Thermal management system

Abstract

The invention relates to a thermal management system (1), in particular for a motor vehicle, comprising a coolant circuit (2) and a heat pump (8) which has a refrigerant circuit (7) and a compressor (9) designed to convey refrigerant in the refrigerant circuit (7), wherein the heat pump (8) has a condenser heat exchanger (10) and an evaporator heat exchanger (11) which are designed to exchange heat between the refrigerant circuit (7) and the coolant circuit (2), and the coolant circuit (2) has at least one low-temperature portion (6), which is provided on the evaporator heat exchanger (11) in particular, and at least one high-temperature potion (5), which is provided on the condenser heat exchanger (10) in particular, the evaporator heat exchanger (11) being connected or connectable to the high-temperature portion (5) and to the low-temperature portion (6).

Description

[0001] ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0002] Thermal management system

[0003] The invention relates to a thermal management system, in particular for a motor vehicle, with a coolant circuit and a heat pump having a refrigerant circuit, which has a compressor designed for conveying refrigerant in the refrigerant circuit, wherein the heat pump has a condenser heat exchanger and an evaporator heat exchanger designed for heat exchange between the refrigerant circuit and the coolant circuit.

[0004] Thermal management systems with a coolant circuit for transferring heat to various components or an interior, and a heat pump with an associated refrigerant circuit, are generally known from the prior art, particularly for vehicle temperature control. Such vehicle cooling systems usually have several cooling circuits, some of which can be coupled to form a thermal management system. Typically, a water-glycol-based coolant circuit is present, through which heat is dissipated to the environment. Another circuit includes a heat pump for air conditioning the passenger compartment or for assisting heat dissipation from the components. A third circuit is provided in some systems for heat dissipation from the transmission's lubrication and cooling oil system.

[0005] The passenger compartment is typically heated by coolant heat exchangers from the electric drive's cooling circuit and cooled via the heat pump's refrigerant circuit, requiring additional heat exchangers for air conditioning. For higher heating loads, additional electric heaters are usually provided, which either directly heat the coolant or the interior air.

[0006] The heat pump can only operate if it can be ensured that the compressor draws in only gaseous refrigerant. For this to happen, the suction pressure must be low enough that the refrigerant can still absorb heat in the evaporator and thus become gaseous. If this vapor pressure cannot be reduced further, the compressor cannot operate. ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0007] To maintain the cycle, it is therefore necessary to supply sufficient energy to the refrigerant at the evaporator so that it evaporates. If this is no longer possible, the heat pump must be switched off. Furthermore, the efficiency of the heat pump decreases significantly at low temperatures and, depending on the refrigerant used, reaches a limit below which it is no longer possible to extract heat from the ambient air, as the refrigerant pressure would reach unacceptable levels, or the refrigerant cycle would cease.

[0008] A further disadvantage is the decreasing evaporation pressure that accompanies decreasing temperatures. This pressure corresponds to the compressor's suction pressure and is directly related to the gas density and, consequently, to the refrigerant flow rate. The refrigerant flow rate, in turn, determines the compression effort and thus the required torque of the compressor drive, and therefore also the compressor's electrical power consumption. This means that at low temperatures, not only does the efficiency of the cycle decrease, but the compression power also diminishes. This is disadvantageous because the compressor's electrical power consumption is largely supplied to the refrigeration circuit and thus contributes to the provision of heating power.

[0009] This reveals a paradox, since the compression work and thus the compressor power is low precisely when the heating demand becomes dominant.

[0010] Therefore, in order to meet the heating demand, additional electric direct heaters are usually provided in existing systems for cases with high heating power requirements. However, these significantly increase the complexity, installation space requirements, weight, and costs of the overall system.

[0011] The invention is based on the objective of providing an improved thermal management system that enables improved operation of the heat pump. ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0012] The problem is solved by a thermal management system with the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0013] As described at the outset, the invention relates to a thermal management system, specifically for a motor vehicle. The thermal management system can alternatively be arranged in a stationary configuration, e.g., in a building. The thermal management system is fundamentally designed for temperature control of at least one associated component, for example, an electric motor, an electrical energy storage device, an interior space, a control unit, and the like. The flow of coolant to the individual components can be controlled, for example, by actuators or valves. In the present invention, temperature control is understood to mean cooling or heating.

[0014] The thermal management system thus comprises at least one coolant circuit that is thermally coupled to a refrigerant circuit that is part of, or associated with, a heat pump. In the heat pump, the refrigerant is circulated by a compressor within the refrigerant circuit, specifically in a closed-loop process. Following a known design, the heat pump includes, in addition to the compressor, a condenser heat exchanger, an evaporator heat exchanger, and an expansion valve. Thermal coupling exists between the coolant circuit and the refrigerant circuit in the heat exchangers, allowing heat to flow between them.

[0015] In this description, a thermal management system is generally defined as a system that regulates the temperature of at least two consumers. A consumer is therefore a device that needs to be cooled or heated. One consumer can be cooled and another can be heated. A consumer can also be cooled or heated in different operating states. Consumers requiring different temperatures can even be located in the same cooling circuit, as will be shown below. Preferably, a consumer can be an electric machine, specifically a drive unit of a motor vehicle. Furthermore, a ZF Friedrichshafen AG file 304129 Friedrichshafen 2024-09-25

[0016] The consumer could be an inverter. Additionally or alternatively, a consumer could be a passenger compartment. Advantageously, a consumer could also be a battery.

