COOLING SYSTEM FOR TWO-PHASE REFRIGERANT

Abstract

A cooling system containing a two-phase refrigerant, which cooling system includes a condenser, an evaporator and a conveying device. Liquid and gaseous refrigerant from the evaporator are collected in a collection vessel to which a first discharge line and a second discharge line are connected. Gaseous refrigerant is guided through the first discharge line to the condenser, whereas liquid refrigerant is conducted through the second discharge line to a part of the cooling system downstream of the condenser. Furthermore, a corresponding fuel cell cooling system is described which includes a fuel cell which forms the evaporator of the cooling system.

Claims

1. A cooling system containing a two-phase refrigerant, comprising: a condenser configured to cool the two-phase refrigerant and to convert gaseous refrigerant into liquid refrigerant; an evaporator configured to heat the two-phase refrigerant, wherein at least some of the refrigerant vaporizes to form gaseous refrigerant; a conveying device configured to convey the two-phase refrigerant from the condenser to the evaporator; a control system configured to control a delivery rate of the two-phase refrigerant through the conveying device; a first collection vessel configured to collect the liquid refrigerant and gaseous refrigerant from the evaporator; a first discharge line fluidically connecting the first collection vessel to a part of the cooling system upstream of the condenser and being configured to discharge gaseous refrigerant from the first collection vessel; and a second discharge line fluidically connecting the first collection vessel to a part of the cooling system downstream of the condenser and being configured to discharge the liquid refrigerant from the first collection vessel.

2. The cooling system according to claim 1, further comprising: a first regulating valve arranged in the first discharge line and being configured to regulate a flow rate of the gaseous refrigerant through the first discharge line; wherein the control system is furthermore configured to control the first regulating valve such that the refrigerant in the first collection vessel has a higher pressure than the refrigerant in the part of the cooling system downstream of the condenser.

3. The cooling system according to claim 1, wherein at least a section of the first discharge line has a fixed flow resistance which is predetermined such that the refrigerant in the first collection vessel has a higher pressure than the refrigerant in the part of the cooling system downstream of the condenser.

4. The cooling system according to claim 1, further comprising: a second collection vessel configured to collect the liquid refrigerant from the condenser; wherein the second discharge line fluidically connects the first collection vessel to the second collection vessel.

5. The cooling system according to claim 1, further comprising: a supply line fluidically connecting the conveying device to the evaporator; and a second regulating valve arranged in the supply line and being configured to regulate a flow rate of the refrigerant through the supply line, wherein the control system is furthermore configured to control the second regulating valve such that the evaporator is operated in a wet vaporization process.

6. The cooling system according to claim 5, further comprising: a preheating heat exchanger thermally coupling the refrigerant in the supply line to the refrigerant downstream of the evaporator.

7. The cooling system according to claim 6, wherein at least one of the preheating heat exchanger is arranged in the first collection vessel, or the preheating heat exchanger thermally couples the refrigerant in the supply line to the gaseous refrigerant in the first discharge line, upstream of the condenser.

8. The cooling system according to claim 6, further comprising a second collection vessel configured to collect the liquid refrigerant from the condenser; wherein the second discharge line fluidically connects the first collection vessel to the second collection vessel, and wherein the preheating heat exchanger is arranged in the second collection vessel.

9. The cooling system according to claim 1, further comprising: a supercooler configured to supercool refrigerant downstream of the condenser and upstream of the conveying device.

10. A fuel cell cooling system, comprising: a fuel cell; and a cooling system according to claim 1, wherein the evaporator of the cooling system is the fuel cell.

11. The fuel cell cooling system according to claim 10, wherein the control system of the cooling system is furthermore configured to capture operating conditions of the fuel cell, to ascertain a cooling demand of the fuel cell based on the operating conditions, and to operate the cooling system such that the cooling demand of the fuel cell is covered and the evaporator of the cooling system is operated in a wet vaporization process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Preferred exemplary embodiments of the invention will now be explained in more detail with reference to the appended schematic drawings, in which:

[0063] FIG. 1 schematically shows a first variant of a cooling system;

[0064] FIG. 2 schematically shows a second variant of a cooling system;

