Vehicle with air conditioning

Abstract

Vehicle with an air conditioning system for heating a supply air (I) flowing into a vehicle interior (2), the air conditioning system comprising: a heating heat exchanger (8) which is thermally coupled to a drive unit of the vehicle via a coolant circuit (13), and an additional heat exchanger (7) which is connected to a refrigerant circuit of the air conditioning system and releases heat to the supply air (I) in heating mode, wherein the heating heat exchanger (8) is arranged upstream of the additional heat exchanger (7) in the flow direction of the supply air (I), and wherein the additional heat exchanger (7) is designed in at least two rows, namely in the flow direction of the supply air (I) initially with a subcooling row (31) and subsequently with a desuperheating / condensation row (30), wherein the desuperheating / condensation row (30) is designed such that desuperheating and condensation of a refrigerant takes place, and wherein the subcooling row (31) is designed such that subcooling of the condensed refrigerant takes place, characterized in that the desuperheating / condensing row (30) and the subcooling row (31) are connected to a collector pipe (33) having a separation chamber (34) which collects the liquid refrigerant emerging from the desuperheating / condensing row (30) and transfers it to the subcooling row (31), and that the collector pipe (33) opens into the desuperheating / condensation row (30) and the subcooling row (31) at the bottom.

Description

[0001] The invention relates to a vehicle with an air conditioning system according to the preamble of patent claim 1.

[0002] The vehicle interior is typically heated by a heater core, to which the waste heat from a drive unit, such as an internal combustion engine, is fed via a water-based coolant circuit. A booster heater is typically associated with the heater core. In vehicles with an air conditioning system, the booster heater may be a condenser connected to the air conditioning system's refrigerant circuit, which, during heating operation, transfers heat to the air flowing into the vehicle interior.

[0003] Refrigeration systems of this type for a vehicle are known from DE 103 24 955 A1 or EP 0 401 752 A2.

[0004] Another vehicle with an air conditioning system is known from DE 102 53 357 B4. In heating mode, the supply air flowing into the vehicle interior is heated by a heater core, which is thermally coupled to a drive unit via a coolant circuit, and an auxiliary heat exchanger. The auxiliary heat exchanger is connected in a refrigerant circuit of the air conditioning system. Both the auxiliary heat exchanger and the heater core are arranged in an air-flow air conditioning unit, with the warm air flowing out of the air conditioning unit being divided and directed to several separate passenger vents.

[0005] In addition, reference is made to US 5 181 392 A, US 5 983 652 A and DE 21 49 548 A.

[0006] Future diesel and gasoline engines will not be able to provide the necessary heat to warm the passenger compartment. Additional heating measures such as fuel burners or PTCs will be required. A more efficient and environmentally friendly measure is to use the existing air conditioning system and operate it in heat pump mode.

[0007] In addition to changeover valves, an additional condenser is used, which works as an auxiliary heater and is installed in the air conditioning unit.

[0008] The object of the invention is to provide a vehicle with an air conditioning system for cooling and heating with appropriate heating output and efficiency. Furthermore, the additional heat pump condenser should be designed so that the air exiting it exhibits good homogeneity, synonymous with a uniform temperature distribution, which in turn has a positive influence on the control quality with regard to interior comfort for passengers.

[0009] The object is achieved by a vehicle with air conditioning having the features of patent claim 1. Preferred developments of the invention are disclosed in the subclaims.

[0010] According to the invention, the condenser, which operates as an auxiliary heater in heating mode, is designed in at least two rows with a first heat exchanger row and a second heat exchanger row connected to it. The two heat exchanger rows and the heater core heat exchanger connected in the coolant circuit are connected in series with one another in the flow direction of the incoming supply air. Depending on the application, the heater core heat exchanger is arranged first, followed by the auxiliary heat exchanger, or the auxiliary heat exchanger is arranged first, followed by the heater core heat exchanger. The two-row design of the auxiliary heat exchanger results in a flow pattern of the warm air flow exiting the air conditioning unit that has a constant air temperature across the entire flow cross-section of the warm air flow.The main supply air flow, which is guided through the two-row additional heat exchanger, can thus be divided into partial flows, each with an identical warm air temperature, whereby the warm air exiting at the different person outlets reliably has the warm air temperature set by the user.

