DE102017124814B4 - Air conditioning system for conditioning the air of a passenger compartment of a motor vehicle and method for operating the air conditioning system - Google Patents

Abstract

Air conditioning system (1a, 1b) for conditioning the air of a passenger compartment of a motor vehicle with a refrigerant circuit (2a, 2b), comprising:
- a compressor (4), a first refrigerant-to-air heat exchanger (5) for heat transfer between the refrigerant and ambient air, an expansion element (7) and a second refrigerant-to-air heat exchanger (8) for conditioning the supply air for the passenger compartment, wherein the second refrigerant-to-air heat exchanger (8) is arranged such that the refrigerant is always passed completely through,
- a flow path (10) extending from a branching point (12) to a mouth point (13) and formed with a heat exchanger (11), wherein the branching point (12) at an outlet of the compressor (4) and the mouth point (13) between the first refrigerant-air heat exchanger (5) and the expansion element (7) are formed such that refrigerant can flow through the heat exchanger (11) parallel to the first refrigerant-air heat exchanger (5) or instead of the first refrigerant-air heat exchanger (5), and an air conditioning unit (20) having a housing for conducting and distributing the supply air for the passenger compartment with
- a first flow channel (21) in which the second refrigerant-air heat exchanger (8) is arranged, and
- a second flow channel (22) which is designed as a bypass around the second refrigerant-air heat exchanger (8), wherein
- the heat exchanger (11) arranged within the flow path (10) is designed as a refrigerant-air heat exchanger for heating the supply air and is arranged within the air conditioning unit (20) in the flow direction (24) of the supply air after the second refrigerant-air heat exchanger (8) is arranged or the heat exchanger (11) arranged within the flow path (10) is designed as a refrigerant-coolant heat exchanger of a coolant circuit (3), wherein the coolant circuit (3) has a coolant-air heat exchanger (18) for heating the supply air, which is arranged within the air conditioning unit (20) in the flow direction (24) of the supply air after the second refrigerant-air heat exchanger (8),
- the air conditioning unit (20) has a flow guiding device (29) for closing and opening the first flow channel (21) and a flow guiding device (23) for closing and opening the second flow channel (22).

Description

The invention relates to an air conditioning system for conditioning the air of a passenger compartment of a motor vehicle, comprising a refrigerant circuit and an air conditioning unit. The refrigerant circuit comprises a compressor, a first refrigerant-to-air heat exchanger for heat transfer between the refrigerant and ambient air, an expansion element, and a second refrigerant-to-air heat exchanger for conditioning the supply air for the passenger compartment, as well as a flow path with an additional heat exchanger. The air conditioning unit comprises a housing for conducting and distributing the supply air for the passenger compartment, comprising a first flow channel for receiving the second refrigerant-to-air heat exchanger and a second flow channel designed as a bypass of the second refrigerant-to-air heat exchanger.

Furthermore, the invention relates to a method for operating the air conditioning system.

In prior art motor vehicles, the engine's waste heat is used to heat the air supply to the passenger compartment. The waste heat is transported to the air conditioning system by means of the coolant circulated in the engine coolant circuit, where it is transferred to the air flowing into the passenger compartment via the heating heat exchanger. Known systems with coolant-to-air heat exchangers, which draw their heating power from the coolant circuit of an efficient internal combustion engine in the vehicle's drive system, do not generate enough waste heat to heat the air in the passenger compartment to meet thermal comfort requirements, particularly at low ambient temperatures, or to achieve the level required for comfortable heating of the passenger compartment and to cover the total heat demand of the passenger compartment. The same applies to systems in vehicles with hybrid drives, i.e., vehicles with both electric motor and internal combustion engine drive.

If the total heat requirement of the passenger compartment cannot be met using heat from the engine coolant circuit, additional heating measures such as electrical resistance heaters (PTC resistors for "Positive Temperature Coefficient - Thermistor") or fuel heaters are required. The same applies to systems in purely electric-powered vehicles or fuel cell vehicles. A more efficient option for heating the air in the passenger compartment is an air conditioning system with a refrigerant circuit with heat pump function, also known as a heat pump, with air as the heat source. In this system, the refrigerant circuit serves both as the sole heating source and as an additional heating source.

An air conditioning system with downstream electrical resistance heating is, on the one hand, inexpensive to manufacture and can be used in any motor vehicle, but it has a very high demand for electrical energy, since the supply air for the passenger compartment is first cooled and/or dehumidified when flowing over an evaporator of the refrigerant circuit and then heated by means of the electrical resistance heating, which transfers the heat directly to the supply air or a coolant circuit.

From the JP 2016 107979 A An air conditioning system for a motor vehicle is disclosed, comprising a refrigerant circuit and a coolant circuit for controlling the temperature of a drive engine. The coolant circuit also includes a heating heat exchanger for conditioning the supply air for the passenger compartment. The refrigerant circuit is configured with a compressor, a refrigerant-to-coolant heat exchanger operable as an evaporator for transferring heat from the coolant to the refrigerant, a refrigerant-to-coolant heat exchanger operable as a condenser for transferring heat from the refrigerant to the coolant, and an expansion element. The refrigerant circuit also includes a refrigerant-to-air heat exchanger operable as an evaporator for transferring heat from the supply air for the passenger compartment to the refrigerant. The refrigerant-to-air heat exchanger and the heating heat exchanger are arranged within an air conditioning unit.

In the DE 10 2013 214 267 A1 A heat pump system for a motor vehicle, in particular for an electric or hybrid vehicle, with a refrigerant circuit is described. The refrigerant circuit has a compressor for compressing the refrigerant to a high-pressure level, a high-pressure heat exchanger for dissipating heat from the refrigerant, a first expansion element in a low-pressure path for expanding the refrigerant to a low-pressure level, a low-pressure heat exchanger for transferring heat to the refrigerant, and a second expansion element for expanding the refrigerant to an intermediate pressure level for a first intermediate-pressure heat exchanger. The intermediate-pressure heat exchanger is arranged in an intermediate-pressure flow path between the high-pressure heat exchanger and the first expansion element and at an intermediate-pressure inlet of the compressor.

