show an embodiment of the present invention, which shows a heat exchanger that is used as an evaporator of a refrigeration circuit, for example, and circulates a carbon dioxide refrigerant as a refrigerant.

  The heat exchanger according to the present embodiment includes a pair of cylindrical headers 10 that are vertically spaced apart from each other in the radial direction, and are spaced apart from each other in the axial direction of the header 10. And a plurality of flat tubes 20 connected to each other.

  Each header 10 is made of a member formed of a metal such as aluminum in a cylindrical shape extending in the left-right direction (horizontal direction), and a plurality of connections to which end portions of the tubes 20 are connected to the side surfaces (circumferential wall surfaces). The holes 11 are provided at equal intervals in the axial direction of the header 10. The connection hole 11 is formed in a long hole shape extending in the circumferential direction of the header 10, and is formed so as to penetrate the peripheral wall portion of the header 10. Further, both ends of each header 10 in the axial direction are respectively closed by the lid member 12. Further, an inflow pipe (not shown) is connected to one end of the upper header 10, and an outflow pipe (not shown) is connected to the other end of the upper header 10.

  Each tube 20 is made of an extruded product of a metal such as aluminum, and is formed in a flat shape in which the dimension in the thickness direction is smaller than the dimension in the width direction. Moreover, the width direction both ends of the tube 20 are formed in the semicircle curved surface shape. The tube 20 is provided with a plurality of refrigerant flow holes 21 that form a flow path in the tube 20 at equal intervals in the width direction of the tube 20, and each refrigerant flow hole 21 is formed in an elliptical cross section that is long in the vertical direction. Has been.

  Each heat transfer fin 30 is made of a member in which a metal plate such as aluminum is formed in a corrugated shape, and is disposed between each tube 20.

  Each header 10 is provided with a partition plate 13 for partitioning the header 10 in the axial direction. In the upper header 10, partition plates 13 are disposed at two axial positions (both axial ends of the header 10), and are partitioned into three refrigerant circulation spaces 10 a by the partition plates 13. In the lower header 10, a partition plate 13 is disposed at one axial position (substantially the center in the axial direction of the header 10), and is partitioned into two refrigerant circulation spaces 10 a by the partition plate 13. Thereby, each tube 20 is the 1st refrigerant | coolant which consists of the several tube 20 arranged from one end (left side edge part in the figure) of each header 10 to one partition plate 13 (left side in the figure) of the upper header 10. The distribution path P1, the second refrigerant distribution path P2 including a plurality of tubes 20 arranged from one partition plate 13 of the upper header 10 to the partition plate 13 of the lower header 10, and the partition plate of the lower header 10 13 to the other partition plate 13 (the right side in the figure) of the upper header 10, the third refrigerant flow path P <b> 3 including a plurality of tubes 20, and the other partition plate 13 of the upper header 10 to each header 10. And a fourth refrigerant flow path P4 composed of a plurality of tubes 20 arranged up to the other end (right end portion in the figure).

  In the heat exchanger configured as described above, the refrigerant of the refrigeration circuit (not shown) flows into one axial end of the upper header 10 from an inflow pipe (not shown) as indicated by the white arrow in FIG. Then, after sequentially flowing through the tubes 20 of the first to fourth refrigerant flow paths P1 to P4, it flows out from the other axial end of the upper header 10 to the outside via an outflow pipe (not shown). In this case, the refrigerant flows from the upper side to the lower side in the first and third refrigerant flow paths P1, P3, and the refrigerant flows from the lower side to the upper side in the second and fourth refrigerant flow paths P2, P4. . That is, the second and fourth refrigerant circulation paths P2 and P4 are respectively rising core parts, and the first and third refrigerant circulation paths P1 and P3 are respectively descending core parts.

  In the configuration in which the refrigerant flows alternately through the ascending core portion and the descending core portion as in the present embodiment, since the refrigerant circulates through the tubes 20 in the vertical direction, the ascending core portion and the descending core portion are separated by the influence of gravity. As a result, the flow of the refrigerant becomes non-uniform, and the cooling capacity of the evaporator decreases.

  Therefore, from many experimental data, the shape factor that greatly affects the flow of the refrigerant is identified, and the numerical range in which the flow of the refrigerant becomes uniform is derived by the following relational expression.

