DEVICE FOR HEAT TRANSFER AND METHOD FOR OPERATING THE DEVICE

Abstract

A device for the heat exchange between a first fluid and a second fluid, in particular for a refrigerant circuit of an air conditioning system for treating the incoming air of a passenger compartment of a motor vehicle comprising at least one first row and one second row which are each implemented of tubes for conducting the first fluid, the tubes being disposed in parallel and spaced apart from one another and, with respect to one another, such that the second fluid flows sequentially around the rows in a direction of flow. The tubes are disposed such that second can flow in parallel around the tubes. Rows are each implemented with an inlet and an outlet for the first fluid and spaced apart from one another. Between rows a gap is implemented in each instance. A method for operating the device is also provided.

Claims

1. A device for the heat exchange between a first fluid and a second fluid, comprising at least one first row and one second row which are each implemented of tubes for conducting the first fluid and disposed in parallel and spaced apart, wherein the tubes are disposed such that the second fluid can flow around them in parallel, and disposed such with respect to one another that the second fluid flows sequentially around the rows in a direction of flow, wherein the rows are each implemented with an inlet and an outlet for the first fluid and are disposed spaced apart from one another, wherein between the rows in each instance a gap is implemented.

2. A device as in claim 1, wherein the rows are mechanically connected with one another across connection elements.

3. A device as in claim 2, wherein the connection elements are implemented of a material and with a heat-transferring cross-section area such that the thermal resistivity of a connection element is at least 10 K/W.

4. A device as in claim 2, wherein the connection elements are implemented of a material with a coefficient of thermal conductivity of maximally 3 W/mK.

5. A device as in claim 2, wherein each of the connection elements has a heat-transferring cross-section area of maximally 1.5 mm.sup.2.

6. A device as in claim 1, wherein each row comprises a first collector tube as well as a second collector tube and the tubes of each row are in each instance implemented such that they extend between the first collector tube and the second collector tube.

7. A device as in claim 6, wherein the inlet and the outlet for the first fluid are implemented together on one of the collector tubes of the row.

8. A device as in claim 6, wherein the inlet for the first fluid is implemented on the first collector tube and the outlet for the first fluid is implemented on the second collector tube of the row.

9. A device as in claim 1, wherein the tubes of the row are implemented such that they are thermally connected with one another on an outer side across fins, wherein the fins of different rows are disposed spaced apart from one another.

10. An air conditioning system for treating the incoming air of a passenger compartment of a motor vehicle, wherein said system comprises a refrigerant circuit, and said refrigerant circuit comprises the device of claim 1.

11. An air condition system as in claim 10 wherein the device is a condenser/gas cooler of the refrigerant circuit, wherein the refrigerant is carbon dioxide and wherein transfer of heat is in the supercritical range of the refrigerant.

12. A method for operating a device for the heat exchange between a first fluid and a second fluid as in claim 1 in a refrigerant circuit of an air conditioning system of a motor vehicle, wherein through the tubes of each row flows the refrigerant as the first fluid and around which flows air as the second fluid, and wherein a mass flow of the refrigerant is divided into partial mass flows over the rows of the device and the partial mass flows are conducted in parallel through the rows.

13. A method as in claim 12, wherein a direction of flow of a partial mass flow of the refrigerant in a first row and a direction of flow of a partial mass flow of the refrigerant in a second row are aligned opposite to one another.

14. A method as in claim 12, wherein the rows of the device are sequentially acted upon by air in a direction of flow.

15. A method as in one of claims 12, wherein the mass flow of the refrigerant is divided into partial mass flows each between 0 and 100%.

16. A method as in claim 15, wherein a ratio of the partial mass flow flowing through a first row to the total mass flow of the refrigerant is in the range of 30% to 70%.

17. A method as in claim 12, wherein the device with the direction of flow of a refrigerant and the direction of flow of the air is operated along the principle of cross-counterflow.

18. A device as in claim 3, wherein the connection elements are implemented of a material with a coefficient of thermal conductivity of maximally 3 W/mK.

19. A device as in claim 2, wherein each row comprises a first collector tube as well as a second collector tube and the tubes of each row are in each instance implemented such that they extend between the first collector tube and the second collector tube.

20. A device as in claim 3, wherein each row comprises a first collector tube as well as a second collector tube and the tubes of each row are in each instance implemented such that they extend between the first collector tube and the second collector tube.

Description

[0043] Further details, characteristics and advantages of implementations of the invention are evident based on the following description of embodiment examples with reference to the associated drawing. Therein depict:

[0044] FIG. 1a: a pressure-enthalpy diagram for the operation of a refrigerant circuit in the subcritical range,

[0045] FIG. 1b: a pressure-enthalpy diagram for the transcritical operation of a refrigerant circuit with heat emission in the supercritical range,

[0046] FIG. 2: a multi-row refrigerant-air heat exchanger of prior art in top view, and

[0047] FIG. 3: a multi-row refrigerant-air heat exchanger according to the invention with indication of the directions of flow of the heat-transferring fluids.