[0017] The invention is based on the finding that the refrigerant circuit comprises at least one low-temperature section, in particular arranged at the evaporator heat exchanger, and at least one high-temperature section, in particular arranged at the condenser heat exchanger, wherein the evaporator heat exchanger is connectable to or connected with the high-temperature section and the low-temperature section. As previously described, the thermal management system comprises the refrigerant circuit, in which refrigerant is circulated and which is associated with the heat pump, and the coolant circuit, in which coolant is circulated, wherein the heat exchange between refrigerant and coolant is effected by the heat exchangers. The heat exchange takes place at different points in the circuits, resulting in different temperature conditions.

[0018] It is therefore proposed that the evaporator heat exchanger not be connected exclusively to the low-temperature section, as is usually the case, but that heat exchange should also take place with coolant drawn from the high-temperature section. This can be achieved, as described below, by mixing coolant from the high-temperature section into the low-temperature section, or by connecting the two sections in such a way that the coolant from the high-temperature section flows into the low-temperature section. Alternatively, a thermal connection or thermal coupling without mixing the coolant can also be provided.

[0019] The thermal connection or mixing primarily results in an increase in the temperature of the evaporator heat exchanger, thus allowing for precise adjustment of the compressor's operating conditions. By raising the temperature through the extraction of refrigerant or heat from the high-temperature section, operating points for the heat pump are enabled that would not be possible without connecting the evaporator heat exchanger to the high-temperature section (ZF Friedrichshafen AG File 304129, Friedrichshafen, 2024-09-25). This allows, for example, the heat pump to be used in temperature ranges that would otherwise be inaccessible.

[0020] For example, it is possible to operate the heat pump in temperature ranges below -20 °C, specifically -25 °C, and preferably even below -30 °C. Introducing the refrigerant or heat from the high-temperature section into the evaporator heat exchanger can be used, for instance, for a targeted start-up procedure. Once the refrigerant in the refrigerant circuit or the individual components are sufficiently warmed up, the addition of refrigerant or the extraction of heat from the high-temperature section into the evaporator heat exchanger can be stopped. This will be explained in more detail later in the description.

[0021] As is known, the condenser heat exchanger is located in the refrigerant circuit after the compressor and before the expansion valve, and the evaporator heat exchanger is located after the expansion valve and before the compressor. Furthermore, the thermal management system can have at least two, and in particular exactly two, coolant circuits and (exactly) one refrigerant circuit. At least one cooling device can be arranged in the refrigerant circuit.

[0022] The different temperature sections, i.e., the high-temperature section and the low-temperature section, can be configured as separate sub-circuits of the refrigerant circuit, particularly when the refrigerant circuit is designed as a so-called "dual circuit." Alternatively, the refrigerant circuit can be configured as a single circuit, in which case the temperature sections are connected sequentially. The high-temperature section is thermally connected to the refrigerant circuit at a first point, namely the condenser heat exchanger, and the low-temperature section at a second point, namely the evaporator heat exchanger. The first point typically has a higher temperature than the second. In particular, the high-temperature section can be connected downstream of a compressor. Preferably, the low-temperature section can be connected upstream of the compressor.ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25.

[0023] Preferably, the thermal management system includes valves that allow for the selective distribution of coolant to different consumers and / or fluidic connection of the coolant circuits.

[0024] Furthermore, the thermal management system has at least one pump, preferably at least two, in particular exactly two pumps.

[0025] A thermal management system is proposed, for example for a motor vehicle, particularly an electrically powered vehicle, designed to ensure high electrical power consumption by the heat pump even at low temperatures. It comprises a heat pump with at least one evaporator heat exchanger capable of transferring heat from a liquid refrigerant to the refrigerant, and at least one condenser heat exchanger capable of transferring heat from the refrigerant to a liquid refrigerant. Furthermore, a compressor is used to compress the refrigerant in its gaseous state, and at least one expansion device is used to reduce the pressure in the refrigerant circuit. The compressor is preferably electrically driven.

[0026] Furthermore, at least one coolant circuit is present, with a low-temperature section formed downstream of the evaporator and a high-temperature section formed downstream of the condenser. The sections can be parts of a common coolant circuit (single circuit) or form separate coolant circuits (dual circuit). At least one circulation pump is provided for each section or circuit. Furthermore, at least one flow control device is provided, which makes it possible to assign the high-temperature section fluidically to the evaporator inlet and the low-temperature section to the condenser inlet, resulting in a series arrangement with respect to the flow (so-called single circuit). ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0027] Furthermore, an air-coolant heat exchanger is present, designed to heat the air supplied to the passenger compartment. Optionally, additional thermal consumers can be provided, such as energy storage devices, a radiator for exchanging energy between the coolant and the ambient air, an electronic power unit, an air-coolant heat exchanger designed to cool the air to the passenger compartment, a device for cooling an electric drive motor or another component requiring temperature control, or a variety of other components that can serve as heat sources or sinks. These consumers can also optionally be fluidically coupled.

[0028] Advantageously, the proposed design of the thermal management system ensures that the load on the compressor is increased, regardless of the ambient air temperature, so that the compressor's electrical power consumption at least meets the system's target heat demand. Preferably, the heating output can be controlled by the compressor's electrical power consumption by setting a target value between 50% and 90% of the compressor's rated power consumption. The compressor's drive speed should preferably be selected as low as possible or limited, taking into account the system's noise and vibration characteristics.