That is, as a factor for specifying the shape of the heat exchanger, the number of tubes 20 in one rising core portion or the falling core portion is N, and the total flow passage cross-sectional area of the N tubes 20 is St [mm ² ], The length in the header axial direction of the refrigerant circulation space 10a of the header 10 is L [mm], the maximum cross-sectional area in the header radial direction of the refrigerant circulation space 10a of the header 10 is Sh1 [mm ² ], and the header diameter of the refrigerant circulation space 10a of the header 10 The minimum cross-sectional area in the direction is Sh2 [mm ² ], and the factors that specify the physical properties of the refrigerant flowing through the heat exchanger are Gr [kg / m ² s] for the mass flux of the refrigerant and Mr [ kg / s], the dryness of the refrigerant at the core inlet x, the liquid phase velocity of the refrigerant in the header 10 v1 [m / s], the vapor phase velocity of the refrigerant in the header 10 v2 [m / s], Slip ratio is s, at the core entrance The refrigerant density ρ1 [kg ^{/ m} 3], the core portion inlet of the gas refrigerant density ρ2 [kg ^{/ m} 3], a void fraction alpha, when the gravitational acceleration and g [m / ^{s 2],} the following equation (10 9 and FIG. 10 when the characteristic coefficient εu of the ascending core portion obtained by (1) is 0.02 or more and the characteristic coefficient εd of the descending core portion obtained by the following formula (11) is 0.005 or more. Experimental data confirmed that the cooling capacity did not decrease. As shown in FIGS. 5 and 6, the total channel cross-sectional area St of the tube 20 is obtained by adding the channel cross-sectional area St2 of each refrigerant flow hole 21 per tube to the total channel cross-sectional area St2. It is a channel cross-sectional area multiplied by the number N of 20. Moreover, the header radial direction minimum cross-sectional area Sh2 of the refrigerant | coolant distribution space of the header 10 is an area remove | excluding the insertion part of the tube 20 from the header radial direction maximum cross-sectional area Sh1, as shown in FIG.

  In the above formulas (10) and (11), the following formulas (12) to (16) are satisfied. However, e = 0.4.

  Equation (10) for the characteristic coefficient εu of the rising core portion includes a factor that specifies the shape of the heat exchanger and a factor that specifies the physical properties of the refrigerant flowing through the heat exchanger. The characteristic coefficient εu is expressed by the following formula (εu1), which is divided into a shape factor εu1 consisting only of a factor specifying the shape of the heat exchanger and a physical property coefficient εu2 consisting only of a factor specifying the physical property of the refrigerant flowing through the heat exchanger. 17) to (19).

  Similarly, the equation (11) of the characteristic coefficient εd of the descending core portion includes a factor for specifying the shape of the heat exchanger and a factor for specifying the physical properties of the refrigerant flowing through the heat exchanger. 11) is divided into a shape factor εd1 consisting only of a factor specifying the shape of the heat exchanger and a physical property factor εd2 consisting only of a factor specifying the physical property of the refrigerant flowing through the heat exchanger. (20) to (22).

  Using the above formulas (17) to (22), the factor specifying the physical property is set within a predetermined range, and the minimum value and the maximum value of the shape factor εu1 when the characteristic coefficient εu of the rising core portion is 0.02 or more, FIGS. 29 to 46 show the results of obtaining the minimum value and the maximum value of the shape factor εd1 of the descending core portion when the characteristic coefficient εd of the descending core portion is 0.005 or more. In this case, as shown in FIGS. 11 to 28, the shape factors εu1 and εd1 were obtained for the heat exchanger having 2 to 10 refrigerant flow paths. The range of factors that specify the physical properties is that the flow rate of the refrigerant is 40 kg / h or more and 180 kg / h or less, the refrigerant pressure is 2.5 MPaG or more and 5.0 MPaG or more, and the dryness range is 0.08 to 0.94. (See FIG. 29 to FIG. 46).

As a result, as shown in FIGS. 29 to 46, the minimum value of the shape factor εu1 of the ascending core portion is 0.06 × 10 ⁶ , the maximum value is 429.33 × 10 ⁶ , and the shape factor εd1 of the descending core portion is The minimum value was 3.73 × 10 ⁶ and the maximum value was 230.67 × 10 ⁶ .

