Air conditioning system for rail vehicles

Abstract

The present invention relates to an air-conditioning system for rail vehicles, wherein the air-conditioning system is suitable for A2, A2L and A3 flammable refrigerants and is designed in the form of a compact device for installation on the roof, and has at least a device part for the air handling section B and the compressor liquefier unit section D, as well as an optional exhaust section A and / or an electrical switch box C and / or a silencer. The problem solved by the present invention is that for such an air-conditioning system, a direct evaporation system is realized, and the air to be conditioned in the passenger area is sealed within the air-conditioning system, so that in the event of a leak in the refrigerant conduction assembly, the flammable refrigerant is prevented from entering the vehicle interior. This problem is solved in that the refrigerant conduction assembly and components are located outside the comfort air conduction area, in a separate housing and open to the surrounding environment, that is, at least the mixing air flap (2) for outside air / environmental air, the air filter (3), the supply air flap (7), the supply air fan (4), the evaporator (5), the thermal regulator (6) and their interfaces with the outside air inlet (a) and / or the environmental air inlet (b) and the supply air outlets (e1 and / or e2) are located in an airtight or pressure-sealed duct in the housing of the air-conditioning system, which is designed in the form of a compact device.

Description

Technical Field

[0001] The present invention relates to an air - conditioning system for rail vehicles, wherein the air - conditioning system is suitable for flammable refrigerants and is designed as a compact device to be installed on the roof, and has at least a device part for air treatment, a compressor - liquefier unit, and optionally an exhaust device part, an electrical switch box, and / or a silencer. Background Art

[0002] Various refrigerants are known for use in air - conditioning systems in vehicles. From an ecological perspective, the use of synthetic refrigerants is particularly problematic. Thus, refrigerant R134a has been very widely used in motor vehicles and also in rail vehicles. However, when this refrigerant escapes into the atmosphere, it acts as a greenhouse gas. Therefore, as of January 1, 2017, the use of refrigerant R134a has been discontinued in new passenger cars in the European Union.

[0003] As a substitute for R134a, refrigerant R1234yf is currently mainly used. Refrigerant R1234yf has a much lower greenhouse effect, but it is flammable and is classified as an A2L refrigerant. However, even the use of this refrigerant is now criticized by experts. For example, highly toxic hydrofluoric acid (HF) is formed when released at temperatures greater than 250 °C, and persistent trifluoroacetic acid (TFA) is formed as a degradation product in the atmosphere, especially accumulating in water. Due to the associated risks, the use of HFO refrigerants such as R1234yf is also generally abandoned in principle.

[0004] Another approach is to use carbon dioxide (R744) as a natural refrigerant. However, compared with other refrigerants, the use of R744 leads to relatively complex equipment technology due to the need for higher system pressures. In addition, at high ambient temperatures, the coefficient of performance (COP) decreases significantly, so the energy demand of the air - conditioner increases significantly. Moreover, as the ambient temperature rises, the cooling capacity drops sharply, which can be offset by appropriately increasing the component size.

[0005] Therefore, it is obvious that the refrigerants used so far ultimately represent a compromise between different functional, environmental, and safety requirements. Vehicle air - conditioning systems, especially rail vehicles, require the use of refrigerants that are not ecologically critical when discharged into the atmosphere, have high energy efficiency over the entire operating range, and can continue to utilize the knowledge and experience of the cold - vapor technology used so far. For rail vehicles, these units are mainly designed as compact units on the roof. Regardless of their specific design, such compact air - conditioning units generally include an air - treatment and a compressor - liquefier unit part, and may optionally include an exhaust device, an electrical switch box, and / or a silencer part.

[0006] As a solution to the above requirements, flammable hydrocarbons such as propane (R290), propylene (R1270), or isobutane (R600a) are attracting attention as alternative refrigerants. These refrigerants are widely used in direct expansion systems with limited refrigerant charge (<150 g or <500 g), especially in stationary applications. If a larger refrigerant charge is required to generate higher cooling capacity, an indirect system is preferred due to the flammability of these direct expansion systems.

[0007] For air conditioning of rail vehicles, flammable refrigerants have hardly been used as direct evaporation systems or indirect evaporation systems so far due to the explosion and fire hazards associated with the refrigerants. In an indirect evaporation system, the above risks can be reduced by designing an air conditioning system with a secondary circuit system. In this case, a flammable refrigerant in a conventional compression refrigeration circuit is used to provide the required cooling (or heating) power in a primary circuit that is located outside the vehicle and thus has no direct connection to the vehicle interior. This cooling power is transferred to the secondary circuit, for example, designed as a brine circuit with a water - glycol mixture, via a heat exchanger (preferably, a plate heat exchanger).

