Secure refrigeration system, ground-based vehicle with it and procedure for it

Abstract

Refrigeration system (1) for a ground-based vehicle (10) comprising at least one heating and / or cooling circuit (13) equipped with a first pump (15) and a first refrigerant circuit (3) with at least one compressor (5), at least one condenser / gas cooler (7), at least one expansion element (9) and at least one evaporator (11), wherein at least one condenser / gas cooler (7) and at least one evaporator (11) are each designed as a fluid-fluid heat exchanger, wherein - the first refrigerant circuit (3) is arranged within a gas-tight housing (37), - an area (41) of an interior of the gas-tight housing (37) located around the first refrigerant circuit (3) can be filled with an inert gas through a gas-tight sealable inlet (39), and - the gas-tight housing (37) is designed for a higher maximum pressure of the inert gas than the normal pressure, characterized by the fact that at least partially inside the gas-tight housing (37) a further refrigerant circuit (81) for the inert gas, such as CO2 in particular, as a refrigerant of the further refrigerant circuit (81) is arranged, and from the further refrigerant circuit (81) the inlet (39) for the refrigerant, which can be closed gas-tight with a controllable inlet valve (38), exists in the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3).

Description

Field of technology:

[0001] The invention relates to a refrigeration system for a ground-based vehicle comprising at least one heating and / or cooling circuit equipped with a first pump and a refrigerant circuit with at least one compressor, at least one condenser / gas cooler, at least one expansion element, and at least one evaporator, wherein at least one condenser / gas cooler and one evaporator are each designed as a fluid-fluid heat exchanger. The invention further relates to a ground-based vehicle and a method for ensuring the safety of such a refrigeration system. These refrigeration systems are used particularly in road and rail vehicles.

[0002] In a refrigerant circuit, refrigerant circulates during operation. It is compressed by the compressor, thereby heating it, and then flows through refrigerant lines to the condenser / gas cooler, where it releases heat. In the refrigerant circuit downstream of the condenser / gas cooler, the refrigerant expands in the expansion vessel, causing it to cool. It then absorbs heat in the evaporator before flowing back to the compressor's suction inlet. Refrigerant lines are used to transfer refrigerant between components in the refrigerant circuit. A condenser / gas cooler is designed either as a gas cooler for a refrigerant circuit operating under transcritical or supercritical conditions, or as a condenser for a refrigerant circuit operating under subcritical conditions, for example, with refrigerants R-1234yf, R-600a, or R-290. State of the art:

[0003] EP 2 634 020 B1 discloses such a refrigeration system comprising, firstly, a heating circuit coupled to the refrigerant circuit via a fluid-fluid heat exchanger acting as a condenser, and, secondly, a cooling circuit coupled to the refrigerant circuit via a fluid-fluid heat exchanger acting as an evaporator. Refrigeration systems constructed in this manner are also referred to as double indirect refrigeration systems. In this system, the object or medium to be heated or cooled is not heated or cooled directly via heat exchangers of the refrigerant circuit, but indirectly via heating and cooling circuits thermally coupled to the refrigerant circuit. EP 2 608 973 B1 and US 2018 / 0 312 034 A1 disclose further embodiments of double indirect refrigeration systems. However, with these known refrigeration systems, there is a risk that in the event of a leak in the refrigerant circuit, refrigerant could escape freely into the vehicle.With a highly flammable refrigerant such as R-1234yf, R-290, or R-600a, there is a risk of fire in the vehicle. If toxic refrigerant escapes from a leak, the health of vehicle occupants is immediately endangered. Simply positioning the refrigerant circuit of a double indirect refrigeration system in an area of ​​the vehicle where the risk to the occupants is minimized, as is known in the prior art, is insufficient to prevent a vehicle fire. Furthermore, restricting the system to only non-flammable, non-toxic refrigerants is too limiting and entails other disadvantages, such as the handling of high pressures, for example, with CO2 as a refrigerant. EP 2 708 436 A1 discloses a double indirect refrigeration system with a sealed wall between the chamber containing the refrigerant circuit and the air handling zone with the air-fluid heat exchanger of the heating circuit.While this protects the air handling zone from refrigerant ingress in the event of a leak in the refrigerant circuit, a fire can still develop unhindered in the refrigerant circuit chamber if refrigerant escapes, posing a risk of spreading to the entire vehicle and thus also to the air handling zone. DE 10 2014 112 545 A1 and DE 91 06 051 U1 each disclose a double indirect refrigeration system with a gas-tight housing around the refrigerant circuit. For the system in DE 10 2014 112 545 A1, filling the interior of the housing with a protective gas is described. DE 10 2016 216 619 A1 discloses a combined cooling and extinguishing system for a motor vehicle.In this system, both the refrigerant in the cooling system's refrigerant circuit and the extinguishing agent in the extinguishing system, which includes a pressure vessel, are CO2. A control valve allows for the exchange of CO2 between the pressure vessel and the refrigerant circuit. However, due to the lack of a gas-tight housing in the cooling and extinguishing system of DE 10 2016 216 619 A1, any toxic gases that may be produced in the event of a fire cannot be reliably kept away from vehicle occupants. The heat and cold supply device disclosed in DE 10 2012 112 347 A1 has a sealed storage container filled with a heat transfer medium, in which at least one refrigerant circuit is located, and wherein the heat transfer medium contains components dimensioned such that for binding and converting the refrigerant, such that when the refrigerant escapes from the refrigerant circuit, it can be completely bound or converted by the components. The heat transfer medium must therefore contain a sufficient number of these components and additionally be suitable as a heat transfer medium.

