Defrosting a heat exchanger in roof-mounted air conditioning systems

Abstract

Device (10) for air treatment, namely a roof air conditioning unit in a flat design, comprising a first heat exchanger (20) for extracting heat from an environment (U), comprising a second heat exchanger (40) for transferring heat to a room (101) to be heated, and comprising a fan (30) which supplies air from the environment (U) to the first heat exchanger (20), wherein the first heat exchanger (20) and the second heat exchanger (40) are fluidly connected to each other in a refrigerant circuit (50) through which a refrigerant circulates, wherein the first heat exchanger (20) is installed at least partially inclined at an angle (W) to a horizontal (70), wherein the first heat exchanger (20) is V-shaped or convexly bent relative to the horizontal (70), characterized in that the first heat exchanger (20) has a bending section (80) which is arranged centrally.wherein the first heat exchanger (20) is kinked or bent in the bending area (80) and is divided by the bending area (80) into two heat exchanger sections (21, 22) or two parts (23, 24), wherein the bending area (80) is designed free of fins (25), so that the respective parts (23, 24) of the first heat exchanger (20) are connected to each other by flat tubes (26).

Description

[0001] The invention relates to an air treatment device, namely a flat-design roof air conditioning unit, comprising a first heat exchanger for extracting heat from an environment and a second heat exchanger for transferring heat to a room to be heated. The invention further relates to a vehicle.

[0002] Electrically powered vehicles often use heat pumps to heat the passenger compartment. In this process, the heat required to heat the passenger compartment is extracted from the vehicle's surroundings and transferred to the passenger compartment. During this process, a heat exchanger thermally coupled to the vehicle's surroundings cools down to such an extent that the dew point of the surrounding air is reached, and frost forms on the surface of the heat exchanger.

[0003] Frost buildup increasingly ices the surface of the heat exchanger, thus preventing the heat pump from operating efficiently. To allow air to flow through the heat exchanger again, defrosting cycles or processes are necessary, during which the iced-up heat exchanger is heated. Consequently, the ice melts, and airflow through the heat exchanger can resume. To reduce the time required for a defrosting process or for a quick restart of the heat pump into heating mode, the meltwater must drain from the heat exchanger as quickly and completely as possible.

[0004] In buses and rail vehicles, compact microchannel heat exchangers are increasingly being installed horizontally on the roof. Due to their horizontal position, only a small amount of water can drain from the heat exchanger during the defrosting process, thus reducing the efficiency of the heat pump.

[0005] JP H08-216 671 A discloses a roof-mounted air conditioning system for a vehicle, consisting of two heat exchangers arranged at opposite angles within a housing. The heat exchangers are fixed within the housing and are not moved or swiveled during operation. DE 10 2018 130 158 A1 also describes a roof-mounted air conditioning system for a vehicle, which has two heat exchangers connected in series or in parallel. US 4,905,478 A discloses a roof-mounted air conditioning system with multiple heat exchangers, which are supplied with an airflow by means of an axial fan.

[0006] Furthermore, a heat exchanger device comprising a rotating device for rotating a first heat exchanger is known from CN 1 08 189 640 A. DE 11 2013 005 361 T5 further discloses a vehicle air conditioning system that can achieve a desired output temperature even when the degree of coolant subcooling of a radiator is changed. KR 10 2016 0 066 821 A further discloses a variable air conditioning system for a vehicle with a rotatable condenser.

[0007] Another air conditioning system for installation on a vehicle roof is known from JP H08-216 671 A. JP S62-221 913 A further discloses a heat pump air conditioning system consisting of a compressor, an interior heat exchanger, an interior fan, an exterior heat exchanger, and an exterior fan, mounted on the roof of a vehicle, with an exterior heat exchanger arranged in an octagonal shape on both sides of the exterior fan.

[0008] Furthermore, DE 69 209 817 T2 discloses an evaporator for cooling devices or heat pump devices with a heat exchanger having first and second pressure-resistant head pieces arranged at a distance, between which a plurality of elongated tubes with a flat cross-section extend parallel to each other at a distance and are fluidically connected to them.