[0011] In addition, the two heat exchanger rows are coordinated in such a way that in the first heat exchanger row (subcooling row), subcooling of the condensed refrigerant takes place in the direction of the air flow. Functionally separate from this, in the second heat exchanger row (desuperheating / condensation row), at least desuperheating and, if necessary, condensation of the refrigerant supplied by the compressor takes place. Desuperheating is understood to mean the cooling of the refrigerant until the dew line of a Mollier diagram is reached. By separating desuperheating / condensation and subcooling, both efficient air heating and uniform air heating are achieved. By specifically and inventively dividing the heat exchanger surfaces for subcooling and desuperheating / condensation, a high condensation temperature is achieved compared to cooling mode.This allows heat transfer from the auxiliary heat exchanger to the incoming supply air to occur with a similarly increased driving temperature difference. The heating arrangement consisting of the auxiliary heat exchanger and the heating system heat exchanger can thus easily cover the heating demand even in extreme situations.

[0012] As mentioned above, the inventive two-row design of the auxiliary heat exchanger with the corresponding distribution of the heat exchanger surfaces achieves an increased condensation temperature in the heat pump process of the air conditioning system. This allows the use of refrigerants in the refrigerant circuit that only achieve reduced compressor outlet or condensation temperatures.

[0013] According to the invention, the subcooling row and the desuperheating / condensing row are fluidically connected by a header pipe. The header pipe collects the liquid refrigerant emerging from the second heat exchanger row and transfers the liquid refrigerant to the first heat exchanger row. For this purpose, the header pipe opens into the underside of the subcooling row and the desuperheating / condensing row, allowing the condensed refrigerant to easily collect in the header pipe. The header pipe also has a separation chamber in which any vaporous refrigerant can be separated from the liquid refrigerant. In this way, a functional separation of the two heat exchanger rows between the desuperheating / condensing function and the subcooling function is achieved. The header pipe can be designed as a receiver. Furthermore, the header pipe can also be designed as a flat tube or as a double tube.In addition, the collector pipe can be positioned horizontally or vertically.

[0014] Raising the condensation temperature of the refrigerant in the condensation row of the heat exchanger can preferably be achieved by reducing the effective condensation surface. Such a reduction in the condensation surface leads to a significantly higher condensation pressure in the condensation row of the additional heat exchanger during heat pump operation of the refrigerant circuit, with a correspondingly increased condensation temperature.

[0015] In contrast to the significantly reduced desuperheating / condensation heat transfer surface, the subcooling heat exchanger surface can be significantly larger. Depending on the refrigerant circuit (with / without internal heat exchanger), the heat exchanger surface for desuperheating is almost negligible. The subcooling section can be many times larger than the heat exchanger surface for condensation. The heat exchanger surface ratio between desuperheating / condensation and subcooling can vary between 70 / 30 and 1 / 99%. With this design, it is important that the internal volumes, especially of the subcooling section and the connecting lines, are kept to a minimum in order to limit the charge to a certain level. The described surface ratios refer to the front surface of a single-row heating heat exchanger.

[0016] In a multi-row design, it makes sense to introduce a standardized volume ratio, since the end face is the same across multiple levels. If a standardized volume ratio is introduced for multi-row heat exchangers with the same area ratio of the heat exchanger levels (otherwise, adjust mathematically), the following design can result: 15% subcooling / 85% condensation to 99% subcooling / 1% condensation.

[0017] In contrast to the inventive dimensioning of the heat exchanger rows, the conventional condensers of an air conditioning system are conversely designed with a comparatively large desuperheating / condensation section and a correspondingly reduced subcooling section (above the mentioned area ratio 70 / 30%).

[0018] For effective heat transfer from the auxiliary heat exchanger to the incoming supply air, it is preferable to arrange the subcooling row first, followed by the desuperheating / condensing row of the auxiliary heat exchanger, in the direction of supply air flow. This allows the supply air to be heated to be first preheated in the subcooling row using the counterflow principle and then brought to the outlet temperature in the desuperheating / condensing row.

[0019] The auxiliary heat exchanger and the heater core form a heating arrangement of the air conditioning unit. The air conditioning unit can also have an evaporator, also connected in the refrigerant circuit, which can cool the incoming supply air in cooling mode and / or for dehumidification. Depending on the desired heat / heating output, the evaporator can be located first in the supply air flow direction, followed by the auxiliary heat exchanger, then the heater core, and possibly a PTC heating element. Alternatively, the heater core can be located directly downstream of the evaporator. The sequence depends on the specific application.