Thus, according to the present embodiment, the number of tubes 20 in one rising core portion or the falling core portion is N, the total flow passage cross-sectional area of the N tubes 20 is St [mm ² ], and the header 10 The header axial direction length of the refrigerant circulation space 10a is L [mm], the header radial direction maximum cross-sectional area of the refrigerant circulation space 10a of the header 10 is Sh1 [mm ² ], and the header radial direction minimum cutoff of the refrigerant circulation space 10a of the header 10 is Assuming that the area is Sh2 [mm ² ], the minimum value of the shape factor εu1 of the rising core portion obtained by the above equation (11) is 0.06 × 10 ⁶ , and the maximum value is 429.33 × 10 ^6. Since the minimum value of the shape factor εd1 of the descending core portion obtained in (14) is 3.73 × 10 ⁶ and the maximum value is 230.67 × 10 ⁶ , a factor for specifying the shape of the heat exchanger, That is, the header axial direction Is L, the header radial maximum cross-sectional area Sh1, headers minimum radial sectional area Sh2, tube total flow path cross-sectional area St, the number of tubes N, can determine the shape of the heat exchanger the flow of refrigerant becomes uniform. Thereby, even in the configuration in which the refrigerant flows alternately through the rising core portion and the falling core portion, the flow of the refrigerant can be made uniform without using a complicated structure, and a heat exchanger with high heat exchange efficiency can be easily and It can be manufactured at a low cost.

  In this case, the shape factors εu1 and εd1 of each core part can be changed by setting only the factor that specifies the shape of the heat exchanger to an arbitrary numerical value. For example, each core part can be changed by changing only the number N of tubes. If the shape factors εu1 and εd1 are in the numerical range, a heat exchanger having a uniform refrigerant flow can be easily designed according to specifications such as the size and capacity of the entire heat exchanger.

Further, the mass flux of the refrigerant is Gr [kg / m ² s], the mass flow rate of the refrigerant is Mr [kg / s], the dryness of the refrigerant at the inlet of the core is x, and the liquidus velocity in the header 10 is v1 [ m / s], the gas phase velocity in the header 10 is v2 [m / s], the slip ratio is s, the liquid refrigerant density at the core inlet is ρ1 [kg / m ³ ], and the gas refrigerant density at the core inlet is ρ2 When [kg / m ³ ], the void ratio is α, the gravitational acceleration is g [m / s ² ], and e is 0.4, when the shape factors εu1 and εd1 satisfy the numerical range, the equation (10) By satisfying at least one of the characteristic coefficient εu of the rising core portion obtained in (16) being 0.02 or more and the characteristic coefficient εd of the falling core portion being 0.005 or more, Factors specifying the physical properties of the refrigerant flowing through the heat exchanger, that is, the mass flux Gr of the refrigerant, the refrigerant Mass flow rate Mr, dryness x of refrigerant at the core inlet, liquid phase velocity v1 in the header 10, gas phase velocity v2 in the header 10, slip ratio s, liquid refrigerant density ρ1 at the core inlet, gas at the core inlet The physical properties of the refrigerant flowing through the heat exchanger can be determined by the refrigerant density ρ2 and the void ratio α so that the refrigerant flow is uniform.

  Further, if the characteristic coefficient εu of the ascending core portion is 0.02 or more and the characteristic coefficient εd of the descending core portion is 0.005 or more regardless of the numerical range of the shape factors εu1 and εd1, the above-mentioned Similarly, the shape of the heat exchanger that makes the flow of the refrigerant uniform and the physical properties of the refrigerant can be determined.

  DESCRIPTION OF SYMBOLS 10 ... Header, 10a ... Refrigerant distribution space, 20 ... Tube, P1-P10 ... 1st-10th refrigerant | coolant distribution path.

Claims (5)

A pair of cylindrical headers that are arranged above and below in the radial direction and spaced apart from each other in the radial direction, and arranged at intervals in the axial direction of the header, and are connected to each header at both ends. A plurality of flat tubes extending in the direction, at least one rising core portion including a refrigerant flow path through which the refrigerant flows from the lower header toward the upper header, and the refrigerant from the upper header toward the lower header. And at least one descending core portion comprising a coolant circulation path for circulating the coolant, and alternately circulating the coolant through the ascending core portion and the descending core portion, and the air flowing outside each tube and the flow path in each tube In a heat exchanger that exchanges heat with the circulating refrigerant,
In one ascending core portion or descending core portion, the number of tubes is N, the total flow passage cross-sectional area of the N tubes is St [mm ² ], and the header axial direction length of the refrigerant circulation space of the header is L [mm] The header radial direction maximum cross-sectional area of the header refrigerant distribution space is Sh1 [mm ² ], and the header radial direction minimum cross-sectional area of the header refrigerant distribution space is Sh2 [mm ² ].
The minimum value of the shape factor εu1 of the rising core portion obtained by the following formula (1) is 0.06 × 10 ⁶ , and the maximum value is 429.33 × 10 ⁶ ,
The minimum value of the shape factor εd1 of the descending core portion obtained by the following formula (2) is 3.73 × 10 ⁶ , and the maximum value is 230.67 × 10 ⁶ .

