Automotive refrigeration system with multiple evaporators of varying cooling capacities

Abstract

Automotive refrigeration system (1) with several evaporators (8, 9, 10) of different cooling capacities, comprising a refrigerant circuit with at least one refrigerant compressor (2), at least one condenser (3), at least one expansion element (4) and evaporators (8, 9, 10) of different cooling capacities arranged in parallel to one another, wherein several evaporators (10) with a lower cooling capacity than battery cell coolers are connected in parallel in the refrigerant circuit, characterized in that a refrigerant receiver (5) for separating the liquid refrigerant is arranged downstream of the expansion element (4) and upstream of the evaporators (10) of lower cooling capacity, and that a refrigerant pump (6) for conveying the liquid refrigerant to the evaporators (10) of lower cooling capacity is arranged between the refrigerant receiver (5) and the evaporators (10), which are supplied with the liquid refrigerant by the refrigerant pump (6).wherein the refrigerant vapor from the evaporators (10) can be guided via the refrigerant collector (5) as a separator and can be drawn in by the refrigerant compressor (2) and wherein the evaporators (10) with lower cooling capacity are designed to be separable from the refrigerant circuit by a central shut-off device (7).

Description

The invention relates to a motor vehicle refrigeration system which operates several evaporators of different cooling capacities in a refrigerant circuit. The requirements for automotive refrigeration systems are highly diverse, and these systems must be designed to be correspondingly flexible in their application. In particular, automotive refrigeration systems for electric or hybrid vehicles must, in addition to their classic function of air conditioning the passenger compartment, also optimally cool electrical and electronic components to ensure their optimal and uninterrupted operation. Therefore, refrigerant circuits for motor vehicles require a particularly high and flexibly controllable cooling capacity compared to conventional refrigeration circuits, making them suitable for electric or hybrid vehicles. A special feature of these types of refrigerant circuits is that, especially in electric or hybrid vehicles, achieving optimal conditions during driving and battery charging necessitates cooling of the battery (or accumulator) and electronic components, as well as cooling of the vehicle interior for climate control. The need for rapid battery charging places particular demands on the vehicle's refrigeration system, as optimal battery charging depends on cooling the batteries during the charging process.Another unique aspect of this application is that the individual cooling capacities required for the various tasks differ significantly. Accordingly, the evaporators are designed and constructed differently. Refrigerant circuits for electric or hybrid motor vehicles are known in various configurations in the prior art. For example, US patent 2009 / 0317697 A1 discloses a refrigeration system for a motor vehicle with a bypass, which is suitable for providing battery cooling by means of a battery cooler. Furthermore, DE 103 13 850 A1 discloses a refrigerant circuit with two-stage compression for combined refrigeration and heat pump operation, particularly for motor vehicles. This refrigerant circuit incorporates two compressors connected in series, achieving two-stage compression, and is further optimized to also enable heat pump operation of the overall system. In WO 2013 / 125 006 A1, a cooling device for a vehicle and a method for controlling the cooling device are described. DE 100 01 470 A1 describes a method for operating an air conditioning system for a vehicle and designs of the required separator collector. The object of the invention is now to provide a refrigerant circuit for motor vehicles, in particular those with electric or hybrid drive, which, in addition to the tasks of generating cold for air conditioning the vehicle cabin, is also suitable for optimally supplying the batteries and electronic components with cold during driving operation as well as during battery charging operation. The problem is solved by an object having the features according to claim 1. Further developments are specified in the dependent claims. The problem is solved in particular by a motor vehicle refrigeration system with several evaporators of different cooling capacities, which includes a refrigerant circuit with at least the standard components of a refrigerant compressor, at least one condenser for liquefying the refrigerant, at least one expansion valve for expanding the refrigerant, and at least two evaporators of different cooling capacities arranged in parallel. The evaporators have a cooling capacity adapted to their respective tasks, and the invention is particularly aimed at optimally supplying one or more evaporators with lower cooling capacities with liquid refrigerant. For this purpose, a refrigerant receiver for separating the liquid refrigerant is arranged downstream of the expansion element and upstream of the evaporator with lower cooling capacity.Furthermore, a refrigerant pump is arranged between the refrigerant receiver and the evaporator with lower cooling capacity to transport the liquid refrigerant to the evaporator with lower cooling capacity. After the evaporator, the refrigerant vapor passes through connecting lines of the refrigerant circuit from the evaporator, via the refrigerant receiver, which acts as a separator for any remaining liquid refrigerant, and finally to the refrigerant compressor, from which the refrigerant vapor is drawn in. A particularly noteworthy feature is that the refrigerant receiver circuit and the subsequent active pumping of the liquid refrigerant to the evaporators with lower cooling capacities ensure a stable supply to these evaporators. This prevents, or even eliminates, local overheating caused by uneven refrigerant supply to the evaporators, for example, in applications such as cooling individual battery cells. The active pumping of the liquid refrigerant allows the individual evaporators with lower cooling capacities to be supplied with a surplus of liquid refrigerant, if necessary, thus ensuring a consistent evaporation temperature across the entire evaporator surface without local overheating.Liquid refrigerant may still be present at the evaporator outlet, but this is separated from the refrigerant