[0029] The described thermal management system can be designed to operate thermal consumers depending on the heat pump's operating state, in particular by extracting a limited amount of heat from the refrigerant circuit. As described below, this allows the heat balance to be maintained, preventing the thermal management system from shutting down.

[0030] To enable maximum power consumption by the heat pump, the mass flow rate must be high enough to apply a load torque close to the maximum torque to the compressor drive. The heat flow that can be transferred to the refrigerant in the evaporator heat exchanger must be at least as high as the heat flow absorbed by the refrigerant. To achieve this, the temperature level in the refrigerant circuit must be regulated independently of the outside temperature. This requires increasing the refrigerant temperature at the evaporator sufficiently to raise the low-pressure level at the compressor and thus the density of the refrigerant upstream of the compressor. To increase the pressure level, the temperature in the evaporator must be raised.

[0031] For this to work, the heat balance at the evaporator must be balanced, meaning the refrigerant temperature at the evaporator outlet remains nearly constant. In other words, the thermal management system ensures that the refrigerant inlet temperature at the evaporator heat exchanger and / or the refrigerant inlet temperature at the condenser heat exchanger is kept constant. To achieve this, a partial heat flow is transferred from the high-temperature section to the low-temperature section. This partial heat flow must be equal to the total heat flow transferred to the refrigerant plus thermal losses. Minor deviations will result in a change in the temperature level, with a tolerance of + / - 5 K being acceptable. In addition to the partial heat flow, the heating power extracted from the high-temperature section also influences the temperature level; this power should also be equal to the excess heat flow at the condenser.If the balance is even, the temperatures remain constant; otherwise, they rise or fall.

[0032] This can be achieved, for example, by diverting a partial heat flow from the high-temperature section and supplying it to the evaporator. At least the amount of heat extracted from the evaporator by the refrigerant must be returned via this thermal bypass. For example, the refrigerant extracts a heat flow of 8 kW from the coolant in the evaporator. The compression work, or the power input of the compressor, is, for example, 7 kW. In the condenser, the refrigerant circuit transfers 15 kW to the coolant. The 8 kW heat flow extracted from the coolant circuit leads to a cooling of the coolant in the low-temperature section, causing the temperature to drop. This also reduces the vapor pressure, and the effects described above become clearly evident. If no external energy source is available to balance the energy consumption, the process will cease. ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0033] If the evaporator is supplied with a heat flow from the high-temperature section (condenser side) that corresponds to the power drawn from the low-temperature section, the energy balance is achieved and the compression power or compressor power can be made available as heating energy. The heating power supplied to the vehicle thus corresponds to the difference between the heat power transferred to the refrigerant in the condenser and the heat power absorbed in the evaporator, which essentially corresponds to the electrical power consumption of the compressor, less any energy losses.

[0034] In one embodiment of the thermal management system, an inlet of the evaporator heat exchanger can be connected to the low-temperature section and, in particular via an orifice plate, to the high-temperature section. This allows a portion of the coolant flow from the high-temperature section to be diverted and fed or mixed into the low-temperature section. The mixing point, where the coolant extracted from the high-temperature section is fed into the low-temperature section, is located, in particular, between the last thermal consumer in the low-temperature section (in the coolant flow direction) and the inlet of the evaporator heat exchanger. In principle, the mixing point can also be located further upstream, for example, before the last thermal consumer upstream of the inlet of the evaporator heat exchanger. However, this reduces the cooling capacity for the last thermal consumer.

[0035] In this design, a coolant flow, or a partial flow, from the high-temperature section is diverted fluidically and fed to the low-temperature section upstream of the evaporator. This achieves or maintains a specific temperature level before or after the evaporator. This value can be defined variably but depends on the target suction pressure level. This allows for an increase in compression performance. Since coolant is diverted from one section to another, or from one circuit to another, a volume flow adjustment is necessary to compensate for the difference. (ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25)

[0036] Coolant from the low-temperature section is fed back into the high-temperature section at the same height.

[0037] It seems particularly advantageous to place the branch, i.e., the mixing point described earlier, only after the components to be heated, so that the highest heating output can be provided to the components being heated, for example, to an interior heater for the passenger compartment. However, it must be ensured that the thermal output from the high-temperature section does not exceed the heat flow at the evaporator. It proves particularly beneficial to keep the refrigerant temperature at the evaporator outlet and the condenser inlet as close to the same level as possible, or to regulate only a slightly lower temperature at the evaporator inlet.

[0038] As previously described, the temperature sections can optionally be subsections of a single circuit or they can be configured as separate circuits of a dual-circuit system. The thermal management system can further be designed with a coolant circuit, particularly a single circuit, in which the connection between the evaporator heat exchanger and the high-temperature section is established via the low-temperature section that follows the high-temperature section. In other words, the coolant is fed from the high-temperature section into the low-temperature section. Advantageously, this ensures that the coolant has already passed through the components to be heated. Furthermore, in the described design, no bypass, valve, or orifice is required to connect the high-temperature section to the mixing point.

