Plate stacking evaporator

Abstract

Improvement of overall performance of an evaporator having a heat transfer surface 1 with a herringbone pattern, taking into account the heat exchange amount, pressure loss, and pressure resistance. [Solution] The specifications for a plate having a heat transfer surface 1 on which a herringbone pattern is formed by irregularities are as follows: when the plane length in the long direction of the heat transfer surface 1 is a and the plane length in the short direction is b, the aspect ratio between them b / a is 0.4 ≤ b / a ≤ 1.3; the pitch Wp (mm) of the waves of the herringbone irregularities on the heat transfer surface 1 is 3 mm ≤ Wp ≤ 4 mm; and the inclination angle Wθ (deg) between the straight line H parallel to the short direction of the plane and the herringbone pattern is 20° ≤ Wθ ≤ 40°.

Description

Technical Field

[0001] The present invention relates to an improvement in the performance of an evaporator in which a plurality of cup-shaped plates each having a heat transfer surface formed with a herringbone pattern due to unevenness are stacked.

Background Art

[0002] Conventionally, the following plate stacked evaporator is known. The plate of this evaporator is formed in a planar rectangle having a pair of opposing long sides and a pair of opposing short sides. In the plate, on one side in the short side direction, which is the direction in which the short side extends, a pair of first flow holes are arranged spaced apart in the long side direction, and on the other side in the short side direction, a pair of second flow holes are arranged spaced apart in the long side direction. Further, the plate has a heat transfer surface formed with a herringbone pattern by unevenness at the central portion of its plane. This evaporator has a core in which the above plates are stacked such that the direction of the herringbone pattern is reversed every other sheet, and a first flow path through which a first fluid flows and a second flow path through which a second fluid flows are alternately formed.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in a conventional plate stacked evaporator having a heat transfer surface formed with a herringbone pattern, when the flow holes are arranged as described above, if the herringbone pattern is adjusted so that the fluid is also dispersed in the short side direction in order to increase the heat exchange amount, the pressure loss tends to increase, and the herringbone pattern also affects the pressure resistance of the plate. Therefore, there is a demand for an evaporator with overall high performance considering the heat exchange amount, pressure loss, and pressure resistance.

[0004] Therefore, an object of the present invention is to improve the overall performance of an evaporator having a heat transfer surface formed with a herringbone pattern.

Means for Solving the Problems

[0005] The first invention that solves the above problem is, In a cup-shaped plate 2 which is a planar rectangle having a pair of opposing long sides and a pair of opposing short sides, On one side of plate 2 in the direction of its short side, a pair of first circulation holes 3a and 3b are arranged spaced apart in the direction of its long side. On the other side of plate 2 in the short direction, a pair of second circulation holes 4a and 4b are arranged spaced apart in the long direction. Plate 2 has a heat transfer surface 1 in which a herringbone pattern is formed by irregularities in the center of its flat surface. Plate 2 is stacked so that every other plate has the herringbone pattern facing in the opposite direction. In a plate stacked evaporator in which a core 5 is formed, in which a first flow path 3 through which a first fluid 6 flows and a second flow path 4 through which a second fluid 7 flows are formed alternately, When the plane length in the long side direction of the heat transfer surface 1 is a and the plane length in the short side direction is b, the aspect ratio between them is b / a. 0.4 ≤ b / a ≤ 1.3 And, The pitch Wp (mm) of the herringbone-like irregularities on the heat transfer surface 1 is 3mm ≤ Wp ≤ 4mm And, The angle of inclination Wθ(deg) between a straight line H parallel to the shorter side of the plane and the herringbone pattern is, 20° ≤ Wθ ≤ 40° This is a plate stacking type evaporator.

[0006] The second invention relates to the plate stacking type evaporator described in the first invention, 20° ≤ Wθ ≤ 30° This is a plate stacking type evaporator.