[0008] Such a technical solution can be learned from WO 2018 / 137 908 A1. According to this document, a rail vehicle has a primary refrigerant circuit that is arranged outside the vehicle and is structurally completely separated from the passenger compartment. The secondary refrigerant circuit is at least partially arranged inside the rail vehicle. The heat exchange between the primary refrigerant circuit and the secondary refrigerant circuit is carried out via an intermediate heat exchanger arranged under the floor in the external area. Thus, the primary refrigerant circuit is completely arranged outside the rail vehicle interior. This design means that when using flammable substances, the safety factors to be considered mainly relate to the external area, while the interior area can be assumed to be as safe as a conventional system. This means that, for safety - related reasons, refrigerants that have hardly been used for passenger compartment air conditioning so far can also be used. Therefore, WO 2018 / 137 908 A1 proposes using flammable refrigerants such as propane, which is very suitable as a refrigerant from a functional point of view but has hardly been used so far due to the above - mentioned fire and explosion hazard problems.

[0009] Taking into account the state of the art according to WO 2018 / 137 908 A1 and similar proposed solutions, it can be expected that the acceptance of using flammable refrigerants in air-conditioning systems for rail vehicles will increase significantly in the medium term. However, it should be noted that indirect circuits still result in disadvantages in terms of energy use due to heat losses in the intermediate heat exchanger, as well as additional weight and the need for additional installation space. Therefore, for the widespread use of flammable refrigerants, a direct evaporation system, a system that avoids these disadvantages, is desired. In order to be able to ensure a high level of safety against fire and explosion, including in the event of possible operating failures, further structural measures for the air-conditioning system of rail vehicles may ultimately be required, thus enabling the specific design of various components.

[0010] A related solution can be learned from DE 195 22 099 A1, which describes the arrangement of a fan and other components in an airtight chamber. In addition, DE 93 19 874 U1 proposes to completely seal several components in the refrigeration circuit of an air-conditioning system in a pressure-sealed structure to prevent the uncontrolled leakage of the refrigerant. A person skilled in the art is interested in this method per se. However, neither of these two printed documents provides any suggestions on how to specifically implement this abstract concept. In addition, they are not applicable to the form described for flammable refrigerants. Summary of the Invention

[0011] The object of the invention is to implement a direct evaporation system in which the air to be conditioned in the passenger area is sealed within the air-conditioning system so that in the event of a leak at the refrigerant transport components, flammable refrigerants are prevented from entering the interior of the vehicle.

[0012] This object is solved in that the refrigerant transport components and parts are arranged outside the area of the comfort ventilation ducts, in a separate housing and open to the environment. Accordingly, the components of the air handler, such as the mixing air flap for outside air / environmental air, the air filter, the flaps, the supply fan, the evaporator and the heating regulator, as well as their interfaces to the outside air inlet and / or environmental air inlet and the supply fan inlet, are arranged in airtight and / or pressure-sealed ducts within the housing of a compact unit, or within an air-conditioning system designed in this way. All components outside the ducts are designed to be open to the environment so that any possible final leakages will be discharged or vented to the outside.

[0013] Thus, the comfort ventilation duct, i.e., the air supplied to the vehicle occupants, is separated in the device and sealed relative to the refrigeration circuit, where the refrigerant technology components are designed as a conventional and known sealed refrigeration circuit. Thus, the novelty compared to the known prior art is that all refrigerant transport components are located outside the comfort ventilation duct and arranged in a housing, such that they are protected from damage or accidental entry. In this way, the refrigerant transport components are arranged to be open to the environment to vent any leaks to the outside by passive ventilation and prevent the occurrence of flammable concentrations over a long period of time. As long as there is no potential ignition source, the refrigerant transport components can be arranged in a separately enclosed non-airtight area. In addition, in order to prevent refrigerant from entering the area of the comfort ventilation duct, appropriate sealing (technical sealing) is carried out between the two areas of the comfort ventilation duct and the housing having the refrigerant transport components. Other advantageous embodiments are the subject of the dependent claims, the technical features of which are described in the example embodiments.

[0014] By the technical solution according to the present invention, the sub-components of the air-conditioning system for a rail vehicle that are important for air treatment are sealed, such that these sub-components are prevented from coming into contact with the flammable refrigerant generated by leaks through an airtight and / or pressure-sealed duct design. In this way, the acceptance of using flammable refrigerants in the air-conditioning system for a rail vehicle is increased. This is because even in the case of an out-of-control leak of flammable refrigerant in the external area, fire prevention and explosion protection in the internal area can now be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Hereinafter, example embodiments of the present invention are explained in more detail with reference to the accompanying drawings.