[0004] The safety problem of refrigerant leakage from a refrigerant circuit, without limiting itself to non-toxic, non-flammable refrigerants, is not adequately solved in currently known refrigeration systems. The invention described in claim 1 therefore addresses the problem of providing a refrigeration system, improved particularly with regard to safety, comprising at least one heating and / or cooling circuit equipped with a pump and a refrigerant circuit.

[0005] A corresponding problem exists regarding the provision of a ground-based vehicle.

[0006] A similar problem also exists with regard to the invention specified in claim 13 concerning a method for the safety of such a refrigeration system. Summary of the invention:

[0007] The problem underlying the invention specified in claim 1 is solved by the features listed in claim 1. The problem is solved by arranging the first refrigerant circuit within a gas-tight housing in a refrigeration system for a ground-based vehicle comprising a heating and / or cooling circuit equipped with a first pump and a first refrigerant circuit with at least one compressor, at least one condenser / gas cooler, at least one expansion element, and at least one evaporator, wherein at least one condenser / gas cooler and at least one evaporator are each designed as a fluid-fluid heat exchanger. Furthermore, the first refrigerant circuit is arranged within a gas-tight housing, and an interior area of ​​the gas-tight housing surrounding the first refrigerant circuit can be filled with an inert gas through a gas-tight sealable inlet. The gas-tight housing is designed for a maximum pressure of the inert gas higher than atmospheric pressure.

[0008] "Gas-tight" means that with the inlet and outlet closed, neither air nor the intended inert gas can flow in, nor can the intended inert gas or gaseous refrigerant flow out, although any minute, insignificant leaks below a leakage rate of q L = 1×10 -4 mbar l / s, for example, due to diffusion through the material, may be disregarded.

[0009] The area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit is often the entire free part of the interior of the housing that can be filled with gas.

[0010] An inert gas is a gas that is unreactive, meaning it participates in only a few chemical reactions.

[0011] The gas-tight sealable inlet for filling with inert gas is not so narrowly defined that it must be routed from the outside through the gas-tight housing; rather, a gas-tight sealable inlet within the gas-tight housing is also conceivable, such as a gas-tight sealable inlet from another refrigerant circuit located within the gas-tight housing and operating with inert gas as a refrigerant, or from a supply of inert gas in a tank within the gas-tight housing.

[0012] The invention has the advantage that, in the event of a leak in the first refrigerant circuit, refrigerant cannot escape from the interior of the gas-tight housing. This significantly reduces the risk of fire and / or poisoning in the event of unimpeded refrigerant leakage, thus eliminating the need for a restriction to a non-flammable and non-toxic refrigerant, which would otherwise be required for safety reasons. Furthermore, the possibility of filling the area of ​​the gas-tight housing interior surrounding the first refrigerant circuit with an inert gas at a pressure higher than normal pressure provides an additional means of counteracting the risk of fire or poisoning in the event of refrigerant leakage from the first refrigerant circuit. The non-reactive air in the area surrounding the first refrigerant circuit can thus be replaced by the inert inert gas.