[0039] In the described further development, under the aforementioned condition of ideally equal temperatures at the condenser inlet and evaporator outlet, both temperature sections can be fluidically connected in such a way as to create a series connection (i.e., a single circuit). This means that coolant, which is pumped into the low-temperature section, for example by a first pump, and flows upstream to the evaporator, is fed to the suction side of the second pump, which pumps the volume flow upstream to the condenser and terminates at the suction side of the first pump (ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25). Thermal loads can be routed through the system between these two sections.

[0040] To ensure that the temperature level after the condenser is sufficiently high to meet the heating requirements, it must be guaranteed that no more heat is dissipated between the condenser outlet and the evaporator inlet than the electrical power input of the compressor. Therefore, the heat output to the consumers should be controllable, with the temperature difference between the condenser outlet and the evaporator inlet being < 5 K, preferably < 2 K. For optimal heating performance, the temperature level at the condenser outlet should be as high as possible, in particular > 50°C, preferably > 65°C.

[0041] In a further embodiment of the thermal management system, it can be provided that, particularly in a start-up state, the low-temperature section is separated from the evaporator heat exchanger and the evaporator heat exchanger is integrated into the high-temperature section, particularly downstream of the condenser heat exchanger. This allows, in particular, the complete separation of the low-temperature section from the evaporator heat exchanger. In this separated state, the refrigerant can circulate in the low-temperature section but has no connection to the refrigerant circuit. This allows conditions to be reached in which the temperature level at the evaporator inlet is higher than at the condenser inlet.

[0042] In the described configuration, the entire volume flow in the high-temperature section downstream of the condenser is routed directly through the evaporator. This state can be selectively created or separated, for example, by a valve assembly. Suitable devices (e.g., valves) are required to decouple the evaporator from the low-temperature section and connect it to the high-temperature section.

[0043] In the evaporator, heat is extracted from the high-temperature section to ensure the pressure increase described above, maximizing performance. The slightly cooled refrigerant from the evaporator is then routed to the consumers (ZF Friedrichshafen AG File 304129, Friedrichshafen, September 25, 2024) and used for heating. It is important to ensure that the temperature in the high-temperature section after the evaporator remains high enough to meet the heating requirements at the consumers, for example, reaching the target air temperature at the vents in the passenger compartment. With independent refrigerant circuits, it is possible to shut down or temporarily deactivate the low-temperature section. By appropriately wiring the system, the radiator can be integrated into the low-temperature section, thus ensuring the cooling of all components even without a connection to the heat pump or the refrigerant circuit.

[0044] By decoupling / deactivating the low-temperature section from the heating operation, heat losses in the coolant circuit are minimized. This allows for high heating output and a rapid heating phase, as the heat capacity of the low-temperature section does not need to be considered. For initial rapid heating, all heat sinks should be operated in such a way that there is no, or at most minimal, heat transfer from the high-temperature section. This means that the lowest possible, or even no, flow rate from the consumer side must be ensured at all heat exchangers. The battery should be disconnected from the heating circuit or high-temperature section. Once the target temperature in the high-temperature section is reached, the power outputs should be prioritized accordingly so that the heat flow balance is as even as possible.

[0045] The thermal management system can be further developed by an auxiliary heat exchanger whose low-temperature side, in particular its low-temperature outlet, is connected to the inlet of the evaporator heat exchanger, and whose high-temperature side, in particular its high-temperature inlet, is connected to the outlet of the condenser heat exchanger. The described auxiliary heat exchanger thus allows for targeted heat transfer from the high-temperature section to the low-temperature section. For example, the auxiliary heat exchanger can be arranged downstream of the condenser heat exchanger, so that, for instance, no thermal loads are located between the high-temperature inlet of the auxiliary heat exchanger and the outlet of the evaporator heat exchanger.The low-temperature side of the auxiliary heat exchanger can be designed in such a way that there are no thermal consumers between the low-temperature outlet of the auxiliary heat exchanger and the inlet of the evaporator heat exchanger (ZF Friedrichshafen AG file 304129, Friedrichshafen 2024-09-25).

[0046] In the described design, the heat output is transferred from the high-temperature section to the low-temperature section upstream of the evaporator via a heat exchanger, namely the auxiliary heat exchanger described. It appears particularly advantageous to continuously direct the flow rate of one circuit or section, for example, the low-temperature section or the high-temperature section, through the auxiliary heat exchanger. The other circuit or section, for example, the high-temperature section or the low-temperature section, can, however, be variably integrated or connected, so that it only flows through the auxiliary heat exchanger when needed. If the heating output is not required, the high-temperature section bypasses the auxiliary heat exchanger, for example, by diverting the high-temperature section into a bypass via a valve.

[0047] In comparison to the previously described embodiment, only one device for diverting a circuit is required, but an additional heat exchanger is necessary. A particular advantage of this variant is that all functions of the thermal management system are retained. The temperature at the inlet of the additional heat exchanger should be adjusted so that the heat flow at the evaporator ensures a balanced heat flow. This means that, in order to keep the size of the additional heat exchanger as small as possible, the temperature difference between the high-temperature and low-temperature sections should be at least as large as, or at most 10% greater than, the temperature difference between the high-temperature and low-temperature sections, sufficient to guarantee the heat pump's performance.

[0048] The thermal management system can be further developed by an additional heat exchanger integrated into or connected to the evaporator heat exchanger, wherein the low-temperature side of the additional heat exchanger is connected to or forms the coolant circuit side of the evaporator heat exchanger, and the high-temperature side of the additional heat exchanger is connected to the outlet of the ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0049] The condenser heat exchanger can be connected, in particular optionally by means of a valve. In principle, the embodiments described above with regard to the auxiliary heat exchanger also apply to the auxiliary heat exchanger integrated into or connected to the evaporator heat exchanger. The preceding description is therefore fully applicable.