In the EP 2 716 478 A1 discloses an air conditioning system for a motor vehicle comprising an air conditioning unit and a refrigerant circuit. The air conditioning unit has a flow channel divided into a first flow path and a second flow path by means of a separating element. The refrigerant circuit is configured with a first internal heat exchanger arranged within the first flow path and configured primarily for heating, and a second internal heat exchanger arranged within the second flow path and configured primarily for cooling.

In the KR 10 2005 0 041 435 A An air conditioning system for conditioning the air in a passenger compartment of a motor vehicle with a refrigerant circuit is shown. The refrigerant circuit has an additional heat exchanger for heating the supply air, which is arranged so that the supply air can flow over it in succession with a heating heat exchanger to enable rapid heating of the passenger compartment. The supply air, conveyed by a fan, is selectively directed through a flow guide device in the form of a flap to the heating heat exchanger or to a heat exchanger operated as an evaporator of the refrigerant circuit.

State-of-the-art air conditioning systems designed for combined refrigeration and reheating modes, also known as reheat operation, absorb heat from the supply air to the passenger compartment. The refrigerant is evaporated by absorbing heat from the supply air, which is then transferred directly to the refrigerant, for example, in a refrigerant-to-air heat exchanger. The supply air to the passenger compartment thus serves as a heat source for the evaporation of the refrigerant. The refrigerant-to-air heat exchanger is arranged within an air conditioning unit, in particular for conditioning, conducting, and distributing the air.

In the so-called "reheat" or post-heating mode, the air supplied to the passenger compartment is cooled, dehumidified, and then reheated at least slightly. In this operating mode, the required post-heating power is usually lower than the cooling power required to cool and dehumidify the air.

Especially during a cold start of a vehicle, it is possible to heat the supply air, even at very low ambient air temperatures, by operating the refrigerant circuit in a so-called triangular process, also known as hot gas mode. In this case, only three components of the refrigerant circuit are supplied with refrigerant: the compressor, a heat exchanger operating as a condenser/gas cooler to heat the supply air to the passenger compartment, and an expansion device. 1 shows the changes in state of the refrigerant during operation of the refrigerant circuit in the triangular process in a logarithmic pressure (p) - enthalpy (h) diagram. As the refrigerant circulates in the compressor serving as the refrigerant circuit, the pressure level of the refrigerant is increased A, whereby the refrigerant absorbs the heat generated in the compressor. As it flows through the heat exchanger operated as a condenser/gas cooler, which is arranged downstream of the compressor in the direction of flow, the heat is transferred at a high pressure level to a coolant in a coolant circuit and then, in a coolant-to-air heat exchanger, from the coolant to the supply air for the passenger compartment or directly to the supply air for the passenger compartment B. The coolant-to-air heat exchanger is arranged within an air conditioning unit, just like the refrigerant-to-air heat exchanger operated as an evaporator.

After leaving the condenser/gas cooler, the refrigerant is expanded in the expansion device to a low pressure level C and sucked in by the compressor.

By operating the refrigerant circuit in the triangular process or in hot gas mode, the supply air of the passenger compartment can be heated with similar efficiency as with an electric resistance heater, but without having to rely on additional components.

When the refrigerant is liquefied during subcritical operation of the refrigerant circuit, such as with the refrigerant R134a or, under certain ambient conditions, with carbon dioxide, the heat exchanger is referred to as a condenser. Part of the heat transfer takes place at a constant temperature. During supercritical operation, or with supercritical heat dissipation in the heat exchanger, the temperature of the refrigerant decreases continuously. In this case, the heat exchanger is also referred to as a gas cooler. Supercritical operation can occur under certain ambient conditions or operating modes of the refrigerant circuit, for example, with the refrigerant carbon dioxide.

In the operating modes of a refrigerant circuit in a triangular process known from the state of the art, either no heat exchanger is used on the low-pressure side or the refrigerant-air heat exchanger operated as an evaporator for the refrigerant is charged with refrigerant to condition the supply air for the passenger compartment, so that on the suction side either no defined temperature temperature level is predetermined or the temperature level is defined by the supply air acting on the evaporator, such as the ambient air, which determines the suction pressure of the refrigerant present in the two-phase region.

If, on the one hand, no temperature level and thus no pressure level is specified on the low-pressure side during operation of the refrigerant circuit in the triangular process, or if, on the other hand, the temperature level and thus the pressure level of the refrigerant is determined by the temperature of the supply air for the passenger compartment, especially the ambient air with a low temperature, the suction pressure p _S drops in each case, especially during the cold start of the vehicle, according to 1 drops significantly, increasing the risk of compressor damage, for example, due to liquid hammer. For this reason, the compressor's capacity must be limited, which, however, leads to reduced overall performance of the air conditioning system. Furthermore, very low ambient air temperatures, for example -20°C and below, can lead to such a reduction in the suction pressure _pS that the compressor does not work due to a suction pressure limitation provided, for example, with R134a at 1.34 bar and a suction pressure limitation of approximately 1 bar.

In addition, conventional air conditioning units are designed in such a way that the refrigerant-to-air heat exchanger, which operates as an evaporator, cannot be shut off on the air side. Consequently, the refrigerant evaporator is always exposed to air. State-of-the-art air conditioning units only offer the option of diverting a partial air mass flow past the evaporator through a so-called bypass.

Furthermore, refrigerant circuits in air conditioning systems are known in which the evaporator can be shut off on the refrigerant side. These refrigerant circuits feature a flow path designed as a bypass around the evaporator, through which the entire mass flow of the refrigerant can be conducted. However, the refrigerant circuit, with the bypass and associated peripherals such as valves and refrigerant lines, requires additional components, particularly to ensure operation in hot gas mode. These additional components require additional installation space and incur additional costs, particularly during manufacturing and assembly.

The object of the invention is to provide an air conditioning system for a motor vehicle that can be operated efficiently in refrigeration system mode, heat pump mode, especially in reheating mode, and hot gas mode. The air conditioning system, in particular the refrigerant circuit, should be structurally simple with a minimal number of components, for example, without additional heating measures, in order to incur only minimal operating, manufacturing, and maintenance costs, as well as to have a minimal installation space requirement. The refrigerant circuit should also be designed to efficiently heat, above all, the supply air for the passenger compartment during a cold start of the motor vehicle at maximum power, in particular when operating in hot gas mode.