[0009] The generic patent CN 106 696 639 A relates to an integrated air conditioning unit with a heat pump, comprising a base and a top cover. The base contains an electric compressor cavity, two independent cavities, and a cavity for the electrical control system. The base includes a variable-frequency electric compressor, a four-way reversing valve, a gas-liquid separator, and a system piping section within the electric compressor cavity. The unit also includes an evaporator, an evaporator fan, and a thermal expansion valve. The condensing fan is matched to the condenser. The evaporating fan is matched to the evaporator, the condensing fan is matched to the condenser, and the evaporating fan is matched to the evaporator.A high-voltage protection device and an energy-saving frequency conversion control device are arranged within the cavity of the electrical control system, along with an electric variable frequency compressor, a condenser, and an evaporator. A reversing four-way valve is connected to an air intake port of the electric variable frequency compressor via a gas-liquid separator. The condenser is connected to an evaporator via a thermal expansion valve. Furthermore, the condenser has an integrated flat-plate or V-shaped structure, with the condensing fan located on the top of the condenser and an evaporator on each side of the condenser.

[0010] DE 10 2006 062 261 A1 relates to an air conditioning system for vehicles, preferably for buses, with a fluid circuit, with a condenser assembly, an evaporator assembly and a compressor assembly, wherein the condenser assembly has a non-modular heat exchanger assembly whose surface area is greater than or equal to 0.5 m² 2 is designed. For the mechanical stabilization of this relatively large heat exchanger unit, a frame element can be provided that surrounds the extensibility area of ​​the heat exchanger unit and in which the collector tubes are integrated at the front.

[0011] The invention is based on the objective of creating an air treatment device that enables rapid and technically simple defrosting of the heat exchanger while maintaining a minimal installation height.

[0012] This problem is solved by the features specified in claim 1. Further advantageous embodiments of the invention are described in the dependent claims.

[0013] According to one aspect of the invention, an air treatment device, namely a flat-roof air conditioning unit, is provided. The device comprises a first heat exchanger for extracting heat from the environment and a second heat exchanger for transferring heat to a room to be heated. A fan supplies air from the environment to the first heat exchanger. The first and second heat exchangers are fluidly connected in a refrigerant circuit through which a refrigerant circulates. The refrigerant can, for example, be circulated within the refrigerant circuit by a refrigerant compressor. According to the invention, the first heat exchanger can be installed at an angle to the horizontal by means of a mounting unit to perform a defrosting process, or at least partially at an angle to the horizontal.Furthermore, the first heat exchanger is V-shaped or curved relative to the horizontal.

[0014] When the heat pump is in defrost mode, water forms on the surface of the first heat exchanger. To minimize blockage for the subsequent icing cycle, it is advantageous to displace as much water as possible from the first heat exchanger. This increases the time the first heat exchanger would otherwise remain frozen in the next cycle.

[0015] Preferably, during a defrost cycle, the first heat exchanger can be tilted unilaterally by the installation unit, thus assuming a preset or variably adjustable tilt angle. After the defrost cycle is complete, the installation unit can return the first heat exchanger to a horizontal or lying position. The installation unit can be hydraulically, pneumatically, or electrically driven. This design ensures that the device can operate at a minimal height. The height of the device is briefly increased as needed to carry out the defrost cycle.

[0016] When the device is mounted on the roof, the horizontal plane can, for example, be designed as a roof surface of the vehicle.

[0017] The first heat exchanger can, for example, be designed as a heat pump evaporator, which utilizes the effect of capillary forces through the louvers or the orientation at the angle of inclination for the drainage of the first heat exchanger.

[0018] When the first heat exchanger is set up, the capillary force and the gravitational force of the thawed water film add up, and the water can drain optimally.

[0019] The device can also be used to eliminate condensation before icing occurs or to allow the condensation that has formed to drain away.