[0050] Integrating the auxiliary heat exchanger into the evaporator heat exchanger allows for a particularly compact design. Furthermore, the number of components and the need for corresponding fluid connections are reduced. The auxiliary heat exchanger is integrated into the evaporator heat exchanger in such a way that it has only one inlet for refrigerant from the low-temperature section. The refrigerant from the low-temperature section flows through the auxiliary heat exchanger, which is connected to the evaporator heat exchanger in such a way that the refrigerant flowing through the low-temperature side undergoes heat exchange with the refrigerant circuit.

[0051] As previously described, the thermal management system should always aim for a balanced heat budget. It can be designed to regulate a temperature level in the high-temperature section and / or the low-temperature section by controlling the flow rate in the high-temperature section and / or the low-temperature section. The flow rates can be specifically adjusted, for example, by at least one pump or pumping unit. Depending on which flow rate is set in which temperature section, the corresponding temperature levels are achieved.

[0052] Furthermore, it can be additionally or alternatively provided that the heating power delivered to the refrigerant circuit is regulated by controlling the compressor, in particular its speed and / or torque. The heating power delivered to the refrigerant circuit is adjusted according to the compressor's power consumption. This allows the temperature and volume flow rate at the condenser inlet to be used as control variables for the compressor setting. (Compensation of ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25)

[0053] The power balance, as previously described, is achieved in particular via the volume flows in the individual temperature sections or sub-circuits.

[0054] Based on this, the initial temperature adjustment is advantageously carried out according to the following procedure. If a heating output is required that exceeds the current potential of the heat pump, either because the outside temperature level does not allow sufficient energy harvesting, or because the total heating output in heat pump mode is unattainable for other reasons, the temperature level in the circuits or temperature sections is first raised by supplying energy to the high-temperature section via the heat pump, while initially minimizing energy withdrawal from the high-temperature section, for example, by consumers.

[0055] This means that in the first step, only the refrigerant circuit should be heated using the electrical power of the compressor. It is advantageous to feed as much of the heat flow as possible, which is transferred via the condenser to the high-temperature section, back into the low-temperature section so that the temperature level at the evaporator rises. The parameters volume flow, compressor power, etc., should be selected with a view to maximizing heat output. This will initially raise the temperatures of the refrigerant circuits or temperature sections until the high-temperature section reaches a target temperature level that enables the desired heating output at the consumers.

[0056] In addition to the net heating output, other target parameters, such as the air temperature at the air outlets in the passenger compartment, must be considered. Once the target temperature is reached, the partial heat flow to the evaporator can be reduced, or the heat output to the consumer(s) can be increased. However, the heat flow extracted from the high-temperature section should only be adjusted to a level that largely balances the heat budget. This is ensured when the refrigerant temperature levels at the evaporator outlet and condenser inlet remain largely constant. As the temperature increases, the pressure and thus the power consumption of the compressor also increase, so the achievable heating output also rises. ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0057] The heat balance of a heat pump can be described as follows: In the evaporator, the refrigerant is converted into a gaseous state by energy input from the lower-temperature section. This cools the refrigerant in the lower-temperature section. The gaseous refrigerant is then drawn in by the compressor and compressed to a higher pressure level, thereby increasing its density and temperature. This process requires compression work, which is supplied by the compressor as mechanical power. An electric compressor also incurs electrical losses, which are usually also absorbed by the refrigerant. This ensures the cooling of the compressor. The high-pressure gas then flows to the condenser, where the refrigerant releases energy to the refrigerant in the high-temperature section.The amount of heat delivered to the high-temperature section is therefore equal to the sum of the compressor power and the heat flow transferred in the evaporator, reduced by any heat losses between heat absorption and heat release, which results in a lower actual achievable power output.

[0058] In principle, the compressor's drive unit, for example an electric motor, can always be operated at optimal efficiency to maximize energy efficiency. In one embodiment, the thermal management system can be configured to operate the compressor at a defined efficiency, particularly a reduced efficiency compared to maximum efficiency, by means of compressor trimming. In other words, the compressor's drive unit can be deliberately operated with operating parameters that deviate from optimal operating parameters, i.e., in a trimmed state. This allows for further control of the heating power delivered to the system.

[0059] In addition to the described thermal management system, the invention relates to a motor vehicle that includes such a thermal management system.The invention further relates to a method for controlling the operation of a thermal management system, in particular for a motor vehicle, with a coolant circuit and a heat pump (ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25) having a refrigerant circuit, which has a compressor designed for conveying refrigerant in the refrigerant circuit, wherein the heat pump has a condenser heat exchanger and an evaporator heat exchanger designed for heat exchange between the refrigerant circuit and the coolant circuit, wherein the coolant circuit has at least one low-temperature section, in particular arranged on the evaporator heat exchanger, and at least one high-temperature section, in particular arranged on the condenser heat exchanger, wherein the evaporator heat exchanger is connected to the high-temperature section and the low-temperature section.