[0007] The third invention relates to a plate stacking evaporator described in the first or second invention, The first fluid 6 is a refrigerant used in the air conditioning of a vehicle equipped with an electric motor. The second fluid 7 is LLC (Long Life Coolant) used for cooling the batteries of vehicles equipped with electric motors, and is a plate-stacked evaporator. [Effects of the Invention]

[0008] As in the first invention described above, the specifications of the plate having a heat transfer surface 1 in which a herringbone pattern is formed by irregularities are as follows: 0.4 ≤ b / a ≤ 1.3 3mm ≤ Wp ≤ 4mm 20° ≤ Wθ ≤ 40° By doing so, pressure loss is suppressed, pressure resistance is ensured, and a sufficiently large amount of heat is exchanged, resulting in an overall high-performance evaporator.

[0009] Furthermore, as in the second invention described above, 20° ≤ Wθ ≤ 30° By doing so, pressure loss is suppressed, pressure resistance is ensured, and a larger amount of heat is exchanged, resulting in an overall high-performance evaporator.

[0010] Furthermore, as in the third invention described above, The first fluid 6 is used as a refrigerant for the air conditioning of a vehicle equipped with an electric motor. By using LLC (Long Life Coolant) as the second fluid 7 for battery cooling in vehicles equipped with electric motors, its evaporator can be utilized for cooling batteries in electric vehicles. [Brief explanation of the drawing]

[0011] [Figure 1] Exploded perspective view of the main components of the plate stacking evaporator of the present invention. [Figure 2] Cross-sectional view taken along the line II-II in Figure 1. [Figure 3] A plan view of plate 2, which constitutes the evaporator. [Figure 4] A block diagram showing the fluid pathways of each fluid in an electric vehicle using the same evaporator as a chiller. [Figure 5]A graph showing the relationship between the inclination angle Wθ of the waves formed by the herringbone pattern of the same evaporator and the refrigerant pressure loss ratio, where the pitch Wp of the waves is 3 mm. [Figure 6] A graph showing the same relationship, where the pitch Wp of the waves is 4 mm. [Figure 7] A graph showing the relationship between the inclination angle Wθ of the waves formed by the herringbone pattern of the same evaporator and the heat exchange quantity ratio, where the pitch Wp of the waves is 3 mm. [Figure 8] A graph showing the same relationship, where the pitch Wp of the waves is 4 mm.

Embodiments for Carrying Out the Invention

[0012] Next, based on the drawings, the embodiments of the present invention will be described. The plate 2 constituting the plate stacked evaporator of the present invention is formed in a planar rectangular cup shape having a pair of opposing long sides and a pair of opposing short sides, as shown in FIG. 1. As shown in FIG. 3, on one side in the short side direction, which is the direction in which the short side extends, of this plate 2, a pair of first flow holes 3a and 3b are arranged at intervals in the long side direction, and on the other side in the short side direction, a pair of second flow holes 4a and 4b are arranged at intervals in the long side direction. Further, at the central portion of the plane of the plate 2, there is a heat transfer surface 1 formed with a herringbone pattern by concavities and convexities.

[0013] As shown in FIG. 2, the longitudinal section of the herringbone pattern of the heat transfer surface 1 is formed by continuously arranging concavo-convex waveforms at a constant pitch. Also, as shown in FIGS. 1 and 3, the herringbone pattern formed on the heat transfer surface 1 is a V-shaped pattern 8 in plan view. Here, if a virtual line connecting the central portions of a pair of opposing short sides of the plate 2 and parallel to the long side direction is taken as the center line P, and a virtual line orthogonal to the center line P and parallel to the short side direction is taken as the straight line H, in this example, as shown in FIG. 3, the top of the V-shaped pattern 8 is located on the center line P. The top of the V-shaped pattern 8 faces the short side.

[0014] As shown in Figure 1, plates 2 having the above structure are stacked alternately so that the orientation of the tops of the V-shaped patterns 8 is reversed, thereby forming the core 5 of the plate stacking type evaporator. Furthermore, as shown in Figure 2, the core 5 is formed by alternately stacking first flow channels 3 through which the first fluid 6 flows and second flow channels 4 through which the second fluid 7 flows. An end plate 9 is positioned at the upper end of the core 5, and a first fluid introduction passage 17 is positioned on the end plate 9. The inlet 17a and outlet 17b of the first fluid introduction passage 17 are in communication with each stage of the first flow path 3. As shown in Figures 1 and 2, the first fluid 6 flows from the inlet 17a through each stage of the first flow path 3 of the core 5 and flows out from the outlet 17b. As shown in Figure 1, the second fluid 7 flows from the second fluid inlet 18 located on the end plate 9 through each stage of the second flow path 4 and flows out from the second fluid outlet 19. Then, heat exchange takes place between the first fluid 6 and the second fluid 7.

