Air conditioning system for railway vehicle

Abstract

The invention relates to an air-conditioning system for a rail vehicle, said air-conditioning system being suitable for flammable refrigerants of the class A2, A2L and A3 and being designed in the form of a compact device for installation on the roof, and at least equipment parts for the air treatment part and the compressor liquefier unit part, and an optional exhaust part and / or an electric switch box and / or a silencer. Refrigerant conducting assemblies and components are located outside the comfortable air conducting area in a separate housing and open to the ambient environment, the invention relates to an air conditioning system, in particular a mixed air valve for outside / ambient air having at least an air handling section, an air filter, an air supply valve, an air supply fan, an evaporator, a heat conditioner and the interfaces thereof with an outside air inlet and / or an ambient air inlet and an air supply outlet, are located in an air-tight or pressure-tight conduit in a housing of the air conditioning system.

Description

[0001] This patent application is a divisional application of the Chinese invention patent application with application number 202080032651.2 filed on August 18, 2020, and invention name “Air conditioning system for rail vehicles (with airtight or pressure-tight pipes in the air handling part)”. Technical Field

[0002] The invention relates to an air-conditioning system for a rail vehicle, wherein the air-conditioning system is suitable for flammable refrigerants and is designed as a compact device for installation on the vehicle roof and comprises at least a device part for air treatment and a compressor-liquefier unit and optionally an exhaust device part, an electrical switch box and / or a silencer. Background Art

[0003] Various refrigerants are known for use in vehicle air conditioning systems, but the use of synthetic refrigerants is particularly problematic from an ecological perspective. Consequently, the refrigerant R134a has been widely used in motor vehicles and even rail vehicles. However, when this refrigerant escapes into the atmosphere, it contributes to greenhouse gas emissions. Consequently, the use of R134a in new passenger cars in the European Union was discontinued on January 1, 2017.

[0004] As an alternative to R134a, the refrigerant R1234yf is currently the main choice. This refrigerant has a significantly lower greenhouse gas impact, but it is flammable and classified as an A2L refrigerant. However, even this refrigerant is now facing criticism from experts. For example, when released at temperatures above 250°C, it forms highly toxic hydrofluoric acid (HF), while persistent trifluoroacetic acid (TFA) forms as a degradation product in the atmosphere, accumulating particularly in water. Due to the associated risks, the use of HFO refrigerants such as R1234yf has generally been abandoned.

[0005] Another approach is to use carbon dioxide (R744) as a natural refrigerant. However, compared to other refrigerants, the use of R744 results in relatively complex equipment technology due to the required higher system pressure. Furthermore, at high ambient temperatures, the coefficient of performance (COP) decreases significantly, significantly increasing the energy demand for air conditioning. Furthermore, the cooling capacity decreases sharply with increasing ambient temperature, which can be offset by appropriately increasing component size.

[0006] It's clear, then, that the refrigerants used to date ultimately represent a compromise between different functional, environmental, and safety requirements. Vehicle air conditioning systems, particularly for rail vehicles, require refrigerants that are ecologically non-critical when discharged to the atmosphere, offer high energy efficiency across the entire operating range, and can continue to leverage the knowledge and experience gained from the cold steam technology used to date. For rail vehicles, these units are primarily designed as compact rooftop units. Regardless of their specific design, such compact air conditioning units typically consist of an air handling and compressor-liquefier unit, and may optionally include exhaust equipment, an electrical switch box, and / or a silencer.

[0007] As a solution to these requirements, flammable hydrocarbons such as propane (R290), propylene (R1270), or isobutane (R600a) are gaining attention as alternative refrigerants. These refrigerants are widely used in direct expansion systems with limited charge capacity (<150g or <500g), especially in stationary applications. If a larger charge capacity is required to produce higher cooling capacity, an indirect system is preferred due to the flammability of these direct expansion systems.

[0008] For rail vehicle air conditioning, flammable refrigerants have been used almost exclusively in direct evaporation systems, even in indirect evaporation systems, due to the associated explosion and fire risks. In indirect evaporation systems, these risks can be mitigated by designing the air conditioning system with a secondary circuit system. In this case, the required cooling (or heating) capacity is provided in a primary circuit located outside the vehicle and therefore without a direct connection to the interior, using a flammable refrigerant in a conventional compression refrigeration circuit. This cooling capacity is transferred via a heat exchanger (preferably a plate heat exchanger) to a secondary circuit, which can be designed, for example, as a brine circuit containing a water-glycol mixture.