flow by guiding the refrigerant through the refrigerant collector, and only the vaporous refrigerant is subsequently drawn in by the refrigerant compressor. Preferably, several evaporators with lower cooling capacities than battery cell coolers are arranged in parallel within the refrigerant circuit. The refrigerant pump supplies the parallel-connected battery cell coolers evenly with liquid refrigerant. Evaporator modules consisting of four to twenty or thirty individual evaporators with lower cooling capacities are preferably used. A cumulative cooling capacity of ten to twenty or thirty kW is required. In this system, evaporators with lower cooling capacity, such as battery cell coolers, are preferably supplied with liquid refrigerant at a uniform pressure level. For this purpose, the expansion device is positioned upstream of the refrigerant receiver, and the liquid refrigerant collected in the receiver is then at a pressure level consistent with that of all evaporators supplied by the refrigerant pump. Advantageously, evaporators with lower cooling capacity are designed to be separable from the refrigerant circuit by means of a central shut-off device. This ensures that, for example, the supply of refrigerant to certain areas can be completely interrupted in certain operating conditions, in order to have a sufficient quantity of refrigerant available for other tasks or to isolate specific sections of the circuit in the event of a failure. One embodiment of the invention consists in several evaporators being arranged in parallel as air coolers in the refrigerant circuit upstream of the evaporators with lower cooling capacity. Overall, the automotive refrigeration system allows for the implementation of cooling and air conditioning concepts that supply a large number of cooling consumers. Thus, for example, it is common practice to position evaporators for air conditioning the vehicle cabin as air coolers in different areas of the passenger compartment and to supply them separately with refrigerant via a parallel connection of the evaporators. These evaporators are particularly preferably equipped with separate expansion devices as air coolers, which allows for optimal adaptation of the cooling sources to the respective requirements in the individual areas of the passenger compartment. Alternatively or cumulatively, it may be advantageous to have separate shut-off devices assigned to the evaporators as air coolers in order to shut off the relevant areas of the refrigerant circuit in certain situations and thus disconnect them from a supply of refrigerant. A particularly preferred design for a vehicle refrigeration system is one that, in addition to the evaporators acting as air coolers, also includes an evaporator as a battery cooler connected in parallel within the refrigerant circuit. The battery cooler thus serves to cool the batteries under normal operating conditions. Therefore, such a circuit can be operated in a normal battery cooling mode using the battery cooler and, furthermore, in a mode with maximum cooling capacity of up to 20 kW. Alternatively, a separate expansion element can be assigned to the battery cooler, so that the cooling of the battery can also be easily regulated by appropriate control. Alternatively or cumulatively, the battery cooler is designed to be isolated from the refrigeration circuit by a separate shut-off device. In a particularly advantageous embodiment, the refrigerant compressor is designed in multiple stages or several compressors are provided. The concept of the invention consists in a refrigerant collector being arranged in front of a plurality of evaporators of any order of cooling capacity and in the motor vehicle refrigeration system being designed with one or more expansion devices for flexible adjustment of the individual evaporators. The refrigerant pump transports the refrigerant to the various evaporators, ensuring a constant and efficient supply of liquid refrigerant. Due to the high refrigerant flow rate in the evaporators, the refrigerant does not completely evaporate. This effectively prevents areas of the evaporators from experiencing localized overheating or higher temperatures, maintaining a consistent temperature within the evaporator. This is particularly advantageous when used to cool battery cells, which are subject to temperature fluctuations that can negatively impact their efficiency. The refrigerant vapor and liquid mixture exiting the evaporators flows to the receiver, where it is separated. The liquid refrigerant is then drawn in by the refrigerant pump and returned to the evaporators.The refrigerant gas is fed from the refrigerant collector, which acts as a separator, to the refrigerant compressor or drawn in by it. With the assistance of the refrigerant pump, improved oil transport within the liquid refrigerant is achieved. The saturated refrigerant gas is drawn in by the refrigerant compressor. This prevents problems caused by an uneven distribution of the refrigerant liquid. A further advantage is the reduced pressure drop resulting from the refrigerant pump's compensation of flow losses. A particular advantage is that different refrigerant circuits can be adapted to this system. For example, two compressors arranged in parallel with separate intakes can be configured for high and normal cooling capacities. Likewise, it is possible to separate the compression stages using a high-end refrigerant compressor with an inverter and a low-end compressor without an inverter to ensure consistently high performance during peak load phases of the refrigerant circuit. The advantages of the invention can thus be summarized as high cooling capacity, low pressure loss across the evaporators with lower cooling capacity, and better refrigerant distribution to the various evaporators. Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1: Automotive refrigeration system in the embodiment with one expansion valve; Fig. 2: Automotive refrigeration system with multiple evaporators and separate expansion; Fig. 3: Automotive refrigeration system with a plurality of battery cell coolers. Figure 1 shows a schematic diagram of a vehicle refrigeration system that operates with only one expansion element 4 and thus a single evaporation temperature level for all connected evaporators 8 and 10. The circuit begins with a refrigerant compressor 2, which compresses the gaseous refrigerant to a high pressure and delivers the high-pressure refrigerant gas to the condenser 3. In the condenser 3, the hot refrigerant gas is liquefied at high pressure; the heat transfer is indicated by an airflow symbolized by an arrow. The liquefied refrigerant is then expanded to the evaporation pressure in the expansion element 4, and any resulting mixture of refrigerant vapor and liquid refrigerant is separated in the refrigerant receiver 5. The liquid refrigerant flows from the refrigerant receiver 5 to the refrigerant pump 6 (shown at the bottom of the diagram) and is actively pumped into the cycle.Two evaporators 8 are arranged in parallel as air coolers, and a plurality of evaporators 10 serve as battery cell coolers. The air coolers 8 and the plurality of battery cell coolers 10 can each be isolated from the refrigerant circuit by a shut-off device 7, thus enabling precise control of the system. As schematically indicated in Fig. 1, the battery cell cooling is achieved by a plurality of smaller-capacity evaporators 10, enabling targeted cooling of individual battery cells with high efficiency and a constant temperature.After flowing through the evaporators 8 and 10 in parallel, the refrigerant gas enters the refrigerant receiver 5, which acts as a separator. Any unevaporated refrigerant is separated as a liquid and returned to the evaporators 8 and 10 via the refrigerant pump 6. Meanwhile, the refrigerant gas is drawn in and compressed by the refrigerant compressor 2, thus completing the cycle. A particularly advantageous feature is the lower pressure drop in the evaporators, as only liquid refrigerant is present at the evaporator inlet. This ensures a more uniform distribution of the incoming refrigerant compared to a two-phase mixture of refrigerant vapor and liquid. Furthermore, the design is simplified, as, for example, baffles or similar components are not required to guarantee uniform distribution. Figure 2 shows a modification of the circuit according to Figure 1, wherein the vehicle refrigeration system 1 additionally includes an evaporator 9 as a battery cooler for normal battery cooling conditions. Furthermore, up to thirty small battery cell coolers are used as evaporators 10 in the circuit. The air coolers 8 and the battery cooler 9 are each connected in parallel to the refrigerant circuit with a separate expansion element 4. Another parallel branch of the circuit is formed with a shut-off device 7 with separate expansion through the downstream expansion element 4, the refrigerant receiver 5, and the refrigerant pump 6 with the battery cell coolers 10. The refrigerant gas from the evaporators 10 is, as described above, routed via the refrigerant receiver 5, which acts as a separator, to the suction side of the refrigerant compressor 2.An advantageous aspect of this design is that the numerous smaller evaporators are arranged decentrally to the other evaporators. Figure 3 shows an embodiment of the vehicle refrigeration system 1 which, unlike the embodiment shown in Figure 2, does not have a battery cooler 9 as an evaporator for normal battery cooling operation. Again, it is possible to shut off the parallel flow through the battery cell coolers 10 by means of the shut-off device 7. The automotive refrigeration systems 1 of Figs. 1, 2 and 3 have the characteristic that the condenser 3 can be designed as an air, water or combined air and water condenser. Furthermore, the condenser 3 can be configured with a separate receiver or a subcooling surface. A particular advantage of the configuration shown in Fig. 1 is that only one expansion element is required for all evaporators 8 and 10. Furthermore, the evaporators 8 and 10 are arranged close to the refrigerant receiver 5, resulting in short paths and minimal losses. Another advantage is the particularly safe storage of the refrigerant within the circuit on the low-pressure side. It is also advantageous that the circuit can be completed by an internal heat exchanger or, for example, a work-generating expansion valve. The shut-off devices used are simple on / off valves, which enables particularly cost-effective operation and construction of the system. When using two refrigerant compressors, one compressor with an inverter can be combined with a second compressor without an inverter, resulting in cost savings. A high-pressure receiver is not required but is possible, and subcooling in the condenser is also feasible. Overall, a vehicle refrigeration system 1 according to Fig. 1 is capable of simply and effectively distributing refrigerant to the battery cell coolers 10. In Fig. 2, the design of the condenser 3 and the use of a simple single-stage refrigerant compressor 2 up to multi-stage refrigerant compressors are the same as those described in Fig. 1. The refrigerant-to-air heat exchangers, also referred to as air coolers 8, and the standard battery cooler 9 are operated with thermostatic expansion valves 4. The maximum battery cooling capacity is achieved by the low-pressure refrigerant receiver 5 and the refrigerant pump 6 of the battery cooler segment. The distribution of the refrigerant to the battery cell coolers 10 is possible without an additional expansion valve at low cost. An internal heat exchanger or a work-generating expansion element can also be integrated into the circuit in this system, resulting in two battery cooling systems: one for standard cooling via the battery cooler 9 and, alternatively, for high-temperature cooling loads using the battery cell coolers 10.As noted, up to 30 battery cell coolers 10 are required and operated. Finally, it should be added to Fig. 3 that the illustrated automotive refrigeration system 1 does not require the battery cooler 9 of the circuit shown in Fig. 2. The refrigerant pump 6 operates at a high pressure level, and overheating of the battery cooler segments is prevented by the cooling provided by the separate battery cell coolers 10. In all embodiments shown in Fig. 1, Fig. 2 to Fig. 3, the expansion elements can be designed as desired, for example as an orifice, as a thermostatic expansion valve, as an electric expansion valve, as a capillary, as an expander or as an ejector. Preferred refrigerants for automotive air conditioning systems are R1234yf, R152a, R290, R744, R717 or R1270. Reference symbol list 1 Automotive refrigeration system 2 Refrigerant compressor 3 Condenser 4 Expansion device, thermostatic expansion valve 5 Refrigerant receiver, low-pressure refrigerant receiver 6 Refrigerant pump 7 Shut-off device 8 Air cooler, evaporator 9 Battery cooler, evaporator 10 Battery cell cooler, evaporator