[0020] According to one embodiment, the tilt angle of the first heat exchanger can be adjusted from 5° to 70° relative to the horizontal during the defrosting process by the installation unit. Selecting a tilt angle between 5° and 70°, including 5° and 70°, allows for particularly efficient water drainage. For example, the amount of drained water can be increased by 50% if a tilt angle of 15% is set temporarily or permanently. Preferably, the tilt angle can be selected in the range between 45° and 60°.

[0021] An advantageous angle of inclination can be achieved while maintaining a low overall height of the device, since, according to the invention, the first heat exchanger is bent in a V-shape or convexly relative to the horizontal. A drip tray for collecting and draining condensation can be arranged at one or two of the lowest positions of the V-shaped or convexly bent first heat exchanger.

[0022] According to the invention, the first heat exchanger has a bending section which is arranged centrally. The first heat exchanger is kinked or bent in this bending section. The heat exchanger sections on both sides of the bending section preferably each have an angle of inclination and are oriented as mirror images of each other.

[0023] According to a further embodiment, the first heat exchanger has flat tubes for conveying the refrigerant and fins thermally coupled to these flat tubes. The curved first heat exchanger has fins thermally coupled to the flat tubes outside the bending area of ​​the first heat exchanger. This design makes the curved or bent first heat exchanger particularly easy to manufacture. In particular, the flat tubes can be pre-bent or pre-kinked in the bending area. In a subsequent step, the fins can be applied to the flat tubes, with the fins being arranged on the sections of the flat tubes extending beyond the bending area. The bending area remains free of fins, allowing for the effective drainage of condensate or dew.

[0024] The defrosting process can be further optimized if the fins are angled in a direction that lies between gravity and the horizontal. This allows the fins to be angled in such a way that gravity facilitates the drainage of condensate even without an incline of the first heat exchanger.

[0025] According to the invention, the first heat exchanger is designed as two heat exchanger sections or parts arranged adjacent to each other, which can be introduced into the refrigerant circuit in parallel or in series. The heat exchanger sections thus form the first heat exchanger. This allows the first heat exchanger to be divided into two parts or heat exchanger sections arranged side by side. The heat exchanger sections are preferably inclined in opposite directions to each other, and can form a V-shape or a roof shape. This design allows the height of the device to be reduced compared to a one-piece heat exchanger with the same angle of inclination and the same surface area.

[0026] A symmetrical design of the device with a uniform mass distribution can be achieved if the heat exchanger sections are each inclined relative to each other by the angle of inclination, in particular in a mirror image relative to each other.

[0027] According to another aspect of the invention, a vehicle is provided which has an air treatment device according to the invention.

[0028] The vehicle can be designed, for example, as a bus, a rail vehicle, a shuttle, or the like. The air treatment device can be used to regulate the temperature of the vehicle's passenger compartment.

[0029] The first heat exchanger of the device can therefore be located on an external surface, such as the vehicle roof. The second heat exchanger is located in the passenger compartment or is connected to the passenger compartment via a fluid circuit. By connecting the first and second heat exchangers via the refrigerant circuit, heat can be extracted from the vehicle's ambient air and the passenger compartment heated, or heat can be supplied to the ambient air and the passenger compartment cooled.

[0030] The defrosting process of the first heat exchanger is relevant when the second heat exchanger is operating in heating mode, because by extracting heat from the ambient air, the first heat exchanger can cool down below the dew point of the ambient air.

[0031] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. The drawings show: Fig. 1 a schematic side view of a vehicle with a device according to a first embodiment, Fig. 2 a schematic side view of a vehicle with a device according to a second embodiment, Fig. 3 a schematic side view of a vehicle with a device according to a third embodiment, Fig. 4 a schematic side view of a vehicle with a device according to a fourth embodiment, Fig. 5 a schematic side view of a vehicle with a device according to a fifth embodiment, and Fig. 6A, Fig. 6B a comparison of a first heat exchanger with the state of the art.

