DE102020106625B4 - Reheating method for operating a refrigeration system for a motor vehicle, refrigeration system and motor vehicle with such a refrigeration system - Google Patents

Abstract

Post-heating method (500) for operating a refrigeration system (10) with a heat pump function for a motor vehicle, wherein the refrigeration system (10) comprises: a refrigerant compressor (12) which is connectable or connected to a primary line (14) and a secondary line (16); an external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); a heating register (26) which is arranged in the secondary line (16); a primary line valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary line valve (A3) arranged between the refrigerant compressor (12) and the heating register (26); at least one post-heating expansion valve (AE4) which is arranged between the heating register (26) and the external heat exchanger (18) in the secondary line (16); wherein the Reheating method comprises the following steps:Setting the primary branch valve (A4) and the secondary branch valve (A3) in an at least partially open position such that refrigerant conveyed by the refrigerant compressor (12) is conveyed both into the primary branch (14) and into the secondary branch (16), wherein when the primary branch valve (A4) (S503) is fully open, the secondary branch valve (A3) is gradually opened (S505) in order to cover an emerging or increasing heating requirement (S506).

Description

The invention relates to a reheating method (RH IV) for operating a refrigeration system with heat pump function for a motor vehicle, a refrigeration system and a motor vehicle with such a refrigeration system.

A refrigeration system with a heat pump function usually comprises a refrigerant compressor that is connectable or connected to a primary line and a secondary line; an external heat exchanger arranged in the primary line; an evaporator arranged in the primary line; a heating register arranged in the secondary line; at least one movable temperature flap arranged upstream or downstream of the heating register with respect to a supply air flow direction; and at least one post-heating expansion valve arranged between the heating register and the external heat exchanger in the secondary line.

Such a refrigeration system with heat pump function is used, for example, in the EN 10 2018 213 232 A1 described.

From the EN 10 2012 111 672 A1 A refrigeration system is known in which a primary branch valve and a secondary branch valve can be open at the same time.

Further background information on refrigeration systems and heat pumps can be found, for example, in the publications DE 100 29 934 A1 , EP 1 451 031 B1 and DE 102 15 587 A1 .

In a reheating process, which in technical jargon is also referred to as reheat, reheat operation, reheat process, the air cooled and dehumidified by the evaporator is brought to a desired outlet temperature by at least partially heating it by means of the heating register when air conditioning a vehicle interior.

The heating register is a heat source in which heat stored in the coolant is released to another medium, such as air, water, a water-glycol mixture, and the like. The heating register can be designed as a heating condenser or heating gas cooler if (ambient) air flows directly around it as the cabin supply air, which absorbs the released heat. The heating register can be designed as a fluid heat exchanger if a fluid other than (ambient) air, such as water, a water-glycol mixture, or the like, flows through or around it, with the heat stored in the coolant being released to the fluid. When designed as a fluid heat exchanger, further heat is transferred from the heated fluid to the (ambient) air. In this respect, a fluid heat exchanger indirectly heats (ambient) air as the cabin supply air flow.

In this case, at least one temperature flap can be used in the air flow path between the evaporator and the heating register (i.e. upstream of the heating register), which is completely closed (0% open position or closed position) when the air is to be fed into the vehicle interior cooled and not heated. When the temperature flap is completely open (100% open position), essentially the entire dehumidified air flow coming from the evaporator is fed over the heating register and heated. When the temperature flap is partially opened, part of the air is fed over the heating register and the other part of the air is fed around the heating register and not heated, so that a mixture of heated and cooled air is formed downstream of the heating register, which is then fed into the vehicle interior. Alternatively, the adjustable temperature flap can also be arranged downstream of the heating register.

Up to now, the desired outlet temperature has been adjusted by gradually adjusting the temperature flap, with the reheating expansion valve being adjusted downstream of this gradual adjustment of the temperature flap in order to achieve an optimal pressure level in the refrigeration system. However, if the temperature flap is closed very quickly, for example, this can lead to undesirable pressure changes in the refrigerant circuit due to the associated rapid drop in heat dissipation at the heating register. The pressure in the refrigeration system increases, but only up to a system cut-off limit at a maximum permissible pressure. As a result, the temperature in the refrigerant and consequently in the heating register increases, even though closing the temperature flap would actually mean that there would be less need for reheating. This results in inefficient operation of the refrigeration system because if the heating register is poorly ventilated and the temperature of the refrigerant increases, heat dissipation is made more difficult or impossible due to the temperature flap being opened or closed only a little.

The object underlying the invention is to provide a post-heating method in which the above disadvantages can be avoided.