[0048] In FIG. 3 is depicted a device 1 for heat transfer, in particular a multi-row heat exchanger 1 with indication of the directions of flow 5a, 5b, 8 of the heat-exchanging fluids.

[0049] The device 1, specifically implemented as a refrigerant-air heat exchanger, comprises tubes, not shown, disposed in several rows 2, in particular two rows 2a, 2b, aligned parallel to one another. The tubes, specifically implemented as refrigerant tubes, are herein flowed through in parallel in the particular row 2a, 2b, on the one hand by refrigerant as the first fluid and, on the other hand, in parallel flowed around by the air as the second fluid. Rows 2a, 2b, that is the refrigerant tubes of the individual rows 2a, 2b, are acted upon sequentially by air in the direction of flow 8. The air can herein be conducted first through the first row 2a and subsequently through the second row 2b, or first through the second row 2b and subsequently through the first row 2a.

[0050] According to an alternative embodiment, not shown, the device is implemented with more than two rows, which are disposed identically to the rows of device 1 of FIG. 3. The air herein flows advantageously in each instance according to the cross-counterflow principle with respect to the refrigerant through all rows, wherein the air flows either first into the first row or first into the last row.

[0051] A refrigerant mass flow circulating through a refrigerant circuit, comprising the device 1 as a component, is divided over the rows 2 such that one partial mass flow of the refrigerant each is conducted through each row. The refrigerant mass flow can herein be divided into partial mass flows between 0 and 100%.

[0052] In the embodiment according to FIG. 3 with two rows 2a, 2b, the ratio of the partial mass flow flowing through the first row 2a to the total mass flow of the refrigerant is preferably in the range of 30% to 70%. The ratio of the partial mass flow flowing through the second row 2b to the total mass flow of the refrigerant is therewith preferably in the range of 70% to 30%.

[0053] The refrigerant tubes of each row 2a, 2b extend each between a first collector tube, not shown, and a second collector tube, not shown. The refrigerant flows herein in each case in the direction of flow 5a, 5b through an inlet 6a, 6b into the first collector tube of each row 2a, 2b and is subsequently divided over a first group of refrigerant tubes of the row 2a, 2b. After the refrigerant has flowed in parallel through the refrigerant tubes of the first group of each row 2a, 2b, it is mixed in the second collector tube, its directional flow is changed and divided over a second group of refrigerant tubes. The refrigerant flows in the direction reversely to the flow through the first group of the refrigerant tubes in parallel through the second group of the refrigerant tubes back to the first collector tube. The refrigerant flows with a reversal of direction in dual flow through the first and the second group of the refrigerant tubes of rows 2a, 2b. The incoming air flows in the direction of flow 8 first around the refrigerant tubes of the second row 2b and subsequently around the refrigerant tubes of the first row 2a. The refrigerant-air heat exchanger 1 is operated in cross-counterflow with respect to the directions of flow 5a, 5b of the refrigerant and the direction of flow 8 of the air.

[0054] Inlets 6a, 6b and outlets 7a, 7b of the refrigerant are both implemented on the first collector tube of rows 2a, 2b and therewith on one side of the heat exchanger 1.

[0055] According to an alternative embodiment, the refrigerant flows in each instance through an inlet into the first collector tube of each row and is subsequently divided over the refrigerant tubes of the row. After the refrigerant has flowed in parallel through the refrigerant tubes of the row, it is mixed in the second collector tube and conducted through an outlet out of the heat exchanger. The refrigerant herein flows only in one direction and thus from a first side to a second side of the heat exchanger through the refrigerant tubes of the rows. The refrigerant-air heat exchanger is also operated in cross-counterflow with respect to the directions of flow of the refrigerant and also with respect to the direction of flow of the air. The inlets of the refrigerant are herein in each instance located on the first collector tube of each row while the outlets of the refrigerant are each implemented on the second collector tube of the rows. The inlets and the outlets of the refrigerant are either located on one side or on both sides of the heat exchanger.

[0056] According to a further alternative embodiment, the refrigerant flows with multiple direction reversals in the form of a meander and therewith with multi-flow through each row. Depending on the number of direction reversals, and therewith the number of flows, the inlets and the outlets of the refrigerant are disposed on the first collector tube and/or on the second collector tube, or on one side or both sides of the heat exchanger.

[0057] The direction of flow 5a of the refrigerant in the first row 2a and the direction of flow 5b of the refrigerant in the second row 2b, independently of the embodiment of the heat exchanger 1, are opposite to one another at identically implemented flow paths. The directions of flow 5a, 5b extend in opposite directions.

[0058] When the refrigerant in a row 2a, 2b, for example with or without direction reversal, flows essentially in the vertical direction from below upwardly, the refrigerant within the adjacently disposed row 2b, 2a flows with or without direction reversal essentially in the vertical direction from above downwardly.