The problem is solved by the subject matter and the method having the features of the independent patent claims. Further developments are specified in the dependent patent claims.

The object is achieved by an air conditioning system according to the invention for conditioning the air of a passenger compartment of a motor vehicle with a refrigerant circuit and an air conditioning unit.

The refrigerant circuit includes a compressor, a first refrigerant-to-air heat exchanger for heat transfer between the refrigerant and ambient air, an expansion element, and a second refrigerant-to-air heat exchanger for conditioning the supply air for the passenger compartment. The refrigerant circuit also includes a flow path extending from a branch point formed at an outlet of the compressor to a mouth point formed between the first refrigerant-to-air heat exchanger and the expansion element. A further heat exchanger is arranged within the flow path.

The air conditioning unit has a housing for directing and distributing the supply air for the passenger compartment, with a first flow channel and a second flow channel. The second refrigerant-to-air heat exchanger of the refrigerant circuit is arranged within the first flow channel. The second flow channel is designed as a bypass around the second refrigerant-to-air heat exchanger.

According to the concept of the invention, the air conditioning unit has a flow guide device for closing and opening the first flow channel, so that the second refrigerant-air heat exchanger of the refrigerant circuit can be completely shut off on the air side for conditioning the supply air for the passenger compartment.

The cross-sectional area of the first flow channel of the air conditioning unit is preferably completely covered by the first refrigerant-air heat transfer ger of the refrigerant circuit to avoid disruptive flows.

According to a further development of the invention, the flow guide device is arranged upstream of the second refrigerant-to-air heat exchanger in the direction of flow of the supply air for the passenger compartment. The flow guide device is advantageously designed as an air flap. Furthermore, the flow guide device is preferably continuously adjustable between two end positions: "fully open" and "fully closed."

In a first conceptual air conditioning system, the heat exchanger arranged within the flow path of the refrigerant circuit extending from the branch point formed at the compressor outlet to the outlet point formed between the first refrigerant-to-air heat exchanger and the expansion element is designed as a refrigerant-to-air heat exchanger for heating the supply air. The heat exchanger is arranged within the air conditioning unit downstream of the second refrigerant-to-air heat exchanger in the flow direction of the supply air, in particular downstream of an outlet of the first flow channel.

In a second air conditioning system according to the concept, the heat exchanger arranged within the flow path of the refrigerant circuit extending from the branch point formed at the compressor outlet to the mouth point formed between the first refrigerant-to-air heat exchanger and the expansion element is designed as a refrigerant-to-coolant heat exchanger of a coolant circuit. The coolant circuit also has a coolant-to-air heat exchanger arranged within the air conditioning unit through which supply air for the passenger compartment flows. The coolant-to-air heat exchanger of the coolant circuit is arranged within the air conditioning unit in the flow direction of the supply air downstream of the second refrigerant-to-air heat exchanger of the refrigerant circuit, in particular downstream of the outlet of the first flow channel.

According to the invention, the heat exchanger arranged within the flow path can be flowed through by refrigerant parallel to the first refrigerant-to-air heat exchanger for heat transfer between the refrigerant and ambient air, or instead of the first refrigerant-to-air heat exchanger. According to a first alternative embodiment of the invention, the branch point of the flow path of the refrigerant circuit is designed as a three-way valve.

According to a second alternative embodiment of the invention, the branch point of the flow path of the refrigerant circuit is designed as a valve arrangement with a T-piece, a first valve, and a second valve. The first valve is arranged upstream of the first refrigerant-to-air heat exchanger in the direction of refrigerant flow, in particular between the T-piece and the refrigerant-to-air heat exchanger. The second valve is arranged within the flow path, in particular upstream of the heat exchanger formed within the flow path.

According to a further development of the invention, an accumulator is provided as a refrigerant storage device within the refrigerant circuit upstream of the compressor in the direction of refrigerant flow. Additionally or alternatively, a collector can be provided downstream of the first refrigerant-to-air heat exchanger in the direction of refrigerant flow. A refrigerant circuit can also be designed without a collector and accumulator.

According to the invention, the air conditioning unit comprises a flow guide device for closing and opening the second flow channel, which is designed as a bypass around the second refrigerant-to-air heat exchanger. The flow guide device of the second flow channel is advantageously designed as an air flap and is also preferably continuously adjustable between two end positions: "fully open" and "fully closed."

The object of the invention is also achieved by a method according to the invention for operating an air conditioning system of a motor vehicle with a refrigerant circuit and an air conditioning unit for operation in a refrigeration system mode, in a heat pump mode, in particular in a reheating mode, and in a hot gas mode for the supply air of the passenger compartment to be conditioned.

The refrigeration system mode is primarily used for cooling, the heat pump mode and the hot gas mode for heating, and the reheating mode for cooling and/or dehumidifying as well as reheating the supply air of the passenger compartment.

• - Leiten eines aus einem Verdichter ausströmenden Kältemittels auf einem Hochdruckniveau durch einen Strömungspfad und einen als Kondensator/Gaskühler betriebenen Wärmeübertrager, wobei Wärme vom Kältemittel abgegeben wird,
• - Leiten des aus dem Wärmeübertrager austretenden Kältemittels durch ein Expansionsorgan, wobei das Kältemittel auf ein Niederdruckniveau entspannt wird,
• - Leiten des aus dem Expansionsorgan austretenden Kältemittels durch einen in einem ersten Strömungskanal des Klimagerätes angeordneten Kältemittel-Luft-Wärmeübertrager und
• - Ansaugen des Kältemittels durch den Verdichter.