The mass flux of the refrigerant is Gr [kg / m ² s], the mass flow rate of the refrigerant is Mr [kg / s], the dryness of the refrigerant at the core inlet is x, and the liquidus velocity in the header is v1 [m / s], the gas phase velocity in the header is v2 [m / s], the slip ratio is s, the liquid refrigerant density at the core inlet is ρ1 [kg / m ³ ], and the gas refrigerant density at the core inlet is ρ2 [kg / m ³ ], the void ratio is α, the gravitational acceleration is g [m / s ² ], and e is 0.4.
The void ratio α is the following equation (3), the liquid phase velocity v1 is the following equation (4), the gas phase velocity v2 is the following equation (5), the mass flux Gr is the following equation (6), and the slip ratio s. Satisfies the relationship of the following formula (7),
The heat exchanger according to claim 1, wherein a characteristic coefficient εu of the rising core portion obtained by the following formula (8) is 0.02 or more.

The mass flux of the refrigerant is Gr [kg / m ² s], the mass flow rate of the refrigerant is Mr [kg / s], the dryness of the refrigerant at the core inlet is x, and the liquidus velocity in the header is v1 [m / s], the gas phase velocity in the header is v2 [m / s], the slip ratio is s, the liquid refrigerant density at the core inlet is ρ1 [kg / m ³ ], and the gas refrigerant density at the core inlet is ρ2 [kg / m ³ ], the void ratio is α, the gravitational acceleration is g [m / s ² ], and e is 0.4.
The void ratio α is the following equation (9), the liquid phase velocity v1 is the following equation (10), the gas phase velocity v2 is the following equation (11), the mass flux Gr is the following equation (12), and the slip ratio s. Satisfy the relationship of the following formula (13),
The heat exchanger according to claim 1, wherein a characteristic coefficient εd of the descending core portion obtained by the following formula (14) is 0.005 or more.

A pair of cylindrical headers that are arranged above and below in the radial direction and spaced apart from each other in the radial direction, and arranged at intervals in the axial direction of the header, and are connected to each header at both ends. A plurality of flat tubes extending in the direction, at least one rising core portion including a refrigerant flow path through which the refrigerant flows from the lower header toward the upper header, and the refrigerant from the upper header toward the lower header. And at least one descending core portion comprising a coolant circulation path for circulating the coolant, and alternately circulating the coolant through the ascending core portion and the descending core portion, and the air flowing outside each tube and the flow path in each tube In a heat exchanger that exchanges heat with the circulating refrigerant,
In one ascending core portion or descending core portion, the number of tubes is N, the total flow passage cross-sectional area of the N tubes is St [mm ² ], and the header axial direction length of the refrigerant circulation space of the header is L [mm] , The header radial maximum cross-sectional area of the header refrigerant distribution space is Sh1 [mm ² ], the header radial direction minimum cross-sectional area of the header refrigerant distribution space is Sh2 [mm ² ], and the refrigerant mass flux is Gr [kg / m]. ² s], the mass flow rate of the refrigerant Mr [kg / s], the dryness of the refrigerant at the core inlet x, the liquid phase velocity in the header v1 [m / s], and the gas phase velocity in the header v2 [ m / s], slip ratio s, liquid refrigerant density at the core inlet ρ1 [kg / m ³ ], gas refrigerant density at the core inlet ρ2 [kg / m ³ ], void fraction α, gravity acceleration When g [m / s ² ] and e is 0.4,
The void ratio α is the following equation (15), the liquid phase velocity v1 is the following equation (16), the gas phase velocity v2 is the following equation (17), the mass flux Gr is the following equation (18), and the slip ratio s. Satisfies the relationship of the following equation (19), the characteristic coefficient εu of the rising core portion obtained by the following equation (20) is 0.02 or more, and the characteristic coefficient of the falling core portion obtained by the following equation (21) εd is 0.005 or more.

The heat exchanger according to claim 1, 2, 3, or 4, wherein the refrigerant is a carbon dioxide refrigerant.

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