[0059] When the refrigerant flows in a row, for example with or without direction reversal, essentially in the horizontal direction from right to left, the refrigerant within the adjacently disposed row flows with or without direction reversal essentially in the horizontal direction from left to right.

[0060] According to an alternative embodiment, not shown, the directions of flow of the refrigerant in the first row 2a and in the second row 2b, independently of the embodiment of the heat exchanger 1, at identically implemented flow paths, can also be disposed in the same direction. The directions of flow of the refrigerant within the rows 2a, 2b extend in parallel.

[0061] The inlets 6a, 6b and the outlets 7a, 7b are disposed with respect to each other depending on the desired direction of flow 5a, 5b of the refrigerant through the different rows 2a, 2b.

[0062] According to the embodiment of FIG. 3, the inlet 6a of the refrigerant of the first row 2a is above in the vertical direction and the inlet 6b of the refrigerant of the second row 2b is below in the vertical direction. The outlet 7a of the refrigerant of the first row 2a, furthermore, is disposed below in the vertical direction while outlet 7b of the refrigerant of the second row 2b is implemented above in the vertical direction.

[0063] According to an embodiment, not shown, the inlet of the refrigerant of the first row can be disposed below in the vertical direction and the inlet of the refrigerant of the second row can be disposed above in the vertical direction. The outlet of the refrigerant of the first row, furthermore, can be disposed above in the vertical direction while the outlet of the refrigerant of the second row can be implemented below in the vertical direction.

[0064] The inlet 6a, 6b and the outlet 7a, 7b of the refrigerant of each row 2a, 2b, can each be disposed on the same side or on opposite sides of the heat exchanger 1. The inlets 6a, 6b and the outlets 7a, 7b, respectively, of the refrigerant of rows 2a, 2b can each be implemented on the same side or on opposite sides of the heat exchanger 1.

[0065] The refrigerant tubes of each row 2a, 2b are thermally connected with one another via fins 9, wherein the refrigerant tubes are heat-conductingly coupled with one another. In comparison to a heat exchanger 1 according to FIG. 2 known from prior art, the refrigerant tubes of the different rows 2a, 2b, however, are not connected with one another so as to conduct heat. The fins 9 of the different rows 2a, 2b are disposed spaced apart from one another. Between the fins 9 of the different rows 2a, 2b there is, in each instance, a gap.

[0066] Rows 2a, 2b of the heat exchanger 1 according to FIG. 3 are mechanically coupled with one another across connection elements 10 such that the heat exchanger 1 is implemented as an integral component. Between the rows 2a, 2b and in particular between the fins 9 of the different rows 2a, 2b, a gap is formed which is ensured to be of a certain dimension by means of the connection elements.

[0067] The connection elements 10, disposed between rows 2a, 2b and maintaining the spacing to the adjacently disposed rows 2a, 2b, have a high thermal resistivity in order to exclude or minimize the heat transfer through heat conduction, and therewith the heat flow, between rows 2a, 2b of the heat exchanger 1.

[0068] Each of the connection elements 10 has a thermal resistivity of minimally 10 K/W or a heat conductance value or a thermal transmittance value of maximally 0.1 W/K. The thermal resistivity is derived, inter alia, from the thermal conductivity or the coefficient of thermal conductivity and the heat-transferring cross-section area.

[0069] The connection elements 10 can herein be implemented of a material, in particular a synthetic material, with a very low coefficient of thermal conductivity, for example less than or equal to 3 W/mK.

[0070] In addition, or alternatively, the effective cross-section area of the connection elements 10 for heat conduction can be implemented to be minimal. If each connection element 10 has a heat-transferring cross-section area of maximally 1.5 mm.sup.2, the connection elements 10 can also be implemented of a well heat-conducting material, that means of a material, for example of aluminum, with a coefficient of thermal conductivity greater than 3 W/mK. The device 1 herein has a minimal number of connection elements 10, for example four, with which sufficient mechanical stability of the device 1 is ensured.

LIST OF REFERENCE NUMBERS

[0071] 1, 1 Device, heat exchanger, refrigerant-air heat exchanger

[0072] 2 Row

[0073] 2a First row

[0074] 2b Second row

[0075] 2c Third row

[0076] 3 First collector tube

[0077] 4 Second collector tube

[0078] 5 Direction of flow refrigerant

[0079] 5a Direction of flow refrigerant first row 2a

[0080] 5b Direction of flow refrigerant second row 2b

[0081] 6 Inlet refrigerant

[0082] 6a Inlet refrigerant first row 2a

[0083] 6b Inlet refrigerant second row 2b

[0084] 7 Outlet refrigerant

[0085] 7a Outlet refrigerant first row 2a

[0086] 7b Outlet refrigerant second row 2b

[0087] 8 Direction of flow air

[0088] 9 Fins

[0089] 10 Connection elements