This object is achieved by a reheating method having the features of patent claim 1 or claim 5, by a refrigeration system having the features of patent claim 10 and by a motor vehicle having the features of patent claim 15. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

• einen Kältemittelverdichter, der mit einem Primärstrang und einem Sekundärstrang verbindbar oder verbunden ist;
• einen äußeren Wärmeübertrager, der im Primärstrang angeordnet ist;
• einen Verdampfer, der im Primärstrang angeordnet ist;
• ein Heizregister, das im Sekundärstrang angeordnet ist
• ein zwischen dem Kältemittelverdichter und dem äußeren Wärmeübertrager angeordnetes Primärstrangventil;
• ein zwischen dem Kältemittelverdichter und dem Heizregister angeordnetes Sekundärstrangventil;
• wenigstens ein Nachheiz-Expansionsventil, das zwischen dem Heiz-register und dem äußeren Wärmeübertrager im Sekundärstrang angeordnet ist. Dabei ist vorgesehen, dass das Nachheizverfahren folgende Schritte umfasst:
• Einstellen des Primärstrangventils und des Sekundärstrangventils in einer zumindest teilweise geöffneten Stellung, derart dass von dem Kältemittelverdichter gefördertes Kältemittel sowohl in den Primärstrang als auch in den Sekundärstrang gefördert wird.

A post-heating method for operating a refrigeration system with heat pump function for a motor vehicle is therefore proposed, the refrigeration system comprising:

• a refrigerant compressor connectable or connected to a primary line and a secondary line;
• an external heat exchanger arranged in the primary line;
• an evaporator arranged in the primary line;
• a heating register arranged in the secondary line
• a primary branch valve arranged between the refrigerant compressor and the external heat exchanger;
• a secondary branch valve arranged between the refrigerant compressor and the heating coil;
• at least one post-heating expansion valve which is arranged between the heating register and the external heat exchanger in the secondary line. It is provided that the post-heating process comprises the following steps:
• Setting the primary branch valve and the secondary branch valve in an at least partially open position such that refrigerant delivered by the refrigerant compressor is delivered into both the primary branch and the secondary branch.

The method proposed here enables the control of heating requirements by parallel flow through the primary branch and the secondary branch. The continuous adjustment of the primary branch valve and the secondary branch valve in particular enables a smooth transition, for example, from pure AC operation (primary branch valve is fully open and secondary branch valve is fully closed) to post-heating operation. An abrupt transition from AC operation to post-heating operation, in which the secondary branch valve is fully open and the primary branch valve is fully closed, can thus be avoided or prevented, so that the corresponding switching process or procedure can also be simplified.

In a further embodiment, the reheating expansion valve can be at least partially opened in the reheating process when the secondary branch valve is at least partially open. This ensures that the coolant fed into the secondary branch to the heating register leaves the secondary branch downstream of the heating register in a controlled manner, in particular can be expanded in the direction of the external heat transfer.

According to a first aspect of the invention, when the primary branch valve is fully open, the secondary branch valve is opened step by step, in particular when the post-heating expansion valve simultaneously releases a flow cross-section, in order to cover an increasing or emerging heating requirement. The secondary branch valve can be continuously adjustable and the step-by-step opening simply expresses that the setting of a certain opening position can be regularly adjusted.

The secondary branch valve can remain in an open position when the heating demand is met. Such an opening position can also be referred to as an intermediate opening position.

The secondary branch valve can be closed gradually when the heating requirement decreases or when there is a heating surplus. Accordingly, when the secondary branch valve is closed, the reheating expansion valve is also closed and the removed refrigerant can be returned to the active system section via a suction valve.

According to a second aspect of the invention, starting from a state in which the secondary branch valve is fully open and the primary branch valve is at least partially open, the primary branch valve is gradually closed in order to cover an increasing heating demand.

The primary branch valve can remain in one or the (intermediate) open position when the heating requirement is met.

The primary branch valve can be opened gradually when the heating requirement decreases or when there is a heating surplus. The primary branch valve can be infinitely adjustable and the gradual opening simply expresses that the setting of a certain opening position can be regularly adjusted.

The reheating process presented here (Reheat IV) can be completed when the primary branch valve is fully open and the secondary branch valve is fully closed, or when the primary branch valve is fully closed and the secondary branch valve is fully open. This means that the reheating process presented here can be completed In the reheating process (Reheat IV), a transition can take place between an AC operation (primary branch valve fully open and secondary branch valve fully closed) and a reheating operation that is implemented or controlled differently on the system side (with the primary branch valve fully closed and the secondary branch valve fully open; the so-called Reheat I, Reheat II or Reheat III).