[0015] As shown in Figure 1, the flow of the first fluid 6 in each stage of the first channel 3 includes flows along the long side of the plate 2 and flows that circulate in an arc towards the short side before joining the flow along the long side. The flow of the second fluid 7 in each stage of the second channel 4 is similar. In this example, the first fluid 6 and the second fluid 7 are in opposing flow, but they can also be in parallel flow. Plate 2 of the evaporator is made of aluminum, aluminum alloy, SUS, etc.

[0016] This evaporator is suitable as a chiller for the cooling system of electric vehicle batteries. When used as such a chiller, the first fluid 6 is a refrigerant used for the air conditioning of a vehicle with an electric motor, and the second fluid 7 is LLC (Long Life Coolant) used for cooling the batteries of a vehicle with an electric motor. Figure 4 is a block diagram showing the fluid pathways of each fluid in an electric vehicle using the evaporator as a chiller. The first fluid 6, a refrigerant, becomes a gas-liquid two-phase state via the expansion valve 12 and is supplied to the first channel 3 of the chiller core 5, where it absorbs heat from the second fluid 7 and evaporates. The LLC of the second fluid 7, cooled by the chiller, absorbs heat 14 from the battery 10 and cools it as it flows through the battery cooler 13, before returning to the second channel 4 of the core 5.

[0017] The present invention is characterized by the aspect ratio (b / a) of the heat transfer surface 1 of the plate 2, and the specifications of the herringbone pattern on the heat transfer surface 1 (pitch Wp (mm) of the herringbone-like unevenness waves, and the inclination angle Wθ (deg) of the herringbone-like pattern). The aspect ratio (b / a) is the ratio of the length of the plane in the direction of the long side and the length of the plane in the direction of the short side of the heat transfer surface 1 shown in Figure 3, where a is the length of the plane in the direction of the long side and b is the length of the plane in the direction of the short side. The range of this ratio is 0.4 ≤ b / a ≤ 1.3. The wave pitch Wp is the distance between the convex waves in the herringbone-like unevenness in Figure 3. The inclination angle Wθ is the inclination angle between the straight line H, which is parallel to the short side direction of the plane of plate 2, and the herringbone pattern in Figure 3.

[0018] Figures 5 and 6 are graphs showing the relationship between the slope angle Wθ (horizontal axis) of the herringbone pattern of the evaporator and the refrigerant pressure loss ratio (vertical axis). Figure 5 shows the case when the wave pitch Wp is 3 mm, and Figure 6 shows the case when the wave pitch Wp is 4 mm. Note that in each figure, the refrigerant pressure loss at an inclination angle Wθ of 40° is set to 100% (reference). When Wθ changes from 20° to 10°, the pressure loss increases by 4 to 6 times, which may interfere with the circulation control by the expansion valve 12 that controls the circulation rate of the first fluid 6. Therefore, it is reasonable to set the lower limit of Wθ to 20°.

[0019] Furthermore, reducing Wp increases the pressure loss of the first fluid 6, which raises the pressure of the first fluid 6 in the first flow path 3. This increases its saturation temperature, reduces the temperature difference with the second fluid 7, and decreases the amount of heat exchanged. However, this decrease becomes significant when Wp is less than 3 mm, so it is appropriate to set the lower limit of Wp at 3 mm.

[0020] Conversely, increasing Wp reduces the number of joints on the heat transfer surface 1 between the stacked upper and lower plates 2, thus lowering the pressure resistance. Therefore, to ensure pressure resistance at the normal operating pressure of 0.2 MPaG to 0.4 MPaG, it is appropriate to set the upper limit of Wp to 4 mm.