[0013] The dependent claims specify advantageous embodiments, further developments and improvements of the respective subject matter of the invention.

[0014] According to an advantageous embodiment of the present invention, the heating and / or cooling circuit is configured as a heating circuit, and a separate cooling circuit with a second pump is arranged therefrom. This allows the heating circuit and the cooling circuit to be operated independently of each other, each with its own pump for circulating its respective heating medium or coolant.

[0015] According to an advantageous embodiment of the refrigeration system according to the invention, the first refrigerant circuit is designed for a flammable refrigerant, and a gaseous fire retardant is provided as an inert gas for the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit. This makes the refrigeration system, which can be operated with flammable refrigerant, particularly effective in protecting it against fires caused by leaks in the first refrigerant circuit. Inert gas mixtures containing at least one of these gases are also possible, such as a gas mixture of helium and carbon dioxide.

[0016] According to an advantageous embodiment of the refrigeration system according to the invention, at least one of the at least one condenser / gas cooler designed as a fluid-fluid heat exchanger is arranged in it for heat exchange of refrigerant of the first refrigerant circuit with heating medium in a heating and / or cooling circuit designed as a heating circuit, and at least one of the at least one evaporator designed as a fluid-fluid heat exchanger is arranged for heat exchange of refrigerant of the first refrigerant circuit with coolant of the cooling circuit, or both the condenser / gas cooler and the evaporator are arranged for heat exchange of the refrigerant of the first refrigerant circuit with coolant in a heating and / or cooling circuit designed as a heating and cooling circuit.

[0017] In such a double indirect refrigeration system, the first refrigerant circuit contributes particularly effectively to both heating and cooling, while the first refrigerant circuit is nevertheless protected against hazards emanating from it by the gas-tight housing around it which can be filled with inert gas.

[0018] Preferably, the refrigeration system includes a pressure sensor for detecting pressure values ​​in the area surrounding the first refrigerant circuit within the gas-tight housing. This allows the pressure of the inert gas in this area to be determined. Any pressure changes that may occur, for example, due to a leak in the first refrigerant circuit or in the gas-tight housing, can thus be detected. An advantageous design of such a refrigeration system is one that includes a fault detection device for detecting a malfunction in the refrigeration system when the pressure value detected by the pressure sensor exceeds a predefined upper threshold. In this way, a malfunction due to a leak in the first refrigerant circuit is automatically detected, because the pressure in the area surrounding the first refrigerant circuit within the gas-tight housing is correspondingly increased.

[0019] An improvement to the refrigeration system according to the invention is achieved by designing the gas-tight housing for a maximum pressure of at least 6 bar. The area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit can thus be filled with inert gas at a significant overpressure, which increases the effectiveness of the protection provided by the inert gas.

[0020] According to an advantageous embodiment of the present invention, the refrigeration system comprises a gas sensor for detecting refrigerant that has escaped from the first refrigerant circuit in the area surrounding the first refrigerant circuit within the gas-tight housing, and a fault detection device designed to detect a fault in the refrigeration system when the concentration of refrigerant from the first refrigerant circuit, as detected by the gas sensor, exceeds a predetermined threshold. This allows for the direct detection of escaping refrigerant in the event of a leak in the first refrigerant circuit, and automatically identifies a fault if the concentration of such escaping refrigerant exceeds the threshold. This increases the safety of the refrigeration system.

[0021] Preferably, the first pump and / or the second pump are arranged inside the gas-tight housing. This allows the gas-tight housing, which can be filled with inert gas, to also act as protection against hazards emanating from the two pumps, particularly the risk of fire.

[0022] The gas-tight housing is preferably made of metal, such as aluminum or sheet steel. This makes the housing robust and allows for a reliable, gas-tight installation around the first refrigerant circuit.

[0023] According to the invention, in the refrigeration system according to the invention, a further refrigerant circuit for the inert gas, such as CO2 in particular, is arranged at least partially within the interior of the gas-tight housing. An inlet for the refrigerant from this further refrigerant circuit, which can be closed by an adjustable inlet valve, leads into the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit. A separate tank for inert gas is unnecessary, because the refrigerant from the second refrigerant circuit can be supplied as an inert gas from this circuit into the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit, particularly in the event of a pressure drop there. For example, cascade refrigeration systems have two refrigerant circuits.