[0060] All the advantages, details, and features described in relation to the thermal management system are fully transferable to the motor vehicle and the procedure. As previously described, the procedure for controlling the operation or the operating state of the thermal management system can be specifically used to execute a start-up or warm-up state. For example, if the ambient temperature of the thermal management system falls below a certain limit, specifically below -20 °C, or more specifically below -25 °C, or even -30 °C, the procedure can be executed to still enable the operation of the heat pump or to achieve more efficient operation of the heat pump for providing heating power.

[0061] For example, the heat pump can be operated to preheat the system or the refrigerant circuit. The temperature in the temperature sections or circuits can then be raised. In this state, thermal consumers, such as the passenger compartment, battery, electric motor, and the like, are advantageously switched off or decoupled from the refrigerant circuit, or connected only with a very low mass flow. As soon as the refrigerant circuit reaches a defined temperature, for example -5 °C, the thermal consumers can be switched on. This switching on can, for example, follow a predefined prioritization. This can be achieved by specifically exploiting the fact that the compressor has to perform more work at higher pressure in the refrigerant circuit, and in particular, must be operated at higher torque.Therefore, the higher the temperature is set at the evaporator (ZF Friedrichshafen AG File 304129, Friedrichshafen, 2024-09-25), the higher the pressure. At the same time, this results in a higher mass flow rate in the refrigerant circuit, which in turn increases the power consumption.

[0062] The invention is explained below with reference to exemplary embodiments and the figures. The figures are schematic representations and show:

[0063] Fig. 1 shows a schematic representation of a thermal management system according to a first embodiment;

[0064] Fig. 2 shows a schematic representation of a thermal management system according to a second embodiment;

[0065] Fig. 3 shows a schematic representation of a thermal management system according to a third embodiment;

[0066] Fig. 4 shows a schematic representation of a thermal management system according to a fourth embodiment; and

[0067] Fig. 5 shows a schematic representation of a thermal management system according to a fifth embodiment.

[0068] Fig. 1 shows a thermal management system 1, specifically for a motor vehicle not shown in detail. The thermal management system 1 has a coolant circuit 2 in which coolant is circulated, for example by means of two pumps 3, 4. The coolant circuit 2 generally has a high-temperature section 5 and a low-temperature section 6. These are shown in Fig. 1 as separate circuits, for example as a high-temperature circuit and a low-temperature circuit. Such a dual-circuit system is also shown, for example, in Figs. 3-5. Alternatively, the high-temperature section 5 and the low-temperature section 6 can also form subsections of a single-circuit coolant circuit 2.The basic functionality of the thermal management system 1 is the same, so that the corresponding details can be transferred to the individual embodiments of ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25 or exchanged and combined with each other.

[0069] In addition to the coolant circuit 2, the thermal management system 1 has a refrigerant circuit 7, which is assigned to a heat pump 8. The heat pump 8 has a compressor 9 that circulates the refrigerant in the refrigerant circuit 7, drawing it in from a suction side and compressing it. A condenser heat exchanger 10, an evaporator heat exchanger 11, and an expansion valve 12 are also arranged in the refrigerant circuit 7. In this cycle, the compressor 9 draws in refrigerant on its suction side, which exits the evaporator heat exchanger 11, and delivers it, compressed, to the inlet of the condenser heat exchanger 10. After passing through the condenser heat exchanger 10, the refrigerant is expanded by the expansion valve 12 and returned to the evaporator heat exchanger 11. The basic design of the thermal management system 1, in particular of the coolant circuit 2 and the refrigerant circuit 7, is applicable to all subsequent embodiments shown in Figures 2-5.

[0070] In principle, various thermal consumers can be integrated into the coolant circuit 2, in particular into the high-temperature section 5 and the low-temperature section 6. By way of example, a radiator 13, an air conditioning unit 14 for a passenger compartment, and control electronics 15 are integrated into the low-temperature section 6. An electric motor 16, an interior heater 17, and an electrical energy storage device 18 are integrated into the high-temperature circuit 5. By means of appropriate switching positions of a distribution unit or valve assembly 19, which has a multitude of valves, the individual thermal consumers can be selectively supplied to or disconnected from either the high-temperature section 5 or the low-temperature section 6, depending on their temperature requirements.

[0071] Particularly during startup or at comparatively low ambient temperatures, especially so low that heat harvesting via the radiator 13 is no longer possible, heat from the high-temperature circuit 5 is supplied to the low-temperature section 6. Figure 1 illustrates this by way of example, showing that coolant (ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25) is diverted from the high-temperature section 5 after passing through the thermal consumers, in particular after the interior heater 17 and the energy storage unit 18, and is fed, for example via a throttle, to the mixing point 20. Although the mixing point 20 can, in principle, be located at various points in the low-temperature section 6, in the embodiment shown, the mixing point 20 is located before the inlet of the evaporator heat exchanger 11, i.e., between the control electronics 15 and the evaporator heat exchanger 11.In other words, the mixing point 20 lies between the last thermal consumer in the direction of coolant flow and the inlet of the evaporator heat exchanger 11.

[0072] Furthermore, it may be provided that a valve can be used instead of a throttle, so that the mixing of refrigerant from the high-temperature section 5 into the low-temperature section 6 can be controlled or regulated. Mixing refrigerant from the high-temperature section 5 into the low-temperature section 6 increases the temperature at the evaporator heat exchanger 11 and thus increases heat transfer into the refrigerant circuit 7. This increases the pressure and temperature in the refrigerant, allowing the heating power supplied via the compressor 9 to be increased.