[0065] FIG. 3 schematically shows a third variant of a cooling system; and

[0066] FIG. 4 schematically shows a fourth variant of a cooling system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] FIG. 1 schematically shows a first variant of a cooling system 10 which comprises a condenser 110, an evaporator 130 and a conveying device 120. The evaporator 130 is, for example, connected to the conveying device 120 via a supply line P1, P2, so that a refrigerant of the cooling system 10 can be conducted from the conveying device 120 into the evaporator 130. In the evaporator 130, the refrigerant, which is a two-phase refrigerant, can absorb heat energy and, as a result, at least some of the refrigerant vaporizes. In the further course of the cooling system 10, which will be described in more detail, the refrigerant flows to the condenser 110, in which it is cooled and condensed and is subsequently resupplied to the conveying device 120 in a liquid state. For this purpose, the condenser 110 can be thermally coupled to a heat sink A2, for example in the form of a cold fluid stream (outside air in the case of a vehicle).

[0068] Downstream of the evaporator 130 (or integrated therein or connected thereto) is a first collection vessel 135 which is configured for collection and separation of the liquid and gaseous refrigerant from the evaporator 130. For example, the first collection vessel 135 can be fluidically connected to an outlet of the evaporator 130 via a line P15.

[0069] The cooling system 10 has a first discharge line P21 which fluidically connects the first collection vessel 135 to a part of the cooling system 10 upstream of the condenser 110. As a result, gaseous refrigerant can be discharged from the first collection vessel 135 and be conducted into the condenser 110 for condensation. In the first discharge line P21, there can be arranged a first regulating valve 137 which is configured to regulate a flow rate of the gaseous refrigerant through the first discharge line P21. In this connection, the first discharge line is formed by the line sections P21 and P25. A pressure in the first collection vessel 135 can be controlled by means of the first regulating valve 137.

[0070] Alternatively, a section of the first discharge line, for example the line section P21 directly after the first collection vessel 135, can have a fixed flow resistance. In this connection, the fixed flow resistance can be adapted to the entire system in order to build up a higher pressure in the first collection vessel 135 than in the part of the cooling system 10 downstream of the condenser 110. As a result, the first regulating valve 137 can be dispensed with.

[0071] Furthermore, the cooling system 10 has a second discharge line P22 which fluidically connects the first collection vessel 135 to a part of the cooling system 10 downstream of the condenser 110. By means of the second discharge line P22, liquid refrigerant can be discharged from the first collection vessel 135 and be resupplied to the cooling system in a region which guides liquid refrigerant, that is to say, downstream of the condenser 110. From there, it can be resupplied to the conveying device 120, for example via the lines P30 and P5. The liquid refrigerant in the second discharge line P22 can be brought about solely on the basis of a pressure difference between the first collection vessel 135 and the section of the cooling system 10 downstream of the condenser 110. An additional conveying device is not necessary. Optionally, a regulating valve (not shown) can be integrated in the second discharge line P22 in order, for example, to build up the pressure difference (the higher pressure in the first collection vessel 135) and/or a fill level of liquid refrigerant in the evaporator 130 more rapidly.

[0072] FIG. 1 furthermore shows a second collection vessel 115 which is configured to collect the liquid refrigerant from the condenser 110. In this connection, the second discharge line P22 can fluidically connect the first collection vessel 135 to the second collection vessel 115. The second collection vessel 135 may also be integrated into the condenser 110 or may be a (widened) section of a refrigerant line P28, P30 downstream of the condenser 110.

[0073] If gaseous refrigerant accumulates in the second collection vessel 135, the second collection vessel 135 can be fluidically connected via a return line P29 to an inlet side of the condenser 110. For example, the return line P29 can open into a line section P27 of the cooling system upstream of the condenser 110. In order to avoid a bypass of the condenser 110, a check valve can be provided at the end of the return line P29.

[0074] In order to prevent gaseous refrigerant from getting into the conveying device 120, a supercooler 117 can be provided in a section of the cooling system between condenser 110 and conveying device 120, for example between second collection vessel 115 and conveying device 120. The supercooler 117 can have its own heat sink A1 (air stream or other cold fluid) and not that of the condenser 110. Alternatively, the supercooler 117 and the condenser 110 can share a heat sink (not depicted) and/or the supercooler 117 and the condenser 110 form a unit (not shown), that is to say, are mutually integrated.