Claims

Automotive refrigeration system (1) with several evaporators (8, 9, 10) of different cooling capacities, comprising a refrigerant circuit with at least one refrigerant compressor (2), at least one condenser (3), at least one expansion element (4) and evaporators (8, 9, 10) of different cooling capacities arranged in parallel to one another, wherein several evaporators (10) with a lower cooling capacity than battery cell coolers are connected in parallel in the refrigerant circuit, characterized in that a refrigerant collector (5) for separating the liquid refrigerant is arranged downstream of the expansion element (4) and upstream of the evaporators (10) of lower cooling capacity, and that a refrigerant pump (6) for conveying the liquid refrigerant to the evaporators (10) of lower cooling capacity is arranged between the refrigerant collector (5) and the evaporators (10), which are supplied with the liquid refrigerant by the refrigerant pump (6).wherein the refrigerant vapor from the evaporators (10) can be guided via the refrigerant collector (5) as a separator and can be drawn in by the refrigerant compressor (2) and wherein the evaporators (10) with lower cooling capacity are designed to be separable from the refrigerant circuit by a central shut-off device (7). Motor vehicle refrigeration system (1) according to claim 1, characterized in that the evaporators (10) with lower cooling capacity are supplied with liquid refrigerant at a pressure level. Motor vehicle refrigeration system (1) according to claim 1 or 2, characterized in that several evaporators (8) are arranged in parallel as air coolers in the refrigerant circuit in front of the evaporators (10) of lower cooling capacity. Motor vehicle refrigeration system (1) according to claim 3, characterized in that separate expansion elements (4) are assigned to the evaporators (8). Motor vehicle refrigeration system (1) according to claim 3, characterized in that separate shut-off devices (7) are assigned to the evaporators (8). Motor vehicle refrigeration system (1) according to one of claims 1 to 5, characterized in that an evaporator (9) is additionally arranged in parallel in the refrigerant circuit as a battery cooler. Motor vehicle refrigeration system (1) according to one of claims 1 to 6, characterized in that a separate expansion element (4) is assigned to the evaporator (9). Motor vehicle refrigeration system (1) according to one of claims 1 to 6, characterized in that a separate shut-off device (7) is assigned to the evaporator (9). Motor vehicle refrigeration system (1) according to one of claims 1 to 8, characterized in that the refrigerant compressor (2) is designed in multiple stages.

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