[0024] The refrigeration system is further improved by a control unit designed to regulate the adjustable inlet valve based on the pressure detected by the pressure sensor in the area surrounding the first refrigerant circuit within the gas-tight housing. This allows for automatic control of the gas pressure in this area. Pressure drops in this area, caused by a minor, but harmless, leak in the gas-tight housing, can thus be automatically compensated for.

[0025] Finally, the features of the dependent claims for the refrigeration system according to the invention can be combined essentially freely with one another and not be determined by the order given in the claims, provided that they are independent of one another and do not exclude each other.

[0026] The problem underlying a ground-based vehicle is solved by using a refrigeration system according to the invention in a ground-based vehicle, such as a rail or road vehicle in particular. The above information on the refrigeration system according to the invention applies accordingly with regard to advantageous embodiments and further developments and their advantages.

[0027] The corresponding problem regarding a method is solved by a method for the safety of a refrigeration system according to the invention, comprising step a) filling the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit with inert gas through the inlet up to a predetermined setpoint pressure, as well as step b) monitoring the concentration of refrigerant and / or the pressure in the area of ​​the interior of the gas-tight housing filled with inert gas surrounding the first refrigerant circuit, and step c) detecting a fault if a pressure value at monitored pressure exceeds a predetermined upper threshold or the concentration at monitored concentration of the refrigerant exceeds a predetermined concentration threshold.

[0028] Regarding advantageous embodiments and further developments and their benefits, the above information on the refrigeration system according to the invention applies accordingly. This method increases protection against hazards in the event of a leak in the refrigerant circuit.

[0029] According to a preferred embodiment of the method according to the invention, in step c) a fault is also detected if a pressure value at the monitored pressure falls below a predetermined lower threshold. This also allows a leak in the gas-tight housing to be recognized as a fault.

[0030] According to an advantageous embodiment of the method according to the invention, it comprises the further step d) of switching off the operation of the refrigeration system, if it is in operation, in the event of a fault detected in step c), and the further step e) of releasing the gas from the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit into a safe environment in the event of a fault detected in step c), as well as the further step f) of checking the first refrigerant circuit for leaks, and the further step g) of repairing any leak(s) found, and the further step h) of refilling the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit with inert gas up to the predetermined setpoint pressure. Thus, the method according to the invention encompasses not only the detection but also the rectification of a detected fault.With appropriate means, such as appropriately programmed control systems and suitable robots, these further steps d) to h) of the procedure can also be carried out automatically.

[0031] An improvement of the method according to the invention is provided, after step b), by the intermediate step aa) of detecting a reduced pressure when a pressure value at the monitored pressure lies within a range between a predetermined intermediate value and the corresponding lower threshold value, and then by the further intermediate step bb) of opening the inlet valve of an inlet of inert gas into the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit for at least a time interval. This allows the refrigeration system to continue operating without disruption in the event of only a small leak in the gas-tight housing, which does not significantly increase the risk of fire or poisoning, because the pressure reduction caused by the escape of gas from the interior of the gas-tight housing, which has become slightly leaky due to the leak, is thus counteracted within predetermined limits.The time interval in intermediate step bb) can, for example, be a fixed time period, depend on the magnitude of the reduced pressure, or last until the pressure reaches a predetermined setpoint or the lower threshold. In the configuration where the inlet valve remains continuously open at a pressure between the setpoint and the lower threshold, the opening size of the inlet valve should be limited so that a dangerously large leak in the housing would no longer compensate for the pressure drop, thus enabling early detection of a fault in step c).

[0032] It is also conceivable to use a method in which the number of short time intervals for opening the inlet valve depends on the amount of inert gas required for pressure equalization in the intermediate step bb).

[0033] Finally, the features of the dependent claims for the method according to the invention can be combined essentially freely with one another and not be determined by the order given in the claims, provided that they are independent of one another and do not exclude each other. Brief description of the drawings:

[0034] Exemplary embodiments of the invention are explained with reference to the drawings.