The method for operating the air conditioning system comprises the following steps when operating the refrigerant circuit in hot gas mode to heat the supply air of the passenger compartment:

• - passing a refrigerant flowing out of a compressor at a high pressure level through a flow path and a heat exchanger operated as a condenser/gas cooler, whereby heat is released from the refrigerant,
• - Passing the refrigerant leaving the heat exchanger through an expansion device, whereby the refrigerant is expanded to a low pressure level,
• - guiding the refrigerant emerging from the expansion element through a refrigerant-air heat exchanger arranged in a first flow channel of the air conditioning unit and
• - Suction of the refrigerant by the compressor.

In this case, a flow guide device arranged in the flow direction of the supply air in the first flow channel upstream of the refrigerant-air heat exchanger is completely closed and the supply air is completely guided around the refrigerant-air heat exchanger through an open second flow channel so that the heat transferred in the refrigerant-air heat exchanger is zero.

According to a first alternative embodiment of the invention, heat is transferred from the refrigerant to the supply air of the passenger compartment in the heat exchanger operated as a condenser/gas cooler and designed as a refrigerant-air heat exchanger, which is arranged within the air conditioning unit for guiding and distributing the supply air for the passenger compartment.

According to a second alternative embodiment of the invention, heat is transferred from the refrigerant to a coolant of a coolant circuit in the heat exchanger, which operates as a condenser/gas cooler and is designed as a refrigerant-to-coolant heat exchanger. The heat absorbed by the coolant is then transferred from the coolant to the passenger compartment's supply air in a coolant-to-air heat exchanger, which is arranged within the air conditioning unit for directing and distributing the supply air to the passenger compartment.

The air conditioning system according to the invention offers the possibility of heating the supply air of the passenger compartment by operating the refrigerant circuit in a triangular process, in which the second refrigerant-to-air heat exchanger, which operates as an evaporator during operation in other modes, can be completely shut off on the air side, so that the refrigerant-to-air heat exchanger is not exposed to or overflowed by air. By shutting off the refrigerant-to-air heat exchanger on the air side, the suction pressure of the refrigerant circuit during operation in the triangular process is not dependent on the temperature of the air otherwise flowing over the refrigerant-to-air heat exchanger, in particular the ambient air. Consequently, the suction pressure level of the refrigerant circuit can be raised, which leads to an increase in the heat output for heating the supply air for the passenger compartment and reduces the risk of damaging the compressor due to excessively low suction pressures.

• - Klimatisieren, insbesondere Kühlen, Entfeuchten und/oder Heizen der Zuluft des Fahrgastraums mit minimalem Energieeinsatz,
• - Bereitstellen eines ausreichenden Komforts innerhalb des Fahrgastraums, insbesondere beim Betrieb im Heißgasmodus bei geringen Temperaturen der Umgebungsluft, durch Steigerung der Heizleistung und damit Aufheizen der Luft in sehr kurzer Zeit,
• - erhöhte Lebensdauer, da auch eine Schädigung des Verdichters durch einen zu geringen Saugdruck vermieden wird,
• - Kältemittelkreislauf, welcher zum Einsatz in bekannten Schemata und vorhandenen Bauräumen bestehender Kraftfahrzeuge integrierbar ist, sowie
• - minimale Anzahl von Komponenten im Kältemittelkreislauf, dadurch minimaler Bauraum, minimale Herstellungskosten und Wartungskosten auch durch Verzicht auf zusätzliche Komponenten im Klimatisierungssystem, wie elektrische Widerstandsheizungen.

In summary, the air conditioning system according to the invention for conditioning the air in a passenger compartment of motor vehicles has various advantages:

• - Air conditioning, in particular cooling, dehumidifying and/or heating the supply air of the passenger compartment with minimal energy consumption,
• - Providing sufficient comfort within the passenger compartment, particularly when operating in hot gas mode at low ambient air temperatures, by increasing the heating power and thus heating the air in a very short time,
• - increased service life, as damage to the compressor due to insufficient suction pressure is also avoided,
• - Refrigerant circuit, which can be integrated into known schemes and existing installation spaces of existing motor vehicles, as well as
• - minimal number of components in the refrigerant circuit, thus minimal installation space, minimal manufacturing costs and maintenance costs, also by eliminating additional components in the air conditioning system, such as electrical resistance heaters.

• 2: ein Klimagerät mit dem zweiten Kältemittel-Luft-Wärmeübertrager des Kältemittelkreislaufs und einem Heizwärmeübertrager des Kühlmittelkreislaufs aus dem Stand der Technik sowie
• 3a und 3b: ein erfindungsgemäßes Klimagerät mit dem zweiten Kältemittel-Luft-Wärmeübertrager des Kältemittelkreislaufs und dem Heizwärmeübertrager des Kühlmittelkreislaufs mit alternativen Ausführungsformen des Kältemittelkreislaufs.

Further details, features and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, in which air conditioning systems are shown, each with an air conditioning unit, a coolant circuit and a refrigerant circuit, comprising a compressor, a first and a second refrigerant-air heat exchanger and an expansion element.

• 2 : an air conditioning unit with the second refrigerant-air heat exchanger of the refrigerant circuit and a heating heat exchanger of the coolant circuit from the state of the art and
• 3a and 3b : an air conditioning unit according to the invention with the second refrigerant-air heat exchanger of the refrigerant circuit and the heating heat exchanger of the coolant circuit with alternative embodiments of the refrigerant circuit.

Out of 2 an air conditioning system 1' with a refrigerant circuit 2' and a coolant circuit 3 as well as an air conditioning unit 20' emerges from the prior art.

The refrigerant circuit 2' comprises a compressor 4, a first refrigerant-to-air heat exchanger 5, which can be operated in particular as a condenser/gas cooler, for heat transfer between the refrigerant and ambient air, with a collector 6 for separating and collecting refrigerant liquid, an expansion element 7, and a second refrigerant-to-air heat exchanger 8, which can be operated in particular as an evaporator, for conditioning the supply air for the passenger compartment. The collector 6 is arranged on the high-pressure side downstream of the first refrigerant-to-air heat exchanger 5 and thus between the refrigerant-to-air heat exchanger 5 and the expansion element 7.