The partial refrigerant mass flows present in the primary branch and in the secondary branch, with the primary branch valve and secondary branch valve at least partially open at the same time, can be at least partially combined upstream of the external heat exchanger. This makes it possible for the two parallel refrigerant flows to be passed through the external heat exchanger as a total mass flow and the total mass flow to be cooled.

A refrigeration system with heat pump function for a motor vehicle is also proposed, with
a refrigerant compressor that is or can be connected to a primary line and a secondary line;
an external heat exchanger arranged in the primary line;
an evaporator arranged in the primary line;
a heating register arranged in the secondary line
a primary branch valve arranged between the refrigerant compressor and the external heat exchanger;
a secondary branch valve arranged between the refrigerant compressor and the heating coil;
at least one post-heating expansion valve arranged between the heating register and the external heat exchanger in the secondary line;
wherein the refrigeration system is designed to be operated with a post-heating method or in a post-heating mode as described above.

Depending on the system topology, the external heat exchanger can be flowed through monodirectionally or bidirectionally, depending on the design of the refrigeration system. In a monodirectional variant, the refrigerant always flows through the external heat exchanger in the same direction or in the same way in refrigeration system operation and in air heat pump mode. In a bidirectional variant, the refrigerant flows through the external heat exchanger in a different or different direction (opposite) in refrigeration system operation than in air heat pump mode. With regard to the external heat exchanger, it should be noted that - similar to the heating register - it can release heat to the (ambient) air or absorb it from it both directly (as a condenser or gas cooler) and indirectly (as a fluid heat exchanger). To carry out the post-heating process presented here, the external heat exchanger is flowed through in the same direction by both partial refrigerant flows (primary line/secondary line) after they have been combined.

The refrigeration system can have a connecting section with an adjustable valve, the secondary flow end of which is arranged downstream of the heating register and the primary flow end of which is arranged upstream of the evaporator. This allows a partial mass flow of refrigerant to be directed after the heating register to the evaporator and/or a chiller.

The primary flow end of the connecting section can be arranged upstream of an internal heat exchanger. In such an (alternative) design, a partial refrigerant mass flow can be introduced into the primary line after the heating register in such a way that it is passed through the internal heat exchanger before it flows through the evaporator and/or the chiller.

In the refrigeration system, a check valve can be arranged in the secondary line downstream of the heating register. In particular, the check valve can be arranged downstream of the reheating expansion valve. By arranging such a check valve, the flow of refrigerant from the primary line into the secondary line can be prevented.

A motor vehicle can be equipped with such a refrigeration system. The motor vehicle can in particular be an electric vehicle. In an electric vehicle, the efficient operation of the refrigeration system can lead to electricity savings, so that a greater range of the electric vehicle can be achieved.

• 1 ein schematisches und vereinfachtes Schaltbild einer Kälteanlage für ein Kraftfahrzeug,
• 2 ein Flussdiagram einer beispielhaften Umsetzung des Nachheizverfahrens, insbesondere mittels der in 1 beschriebenen Kälteanlage.

Further advantages and details of the invention emerge from the following description of embodiments with reference to the figures.

• 1 a schematic and simplified circuit diagram of a refrigeration system for a motor vehicle,
• 2 a flow chart of an exemplary implementation of the post-heating process, in particular by means of the 1 described refrigeration system.

In 1 an embodiment of a refrigeration system 10 for a motor vehicle is shown schematically and in a simplified manner. The refrigeration system 10 comprises a refrigerant circuit 11, which can be operated both in a refrigeration system mode (also called AC mode for short) and in a heat pump mode. In the embodiment shown, the refrigeration system 10 comprises a refrigerant compressor 12, an external heat exchanger 18, an internal heat exchanger 20, an evaporator 22 and an accumulator or refrigerant collector 24. The external heat exchanger 18 can be designed as a condenser or gas cooler. In particular, the external heat exchanger 18 can be flowed through bidirectionally in the embodiment shown.

The evaporator 22 is shown here as an example as a front evaporator for a vehicle. The evaporator 22 also represents other possible evaporators in a vehicle, such as rear evaporators, which can be arranged parallel to one another in terms of flow. In other words, the refrigeration system 10 comprises at least one evaporator 22.

Downstream of the refrigerant compressor 12 there is a shut-off or expansion valve A4, which is in particular continuously adjustable and is referred to below as the primary branch valve A4. Upstream of the evaporator 22 there is an expansion valve AE2.

For the purposes of this description, in the entire refrigerant circuit 11 of the refrigeration system 10, the section from the refrigerant compressor 12 to the external heat exchanger 18, to the internal heat exchanger 20 and to the evaporator 22 is referred to as the primary line 14.