[0035] They show Fig. 1 in schematic representation an embodiment of a refrigeration system not according to the invention; Fig. 2 in schematic representation a further embodiment of a refrigeration system not according to the invention; Fig. 3. A schematic representation of an embodiment of a cascade-type refrigeration system; Fig. 4 a ground-based vehicle designed as a bus with an embodiment of a refrigeration system according to the invention; Fig. Figure 5 shows an embodiment of a method for the safety of a refrigeration system according to the invention, presented in a flowchart representation; and Fig. Figure 6 shows a further embodiment of a method for the safety of a refrigeration system according to the invention, presented in a flowchart representation. Detailed description of the invention:

[0036] All drawings are to be understood schematically. Scale drawings have been omitted for the sake of clarity.

[0037] In Fig. Figure 1 shows a schematic representation of a non-inventive embodiment of a refrigeration system 1 for a ground-based vehicle. It has a first refrigerant circuit 3 with a compressor 5, a condenser / gas cooler 7, an expansion element 9 designed as a thermostatic expansion valve, and an evaporator 11, which are connected sequentially in the circuit by refrigerant lines. The first refrigerant circuit 3 is designed for the flammable refrigerant R-290. It is conceivable that the first refrigerant circuit 3 could be designed for a different flammable or toxic refrigerant. The condenser / gas cooler 7 is a fluid-fluid heat exchanger. It is arranged for heat exchange between the refrigerant of the first refrigerant circuit 3 and the coolant of the heating and / or cooling circuit 13, which is designed as a heating and cooling circuit.The evaporator 11 is also a fluid-fluid heat exchanger, arranged for heat exchange between refrigerant of refrigerant circuit 3 and coolant of the heating and / or cooling circuit 13, which is configured as a heating and cooling circuit. The heating and / or cooling circuit 13 includes a first pump 15, which is designed to pump coolant, such as water or a water-glycol mixture, through the heating and / or cooling circuit 13. The bypass 17 to the condenser / gas cooler 7 in the heating and / or cooling circuit 13 is controllable via the valve 19, and the bypass 21 to the evaporator 11 in the heating and / or cooling circuit 13 is controllable via the valve 23.Furthermore, in the heating and / or cooling circuit 13, which is designed as a heating and cooling circuit, an air-fluid heat exchanger 25 for heating air is arranged downstream of the condenser / gas cooler 7, and another air-fluid heat exchanger 27 for cooling air is arranged downstream of the evaporator 11. Each of the two air-fluid heat exchangers 25 and 27 is associated with an air conveying device 26 and 28, respectively. Depending on the corresponding configuration of the air flow, the air-fluid heat exchanger 25 is intended for heating or the air-fluid heat exchanger 27 for cooling air in the interior of a ground-based vehicle. The bypass 29 to the air-fluid heat exchanger 25 in the heating and / or cooling circuit 13, which is designed as a heating and cooling circuit, can be controlled via the valve 31, and the bypass 33 to the air-fluid heat exchanger 27 in the heating and / or cooling circuit 13, which is designed as a heating and cooling circuit, can be controlled via the valve 35.

[0038] The first refrigerant circuit 3, as well as parts of the heating and / or cooling circuit 13, which is designed as a heating and cooling circuit, are located within a gas-tight housing 37, i.e., within its interior. Outside the gas-tight housing 37 are parts of the heating and / or cooling circuit 13, such as, in particular, the two air-to-fluid heat exchangers 25 and 27, and the first pump 15. The refrigerant lines to and from the air-to-fluid heat exchangers 25 and 27 are routed through the housing wall of the gas-tight housing 37, with a gas-tight seal between the housing wall of the housing 37 and the refrigerant lines. The gas-tight housing 37 is made of sheet steel. Alternatively, other suitable gas-tight materials, such as aluminum, are also possible.The gas-tight housing 37 has an inlet 39, which can be sealed gas-tightly with the inlet valve 38, for filling the area 41 of the interior of the gas-tight housing 37, located around the first refrigerant circuit 3, with inert gas. Other types of closure known in the prior art for sealing the inlet 39 gas-tightly are also conceivable. The inert gas is, for example, CO2 or N2 or a noble gas such as Ar. An inert gas mixture, for example of CO2 and He, is also possible. Furthermore, the gas-tight housing 37 has an outlet 43, which can be sealed gas-tightly with the outlet valve 42, for releasing inert gas from this area 41. An embodiment of the refrigeration system 1 is also conceivable in which the inlet 39 is also designed as the outlet 43.