[0073] In all embodiments, it can be specifically desired that, particularly in the start-up state of the thermal management system 1, the thermal consumers are operated depending on the performance state of the heat pump 8 or the refrigerant circuit 7. Specifically, only enough heat should be extracted from the high-temperature section 5 to balance the heat balance at the evaporator heat exchanger 11. In other words, precisely enough heat should be supplied to maintain a balanced heat balance and thus prevent the cycle from stalling. For example, the temperatures at the condenser heat exchanger 10 and the evaporator heat exchanger 11 can be kept constant, so that neither heating nor cooling occurs during continuous operation. ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0074] Figure 2 shows an alternative embodiment in which the coolant circuit is designed as a single circuit, i.e., the high-temperature section 5 connects to the low-temperature section 6, or coolant flows from the high-temperature section 5 into the low-temperature section 6. Advantageously, this ensures that the heat balance is always maintained. Furthermore, compared to the previously described embodiment, no branch or mixing point is required. The evaporator heat exchanger 11 is connected to the high-temperature section 5 via the connection between the high-temperature section 5 and the low-temperature section 6. It is also advantageous that the coolant leaving the condenser heat exchanger 10 first passes through the components to be heated or the thermal consumers and is then fed to the inlet of the evaporator heat exchanger 11.

[0075] Fig. 3 shows another embodiment of the thermal management system 1. Here, the supply of coolant from the low-temperature section 6 to the evaporator heat exchanger 11 can be selectively shut off via valves 21, 22 of the valve assembly 19, and coolant leaving the condenser heat exchanger 10 in the high-temperature section 5 can be selectively supplied to the evaporator heat exchanger 11. In the illustrated positions of the valves 21, 22, coolant can be circulated in the low-temperature section 6, namely via the pump 3. It is evident that the low-temperature section 6 is thus completely decoupled from the refrigerant circuit 7, so that no heat transfer can take place between the low-temperature section 6 and the refrigerant circuit 7. Cooling of the components is achieved, for example, by heat dissipation through the radiator 13.

[0076] The coolant leaving the condenser heat exchanger 10 is fed to the inlet of the evaporator heat exchanger 11 via valve 22. This allows the coolant temperature at the inlet of the evaporator heat exchanger 11 to be higher than at the inlet of the condenser heat exchanger 10. When the switching positions of valves 21 and 22 are changed, the inlet of the evaporator heat exchanger 11 is again connected to the low-temperature section 6 and disconnected from the high-temperature section 5. This occurs, for example, when a heating or start-up phase is completed and the desired temperature is reached. (ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25)

[0077] Once the coolant temperature in coolant circuit 2 is reached, the switching positions of valves 21, 22 can be changed.

[0078] Fig. 4 shows a fourth embodiment of the thermal management system 1. The preceding description is essentially applicable here as well. In addition to the thermal management systems 1 described above, the thermal management system 1 of Fig. 4 has an additional heat exchanger 23. The additional heat exchanger 23 is used to supply heat from the high-temperature section 5 to the low-temperature section 6. The additional heat exchanger 23 has a low-temperature side 24 and a high-temperature side 25. The inlet of the high-temperature side 25 is connected to the outlet of the condenser heat exchanger 10, and the outlet of the low-temperature side 24 is connected to the inlet of the evaporator heat exchanger 11.

[0079] Accordingly, heat transfer from the high-temperature section 5 to the low-temperature section 6 takes place before the inlet of the evaporator heat exchanger 11 and after the outlet of the condenser heat exchanger 10. Advantageously, no fluidic connection and therefore no mixing of the coolant is necessary at this point; instead, heat transfer occurs in the auxiliary heat exchanger 23. As shown, the flow of coolant through the low-temperature side 24 can be selectively adjusted or shut off via a valve 21. Alternatively, the valve 21, or a valve not shown, can also be assigned to the high-temperature side 25, so that the connection of the high-temperature section 5 to the auxiliary heat exchanger 23 can also be selectively adjusted or shut off.

[0080] Fig. 5 shows another embodiment of the thermal management system 1, which also includes an auxiliary heat exchanger 23. In the embodiment shown, the auxiliary heat exchanger 23 is integrated into the evaporator heat exchanger 11. Coolant flowing into the low-temperature side 24 of the auxiliary heat exchanger 43 performs a heat exchange with the refrigerant in the refrigerant circuit 7. In other words, the coolant enters the auxiliary heat exchanger 23 and flows through the evaporator heat exchanger 11 in such a way that a heat exchange with the refrigerant circuit 7 takes place.

[0081] Valve 22 allows coolant from the high-temperature section 5 to selectively flow through the high-temperature side 25 of the auxiliary heat exchanger 23. When valve 22 is in the switching position shown in Fig. 5, coolant exiting the condenser heat exchanger 10 flows into the high-temperature side 25 of the auxiliary heat exchanger 23. If the switching position is changed, the coolant in the high-temperature section 5 bypasses the auxiliary heat exchanger 23, for example, flowing into the interior heater 17.

[0082] The method described herein for controlling the operation of a thermal management system 1 can be implemented in all its advantages, details, and features on the thermal management system 1 shown herein. The thermal management system 1 can, for example, be a component of a motor vehicle, so that all advantages, details, and features are also transferable to the method and the motor vehicle. The descriptions of the individual embodiments are fully combinable, so that all advantages, details, and features are also interchangeable and transferable between them.