[0009] A technical solution of this type is known from WO 2018 / 137908 A1. According to this document, a rail vehicle has a primary refrigerant circuit, which is arranged outside the vehicle and structurally completely separated from the passenger compartment. A secondary refrigerant circuit is arranged at least partially inside the rail vehicle. Heat exchange between the primary and secondary refrigerant circuits occurs via an intermediate heat exchanger arranged under the floor in the exterior area. Thus, the primary refrigerant circuit is located completely outside the rail vehicle interior. This design means that when using flammable substances, safety considerations primarily concern the exterior area, while the interior area can be assumed to be as safe as with conventional systems. This also means that, for safety reasons, refrigerants that have previously been rarely used for passenger compartment air conditioning can be used. Therefore, WO 2018 / 137908 A1 proposes the use of flammable refrigerants such as propane, which are functionally very suitable as refrigerants but have rarely been used to date due to the aforementioned fire and explosion hazards.

[0010] Considering the state of the art according to WO 2018 / 137 908 A1 and similar proposed solutions, it is expected that the acceptance of flammable refrigerants in rail vehicle air conditioning systems will increase significantly in the medium term. However, it should be noted that indirect circuits still present energy disadvantages due to heat losses in the intermediate heat exchanger, as well as the additional weight and required installation space. Therefore, with the widespread use of flammable refrigerants, there is a desire to adopt direct evaporation systems, which avoid these disadvantages. In order to ensure a high level of fire and explosion safety, including in the event of operational failures, further structural measures may ultimately be required for rail vehicle air conditioning systems, resulting in a specific design of the various components.

[0011] A related solution is known from DE 195 22 099 A1, which describes the arrangement of fans and other components in an airtight chamber. Furthermore, DE 93 19 874 U1 proposes completely enclosing several components in the refrigeration circuit of an air-conditioning system in a pressure-tight structure to prevent uncontrolled refrigerant leakage. This approach is of particular interest to those skilled in the art. However, neither document provides any suggestions for a concrete implementation of this abstract concept. Furthermore, they are not applicable to the described configurations for flammable refrigerants. Summary of the Invention

[0012] The object of the present 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 assembly, flammable refrigerant is prevented from entering the interior of the vehicle.

[0013] This task is achieved by arranging the refrigerant transport components and parts outside the comfort air duct area, in a separate housing, and open to the environment. Accordingly, the air handling unit components, such as the outside / ambient air mixing flap, air filter, flap, supply air fan, evaporator, and heating regulator, as well as their interfaces to the outside air inlet and / or the ambient air inlet and the supply air fan inlet, are arranged in an airtight and / or pressure-tight duct within the housing of the compact unit, or in an air conditioning system designed in this manner. All components outside the duct are designed to be open to the environment, so that any eventual leaks are discharged or vented to the outside.

[0014] Thus, the comfort air duct, i.e. the air supplied to the passengers in the vehicle, is separated in the device and sealed relative to the refrigeration circuit, wherein the refrigerant technical components are designed as a conventional and known sealed refrigeration circuit. The novelty compared to the known prior art is therefore that all refrigerant transport components are located outside the comfort air duct and are arranged in a housing so that they are protected from damage or accidental ingress. In this way, the refrigerant transport components are arranged to be open to the environment in order to discharge any leaks to the outside by passive ventilation and to prevent the occurrence of flammable concentrations for a longer period of time. As long as there are no potential ignition sources, the refrigerant transport components can be arranged in separately enclosed non-airtight areas. In addition, in order to prevent refrigerant from entering the area of ​​the comfort air duct, appropriate seals (technical seals) are made between the two areas of the comfort air duct and the housing with the refrigerant transport components. Further advantageous embodiments are the subject of the dependent claims, the technical features of which are described in the example of embodiment.

[0015] The technical solution according to the present invention seals subassemblies of rail vehicle air conditioning systems that are essential for air handling, preventing them from coming into contact with flammable refrigerants resulting from leaks through airtight and / or pressure-tight piping. This increases the acceptance of the use of flammable refrigerants in rail vehicle air conditioning systems. This is because even in the event of an uncontrolled leak of flammable refrigerants in the exterior area, fire and explosion protection can now be ensured within the interior. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Hereinafter, embodiment examples of the present invention are explained in more detail with reference to the accompanying drawings.

[0017] Figure 1 Schematic diagram showing the basic structure of an air conditioning system for a rail vehicle, which is suitable for flammable refrigerants and is designed as a compact device to be installed on the vehicle roof; the housing of the air conditioning system is not shown here.