[0039] The gas-tight housing 37 is designed in this case for an overpressure of 5 bar above normal pressure inside the gas-tight housing 37. The inert gas can therefore have a higher maximum pressure than normal pressure. However, versions of the gas-tight housing 37 with any other maximum permissible pressures above normal pressure are also conceivable, depending on the pressure stability of the housing 37, in which the inert gas may have a higher maximum pressure than normal pressure. The pressure stability should depend, firstly, on the type and quantity of the refrigerant in the refrigerant circuit 3 and the inert gas in the area 41 of the interior of the gas-tight housing 37 surrounding the refrigerant circuit 3.In the event of a leak in the first refrigerant circuit 3, the quantity of inert gas in the area 41 of the interior of the housing 37 surrounding the first refrigerant circuit 3 should be sufficient so that, even if the refrigerant completely flows into this area, the concentration of refrigerant in the gas mixture with inert gas is not exceeded, thus preventing any hazardous situations. The area 41 of the interior of the gas-tight housing 37 surrounding the first refrigerant circuit 3 should have a volume and pressure stability adapted to this requirement. For example, a mixture of R-290 as refrigerant and CO2 as inert gas with a CO2 concentration above 35 mol% is no longer flammable in combination with oxygen.Thus, with quantities of 500 g of R-290 as refrigerant in the first refrigerant circuit 3 and of 300 g of CO2 as inert gas in the area 41 of the interior of the gas-tight housing 37 surrounding the first refrigerant circuit 3, the refrigeration system 1 is still protected against fire hazards even in the event of a leak in the first refrigerant circuit 3, provided that the gas-tight housing 37 is sufficiently pressure-stable, as is the case here for 5 bar overpressure above normal pressure.

[0040] A gas sensor 45 is mounted through the housing wall of the gas-tight housing 37. This sensor is designed to detect refrigerant escaping from the first refrigerant circuit 3 in the event of a leak in the area 41 of the interior of the gas-tight housing 37 surrounding the first refrigerant circuit 3. In this embodiment, the gas sensor 45 can therefore measure the concentration of the refrigerant R-290. A fault detection device 47 is connected to the gas sensor 45. This device is designed to detect a fault in the refrigeration system 1 when the refrigerant concentration detected by the gas sensor 45 exceeds a predefined threshold. The threshold is, for example, a concentration of 10 mol%. A variant of the [designation shown in the figure] is conceivable. Fig. 1 refrigeration system 1 shown, in which instead of the gas sensor 45 a pressure sensor has for detecting pressure values ​​of the pressure in the area 41 of the interior of the gas-tight housing 37 located around the first refrigerant circuit 3 and a fault detection device 47 is connected to the pressure sensor, which is designed to detect a fault of the refrigeration system 1 when a pressure value detected by the pressure sensor is above a predetermined upper threshold of, for example, 4.7 bar.

[0041] It is also conceivable to have a variant of the refrigeration system 1 which, instead of a heating and / or cooling circuit 13 designed as a heating and cooling circuit, comprises a heating circuit with the first pump 15 and a cooling circuit with a second pump separately.

[0042] Refrigeration system 1 is designed for a ground-based vehicle, such as a bus.