[0020] Depending on the design, the two auxiliary heat exchanger rows with the refrigerant inlet / outlet can each be designed as single- or multi-flow. The auxiliary heat exchanger can also be designed as three-row with a special desuperheating row, a condensing row, and a subcooling row.

[0021] An embodiment of the invention is described below with reference to the attached figures.

[0022] They show: Fig. 1 the switching of an air conditioning system of a motor vehicle when operating in a heating mode; Fig. 2 in a view corresponding to the Fig. 1 the air conditioning system when performing a cooling mode; and Fig. 3 generally shows a heat pump process in the heating mode of the air conditioning system in a Mollier diagram.

[0023] In the Fig. 1 and Fig. 2 shows an air conditioning system of the motor vehicle, by means of which the vehicle interior 2 can be cooled or heated. Fig. 1 shows the heating mode for heating the vehicle interior 2, with the parts through which refrigerant flows being highlighted by thick lines in comparison to the parts shut down in the heating mode. Accordingly, the refrigerant is fed from a compressor 3, preferably via a 3 / 2-way valve, into a first high-pressure line 6, which leads in the direction of the arrow to an additional heat exchanger 7. The additional heat exchanger 7 is arranged in an air conditioning unit (indicated by dashed lines) within an air duct of an air conditioning unit 9, through which the supply air I is fed into the vehicle interior 2. After heating in the air conditioning unit 9, the warm air is divided into, for example, three separate warm air streams I a , I b , I cto different passenger vents (e.g. defrost vents, passenger vents, footwell vents).

[0024] The heat exchanger 7, which according to the invention is designed in at least two rows, forms, together with a heating heat exchanger 8, a heating arrangement 10 through which the supply air I flows. The heating heat exchanger 8 is arranged in a coolant circuit (coolant line) 13, which is only indicated, with which the waste heat generated in an internal combustion engine (not shown) can be conducted to the heating heat exchanger 8.

[0025] According to the Fig. 1, the two-row additional heat exchanger 7, which functions as a condenser, is fluidly coupled to a cooler-side heat exchanger 17 via a second high-pressure line 11 and a 3 / 2-way valve 12 with an interposed expansion device 15. This cooler-side heat exchanger 17 operates as an evaporator in heating mode, extracting heat from the ambient air. In refrigeration system operation, it functions as a condenser. The cooler-side heat exchanger 17 is routed downstream with a low-pressure line 19 to the suction side of the compressor 3. The low-pressure line 19 is routed via an internal heat exchanger 21, in which heat can be exchanged with the high-pressure side, i.e., from the high-pressure line 11. Direct integration of the line 19 upstream of the compressor 3 is also possible.

[0026] As from the Fig. 1, the additional heat exchanger 7 has a desuperheating / condensation row 30 and a subcooling row 31.

[0027] These are connected in series and fluidically connected to a separation chamber 34 via a collector pipe 33. In this application example, the collector pipe 33 opens into the subcooling row 31 and the desuperheating / condensation row 30 at the bottom.

[0028] The subcooling row 31 and the desuperheating / condensing row 30 are designed according to the invention such that, viewed downstream, desuperheating E and condensation K of the refrigerant can take place in the desuperheating / condensing row 30. In contrast, in the subcooling row 31, subcooling U of the already condensed refrigerant takes place. For illustration, Fig. 3 shows a heat pump process in a Mollier diagram, in which the process steps of desuperheating, condensation, and subcooling are shown as E, K, and U, respectively. The diagram shown uses the refrigerant R134a as an example. It shows that a compressor outlet temperature T a of the refrigerant is approximately 95°C, while the condensation K of the first heat exchanger row 30 is at a condensation temperature T K is at 60°C.

[0029] According to the invention, the subcooling row 31 of the additional heat exchanger 7 is arranged upstream of the desuperheating / condensing row 30 in the flow direction of the supply air I. As a result, the supply air I flowing into the air conditioning unit 9 is preheated by the subcooling row 31 in the counterflow principle and then heated to the air conditioning unit outlet temperature by the desuperheating / condensing row 30. In order to achieve the highest possible condensation temperature T KTo achieve this, the desuperheating / condensing row 30 is designed with a greatly reduced refrigerant-to-air heat exchanger surface. The refrigerant flowing into the desuperheating / condensing row 30 in gaseous form is liquefied at high condensation pressure, resulting in a correspondingly high condensation temperature T K Proportional to the resulting increase in the condensation temperature T K This results in a comparatively large driving temperature difference between the desuperheating / condensing row 30 and the flowing supply air I.