The refrigeration system 10 further comprises a heating register 26 (also referred to as a heating condenser or heating gas cooler, which can enable direct or indirect heat transfer). Upstream of the heating register 26, a shut-off or expansion valve A3, which is in particular continuously adjustable, is arranged, which is referred to below as the secondary branch valve A3. Downstream of the heating register 26, a valve or shut-off valve A1 is arranged. Furthermore, downstream of the heating register 26, a (post-heating) expansion valve AE4 is arranged.

In the context of this description, in the entire refrigerant circuit of the refrigeration system 10, the section from the refrigerant compressor 12 to the heating register 26, to the expansion valve AE4 and to a branch Ab2 is referred to as the secondary branch 16. The secondary branch 16 comprises a heating branch 16.1, which extends from the shut-off valve A3 via the heating register 26 to the shut-off valve A1. The secondary branch 16 also comprises a reheat branch 16.2, which can be fluidly connected upstream to the heating register 26 and downstream to the external heat exchanger 5. The secondary branch 16 or the reheat branch 16.2 flows into the primary branch 14 at a branch Ab2.

The shut-off valve A1 is provided on a connecting section 16.3. The connecting section 16.3 comprises a branch (or end) Ab5 on the secondary flow side. On the primary line side, the connecting section 16.3 has a branch (or end) Ab1. The shut-off valve A1 can also be designed as a continuously adjustable valve, in particular as an expansion valve.

In addition to the variant of the connecting section 16.3 shown as a solid line, this can alternatively also be designed as a connecting section 16.4, which is shown in dashed lines. The connecting section 16.4 also has a branch Ab5 on the secondary line 16, but is connected to the primary line 14 upstream of the inner heat exchanger 20 at a branch (or one end) Ab6. In such an alternative, a further lockable expansion valve AE6 is to be provided in the section between the branch Ab6 and the gas cooler 18 or condenser 18 (external heat exchanger) in order to continue to ensure the previous functionality of the overall system. The expansion valve AE1 could also be designed as a shut-off valve in this variant. If the dashed shut-off valve A1 in the connection section 16.4 is designed as a lockable expansion valve AE7, this can be used to expand the refrigerant in the gas cooler 18 or condenser 18 in the case of an air heat pump. An expansion valve AE7 can also be used to (pre-)expand the chiller 28 in order to reduce the influence of the internal heat exchanger 20 on the water heat pump process. For the control and holistic operation of the refrigeration system, it can be seen as technically more effective in the alternative solution to have a separate, independent expansion valve AE1 and AE6 for each heat exchanger.

The refrigeration system 10 comprises a further evaporator or chiller 28. The chiller 28 is provided in parallel flow terms to the evaporator 22. The chiller 28 can be used, for example, to cool an electrical component of the vehicle, but also to implement a water heat pump function using the waste heat from at least one electrical component. An expansion valve AE1 is connected upstream of the chiller 28.

The refrigeration system 10 can also have an electric heating element 30, which is designed, for example, as a high-voltage PTC heating element. The electric heating element 30 serves as an additional heater for a supply air flow L guided into the vehicle interior. The electric heating element 30 can be housed together with the heating register 26 and the evaporator 22 in an air conditioning unit 32. The electric heating element 30 can be arranged downstream of the heating register 26.

In the 1 check valves R1 and R2 are also visible. A further check valve R3 can be arranged in the secondary line 16 downstream of the heating register 26. The check valve R3 can be connected upstream or downstream of the expansion valve AE4. In the 1 a representation is selected in which the check valve R3 is connected downstream of the expansion valve AE4. In other words, the check valve R3 is arranged between the expansion valve AE4 and the branch Ab2.

Furthermore, some sensors pT1 to pT5 are shown for measuring the pressure and/or temperature of the coolant. It should be noted that the number of sensors and their arrangement are only shown as examples. A refrigeration system 10 can also have fewer or more sensors. In the example shown, combined pressure/temperature sensors are shown as sensors. However, it is also conceivable that separate sensors are used to measure pressure and temperature and, if necessary, are arranged spatially separated from one another along the coolant lines.

The refrigeration system 10 can be operated in different modes, which are briefly described below.

In AC operation of the refrigerant circuit 11, the refrigerant compressed to high pressure flows from the refrigerant compressor 12 with the primary branch valve A4 open and the secondary branch valve A3 closed into the external heat exchanger 18. From there it flows to the high-pressure section of the internal heat exchanger 20 and the fully open expansion valve AE3. The refrigerant can flow via a branch Ab1 to the expansion valve AE2 and into the evaporator 22 (evaporator section 22.1). In parallel or alternatively, the refrigerant can flow via a branch Ab4 and the expansion valve AE1 into the chiller 28 (chiller section 28.1). From the evaporator 22 and/or the chiller 28, the refrigerant flows on the low-pressure side into the refrigerant collector 24 and through the low-pressure section of the internal heat exchanger 20 back to the refrigerant compressor 12.