The refrigerant circuit 2' is also designed with an accumulator 9 for separating and collecting refrigerant liquid, which is arranged upstream of the compressor 4 in the direction of refrigerant flow and thus on the low-pressure side between the second refrigerant-to-air heat exchanger 8 and the compressor 4. The compressor 4 draws gaseous refrigerant from the accumulator 9. The refrigerant circuit 2' can alternatively be designed either with the collector 6 arranged on the high-pressure side or with the accumulator 9 arranged on the low-pressure side.

The refrigerant circuit 2' has a first flow path 10, which extends from a branch point 12 to a discharge point 13. The branch point 12 is arranged in the flow direction of the refrigerant at or after the outlet from the compressor 4. The discharge point 13 of the first flow path 10 is formed between the first refrigerant-to-air heat exchanger 5 and the expansion element 7, specifically between the collector 6 and the expansion element 7. Within the first flow path 10, a heat exchanger 11, designed in particular as a refrigerant-to-coolant heat exchanger, is arranged for transferring heat from the refrigerant to a coolant of the coolant circuit 3. The branch point 12 is designed as a three-way valve 14, in particular as a 3/2-way shut-off valve, so that the refrigerant can be divided into partial mass flows as needed by the first refrigerant-to-air heat exchanger 5 for transferring heat from the refrigerant to the ambient air and/or by the first flow path 10 with the refrigerant-to-coolant heat exchanger 11 for transferring heat from the refrigerant to the coolant. The mass flow of the refrigerant can be divided between 0 and 100% between the heat exchangers 5, 11. The partial mass flows of the refrigerant are mixed again at the outlet point 13.

The refrigerant circuit 2' is also formed with a second flow path 15, which extends from a branch point 16 to a discharge point 17. The branch point 16 is arranged between the expansion element 7 and the second refrigerant-to-air heat exchanger 8 and is advantageously designed as a three-way valve 16, in particular as a 3/2-way shut-off valve. The discharge point 17 of the second flow path 15 is arranged between the second refrigerant-to-air heat exchanger 8 and the accumulator 9. The second flow path 15 is operated as a bypass around the evaporator 8 as required, wherein the refrigerant can be bypassed around the evaporator 8 at least in a partial mass flow. The refrigerant can be divided into partial mass flows by the second refrigerant-to-air heat exchanger 8 for transferring heat from the supply air for the passenger compartment to the refrigerant and/or by the second flow path 15. The refrigerant mass flow can be divided between 0 and 100%. The partial refrigerant mass flows are mixed again at the outlet point 17.

In addition to the refrigerant-to-coolant heat exchanger 11, which is designed as a thermal connection to the refrigerant circuit 2', the coolant circuit 3 has a coolant-to-air heat exchanger 18 for heating the supply air for the passenger compartment, hereinafter also referred to as a heating heat exchanger 18. Furthermore, a conveying device 19, in particular a pump, is provided within the coolant circuit 3 for conveying the coolant through the coolant circuit 3.

The air conditioning unit 20' of the air conditioning system 1' for conditioning, directing, and distributing the supply air for the passenger compartment has a housing with a first flow channel 21. Arranged within the first flow channel 21 is the second refrigerant-to-air heat exchanger 8, which operates as an evaporator for the refrigerant and transfers heat from the supply air to the refrigerant. The coolant-to-air heat exchanger 18 for heating the supply air is arranged within the housing of the air conditioning unit 20' in the flow direction 24, 25 of the supply air after the evaporator 8 for cooling and/or dehumidifying the supply air, in particular after the outlet of the first flow channel 21. The supply air is introduced into the passenger compartment in the flow direction 26.

Since the first flow channel 21 with the refrigerant-air heat exchanger 8 within the air conditioning unit 20' cannot be shut off on the air side, the heat exchanger 8 is always supplied with air flowing in the flow direction 24, in particular ambient air.

The air conditioning unit 20' also has a second flow channel 22, which is designed as a bypass to the first flow channel 21 for receiving a partial air mass flow. A first partial air mass flow guided through the bypass 22 is guided past the evaporator 8 on the air side, with a second partial air mass flow being guided through the first flow channel 21 to the evaporator 8. The second flow channel 22 of the air conditioning unit 20', designed as a bypass, can be completely closed by means of a flow guide device 23, which is designed in particular as an air flap, so that when the air flap 23 is open, a partial air mass flow is guided through the bypass 22 and a partial air mass flow is guided over the heat transfer surface of the evaporator 8. When the air flap 23 is closed and the second flow channel 22 is thus closed, the entire air mass flow is guided through the first flow channel 21 and over the heat transfer surface of the evaporator 8.

When the refrigerant circuit 2' is operated in refrigeration system mode to cool the supply air to the passenger compartment, the heat absorbed by the refrigerant in the evaporator 8 and the power absorbed by the compressor 4 are transferred to the ambient air as they flow through the first refrigerant-to-air heat exchanger 5, which is operated as a condenser/gas cooler, and/or to the coolant of the coolant circuit 3 in the refrigerant-to-coolant heat exchanger 11, which is operated as a condenser/gas cooler. In a coolant-to-air heat exchanger (not shown), the heat can then be released from the coolant to the ambient air or another heat sink. The heating heat exchanger 18 is not supplied with coolant or with supply air for the passenger compartment, so that no heat is transferred in the heating heat exchanger 18. The bypass 15 of the refrigerant circuit 2' is not supplied with refrigerant.

When the refrigerant circuit 2' is operated in reheating mode for cooling and/or dehumidifying as well as reheating the supply air of the passenger compartment, the heat absorbed by the refrigerant in the evaporator 8 and the power absorbed by the compressor 4 are transferred to the coolant of the coolant circuit 3 as it flows through the refrigerant-to-coolant heat exchanger 11, which operates as a condenser/gas cooler. No refrigerant flows through the first refrigerant-to-air heat exchanger 5. The heat absorbed by the coolant is then transferred to the supply air for the passenger compartment in the heating heat exchanger 18, so that the supply air, previously cooled and/or dehumidified as it flows over the heat exchanger surface of the evaporator 8, is reheated as it flows over the heat exchanger surface of the heating heat exchanger 18.

The bypass 22 around the evaporator 8 can be open.