[0075] Finally, FIG. 1 additionally depicts a second regulating valve 132 which is arranged in the supply line P1, P2 and is configured to regulate a flow rate of the refrigerant through the supply line P2. In particular, the second regulating valve 132 can determine the quantity of refrigerant that is supplied to the evaporator 130. As a result, the cooling performance of the evaporator 130 is controlled, and thus also the pressure in the evaporator 130 and in the sections of the cooling system 10 downstream of the evaporator 130.

[0076] Optionally, the second regulating valve 132 can also be a branch of the supply line P2 and conduct at least some of the refrigerant conveyed through the line P1 by the conveying device 120 back into a section of the cooling system 10 downstream of the condenser 110 via a line section P16. For example, the line section P16 can open into the second collection vessel 115. As a result, the conveying device 120 can be operated continuously, whereas the inflow into the evaporator 130 is controlled via the second regulating valve 132.

[0077] The cooling system 10 has furthermore a control system 150 (or control unit, processor or computer) which is configured to control the conveying device 120 and especially its delivery rate of liquid refrigerant through the lines P5 and P1. Furthermore, the control system 150 can also determine and control the opening and closing and also a degree of opening of the regulating valves 132, 137. In addition, the control system 150 is configured to regulate the operation of the condenser 110 and/or the supercooler 117, for example by control of the supply of cold fluid as heat sink A1, A2.

[0078] Furthermore, the cooling system 10 can have sensors, especially pressure sensors and temperature sensors (not depicted). By means of the sensors, the control system 150 can ascertain the pressure and/or the temperature of the refrigerant at the relevant section of the cooling system 10 and control the conveying device 120 and/or regulating valves 132, 137 and/or heat sinks A1, A2. In this connection, the control system 150 is especially designed to ensure a temperature in the evaporator 130 that is as constant as possible. In particular if the evaporator 130 forms a fuel cell or an electrolyzer (or a part thereof), a constant temperature in the fuel cell/electrolyzer is optimal for the operation thereof. Moreover, the pressure difference between first collection vessel 135 and second collection vessel 115 can be built up and held by means of the control system 150 and, as a result, efficient operation of the cooling system 10 is made possible in a rapid and lasting manner.

[0079] Merely by way of example, the control system 150 can carry out various procedures in order to start the cooling system 10. For example, the second regulating valve 132 can be controlled in such a way that only a connection between line P1 and bypass P16 is present, whereas the first regulating valve 137 is open. Now, the heat sink A1 of the condenser 110 is put into operation in order to allow a temperature and pressure of the refrigerant for operation of the evaporator 130 (of the fuel cell or of the electrolyzer). If sufficient liquid refrigerant is present in the section downstream of the condenser 110, for example in the second collection vessel 115, the control system 150 starts the conveying device 120.

[0080] The control system 150 can be configured to determine the cooling demand of the evaporator 130. For example, the control system 150 can be supplied with signals or data which reflect an operating state of the device to be cooled. For example, on the basis of the consumed or generated electricity of a fuel cell or an electrolyzer, it is possible to ascertain how high the cooling demand of the fuel cell or the electrolyzer is. Accordingly, the control system can control the second regulating valve 132 in such a way that the necessary quantity of liquid refrigerant gets into the evaporator 130 through the line P2. As a result of the pressure now rising in the first collection vessel 135, the control system 150 can (at least partially) close the first regulating valve 137 in order to establish the above-described pressure difference between first and second collection vessel 135, 115.

[0081] Here, the control system 150 can limit the pressure in the first collection vessel 135 and thus in the evaporator 130 to a maximum. For example, the pressure in a fuel cell or an electrolyzer should be limited to a certain value, for example 3.5 bar, in order to ensure the reliable operation thereof. By means of the first regulating valve 137, the pressure in the evaporator 130, but also the quantity of liquid refrigerant in the evaporator 130, is controllable. Therefore, optimal operation of the fuel cell or the electrolyzer can be ensured.

[0082] The control system 150 can furthermore be configured to calculate (by means of pressure and temperature sensors) or measure (by means of a fill-level sensor) a fill level of liquid refrigerant in the evaporator 130. If a sufficient fill level has been reached, the control system 150 can close the second regulating valve 132 and/or reduce the delivery rate of the conveying device 120. In particular, the control system 150 can now operate the evaporator 130 in a wet vaporization process.