[0021] Figures 7 and 8 are graphs showing the relationship between the slope angle Wθ (horizontal axis) of the herringbone-like wave pattern in the evaporator and the heat exchange ratio (vertical axis). Figure 7 shows the case when the wave pitch Wp is 3 mm, and Figure 8 shows the case when the wave pitch Wp is 4 mm. Note that the heat exchange rate is set to 100% (reference) when the wave pitch Wp is 3 mm and the inclination angle Wθ is 20°, which results in the maximum heat exchange ratio.

[0022] As mentioned above, a lower limit of Wθ of 20° is appropriate, at which point the heat exchange ratio is maximized. However, if Wθ is up to 30°, more than 60% of the maximum heat exchange ratio is secured in both Figure 7 and Figure 8, and if Wθ is up to 40°, more than 50% of the maximum heat exchange ratio is secured, which is sufficient for practical use. Therefore, it is preferable to set the upper limit of Wθ to 40°, and more preferable to set it to 30°.

[0023] To summarize the above, the specifications of the heat transfer surface 1 of plate 2, which has a herringbone pattern formed on it, which makes for an overall high-performance evaporator, are: In the aspect ratio range b / a, where 0.4 ≤ b / a ≤ 1.3, The range of wave pitch Wp is 3mm ≤ Wp ≤ 4mm. The range of the inclination angle Wθ is 20° ≤ Wθ ≤ 40°. [Industrial applicability]

[0024] The present invention can be used in plate stacking type evaporators having a heat transfer surface with a herringbone pattern formed by irregularities, and is particularly suitable for chillers in the cooling systems of electric vehicle batteries. [Explanation of Symbols]

[0025] 1 Heat transfer surface 2 plates 3. First channel 3a 1st flow hole 3b 1st flow hole 4. Second channel 4a 2nd flow hole 4b 2nd flow hole 5 cores 6 1st fluid 7 Second fluid 8 V-shaped pattern 9 End plate 10 batteries 11 Compressor 12 Expansion valve 13 Battery cooler 14 Heat dissipation 15 Fans 16 Heatsink 17 First fluid introduction path 17a Entrance 17b Exit 18 2nd fluid inlet 19 2nd fluid outlet WP wave pitch Wθ Tilt angle a. Planar length in the long side direction on the heat transfer surface b. Planar length in the short-side direction on the heat transfer surface b / a aspect ratio P center line H straight line

Claims

1. In a cup-shaped plate (2) which is a planar rectangle having a pair of opposing long sides and a pair of opposing short sides, On one side of the plate (2) in the direction of its short side, a pair of first circulation holes (3a, 3b) are arranged spaced apart in the direction of its long side. On the other side of the plate (2) in the short direction, a pair of second flow holes (4a, 4b) are arranged spaced apart in the long direction. The plate (2) has a heat transfer surface (1) in which a herringbone pattern is formed by irregularities in the center of its flat surface. The plates (2) are stacked so that the direction of the herringbone pattern is reversed every other plate. In a plate stacked evaporator in which a core (5) is formed in which a first flow path (3) through which a first fluid (6) flows and a second flow path (4) through which a second fluid (7) flows are alternately formed, When the plane length in the long side direction of the heat transfer surface (1) is a and the plane length in the short side direction is b, the aspect ratio between them is b / a. 0.4 ≦ b / a ≦ 1.3 And, The pitch Wp (mm) of the herringbone-like irregularities on the heat transfer surface (1) is 3mm≦Wp≦4mm And, The angle of inclination Wθ (deg) between a straight line H parallel to the shorter side of the plane and the herringbone pattern is, 20° ≦ Wθ ≦ 40° This is a plate stacking type evaporator.

2. In the plate stacking evaporator according to claim 1, 20° ≦ Wθ ≦ 30° This is a plate stacking type evaporator.

3. In the plate stacking evaporator according to claim 1 or claim 2, The first fluid (6) is a refrigerant used for air conditioning in vehicles equipped with electric motors. The second fluid (7) is LLC used for cooling the batteries of vehicles equipped with electric motors, and is a plate stacked evaporator.

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