When operating the refrigerant circuit 2' in hot gas mode, in particular for quickly heating the supply air of the passenger compartment at very low ambient air temperatures, the refrigerant in the compressor 4 is transferred from the low pressure level to the high pressure level A, according to 1 , compressed, whereby the refrigerant also absorbs heat. The refrigerant then flows through the first flow path 10 to the refrigerant-to-coolant heat exchanger 11, which operates as a condenser/gas cooler. In the refrigerant-to-coolant heat exchanger 11, heat is transferred from the refrigerant to the coolant of the coolant circuit 3 at the high pressure level B. The heat is then transferred from the coolant to the supply air for the passenger compartment in the heating heat exchanger 18. The first refrigerant-to-air heat exchanger 5 is not supplied with refrigerant.

After exiting the first flow path 10, the refrigerant flows through the expansion element 7 and is expanded to the low-pressure level and thus the suction pressure into the two-phase region of liquid and vapor C. The refrigerant flowing out of the heat exchanger 8 or from the bypass 15 on the low-pressure side is directed into the accumulator 9 and subsequently sucked in in the gaseous state by the compressor 4. The refrigerant circuit 2' is closed.

The refrigerant circuit 2' is operated in hot gas mode at very low ambient air temperatures in order to provide high heating output and thus heat the passenger compartment to a comfortable temperature level in a very short time.

When the refrigerant flows through the bypass 15 around the refrigerant-to-air heat exchanger 8, no heat exchanger is applied on the low-pressure side of the refrigerant, so that no defined temperature level is specified on the suction side, which determines the suction pressure of the refrigerant present in the two-phase region. However, if no temperature level and thus no pressure level is specified on the low-pressure side, the suction pressure p _S drops, particularly during the cold start of the vehicle, according to 1 , very sharply.

When the refrigerant flows through the refrigerant-air heat exchanger 8, the temperature level of the refrigerant is defined by the supply air acting on the heat exchanger 8, such as the ambient air, which also determines the suction pressure of the air present in the two-phase region. If the temperature level and thus the pressure level of the refrigerant is determined by the low temperature of the ambient air used as supply air for the passenger compartment, the suction pressure p _S also drops, particularly during the cold start of the vehicle, according to 1 , drops very sharply. The sharp drop in suction pressure p _{S ,} for example, increases the risk of damage to compressor 4, especially due to liquid hammer. To counteract this, the performance of compressor 4 is limited, which, however, also reduces the overall performance of the air conditioning system 1'.

In the 3a and 3b an air conditioning system 1a, 1b according to the invention with a refrigerant circuit 2a, 2b in alternative embodiments and a coolant circuit 3 as well as an air conditioning unit 20 is shown.

The refrigerant circuit 2a, 2b, like the refrigerant circuit 2' from 2 , a compressor 4, a first refrigerant-to-air heat exchanger 5, which can be operated in particular as a condenser/gas cooler, for heat transfer between the refrigerant and ambient air, with a collector 6, an expansion element 7, and a second refrigerant-to-air heat exchanger 8, which can be operated in particular as an evaporator, for conditioning the supply air for the passenger compartment. The compressor 4 draws in gaseous refrigerant from the accumulator 9.

The refrigerant circuit 2a, 2b in turn has a flow path 10 extending from a branch point 12 to a mouth point 13, wherein a heat exchanger 11, designed in particular as a refrigerant-coolant heat exchanger, is arranged within the flow path 10 for transferring heat from the refrigerant to the coolant of the coolant circuit 3.

In the first embodiment of the air conditioning system 1a according to 3a the branch point 12 of the refrigerant circuit 2a is designed as a three-way valve 14, in particular as a 3/2-way shut-off valve.

In the second embodiment of the air conditioning system 1b according to the first alternative 3b The branch point 12 of the refrigerant circuit 2b is designed as a valve arrangement from a T-piece in combination with a first valve 27 and a second valve 28. The first valve 27, designed in particular as a shut-off valve, is preferably arranged upstream of the first refrigerant-air heat exchanger 5 in the flow direction of the refrigerant and is thus arranged between the T-piece of the branch point 12 and the heat exchanger 5. The second valve 28, designed in particular as a shut-off valve, is advantageously arranged upstream of the refrigerant-coolant heat exchanger 11 within the flow path 10 in the flow direction of the refrigerant and is thus arranged between the T-piece of the branch point 12 and the heat exchanger 11.

With the design of the branch point 12 as a three-way valve 14 according to 3a or as a valve arrangement according to 3b The refrigerant can be divided into partial mass flows as required by the first refrigerant-to-air heat exchanger 5 for transferring heat from the refrigerant to the ambient air and/or by the flow path 10 with the refrigerant-to-coolant heat exchanger 11 for transferring heat from the refrigerant to the coolant. The mass flow of the refrigerant can be divided between 0 and 100% between the heat exchangers 5, 11.

In contrast to the refrigerant circuit 2' from 2 The refrigerant circuit 2a, 2b consists of the 3a and 3b no refrigerant line designed as a bypass around the second refrigerant-to-air heat exchanger 8, which is operated as an evaporator. Thus, the refrigerant circuit 2a, 2b is designed without a three-way valve as a branch point and as an inlet to the bypass as well as the flow path to the heat exchanger 8. The total mass flow of the refrigerant mixed from the partial mass flows at the outlet point 13 is passed completely through the heat exchanger 8.

The coolant circuit 3 of the embodiments of the air conditioning systems 1a, 1b according to the 3a and 3b corresponds to the coolant circuit 3 of the air conditioning system 1' according to 3 .

The air conditioning unit 20 of the air conditioning system 1a, 1b for conditioning, directing, and distributing the supply air for the passenger compartment has, within the first flow channel 21, the second refrigerant-to-air heat exchanger 8, which operates as an evaporator for the refrigerant, for cooling and/or dehumidifying the supply air and thus for transferring heat from the supply air to the refrigerant, as well as the coolant-to-air heat exchanger 18 for heating the supply air downstream of the evaporator 8 in the flow direction 24, 26 of the supply air, in particular downstream of the exit of the first flow channel 21. After passing through the heat exchanger 18, the supply air is directed into the passenger compartment in the flow direction 26.

