Heat exchanger and its design method, and heat transfer tube

Claims

1. A first heat transfer tube through which a first fluid can flow from a first inlet to a first outlet, A circular double tube having a second heat transfer tube through which a second fluid can flow from a second inlet to a second outlet, The first heat transfer tube has a first region in which the diameter decreases from the first inlet to the first outlet, a second region in which the diameter increases continuously with respect to the first region, and a third region in which the diameter increases further than that of the second region, The diameter of the second heat transfer tube is constant from the second inlet to the second outlet. A heat exchanger in which the diameter of the second heat transfer tube is the sum of the minimum diameter of the first heat transfer tube and the maximum flow width of the second fluid.

2. The heat exchanger according to claim 1, wherein the rate of increase of the pipe diameter in the third region is greater than the rate of increase of the pipe diameter in the second region.

3. The heat exchanger according to claim 1, wherein the length of the second region from the first inlet to the first outlet is longer than the length of the first region, and the length of the first region from the first inlet to the first outlet is longer than the length of the third region.

4. The heat exchanger according to claim 1, wherein the first fluid is a refrigerant and the second fluid is a heating fluid.

5. The heat exchanger according to claim 1, wherein the first fluid is carbon dioxide and the second fluid is water or brine.

6. A first heat transfer tube through which a first fluid can flow from a first inlet to a first outlet, A circular double tube having a second heat transfer tube through which a second fluid can flow from a second inlet to a second outlet, The first heat transfer tube has a first region in which the tube diameter decreases from the first inlet to the first outlet, and a second region continuous with the first region in which the tube diameter decreases further than that of the first region. The flow path cross-sectional area in the second heat transfer tube is constant from the second inlet to the second outlet. The diameter of the second heat transfer tube is the sum of the minimum diameter of the first heat transfer tube and the maximum flow width of the second fluid. A heat exchanger in which, in the heat exchange region between the first fluid and the second fluid, the flow path cross-section at the first inlet is parallel to the flow path cross-section at the second inlet, and the flow path cross-section at the first outlet is parallel to the flow path cross-section at the second outlet.

7. The heat exchanger according to claim 6, wherein the rate of reduction of the pipe diameter in the first region is greater than the rate of reduction of the pipe diameter in the second region.

8. The heat exchanger according to claim 6, wherein the length of the first region from the first inlet to the first outlet is longer than the length of the second region.

9. The heat exchanger according to claim 6, wherein the first fluid is a refrigerant and the second fluid is a heat dissipation fluid.

10. The heat exchanger according to claim 6, wherein the first fluid is carbon dioxide and the second fluid is water or brine.

11. The first inlet is connected to a first fluid distribution reservoir that causes the first fluid to flow into the first heat transfer tube, The first outlet is connected to a first fluid collection reservoir that collects the first fluid that has flowed through the first heat transfer tube. The second inlet is connected to a second fluid distribution reservoir that causes the second fluid to flow into the second heat transfer tube. The heat exchanger according to claim 6, wherein the second outlet is connected to a second fluid collection reservoir that collects the second fluid that has flowed through the second heat transfer tube.

12. A first heat transfer tube through which a first fluid can flow from a first inlet to a first outlet, A circular double tube having a second heat transfer tube through which a second fluid can flow from a second inlet to a second outlet, The first heat transfer tube has a constant diameter from the first inlet to the first outlet. The second heat transfer tube has a constant diameter from the first inlet to the first outlet. The diameter of the second heat transfer tube is the sum of the diameter of the first heat transfer tube and the width of the flow path of the second fluid. The first fluid is a refrigerant, and the second fluid is water or brine. A heat exchanger in which, in the heat exchange region between the first fluid and the second fluid, the flow path cross-section at the first inlet is parallel to the flow path cross-section at the second inlet, and the flow path cross-section at the first outlet is parallel to the flow path cross-section at the second outlet.

13. The heat exchanger according to claim 12, wherein the refrigerant is carbon dioxide.

14. The first inlet is connected to a first fluid distribution reservoir that causes the first fluid to flow into the first heat transfer tube, The first outlet is connected to a first fluid collection reservoir that collects the first fluid that has flowed through the first heat transfer tube. The second inlet is connected to a second fluid distribution reservoir that causes the second fluid to flow into the second heat transfer tube. The heat exchanger according to claim 6, wherein the second outlet is connected to a second fluid collection reservoir that collects the second fluid that has flowed through the second heat transfer tube.

15. The heat exchanger described in claim 1 is provided as an evaporator, A refrigeration cycle apparatus comprising the heat exchanger described in claim 6 as a condenser.

16. A heat exchanger having a heat transfer tube having a first region in which the tube diameter decreases from a first inlet to a first outlet, a second region in which the tube diameter increases continuously with respect to the first region, and a third region in which the tube diameter increases more than that of the second region, continuous with respect to the second region.

17. A first heat transfer tube in which a first fluid can flow from a first inlet to a first outlet, A method for designing a heat exchanger having a circular double tube, the second heat transfer tube through which a second fluid can flow from a second inlet to a second outlet, Based on the dryness χ in of the first inlet of the first heat transfer tube and equation (1), the standard volume change work E of the first fluid is calculated. The standard volume change work E is divided into n parts, and the cumulative change work E k of the first fluid at each division point k is calculated based on equation (2). Based on conditional equation (3), the density ρk of the first fluid is calculated for each division point k. Based on the cumulative change work Ek of the first fluid at each division point k and equation (4), the velocity uk of the first fluid is calculated at each division point k. A heat exchanger design method for calculating the standard flow channel cross-sectional area A k for each division point k based on the density ρ k and velocity u k of the first fluid at each division point k and equation (5). [Math 1] (In equation (1), E represents the work done on the standard volume change, χ in represents the dryness of the inlet, R represents the gas constant (kJ / kg), T represents the absolute temperature of evaporation (K), vl represents the specific volume of the liquid (m³ / kg), and vg represents the specific volume of the vapor (m³ / kg).) [Math 2] (In equation (2), E k represents the cumulative change work at the division point k, and k represents the division point.) [Math 3] (In equation (3), ρ k represents the density at the division point k, χ k represents the degree of dryness at the division point k, and ρ l represents the density of the liquid.) [Math 4] (In equation (4), u k represents the velocity at the division point k.) [Math 5] (In equation (5), A k represents the standard channel cross-sectional area at the division point k.)