[0032] In the figures, the same constructive elements each have the same reference numerals.

[0033] The Fig. Figure 1 shows a schematic side view of a vehicle 100 with an air treatment device 10 according to a first embodiment. The device 10 is designed as a flat-construction roof air conditioning unit mounted on a vehicle 100 configured as a bus.

[0034] The device 10 has a first heat exchanger 20, which is supplied with ambient air U via a fan 30. This allows the first heat exchanger 20 to extract heat from the ambient air U.

[0035] Furthermore, the device 10 has a second heat exchanger 40. The second heat exchanger 40 is arranged in a passenger compartment or vehicle interior 101 in order to heat or cool the passenger compartment 101.

[0036] The first heat exchanger 20 and the second heat exchanger 40 are connected to each other via a fluid-carrying refrigerant circuit 50. A refrigerant can be circulated through the refrigerant circuit 50 to enable the extraction of heat from the environment U and the supply of heat to the passenger compartment 101.

[0037] By extracting heat from the environment U, the first heat exchanger 20 can ice up and thus lose its efficiency. To carry out a defrosting process, in the illustrated embodiment, the first heat exchanger 20 and the fan 30 arranged above the first heat exchanger 20 can be tilted at an angle W.

[0038] The tilt angle W is adjusted by a positioning unit 60, which raises or rotates the first heat exchanger 20 and the fan 30 on one side. The positioning unit 60 can, for example, be designed as one or more hydraulically actuated cylinders that can raise and thus pivot the first heat exchanger 20 and the fan 30 at any desired position.

[0039] With an inclination of the first heat exchanger 20, a capillary force F results Kapillar and gravitational force F G a resultant force F res Due to the additional effect of the gravitational force F G A larger quantity of water can escape from the first heat exchanger 20 during the defrosting process. The corresponding forces F G , F Kapillar , F res and directions are in the Fig. 1. Illustrated schematically.

[0040] After a defrosting process has been carried out, the installation unit 60 can move the fan 30 and the first heat exchanger 20 into a horizontal position, in which the horizontal fan 30' and the horizontal first heat exchanger 20' have a lower height H.

[0041] In the Fig. Figure 2 shows a schematic side view of a vehicle 100 with an air treatment device 10 according to a second embodiment. In contrast to the first embodiment, the first heat exchanger 20 is designed as two adjacent heat exchanger sections 21, 22. For this purpose, a large-area first heat exchanger 20 was divided into two smaller heat exchanger sections 21, 22, which are positioned side by side along a horizontal plane 70 and each rotated or pivoted in opposite directions by the angle of inclination W. The horizontal plane 70 is exemplified as a vehicle roof.

[0042] The two heat exchanger sections 21, 22 are arranged in a V-shape and are supplied with ambient air by a common fan 30.

[0043] In the Fig. Figure 3 illustrates a schematic side view of a vehicle 100 with a device 10 for air treatment according to a third embodiment, in which the heat exchanger sections 21, 22 are similar to those in Fig. 2, but rotated in the opposite direction, namely arranged in a roof shape.

[0044] The respective heat exchanger sections 21, 22 can be connected in series or in parallel to each other by the refrigerant circuit 50.

[0045] In the Fig. Figure 4 illustrates a schematic side view of a vehicle 100 with an air treatment device 10 according to a fourth embodiment. The first heat exchanger 20 is bent in a V-shape in a bending section 80 and divided into two parts 23, 24 by the bending section 80. The parts 23, 24 of the first heat exchanger 20 are each inclined at an angle W and have fins 25 for thermal coupling of flat tubes 26. The bending section 80 is free of fins 25, so that the respective parts 23, 24 of the first heat exchanger 20 are connected to each other by flat tubes 26.

[0046] The Fig. Figure 5 shows a schematic side view of a vehicle 100 with an air treatment device 10 according to a fifth embodiment. In contrast to the embodiments already shown, the device 10 has a one-piece first heat exchanger 27, which is curved. The curved heat exchanger 27 can thus have an inclination angle W, at least in some areas, to enable optimal drainage of condensation.