Compared to the air conditioner 20' of the air conditioning system 1' from 2 The air conditioning system 1a, 1b of the 3a and 3b each have a flow guide device 29, which is designed as an air flap in the flow direction 24 of the Air is arranged upstream of the heat exchanger 8, in particular within the first flow channel 21. With the air flap 29 arranged in the inflow to the heat exchanger 8, the first flow channel 21 can be completely closed and thus the refrigerant-air heat exchanger 8 can be completely shut off on the air side. The first flow channel 21, in which the heat exchanger 8 is arranged, can be fully opened or fully closed by means of the air flap 29. The air flap 29 is continuously adjustable between the end positions "fully open" and "fully closed".

Since the air conditioning unit 20 also has a second flow channel 22, which is designed as a bypass for directing an air mass flow around the heat exchanger 8, the entire air mass flow directed through the air conditioning unit 20 can be guided through the bypass 22 and thus past the heat exchanger 8 and to the heating heat exchanger 18. The second refrigerant-to-air heat exchanger 8 is then not exposed to air, specifically supply air.

Also provided within the second flow channel 22 is a flow guide device 23, designed in particular as an air flap, with which the second flow channel 22 can be completely opened or completely closed.

For the operating modes of the refrigerant circuit 2a, 2b in the refrigeration system mode for cooling the supply air of the passenger compartment and in the reheating mode for cooling and/or dehumidifying as well as reheating the supply air of the passenger compartment, please refer to the explanations on 2 referred to.

When operating the refrigerant circuit 2a, 2b in hot gas mode, in particular for quickly heating the supply air of the passenger compartment at very low ambient air temperatures, the refrigerant in the compressor 4 is transferred from the low pressure level to the high pressure level A, according to 1 , compressed. In the process, the refrigerant also absorbs heat. The refrigerant is then passed through the flow path 10 and the refrigerant-coolant heat exchanger 11, which operates as a condenser/gas cooler. In the refrigerant-coolant heat exchanger 11, heat is transferred from the refrigerant to the coolant of the coolant circuit 3 at the high pressure level B. The heat transferred to the coolant is subsequently transferred from the coolant to the supply air for the passenger compartment in the heating heat exchanger 18. The refrigerant does not flow through the first refrigerant-air heat exchanger 5.

After exiting the flow path 10, the refrigerant flows through the expansion element 7 and is expanded to a low-pressure level and thus the suction pressure into the two-phase region of liquid and vapor C. The refrigerant exiting the expansion element 7 at the low-pressure level is completely passed through the heat exchanger 8 into the accumulator 9 and then sucked in in the gaseous state by the compressor 4. The refrigerant circuit 2a, 2b, which is operated in hot gas mode particularly at very low ambient air temperatures in order to provide high heating output and thus heat the passenger compartment to a comfortable temperature level in a very short time, is closed.

When the refrigerant circuit 2a, 2b is operated in hot gas mode, the air flap 29 arranged upstream of the heat exchanger 8 in the flow direction 24 and thus the first flow channel 21 are closed. The supply air is completely bypassed around the heat exchanger 8 through the open second flow channel 22. This means that no heat is transferred from the refrigerant to the supply air in the heat exchanger 8, and the refrigerant passed through the heat exchanger 8 is not cooled, which would lower the suction pressure of the refrigerant. The refrigerant has the same temperature level and thus the same pressure level at the inlet and outlet of the heat exchanger 8. The supply air for the passenger compartment, which bypasses the heat exchanger 8, is guided directly to the heating heat exchanger 18 and heated in the heating heat exchanger 18.

The air-side shut-off of the heat exchanger 8 also makes it possible to reduce the suction pressure level of the refrigerant compared to the operation of the air conditioning system 1' after 2 This also allows a higher high pressure level to be achieved, which 1 with the different state curves. The arrow indicates the increase in the low-pressure level. The curve shown with the dotted line illustrates the process of the refrigerant without air-side shut-off of heat exchanger 8, while the curve shown with the dashed line illustrates the process of the refrigerant with air-side shut-off of heat exchanger 8.

When the refrigerant circuit 2a, 2b is operated at higher pressure levels, in particular at a higher high pressure level, a larger amount of heat is provided to heat the coolant in the refrigerant-coolant heat exchanger 11, so that a larger amount of heat is also available to heat the supply air in the heating heat exchanger 18 and the supply air can be heated to a certain temperature in a shorter time.

By operating the air conditioning system 1a, 1b in hot gas mode, it is possible not only to stabilize the suction pressure level and to set a specific low temperature level and thus a defined suction pressure, but also to provide a sufficiently high power to heat the supply air for the passenger compartment even at very low ambient air temperatures during a cold start of the vehicle and thus to meet the requirements of thermal comfort without an additional electrical resistance heater.

By operating the refrigerant circuit in hot gas mode, the passenger compartment's supply air can be heated with similar efficiency to an electric resistance heater, but without the need for additional components. At the same time, the risk of compressor damage due to insufficient suction pressure is minimized.

The refrigerant circuit and operating modes are suitable for any refrigerant that undergoes a phase transition from liquid to gas on the low-pressure side. On the high-pressure side, the medium releases the absorbed heat to a heat sink through gas cooling/condensation and subcooling. Suitable refrigerants include natural substances such as R744, R717 and similar; flammable substances such as R290, R600, R600a; and similar chemical substances such as R134a, R152a, HFO-1234yf; as well as various refrigerant blends.