In AC operation, the heating branch 16.1 or the secondary branch 16 is shut off by means of the shut-off valve A3 so that hot refrigerant cannot flow through the heating register 26. To retrieve refrigerant from the inactive heating branch 16.1, the shut-off element A5 designed as a shut-off valve can be opened so that the refrigerant can flow towards the refrigerant collector 24 via the shut-off element A5 and the check valve R2, with the shut-off element A2 closed at the same time.

In heating mode or reheating mode according to the Reheat I to III modes of the refrigerant circuit 11, the primary branch valve A4 is closed and the secondary branch valve A3 is open so that hot refrigerant can flow into the heating branch 16.1.

To carry out the heating function using the chiller 28 to implement water heat pump operation, the coolant compressed by the coolant compressor 12 flows through the open shut-off valve A3 into the heating register 26. At the heating register 26, heat is given off to a supply air flow L guided into the vehicle interior. The coolant then flows through the open shut-off valve A1 and the branch Ab1. It is expanded by means of the expansion valve AE1 in the chiller 28 to absorb waste heat from the electrical and/or electronic components arranged in a coolant circuit 28.2. With this heating function, the expansion valves AE3 and AE4 are closed, the shut-off device A5 is closed and the shut-off device A2 is open. In this case, coolant removed during water heat pump operation can be extracted from a bidirectional branch 14.1 or the primary line 14 via the shut-off device A2 and fed to the coolant collector 24 via the check valve R2.

To carry out the heating function using the external heat exchanger 18 as a heat pump evaporator, the refrigerant compressed by the refrigerant compressor 12 flows into the heating register 26 via the open shut-off valve A3 to release heat to a supply air flow L. It is then expanded via the open shut-off valve A1 using the expansion valve AE3 in the external heat exchanger 18 to absorb heat from the ambient air. The refrigerant then flows via a heat pump return branch 15 to the refrigerant collector 24 and back to the refrigerant compressor 12. The expansion valves AE1, AE2 and AE4 remain closed, as does the shut-off device A5.

An indirect delta connection can be realized by opening the shut-off valve A1 and allowing the refrigerant compressed by the refrigerant compressor 12 to be discharged by means of the expansion valve AE1 is released into the chiller 28, whereby at the same time no mass flow is generated on the coolant side, i.e. in the coolant circuit 28.2, i.e. for example the fluid used as coolant, such as water or a water-glycol mixture, remains on the coolant side of the chiller 28 or the chiller 28 is not actively flowed through by coolant. The expansion valves AE2, AE3 and AE4 remain closed in this switching variant.

During reheating or reheating operation, the supply air flow L fed into the vehicle interior is first cooled and thus dehumidified by means of the evaporator 22. With the heat transferred to the coolant through evaporation and dehumidification as well as the heat supplied to the coolant via the coolant compressor 12, the supply air flow L can be completely or at least partially reheated by means of the heating register 26.

For this purpose, the refrigeration system 10, in particular the air conditioning unit 32, has adjustable, in particular controllable and pivotable, temperature flaps between the evaporator 22 and the heating register 26. In the example shown, a left and a right temperature flap 34L and 34R (in 1 shown schematically). The temperature flaps 34L, 34R can be adjusted or pivoted between an open position, which is referred to as the 100% position, and a closed position, which is referred to as the 0% position. Alternatively, it is also possible to install the temperature flaps 34R, 34L downstream of the heating register 26.

In the 100% position, the entire supply air flow L flowing through the evaporator 22 is guided over the heating register 26 and heated before it can flow into the passenger compartment of the vehicle. In the 0% position, the entire supply air flow L flowing through the evaporator 22 flows in the bypass around the heating register 26 without heating and thus without absorbing heat into the passenger compartment.

In an x-position of the temperature flaps 34L and 34R with 0% < x < 100%, these temperature flaps are only partially opened, so that only a partial air flow of the supply air flow L flowing through the evaporator 22 is guided over the heating register 26. This heated partial air flow can then be mixed with the remaining, cooled and dehumidified partial air flow. The supply air flow L heated in this way is fed into the passenger compartment of the vehicle. For example, a 50% position indicates that the temperature flaps 34R and 34L are only half open, i.e. 50%.

A reheat operation of the refrigerant circuit 11 or the refrigeration system 10 is carried out in different ways depending on the heat balance.

In the following, a possible operating procedure for the reheating or reheat operation is described using the flow chart of the 2 and having regard to the 1 illustrated refrigeration system 10 and its components are explained by way of example. Such an operating method is usually implemented as a control program in a control unit for the refrigeration system or for the air conditioning in a vehicle.