[0016] Figure 1 A schematic diagram showing the basic structure of an air-conditioning system for a rail vehicle, which is suitable for a flammable refrigerant and is designed as a compact device to be installed on the roof. The housing of the air-conditioning system is not shown here.

[0017] Figure 2 A schematic diagram showing a first embodiment of arranging the components of the air-conditioning system in an airtight duct.

[0018] Figure 3 A schematic diagram showing a second embodiment of arranging the components of the air-conditioning system in a pressure-sealed duct.

[0019] Figure 4 A schematic diagram showing a third embodiment of arranging the components of the air-conditioning system in an airtight duct.

[0020] Figure 5 A schematic diagram showing a fourth embodiment of arranging the components of the air-conditioning system in a pressure-sealed duct.

[0021] Figure 6A schematic diagram showing a specific design example of the refrigerant delivery pipeline of the evaporator in the case of an airtight or pressure-sealed pipeline design. Detailed implementation

[0022] Figure 1 Shows the basic structure of an air-conditioning system for a rail vehicle (not shown), which is suitable for flammable refrigerants of classes A2, A2L, and A3 and is designed as a compact device to be installed on the roof of the rail vehicle. Only the main components for air treatment are shown here, excluding the housing of the air-conditioning system. Thus, the air-conditioning system has an optional equipment section A for discharging air, an equipment section B for air treatment, an optional electrical switch box C, and a compressor liquefier unit D. Section B and A may include, as basic components, a pressure wave valve 1, a mixing air flap 2 for external air / environmental air, an air filter 3, a supply fan 4, an evaporator 5, a heating regulator 6, a supply air flap 7, and an exhaust fan 8, as shown. In addition, interfaces are provided for a fresh air inlet a, an environmental air inlet b, an exhaust opening c, an exhaust inlet d, a supply air outlet e1, and a supply air outlet e2.

[0023] Figure 2 Shows Figure 1 The arrangement of several of the shown components within the airtight pipeline in the housing of the air-conditioning system. This airtight pipeline is stylized, with its line profile being more distinct and having discontinuities. Thus, the mixing air flap 2 for external air / environmental air, the air filter 3, the supply air flap 7, the supply fan 4, the evaporator 5, and the heating regulator 6 of the equipment section B for air treatment, as well as their interfaces with the external air inlet a and / or the environmental air inlet B and the supply air outlets e1 and / or e2, are arranged within the airtight pipeline in the housing of the air-conditioning system, where the air-conditioning system is designed in the form of a compact device. In this regard, the reference numeral AB represents the external environment as seen from the pipeline, and the reference numeral IB represents the internal air treatment area as seen from the pipeline, where the area AB is open to the environment and potential leaks are discharged or emitted to the outside, and IB represents a safe internal area where, since the evaporator is designed as a safe evaporator, no leaks are expected to occur.

[0024] Figure 3 Shows Figure 2 A modified design of the arrangement shown in. In this variant, the equipment section A for discharging air having the pressure wave valve 1 and its interfaces with the exhaust inlet d and the exhaust opening c are also arranged within the pressure-sealed pipeline in the housing of the air-conditioning system. Here, the pressure-sealed pipeline is also stylized, with its line profile being more distinct and having discontinuities. Similarly, the reference numeral AB represents the external environment as seen from the pipeline, and the reference numeral IB represents the internal air treatment area as seen from the pipeline.

[0025] Figure 4 ShowsFigure 2 A modified version of the arrangement shown therein. In this variant, the electrical switch box C is also arranged within an airtight duct in the housing of the air-conditioning system. Here, the airtight duct is also stylized, with its line profile being more distinct and having discontinuities. Similarly, the reference sign AB denotes the external environment as seen from the duct line, and the reference sign IB denotes the internal air-treatment area as seen from the duct line, where the area AB is open to the environment and potential leaks are discharged or vented to the outside, and IB denotes a safe internal area where no leaks are expected to occur since the evaporator is designed as a safe evaporator.

[0026] Figure 5 shows an embodiment further modified compared to Figure 4 where (similar to Figure 3 ), the part A of the device for discharging air having the pressure-wave valve 1 and its interfaces with the exhaust inlet d and the exhaust opening c are also arranged within an airtight and pressure-sealed duct in the housing of the air-conditioning system. Here, the airtight and pressure-sealed duct is also stylized, with its line profile being more distinct and having discontinuities. Similarly, the reference sign AB denotes the external environment as seen from the duct line, and the reference sign IB denotes the internal air-treatment area as seen from the duct line, where the area AB is open to the environment and potential leaks are discharged or vented to the outside, and IB denotes a safe internal area where no leaks are expected to occur since the evaporator is designed as a safe evaporator.