List of reference symbols

1', 1a, 1b

Air conditioning system

2', 2a, 2b

Refrigerant circuit

3

coolant circuit

4

compressor

5

Heat exchanger, first refrigerant-to-air heat exchanger, condenser/gas cooler

6

collector

7

expansion organ

8

Heat exchanger, second refrigerant-air heat exchanger, evaporator

9

accumulator

10

(first) flow path

11

Heat exchanger, refrigerant-to-coolant heat exchanger

12

Junction point

13

Mouth

14

Three-way valve

15

second flow path, bypass

16

Branch point, three-way valve

17

Mouth

18

Coolant-air heat exchanger, heating heat exchanger

19

conveying device, pump

20', 20

air conditioner

21

first flow channel

22

second flow channel, bypass

23

Flow guide device, air flap flow channel 22

24

Flow direction supply air flow evaporator 8

25

Flow direction supply air flow heating heat exchanger 18

26

Flow direction supply air passenger compartment

27

first valve, shut-off valve branch point 12

28

second valve, shut-off valve branch point 12

29

Flow guide device, air flap inflow evaporator 8

A, B, C

Change in state of refrigerant

Claims (11)

Air conditioning system (1a, 1b) for conditioning the air of a passenger compartment of a motor vehicle with a refrigerant circuit (2a, 2b), comprising: - a compressor (4), a first refrigerant-air heat exchanger (5) for heat transfer between the refrigerant and ambient air, an expansion element (7) and a second refrigerant-air heat exchanger (8) for conditioning the supply air for the passenger compartment, wherein the second refrigerant-air heat exchanger (8) is arranged such that the refrigerant is always passed completely through, - a flow path (10) extending from a branching point (12) to a mouth point (13) and is formed with a heat exchanger (11), wherein the branching point (12) is at an outlet of the compressor (4) and the mouth point (13) is between the first refrigerant-air heat exchanger (5) and the Expansion element (7) are designed in such a way that the heat exchanger (11) parallel to the first refrigerant-to-air heat exchanger (5) or instead of the first refrigerant-to-air heat exchanger (5), and an air conditioning unit (20), comprising a housing for conducting and distributing the supply air for the passenger compartment with - a first flow channel (21) in which the second refrigerant-to-air heat exchanger (8) is arranged, and - a second flow channel (22) which is designed as a bypass around the second refrigerant-to-air heat exchanger (8), wherein - the heat exchanger (11) arranged within the flow path (10) is designed as a refrigerant-to-air heat exchanger for heating the supply air and is arranged within the air conditioning unit (20) in the flow direction (24) of the supply air after the second refrigerant-to-air heat exchanger (8) or the heat exchanger arranged within the flow path (10) Heat exchanger (11) is designed as a refrigerant-coolant heat exchanger of a coolant circuit (3), wherein the coolant circuit (3) has a coolant-air heat exchanger (18) for heating the supply air, which is arranged within the air conditioning unit (20) in the flow direction (24) of the supply air after the second refrigerant-air heat exchanger (8), - the air conditioning unit (20) has a flow guide device (29) for closing and opening the first flow channel (21) and a flow guide device (23) for closing and opening the second flow channel (22). Air conditioning system (1a, 1b) according to Claim 1 , characterized in that the flow guiding device (29) is arranged in the flow direction (24) of the supply air for the passenger compartment in front of the second refrigerant-air heat exchanger (8). Air conditioning system (1a, 1b) according to Claim 1 or 2 , characterized in that the flow guiding device (29) for closing and opening the first flow channel (21) is designed as an air flap. Air conditioning system (1a, 1b) according to one of the Claims 1 until 3 , characterized in that the flow guiding device (23) for closing and opening the second flow channel (22) is designed as an air flap. Air conditioning system (1a, 1b) according to one of the Claims 1 until 4 , characterized in that the flow guiding device (29) for closing and opening the first flow channel (21) is designed to be continuously adjustable between two end positions “fully open” and “fully closed”. Air conditioning system (1a, 1b) according to one of the Claims 1 until 5 , characterized in that the flow guiding device (23) for closing and opening the second flow channel (22) is designed to be continuously adjustable between two end positions “fully open” and “fully closed”. Air conditioning system (1a) according to one of the Claims 1 until 6 , characterized in that the branch point (12) of the flow path (10) is designed as a three-way valve (14). Air conditioning system (1b) according to one of the Claims 1 until 6 , characterized in that the branch point (12) of the flow path (10) is designed as a valve arrangement with a T-piece, a first valve (27) and a second valve (28), wherein - the first valve (27) is arranged upstream of the first refrigerant-air heat exchanger (5) in the flow direction of the refrigerant and - the second valve (28) is arranged within the flow path (10). Method for operating an air conditioning system (1a, 1b) of a motor vehicle with a refrigerant circuit (2a, 2b) and an air conditioning unit (20) for operation in a refrigeration system mode, in a heat pump mode, in particular in a reheating mode, and in a hot gas mode for the supply air of the passenger compartment to be conditioned according to one of the Claims 2 until 8 , when operated in hot gas mode for heating the supply air of the passenger compartment, comprising the following steps: - guiding a refrigerant flowing out of a compressor (4) at a high pressure level through a flow path (10) and a heat exchanger (11) operated as a condenser/gas cooler, wherein heat is released from the refrigerant, - guiding the refrigerant flowing out of the heat exchanger (11) through an expansion element (7), wherein the refrigerant is expanded to a low pressure level, - guiding the refrigerant flowing out of the expansion element (7) through a refrigerant-air heat exchanger (8) arranged in a first flow channel (21) of the air conditioning unit (20), and - sucking in the refrigerant through the compressor (4), wherein a flow guide device (29) arranged upstream of the refrigerant-air heat exchanger (8) in the flow direction (24) of the supply air in the first flow channel (21) is closed and the Supply air is guided through an open second flow channel (22) around the refrigerant-air heat exchanger (8) so that the heat transferred in the refrigerant-air heat exchanger (8) is zero. Method for operating an air conditioning system (1a, 1b) of a motor vehicle according to Claim 9 , characterized in that in the heat exchanger (11) designed as a refrigerant-air heat exchanger, which is arranged within the air conditioning unit (20) for guiding and distributing the supply air for the passenger compartment, heat is transferred from the refrigerant to the supply air of the passenger compartment. Method for operating an air conditioning system (1a, 1b) of a motor vehicle according to Claim 9 , characterized in that in the heat exchanger (11) designed as a refrigerant-coolant heat exchanger, heat is transferred from the refrigerant to a coolant of a coolant circuit (3) and in a coolant-air heat exchanger (18) which is arranged within the air conditioning unit (20) for conducting and distributing the supply air for the passenger compartment, heat is transferred from the coolant to the supply air of the passenger compartment.

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