A post-heating operation (Reheat IV) is considered, in which the refrigerant, starting from the refrigerant compressor 12, flows simultaneously via the at least partially open secondary branch valve A3 to the heating register 26 (heating condenser or heating gas cooler) and via the at least partially open primary branch valve A4 to the external heat exchanger 18 and to the evaporator. In such a post-heating operation, the shut-off valve A1 (in the connecting section 16.3 or 16.4) is usually closed and the refrigerant flows in the secondary branch 16 via the expansion valve AE4 to the external heat exchanger 18. The partial refrigerant mass flow that has been passed through the secondary branch is passed into the primary branch 14 at the branch Ab2, so that an entire refrigerant volume flow is passed to the external heat exchanger 18.

The refrigerant then passes through the internal heat exchanger 20 on the high-pressure side and reaches the evaporator 22 via the open expansion valve AE3 and the expansion valve AE2. From there, the refrigerant returns to the refrigerant compressor 12 via the refrigerant collector 24 and the low-pressure side section of the internal heat exchanger 20.

The temperature flaps 34L, 34R can be moved or set to suitable positions, which are identified below with “TK”, where TK can assume a value from 0% (temperature flaps 34L, 34R closed) to 100% (temperature flaps 34L, 34R fully open).

According to the 2 In the reheating process 500 shown, after the start (S501) of the refrigeration system 10, a transition to a reheating operation, which is referred to here as Reheat IV (S502), takes place at a point in time not specified here. A possible condition that must be met in order to start the reheating operation (S502) can, for example, be a changing blow-out temperature requirement for the interior, also depending on the ambient conditions, such as the temperature. The post-heating process presented here can be activated in particular when the ambient temperature is up to 25°C, in particular from about 10°C to 25°C. Furthermore, the post-heating process 500 can be activated when either the primary branch valve A4 is open (A4=100%) and the secondary branch valve A3 is still closed (A3=0%) (S503), or the primary branch valve A4 is still closed (A4=0%) and the secondary branch valve A3 is open (A3=100%) (S504). In the second case, the post-heating process is already active and only its effect is changed.

In the following description of the 2 Please note that an upward pointing arrow in the 2 an opening of the relevant shut-off valve A3 or A4 is illustrated. A downward-pointing arrow illustrates the throttling or closing of the relevant shut-off valve A3, A4. If an upward-pointing arrow and a downward-pointing arrow are shown, the relevant shut-off valve A3, A4 is held in a certain or reached opening position. In relation to the heating requirement Hb, an upward-pointing arrow illustrates an increasing heating requirement Hb and a downward-pointing arrow illustrates a decreasing or negative heating requirement or a heating surplus. Furthermore, in the 2 with “Y” or “N” it is indicated to which step the procedure branches if the condition is agreed (“Y”) or not agreed (“N”).

Starting from AC operation in which the primary branch valve A4 is open (A4=100%) and the secondary branch valve A3 is closed (A3=0%) (S503), the secondary branch valve A3 can ideally be opened (partially) in small steps (S505) in the reheating process 500 if an (increasing) heating requirement Hb (arrow pointing up) has been determined (S506). If the process determines that the heating requirement is covered (S506 in combination with S507), the opening of the secondary branch valve A3 is stopped and its open position is maintained (S508). If there is further heating requirement (S506), the secondary flow valve A3 can be opened further (S505), if necessary even up to the fully open position (S509). If a heating surplus or a negative heating requirement (S507) is detected, the secondary flow valve A3 can be throttled (S510). The secondary flow valve A3 can be throttled until the state of covered heating requirements is reached again (open position of the secondary flow valve A3 is maintained, S508) or until the heating requirement increases again (S506).

With reference to 1 It must be ensured that when the reheating operation RH IV begins, the reheating expansion valve AE4 must also be opened in order to allow refrigerant flow in the secondary line.

If the secondary flow valve A3 is fully open (S509) and there is a further heating requirement, the opened primary flow valve A4 can be throttled (S511). If the heating requirement is covered with the secondary branch valve A3 fully open, the primary branch valve A4 can remain set in the currently reached opening position. If there is a further heating requirement, the primary flow valve A4 can be closed further. If a heating surplus or a negative heating requirement is detected, the primary flow valve A4 can be opened again. The primary flow valve A4 can be opened until the state of the covered heating requirement is reached again (open position of the primary flow valve A4 is maintained) or until the heating requirement increases again.

If the secondary branch valve A3 is fully open (S509) and the primary branch valve A4 is closed (S512), the reheating process 500 (Reheat IV) branches to step S504.