[0030] The header pipe 33 provides a functional separation between the desuperheating / condensation in the desuperheating / condensation row 30 and the subcooling in the subcooling row 31. The condensed refrigerant exiting the desuperheating / condensation row 30 collects in the header pipe 33, allowing the still-gaseous refrigerant to be separated. This ensures that only liquid refrigerant is fed into the subcooling row 31.

[0031] In the Fig. Figure 2 shows the cooling mode of the air conditioning system, with the lines through which refrigerant flows highlighted in thick lines. In cooling mode, the 3 / 2-way valve 5 downstream of the compressor 3 blocks line 6 leading to the additional heat exchanger 7 in the air conditioning unit 9, while an intermediate line 23 leading to line 19 is opened. At the branching point to line 19, on the side facing away from the heat exchanger 17, the shut-off valve 25 is in the closed switching position. The refrigerant is therefore passed through the cooler-side heat exchanger 17, which, in cooling mode, acts as a condenser and releases heat to the ambient air.

[0032] The refrigerant is then conducted via a one-way valve 27 connected parallel to the expansion element 15, via the internal heat exchanger 21, and via the 3 / 2-way valve 12 to an evaporator 29 within the air conditioning unit 9. An expansion element 40 is connected upstream of the evaporator 29. The refrigerant flowing out of the evaporator 29 is conducted back to the compressor 3 via line 36, the internal heat exchanger 21, and line 19.

[0033] In principle, this idea can also be used to construct a cooler-side heat exchanger, the condenser of the refrigeration system.

[0034] The function of the heating heat exchanger 8 is significantly influenced by the operation of the heat pump. The air can be heated exclusively by the heat pump or by the heat pump and the engine cooling circuit, which is Fig.1 only shows the coolant line 13. Accordingly, the operating mode of the auxiliary heat exchanger must be differentiated. Depending on the operating mode, the performance and efficiency of the overall system are influenced.

Claims

[1] Vehicle with an air conditioning system for heating a supply air (I) flowing into a vehicle interior (2), the air conditioning system comprising: a heating heat exchanger (8) which is thermally coupled to a drive unit of the vehicle via a coolant circuit (13), and an additional heat exchanger (7) which is connected to a refrigerant circuit of the air conditioning system and releases heat to the supply air (I) in heating mode, wherein the heating heat exchanger (8) is arranged upstream of the additional heat exchanger (7) in the flow direction of the supply air (I), and wherein the additional heat exchanger (7) is designed in at least two rows, namely in the flow direction of the supply air (I) initially with a subcooling row (31) and subsequently with a desuperheating / condensation row (30), wherein the desuperheating / condensation row (30) is designed such that desuperheating and condensation of a refrigerant takes place, and wherein the subcooling row (31) is designed such that subcooling of the condensed refrigerant takes place, characterized by that the desuperheating / condensing row (30) and the subcooling row (31) are connected to a collector pipe (33) having a separation chamber (34), which collects the liquid refrigerant emerging from the desuperheating / condensing row (30) and transfers it to the subcooling row (31), and that the collector pipe (33) opens into the desuperheating / condensation row (30) and the subcooling row (31) at the bottom. [2] Vehicle according to claim 1, characterized by that the subcooling row (31) is larger than the desuperheating / condensing row (30). [3] Vehicle according to one of the preceding claims, characterized by that a heat transfer surface of the subcooling row (31) in relation to a heat transfer surface (single row) of the desuperheating / condensing row (30), with a standardized volume ratio for a multi-row design, results in a ratio of 15% subcooling / 85% condensation to 99% subcooling / 1% condensation. [4] Vehicle according to one of the preceding claims, characterized bythat an air conditioning unit (9) of the vehicle, in addition to a heating arrangement (10) consisting of an additional heat exchanger (7) and a heating heat exchanger (8), additionally has an evaporator (29) connected in the refrigerant circuit. [5] Vehicle according to one of the preceding claims, characterized by that the additional heat exchanger (7) is designed in three rows with a desuperheating row, a condensation row and the subcooling row (31). [6] Vehicle according to one of the preceding claims, characterized by that each of the additional heat exchanger rows (30, 31) is designed with a single-flow or multi-flow refrigerant inlet and outlet.

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