[0018] Figure 2 Schematic diagram showing a first embodiment of an assembly for arranging an air conditioning system in an airtight duct

[0019] Figure 3 Schematic diagram showing a second embodiment of an assembly for arranging an air conditioning system within a pressure-tight duct

[0020] Figure 4 Schematic diagram showing a third embodiment of an assembly for arranging an air conditioning system in an airtight duct

[0021] Figure 5 Schematic diagram showing a fourth embodiment of an assembly for arranging an air conditioning system in a pressure-tight duct

[0022] Figure 6 A schematic diagram showing a specific design example of a refrigerant transport line of an evaporator in the case of a gas-tight or pressure-tight piping design. DETAILED DESCRIPTION

[0023] Figure 1 The basic structure of an air conditioning system for a rail vehicle (not shown) is shown. This air conditioning system is suitable for use with Class A2, A2L, and A3 flammable refrigerants and is designed as a compact unit mounted on the roof of the rail vehicle. Only the main components for air handling are shown here, not the housing of the air conditioning system. The air conditioning system thus comprises an optional equipment section A for exhaust air, an equipment section B for air handling, an optional electrical switch box C, and a compressor-liquefier unit D. Sections B and A may include, as essential components, a pressure wave valve 1, a mixing air flap 2 for outside air / ambient air, an air filter 3, an air supply fan 4, an evaporator 5, a heating regulator 6, an air supply flap 7, and an exhaust fan 8, as shown. Furthermore, connections are provided for a fresh air inlet a, an ambient air inlet b, an exhaust opening c, an exhaust inlet d, a supply air outlet e1, and a supply air outlet e2.

[0024] Figure 2 Shown Figure 1 The arrangement of several components within an airtight duct in the housing of an air-conditioning system is shown. This airtight duct is stylized, with a more pronounced outline and interruptions. Thus, the outside air / ambient air mixing air valve 2, the air filter 3, the air supply valve 7, the air supply fan 4, the evaporator 5 and the heating regulator 6 of the equipment part B for air treatment, as well as their interfaces with the outside air inlet a and / or the ambient air inlet B and the air supply outlets e1 and / or e2, are arranged within the airtight duct of the housing of the air-conditioning system, wherein 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 duct, the reference numeral IB represents the internal air-handling area as seen from the duct, wherein the area AB is open to the environment and potential leaks are exhausted or discharged to the outside, and IB represents the safe internal area, wherein no leaks are expected due to the evaporator being designed as a safety evaporator.

[0025] Figure 3 Shown Figure 2 This is a modified design of the arrangement shown in . In this variation, the exhaust air device portion A, including the pressure wave valve 1 and its connections to the exhaust inlet d and exhaust opening c, is also arranged within the pressure-tight duct within the housing of the air conditioning system. Here, the pressure-tight duct is also stylized, with a more pronounced outline and interruptions. Similarly, reference numeral AB denotes the external environment as viewed from the duct, and reference numeral IB denotes the internal air handling area as viewed from the duct.

[0026] Figure 4 Shown Figure 2 This is a modified version of the arrangement shown in . In this variation, the electrical switch box C is also placed within the airtight duct in the air conditioning system's housing. Here, the airtight duct is also stylized, with more distinct outlines and interruptions. Similarly, reference numeral AB represents the external environment as seen from the ductwork, reference numeral IB represents the internal air handling area as seen from the ductwork, where area AB is open to the environment and potential leaks are exhausted or vented to the outside, and IB represents the safe internal area where leaks are not expected due to the evaporator's design as a safety evaporator.

[0027] Figure 5 Shown with Figure 4 Compared to a further modified embodiment, wherein (with Figure 3 Similarly, the air exhaust device section A, including the pressure wave valve 1 and its connections to the exhaust inlet d and exhaust opening c, is also arranged within the air-tight and pressure-tight ducting within the housing of the air conditioning system. Here, the air-tight and pressure-tight ducting is also stylized, with a more pronounced outline and interruptions. Similarly, reference numeral AB denotes the external environment as viewed from the ducting line, reference numeral IB denotes the internal air handling area as viewed from the ducting line, wherein area AB is open to the environment and potential leaks are exhausted or vented to the outside, and IB denotes the safe internal area, wherein leakage is not expected due to the evaporator's design as a safety evaporator.

[0028] Figure 6 An example of a specific arrangement and design of the refrigerant transport piping portion of the evaporator 5 is shown. Figure 6The figure shows two refrigerant circuit sections, BP (the tube bundle assembly within the evaporator) and BR (the area of ​​the refrigerant circuit piping within the air handling section), as well as an electrical switch box C and a compressor-liquefier unit D. Ports f1 and f2 are provided for enclosing the refrigerant lines in sections BR and C, and partition walls g1 and g2 are provided for sealing the evaporator. Furthermore, the evaporator 5, compressor 9, liquefier 10, suction pressure sensor 11, solenoid valve liquid line 12, solenoid valve suction line 13, optional solenoid valve bypass line 14, suction line 15, liquid line 16, and optional bypass line 17 are shown as essential components of each refrigeration circuit.