Starting from a system-technically differently switched reheating operation (Reheat I, Reheat II or Reheat III) that can be implemented using the refrigeration system 10, in which the primary branch valve A4 is closed (A4=0%) and the secondary branch valve A3 is open (A3=100%) (S504), the primary branch valve A4 can be (re)opened in the reheating process 500 (Reheat IV) if a heating surplus or a negative heating requirement has been determined (S515). If it is determined during the process that the heating requirement is covered or there is no longer a heating surplus (S515 in combination with S516), the opening of the primary branch valve A4 is stopped and its open position is maintained (S517). If there is further heating surplus or negative heating requirement (S515), the primary flow valve A4 can be opened further (S518), if necessary even to the fully open position (S519). If a further heat surplus or negative heat requirement is then detected, the secondary flow valve A3 can be throttled when the primary branch valve A4 (S519) is open. The secondary flow valve A3 can be throttled until the state of covered heat requirement is reached again (the opening position of the secondary flow valve A3 is maintained or the valve is moved until the cross-section is completely closed) or until the heat requirement increases again.

If the primary branch valve A4 is fully open (S519) and the secondary branch valve A3 closed (S520), the reheating process 500 (Reheat IV) branches to step S503.

Whether there is a heating requirement can be determined, for example, by means of a heating requirement balance. For example, a temperature sensor can be taken into account which monitors the heat source level when conditioning supply air. Alternatively or additionally, the position of the temperature flaps 34L, 34R can be taken into account in the heating requirement balance, the position of which is in turn specified depending on the setpoint of the temperature of the cabin supply air flow. When the refrigeration system 10 is in operation, it is therefore determined via at least one parameter which specifies or determines the refrigeration system configuration whether the heating requirement is constant, increasing or decreasing. A size or refrigeration system parameter used here as an example is the temperature flap opening TKan requested by a control unit, which in turn is linked to the setpoint specification of the cabin supply air temperature. If a larger temperature flap opening Tkan is required, the heating requirement increases. If a smaller temperature flap opening Tkan is required, the heating requirement decreases. In the reheating process considered here (Reheat IV), a temperature flap opening Tkan requested by the system does not necessarily lead to a corresponding adjustment of the actual opening position or actual opening position Tkis of the temperature flaps 34L, 34R, but based on the required temperature flap opening Tkan, an adjustment of the opening position(s) of the primary branch valve A4 and/or the secondary branch valve A3 is first made.

In the reheating process 500 (Reheat IV) presented here, the determined heating requirement is responded to when the primary branch valve A4 is open and when the secondary branch valve A3 is open by further opening or closing (throttling) the primary branch valve A4 and/or the secondary branch valve A3 before, if necessary, reacting in a next step by adjusting the temperature flaps 34L, 34R (Tkis).

The primary branch valve A4 and the secondary branch valve A3 can assume 500 opening positions from >0% to 100% simultaneously during the post-heating process presented here. Any combination of simultaneously opened primary branch valve A4 and secondary branch valve A3 is conceivable, for example
both 100% open or
one 100% open, the other 20% open or
one 70% open, the other 40% open or
one 20% open, the other 20% open. The opening positions in percentages listed above are merely examples and in no way a limitation.

The reheating process 500 (Reheat IV) is activated until one of the conditions according to steps S503 or S504 is met and there is no further positive or negative heating requirement, so that the process (Reheat IV) can be ended via steps S503, S506, S507, S508, S523 or S504, S515, S516, S525, S524. Starting from step S503, ending the process (S521) leads to a transition to AC operation (S522). Starting from step S504, ending the process (S513) leads to a transition to another reheating or reheat operation (S514).

In order to ensure that the refrigerant can be cooled optimally or maximally during the process (Reheat IV) with the primary branch valve A4 and the secondary branch valve A3 open at the same time, the partial refrigerant mass flows can be combined at the branch Ab2 upstream of the external heat exchanger 18 so that the total refrigerant mass flow is cooled.

The two individual valves A3 and A4 can be designed as a combination valve in a type of multi-way valve and have the full functionality of the individual valves A3 and A4. In further developments, other valves such as the shut-off devices A2 and/or A5 can also be combined in this valve combination.

Alternatively, at least a partial mass flow can be introduced into the primary line downstream of the heating register 26, for example via the connecting section 16.4 and the adjustable valve A1 upstream of the inner heat exchanger 20 (branch Ab6). In this case, the valve A1 is to be designed as a continuously adjustable valve.