[0047] In the Fig. 6A and Fig. Figure 6B illustrates a comparison of a first heat exchanger 20 according to the invention with a heat exchanger 20" according to the prior art.

[0048] The Fig. Figure 6A shows the heat exchanger 20" according to the prior art, which has a plurality of fins 25'. The fins 25' are each arranged between two flat tubes 26'. The fins 25' are arranged at an angle of 90'. The 90' ​​angle is parallel to the course of the flat tubes 26'. Thus, the fins 25' have an angle of 90' corresponding to the one shown in Figure 6A. Fig. 1 shown capillary force F Kapillar on.

[0049] In contrast to the state of the art, the one in Fig. The first heat exchanger 20 shown in Figure 6B has fins 25 arranged between two flat tubes 26 with an inclined or diagonal angular orientation of 90°. This measure reduces the capillary force F. Kapillar deviating from the horizontal by 70 degrees in the direction of the gravitational force F G This will be adjusted, which will further accelerate the defrosting process of the first heat exchanger 20. Reference symbol list 100 vehicles 101 Passenger compartment / space to be heated 10 Device 20 first heat exchangers installed 20' horizontal first heat exchanger 20" heat exchanger according to the state of the art 21 first heat exchanger section 22 second heat exchanger section 23 first part of the first heat exchanger 24 second part of the first heat exchanger 25 slats 25' slats according to the state of the art 26 flat tubes 26' flat tubes according to the state of the art 27 curved first heat exchanger 30 installed fans 30' horizontal fan 40 second heat exchanger 50 Refrigerant circuit 60 installation units 70 Horizontal / Vehicle roof 80 bending range 90° angle alignment of the slats 90° angle alignment of the slats according to the state of the art H height U environment / ambient air F Kapillar Capillary action F G Gravitational force F res Resultant force during the defrosting process

Claims

[1] Device (10) for air treatment, namely a roof air conditioning system in a flat design, comprising a first heat exchanger (20) for extracting heat from an environment (U), comprising a second heat exchanger (40) for dissipating heat to a room (101) to be heated, and comprising a fan (30) which supplies air from the environment (U) to the first heat exchanger (20), wherein the first heat exchanger (20) and the second heat exchanger (40) are fluidly connected to one another in a refrigerant circuit (50) through which a refrigerant circulates, wherein the first heat exchanger (20) is arranged at an angle of inclination (W) relative to a horizontal (70), at least in some regions, wherein the first heat exchanger (20) is curved in a V-shape or convex manner relative to the horizontal (70), characterized byin that the first heat exchanger (20) has a bending region (80) which is arranged centrally, wherein the first heat exchanger (20) is kinked or bent in the bending region (80) and is divided by the bending region (80) into two heat exchanger sections (21, 22) or two parts (23, 24), wherein the bending region (80) is designed free of fins (25), so that the respective parts (23, 24) of the first heat exchanger (20) are connected to one another by flat tubes (26). [2] Device (10) according to claim 1, wherein the first heat exchanger (20) is arranged at an inclination angle (W) of 5° to 70°, preferably between 45° and 60°. [3] Device (10) according to claim 1, wherein the bent first heat exchanger (20) has fins (25) thermally coupled to the flat tubes (26) outside the bending region (80) of the first heat exchanger (20). [4] Device (10) according to claim 3, wherein the slats (25) have an angular orientation (90) which is between a direction of a gravitational force (F G ) and a direction of the horizontal (70). [5] Device (10) according to one of claims 1 to 4, wherein the parts (23, 24) are introduced into the refrigerant circuit (50) in parallel or in series. [6] Device (10) according to one of claims 1 to 5, wherein the parts (23, 24) are each inclined by the angle of inclination (W) relative to one another, in particular mirror-inverted relative to one another. [7] Vehicle (100) comprising an air treatment device (10) according to one of the preceding claims.

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