[0083] ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25

[0084] Reference mark

[0085] 1 Thermal management system

[0086] 2 Coolant circuit

[0087] 3, 4 pump

[0088] 5 High-temperature section

[0089] 6 Low-temperature section

[0090] 7 Refrigerant circuit

[0091] 8 Heat pump

[0092] 9 Compressor

[0093] 10 condenser heat exchangers

[0094] 11 Evaporator heat exchangers

[0095] 12 Expansion valve

[0096] 13 Radiator

[0097] 14 Air conditioning unit

[0098] 15 Control electronics

[0099] 16 electric machine

[0100] 17 interior heaters

[0101] 18 Energy storage

[0102] 19 Valve assembly

[0103] 20 Mixing Point

[0104] 21, 22 valve

[0105] 23 Auxiliary heat exchangers

[0106] 24 Low temperature side

[0107] 25 High-temperature side

Claims

ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25 Patent claims 1. Thermal management system (1), in particular for a motor vehicle, comprising a coolant circuit (2) and a heat pump (8) having a refrigerant circuit (7), the heat pump having a compressor (9) designed for conveying refrigerant in the refrigerant circuit (7), wherein the heat pump (8) has a condenser heat exchanger (10) and an evaporator heat exchanger (11) designed for heat exchange between the refrigerant circuit (7) and the coolant circuit (2), characterized in that the coolant circuit (2) has at least one low-temperature section (6), in particular arranged on the evaporator heat exchanger (11), and at least one high-temperature section (5), in particular arranged on the condenser heat exchanger (10), wherein the evaporator heat exchanger (11) is connectable to or connected with the high-temperature section (5) and the low-temperature section (6).

2. Thermal management system (1 ) according to claim 1 , characterized in that the thermal management system (1 ) is configured to operate thermal consumers depending on a performance state of the heat pump (8), in particular to extract a quantity of heat limited to a limit value from the coolant circuit (2).

3. Thermal management system (1 ) according to claim 1 or 2, characterized in that the thermal management system (1 ) is configured to keep an inlet temperature of the coolant at the evaporator heat exchanger (11 ) and / or an inlet temperature of the coolant at the condenser heat exchanger (10) constant.

4. Thermal management system (1) according to one of the preceding claims, characterized in that an inlet of the evaporator heat exchanger (11) is connected to the low-temperature section (6) and, in particular via an orifice, to the high-temperature section (5). ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25 5. Thermal management system (1) according to one of the preceding claims, characterized in that the coolant circuit (2) is designed, in particular as a single circuit, wherein the connection of the evaporator heat exchanger (11) with the high-temperature section (5) is established via the low-temperature section (6) adjoining the high-temperature section (5).

6. Thermal management system (1) according to one of the preceding claims, characterized in that, in particular in a start state, the low temperature section (6) is separated from the evaporator heat exchanger (11) and the evaporator heat exchanger (11) is integrated into the high temperature section (5), in particular after the condenser heat exchanger (10).

7. Thermal management system (1) according to one of the preceding claims, characterized by an additional heat exchanger (23) whose low-temperature side (24), in particular its low-temperature outlet, is connected to the inlet of the evaporator heat exchanger (11), and whose high-temperature side (25), in particular its high-temperature inlet, is connected to the outlet of the condenser heat exchanger (10).

8. Thermal management system (1) according to one of the preceding claims, characterized by an auxiliary heat exchanger (23) integrated into or connected to the evaporator heat exchanger (11), wherein the low-temperature side (24) of the auxiliary heat exchanger (23) is connected to or forms the coolant circuit side of the evaporator heat exchanger (11) and the high-temperature side (25) of the auxiliary heat exchanger (23) is connectable to or connected with the outlet of the condenser heat exchanger (10), in particular optionally by means of a valve.

9. Thermal management system (1) according to one of the preceding claims, characterized in that the thermal management system (1) is configured to maintain a temperature level in the high-temperature section (5) and / or the low-temperature section (6) by controlling a flow rate in the high-temperature section (5) and / or the low-temperature section (6). ZF Friedrichshafen AG File 304129 Friedrichshafen 2024-09-25 to control the low-temperature section (6) and / or to control the heating power delivered to the coolant circuit (2) by controlling the compressor (9), in particular a compressor speed and / or a compressor torque.

10. Thermal management system (1) according to one of the preceding claims, characterized in that the thermal management system (1) is designed to operate the compressor (9) with a defined efficiency, in particular with a reduced efficiency compared to a maximum efficiency, in particular by trimming the compressor (9).

11. Motor vehicle comprising a thermal management system (1) according to any of the preceding claims.

12. Method for controlling the operation of a thermal management system (1), in particular for a motor vehicle, comprising a coolant circuit (2) and a heat pump (8) having a refrigerant circuit (7), which has a compressor (9) designed for conveying refrigerant in the refrigerant circuit (7), wherein the heat pump (8) has a condenser heat exchanger (10) and an evaporator heat exchanger (11) designed for heat exchange between the refrigerant circuit (7) and the coolant circuit (2), characterized in that the coolant circuit (2) has at least one low-temperature section (6), in particular arranged on the evaporator heat exchanger (11), and at least one high-temperature section (5), in particular arranged on the condenser heat exchanger (10), wherein the evaporator heat exchanger (11) is connected to the high-temperature section (5) and the low-temperature section (6).

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