Claims (15)

Post-heating method (500) for operating a refrigeration system (10) with heat pump function for a motor vehicle, wherein the refrigeration system (10) comprises: a refrigerant compressor (12) which is connectable or connected to a primary line (14) and a secondary line (16); an external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); a heating register (26) which is arranged in the secondary line (16); a primary line valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a primary line valve (A4) arranged between the refrigerant compressor (12) and secondary branch valve (A3) arranged in the heating register (26); at least one afterheating expansion valve (AE4) arranged between the heating register (26) and the external heat exchanger (18) in the secondary branch (16); wherein the afterheating method comprises the following steps: setting the primary branch valve (A4) and the secondary branch valve (A3) in an at least partially open position such that refrigerant conveyed by the refrigerant compressor (12) is conveyed both into the primary branch (14) and into the secondary branch (16), wherein when the primary branch valve (A4) (S503) is fully open, the secondary branch valve (A3) is opened step by step (S505) in order to cover an emerging or increasing heating requirement (S506). Post-heating process (500) after Claim 1 , wherein when the secondary branch valve (A3) is at least partially opened, the post-heating expansion valve (AE4) is at least partially opened. Post-heating process (500) after Claim 1 or 2 , whereby the secondary branch valve (A3) remains set in an open position (S508) when the heating demand is met (S506, S507). Reheating method (500) according to one of the preceding claims, wherein the secondary branch valve (A3) is gradually closed (S510) as the heating requirement (S507) or heating surplus decreases. Post-heating method (500) for operating a refrigeration system (10) with a heat pump function for a motor vehicle, the refrigeration system (10) comprising: a refrigerant compressor (12) that is connectable or connected to a primary line (14) and a secondary line (16); an external heat exchanger (18) that is arranged in the primary line (14); an evaporator (22) that is arranged in the primary line (14); a heating register (26) that is arranged in the secondary line (16); a primary line valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary line valve (A3) arranged between the refrigerant compressor (12) and the heating register (26); at least one post-heating expansion valve (AE4) that is arranged between the heating register (26) and the external heat exchanger (18) in the secondary line (16); wherein the reheating method comprises the following steps: Setting the primary branch valve (A4) and the secondary branch valve (A3) in an at least partially open position such that refrigerant conveyed by the refrigerant compressor (12) is conveyed both into the primary branch (14) and into the secondary branch (16), wherein starting from a state in which the secondary branch valve (A3) is fully open (S509) and the primary branch valve (A4) is at least partially open (S512), the primary branch valve (A4) is gradually closed (S511) in order to cover an increasing heating requirement (S506). Post-heating process (500) after Claim 5 , whereby the primary branch valve (A4) remains in an open position when the heating demand is met. Post-heating process (500) after Claim 5 or 6 , whereby the primary branch valve (A4) is opened gradually as the heating demand or heating surplus decreases. Reheating method (500) according to one of the preceding claims, wherein the reheating method (500) is completed (S513; S521) when the primary branch valve (A4) is fully opened (S519) and the secondary branch valve (A3) is fully closed (S520), or when the primary branch valve (A4) is fully closed (S512) and the secondary branch valve (A3) is fully opened (S509). Reheating method (500) according to one of the preceding claims, wherein the partial refrigerant mass flows present in the primary branch (14) and in the secondary branch (16) are combined at least partially upstream of the external heat exchanger (18) when the primary branch valve (A4) and secondary branch valve (A3) are simultaneously at least partially open. Refrigeration system (10) with heat pump function for a motor vehicle, with a refrigerant compressor (12) which is connectable or connected to a primary line (14) and a secondary line (16); an external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); a heating register (26) which is arranged in the secondary line (16); a primary line valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary line valve (A3) arranged between the refrigerant compressor (12) and the heating register (26); at least one post-heating expansion valve (AE4) which is arranged between the heating register (26) and the external heat exchanger (18) in the secondary line (16); characterized in that the primary line valve (A4) and the secondary branch valve (A3) are designed as continuously adjustable valves, such that the refrigeration system (10) is adapted to be operated with a post-heating method (500) according to one of the preceding claims. Refrigeration system (10) according to Claim 10 , wherein it has a connecting section (16.3; 16.4) designed with an adjustable valve (A1), the secondary flow side end (Ab5) of which is arranged downstream of the heating register (26) and the primary flow side end (Ab1; Ab6) of which is arranged upstream of the evaporator (22). Refrigeration system (10) according to Claim 11 , wherein the primary flow end (Ab6) of the connecting section (16.4) is arranged upstream of an internal heat exchanger (20). Refrigeration system (10) according to one of the Claims 10 until 12 , wherein a check valve (R3) is arranged in the secondary line (16) downstream of the heating register (26). Refrigeration system (10) according to Claim 13 , wherein the check valve (R3) is arranged downstream of the afterheating expansion valve (AE4). Motor vehicle with a refrigeration system (10) according to one of the Claims 10 until 14 .

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