[0027] Figure 6 Shows an example of the specific arrangement and design of the refrigerant conveyance line part of the evaporator 5. Figure 6 Shows two refrigerant circuit parts BP (the tube bundle assembly within the evaporator) and BR (the area of the refrigerant circuit tube in the air-treatment part), as well as the electrical switch box C and the compressor liquefier unit D. Interfaces f1 and f2 are provided for the closed refrigerant lines in parts BR and C, and partition walls g1 and g2 are provided for sealing the evaporator. In addition, the evaporator 5, the compressor 9, the liquefier 10, the suction pressure sensor 11, the solenoid valve liquid line 12, the solenoid valve suction line 13, the optional solenoid valve bypass line 14, the suction line 15, the liquid line 16, and the optional bypass line 17 are all shown as basic components of each refrigeration circuit.

[0028] The straight pipes of the evaporator 5 (separated by g1 and g2 and located in the IB) are the only components in the refrigeration circuit that are in the area of the gastight or pressure-sealed pipes and can be shut off in case of damage or a significant rapid pressure drop (substantial refrigerant leakage, whether external or internal). In this way, further risk minimization is achieved. The shut-off is effected by closing the solenoid valve liquid line 12 and the solenoid valves 13 and 14 in the suction line 15 and the bypass line 17. In addition, before closing the refrigeration circuit, this shut-off area can also be emptied by means of a "pumping out" function. When the compressor 9 is running, the "pumping out" is carried out by closing the solenoid valve liquid line 12 and the solenoid valve bypass line 14. In this way, the entire pipe connection from the solenoid valve liquid line 12 to the suction side of the compressor 9 is emptied. Specifically, this involves downstream of the liquid line 16 passing through the areas f1 and f2 of the solenoid valve liquid line 12, then continuing through the pipe assembly of the evaporator (BP) via the suction line 15 and the bypass line 17 and back through the areas f1 and f2. When the defined suction pressure is reached, the compressor 9 is switched off and the solenoid valve 13 in the suction line 15 is closed. The positions of the solenoid valves 12, 13 and 14 are given only by way of example and can also be close to the evaporator 5, for example. On this basis, and after closing and emptying the refrigeration circuit, the emptied section can be monitored by means of the suction pressure sensor 11 located in the emptied section and repeating the "pumping out" when a predetermined pressure is reached in the emptied section. In this case, the pressure increase is related to the presence of refrigerant in the emptied section. This provides additional monitoring of the emptied state of the shut-off section.

Claims

1. An air-conditioning system for rail vehicles, wherein, the air-conditioning system is suitable for A2, A2L and A3 class flammable refrigerants and is designed in the form of a compact device for installation on the roof, and has at least a device part for the air handling part B and the compressor liquefier device part D and an exhaust part A, wherein the exhaust part A has at least a first interface with an exhaust inlet and an exhaust opening, and wherein the air handling part B has at least a second interface with an outside air inlet, an ambient air inlet and a supply air outlet, an air filter, an evaporator and a supply air fan, a mixing air valve for fresh air or ambient air, a supply air valve and a heating regulator, characterized in that: the refrigerant conveying components and parts of the air-conditioning system are arranged outside the comfort ventilation duct area in a separate housing and are open to the environment, at least the mixing air valve (2), air filter (3), supply air valve (7), supply air fan (4), evaporator (5) and heating regulator (6) of the air handling part (B) and the second interfaces with the outside air inlet (a) and / or the ambient air inlet (b) and the supply air outlets (e1 and / or e2) are arranged in an airtight or pressure-sealed duct within the housing of the air-conditioning system designed in the form of a compact device.

2. The air-conditioning system according to claim 1, characterized in that: the pressure wave valve (1) of the exhaust part (A) and the first interfaces with the exhaust inlet (d) and the exhaust opening (c) are also arranged in a pressure-sealed duct within the housing of the air-conditioning system designed in the form of a compact device.

3. The air-conditioning system according to claim 1, characterized in that: the electrical switch box (C) is also arranged in an airtight or pressure-sealed duct within the housing of the air-conditioning system designed in the form of a compact device.

4. The air-conditioning system according to claim 2, characterized in that: the electrical switch box (C) is also arranged in an airtight or pressure-sealed duct within the housing of the air-conditioning system designed in the form of a compact device.

5. The air-conditioning system according to any one of claims 1 to 4, characterized in that: the refrigerant conveying pipeline part of the evaporator (5), being the only component in the refrigerant circuit arranged in the area of the airtight or pressure-sealed duct, is designed to be able to be shut off, emptied in an expandable manner, and emptied and monitored in an expandable manner.

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