[0029] The straight pipe of the evaporator 5 (separated by g1 and g2 and located in IB) is the only component in the refrigeration circuit located in an area of ​​airtight or pressure-tight piping and can be shut down in the event of damage or a significant and rapid pressure drop (a large refrigerant leak, either externally or internally). This further minimizes risk. Shutdown is achieved by closing the solenoid valve liquid line 12 and the solenoid valves 13 and 14 in the suction line 15 and bypass line 17. Furthermore, before shutting down the refrigeration circuit, this shut-off area can be emptied using a "pump-out" function. While the compressor 9 is running, "pump-out" is performed by closing the solenoid valve liquid line 12 and the solenoid valve bypass line 14. This empties the entire pipe connection from the solenoid valve liquid line 12 to the suction side of the compressor 9. Specifically, this involves the solenoid valve liquid line 12, downstream of the liquid line 16, passing through areas f1 and f2, and then continuing through the piping assembly of the evaporator (BP) via the suction line 15 and bypass line 17 back through areas f1 and f2. When a defined suction pressure is reached, the compressor 9 is shut down, and the solenoid valve 13 of the suction line 15 is closed. The location of the solenoid valves 12, 13, and 14 is given only as an example and can also be located near the evaporator 5, for example. On this basis, and after the refrigeration circuit has been shut down and emptied, the evacuation section can be monitored by means of a suction pressure sensor 11 located in the evacuation section and by repeating the "pumping out" operation when a predetermined pressure is reached in the evacuation section. In this case, a pressure increase is associated with the presence of refrigerant in the evacuation section. This provides additional monitoring of the evacuation state of the shutoff section.

Claims

1. A vehicle air conditioning system comprising: case; an air handling portion disposed within the housing, the air handling portion being configured to cool air within the housing and comprising an air mixing damper, an air filter, an evaporator, a heating regulator, and an air supply damper, the air mixing damper being configured to introduce ambient air into the air handling portion; an exhaust portion disposed in the housing, the exhaust portion being configured to guide the air cooled by the air processing portion out of the housing; a compressor-liquefier unit disposed within the housing; as well as An airtight duct is arranged in the housing, and the mixed air valve, the air filter, the evaporator, the heating regulator and the air supply valve are arranged in the airtight duct.

2. The vehicle air conditioning system according to claim 1, wherein: The air handling part also includes: an external air inlet, an ambient air inlet and an air supply outlet, and the mixing air valve, the air filter, the evaporator, the heating regulator and the air supply valve include: interfaces with the mixing air valve, the air filter, the evaporator, the heating regulator and the air supply valve.

3. The vehicle air conditioning system according to claim 2, wherein: The interface is also arranged in the airtight pipe.

4. The vehicle air conditioning system according to claim 1, wherein: The exhaust portion includes a pressure wave valve, an exhaust opening, an exhaust inlet, and an interface located between the pressure wave valve and each of the exhaust opening and the exhaust inlet.

5. The vehicle air conditioning system according to claim 4, wherein: The pressure wave valve, the exhaust opening, the exhaust inlet and the interface are arranged in the airtight pipe.

6. The vehicle air conditioning system according to claim 1, further comprising: An electric switch box is arranged in the airtight pipe.

7. A vehicle air conditioning system comprising: case; an air handling portion disposed in the housing, the air handling portion being configured to cool the air in the housing and comprising an air mixing damper, an air filter, an evaporator, a heating regulator, and an air supply damper, the air mixing damper being configured to introduce ambient air into the air handling portion, the air handling portion comprising an external air inlet, an ambient air inlet, and an air supply outlet, wherein the air mixing damper, the air filter, the evaporator, the heating regulator, and the air supply damper comprise interfaces with the air mixing damper, the air filter, the evaporator, the heating regulator, and the air supply damper; an exhaust portion disposed in the housing, the exhaust portion being configured to guide the air cooled by the air processing portion out of the housing; a compressor-liquefier unit disposed within the housing; and An airtight duct is arranged in the housing, and the mixed air valve, the air filter, the evaporator, the heating regulator, the air supply valve and the interface are arranged in the airtight duct.

8. The vehicle air conditioning system according to claim 7, wherein: The interface is a first interface, and the exhaust portion includes a pressure wave valve, an exhaust opening, an exhaust inlet, and a second interface located between the pressure wave valve and each of the exhaust opening and the exhaust inlet.

9. The vehicle air conditioning system according to claim 8, wherein: The pressure wave valve, the exhaust opening, the exhaust inlet and the second interface are arranged in the airtight pipe.

10. The vehicle air conditioning system according to claim 7, further comprising: An electric switch box is arranged in the airtight pipe.

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