[0083] Furthermore, the control system 150 is configured to regulate the operation of the condenser 110 and/or the supercooler 117 in order to provide sufficient liquid refrigerant on the inlet side (upstream) of the conveying device 120. In particular, the heat sink A1 or A2 can be regulated here by the control system 150 in order to condense (liquefy) more or less refrigerant, and to hold it available in the second collection vessel 115, for example.

[0084] Lastly, the control system 150 can prevent the line P25 of the cooling system 10, which line guides gaseous refrigerant, from being flooded with liquid refrigerant. For this purpose, the quantity of liquid refrigerant in the supply line P2 can be controlled by closure of the second regulating valve 132 and can, for example, be diverted into the bypass P16.

[0085] In a further exemplary case, the control system 150 can also be designed to control the device to be cooled (for example the fuel cell or the electrolyzer). This is, for example, necessary if the cooling system 10 cannot achieve sufficient cooling performance in the evaporator 130. In the event of a leakage of the refrigerant from the cooling system 10 or an excessively high temperature of the heat sink A1, A2, it may be necessary to reduce the output of the device to be cooled and the associated heat quantity generated. In particular, the control system 150 is configured to capture the operating parameters of the device to be cooled and of the cooling system 10 and to ascertain in advance whether sufficient cooling of the device to be cooled can be achieved or whether the output (heat generation) of the device to be cooled must be reduced. Here, the control system 150 can take into account the maximum permissible pressure in the evaporator 130 and also minimum fill levels in the first and/or second collection vessel 135, 115 and in the evaporator 130.

[0086] It is self-evident that the control system 150 can also switch off the device to be cooled and the entire cooling system 10 in order to avoid damage to the device to be cooled and/or the cooling system 10. Here, the control system 150 can be configured to open the first regulating valve 137 in order to supply as much gaseous refrigerant as possible to the condenser 110. As a result, sufficient liquid refrigerant can be held available, for example in the second collection vessel 115, for later renewed starting of the cooling system.

[0087] If the refrigerant downstream of the conveying device 120 is too cold to be conducted into the evaporator 130 (for example, the operation of a fuel cell or an electrolyzer may be hindered or stopped in the event of excessively strong cooling), the refrigerant in the line section P1 or P2 can be heated. In the simplest case, a separate heater (not depicted) can be provided in order to provide the optimal temperature of the refrigerant for the evaporator 130.

[0088] Another form of heating of the refrigerant downstream of the conveying device 120 is depicted in FIG. 2. The cooling system 10 shown comprises a multiplicity of components which are also comprised in the cooling system 10 according to FIG. 1, and so the description thereof is not repeated here.

[0089] In the cooling system 10 as per FIG. 2, a preheating heat exchanger 140 is integrated in the supply line P2 and thermally couples the liquid refrigerant in the supply line P2, P2a to the refrigerant at the outlet side of the evaporator 130. For example, as illustrated in FIG. 2, the heat exchanger 140 can be arranged in the first collection vessel 135, such that the refrigerant in the first collection vessel 135 flows around the heat exchanger and the refrigerant in the supply line P2, P2a flows through the heat exchanger, and the heat exchanger provides thermal coupling between the two. In this way, the temperature of the refrigerant that is guided in the evaporator 130 can be kept as constant as possible over the time of operation of the cooling system 10.

[0090] A further alternative or additional possibility for heating the liquid refrigerant is shown in FIG. 3. The cooling system 10 shown comprises a multiplicity of components which are also comprised in the cooling system 10 according to FIG. 1, and so the description thereof is not repeated here. Here, a preheating heat exchanger 142 is integrated into the supply line section P1 between the conveying device 120 and second regulating valve 132. In the preheating heat exchanger 142, the liquid refrigerant, after leaving the conveying device 120, is thermally coupled to the gaseous refrigerant in the first discharge line P21, P25. The resulting cooling of the gaseous refrigerant reduces the cooling demand in the condenser 110.

[0091] FIG. 4, finally, shows a further alternative or additional possibility for heating the liquid refrigerant. The cooling system 10 shown comprises a multiplicity of components which are also comprised in the cooling system 10 according to FIG. 1, and so the description thereof is not repeated here. Here, a preheating heat exchanger 144 is integrated in the supply line P2, the preheating heat exchanger being arranged in the second collection vessel 115. In this way, the heat exchanger 144 can realize thermal coupling between the liquid refrigerant in the supply line P2 of the evaporator 130 and the liquid refrigerant in the second collection vessel 115.

[0092] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.