[0043] In Fig. Figure 2 schematically illustrates another embodiment of a refrigeration system 1 for a ground-based vehicle, not according to the invention. It comprises a first refrigerant circuit 3 with a compressor 5, a condenser / gas cooler 7, an expansion element 9 designed as a thermostatic expansion valve, and an evaporator 11, which are sequentially connected in the first refrigerant circuit 3 by refrigerant lines. The first refrigerant circuit 3 is designed for the flammable refrigerant R-1234yf. It is conceivable that the first refrigerant circuit 3 could be designed for a different flammable or toxic refrigerant. The condenser / gas cooler 7 is a fluid-fluid heat exchanger. It is arranged for heat exchange between the refrigerant of the first refrigerant circuit 3 and the heating medium of the heating and / or cooling circuit 13, which is designed as a heating circuit.The evaporator 11 is also a fluid-fluid heat exchanger, designed for heat exchange between the refrigerant of the first refrigerant circuit 3 and the coolant of the cooling circuit 51. The heating and / or cooling circuit 13, configured as a heating circuit, includes a first pump 15 for pumping a heating medium such as water through it, and the cooling circuit 51 contains a second pump 53 for pumping a coolant such as a water-glycol mixture through it. The bypass 17 to the condenser / gas cooler 7 in the heating and / or cooling circuit 13 is controlled via the valve 19, and the bypass 55 to the evaporator 11 in the cooling circuit 51 is controlled via the valve 57.Furthermore, in the heating and / or cooling circuit 13, which is designed as a heating circuit, an air-fluid heat exchanger 25 for heating air is arranged downstream of the condenser / gas cooler 7, and in the cooling circuit 51, another air-fluid heat exchanger 27 for cooling air is arranged downstream of the evaporator 11. Each of the two air-fluid heat exchangers 25 and 27 is associated with an air conveying device 26 and 28, respectively. Depending on the corresponding configuration of the air supply, the air-fluid heat exchanger 25 is intended for heating or the air-fluid heat exchanger 27 for cooling air in the interior of a ground-based vehicle. The bypass 29 to the air-fluid heat exchanger 25 in the heating and / or cooling circuit 13, which is designed as a heating circuit, can be controlled via the valve 31 and the bypass 59 to the air-fluid heat exchanger 27 in the cooling circuit 51 can be controlled via the valve 61.

[0044] The first refrigerant circuit 3, as well as parts of both the heating and / or cooling circuit 13 (designed as a heating circuit) and the cooling circuit 51, are located within the gas-tight housing 37, i.e., in its interior. The first pump 15 and the second pump 53 are also located within the interior of the gas-tight housing 37. Outside the gas-tight housing 37 are parts of the heating and / or cooling circuit 13 (designed as a heating circuit) and the cooling circuit 51, in particular the two air-to-fluid heat exchangers 25 and 27. The heating medium and coolant lines to and from the air-to-fluid heat exchangers 25 and 27 are routed through the housing wall of the gas-tight housing 37, with a gas-tight seal between the housing wall of the housing 37 and the heating medium and coolant lines. The gas-tight housing 37 is made of aluminum. Alternatively, other suitable gas-tight materials, such as sheet steel, are also possible.

[0045] The refrigeration system 1 comprises a tank 63 located outside the gas-tight housing 37, which is filled, or can be filled, with an inert gas, such as argon, under overpressure. A line, designed as an inlet 39 for inert gas, leads from the tank to the area 41 of the interior of the gas-tight housing 37, which surrounds the first refrigerant circuit 3. This inlet 39 can be closed gas-tight by means of an adjustable inlet valve 38. The control unit 65, located outside the gas-tight housing 37, controls the inlet valve 38 via a Fig. The control line is shown as a dashed line. The controller 65 receives the pressure values ​​measured by the pressure sensor 67 in the area 41 of the interior of the gas-tight housing 37, which is located around the first refrigerant circuit 3. During operation, the inert gas in area 41 has a pressure of, for example, 2.2 bar. If the controller 65 detects a pressure drop below a predetermined intermediate value of, for example, 1.8 bar, but still above a lower threshold value of, for example, 1.5 bar, particularly in the event of a leak in the gas-tight housing 37, it automatically opens the inlet valve 38 for a predetermined time interval of, for example, one second. If the pressure reaches or even falls below the lower threshold value of 1.5 bar, despite the amount of inert gas flowing in through the inlet valve 38, the controller 65 detects a fault in the refrigeration system 1.However, if the pressure sensor 67 measures a pressure increase in the area 41 of the interior of the gas-tight housing 3 surrounding the first refrigerant circuit 3 above a predetermined upper threshold of, for example, 4.5 bar, particularly in the case of a leak in the first refrigerant circuit 3, the fault detection device 47 of the control unit 65 also detects a fault in the refrigeration system 1. After the refrigeration system 1 has been moved to a safe environment, the control unit 65 opens the otherwise gas-tightly sealed outlet valve 42 via a control connection, so that gas can be released through the outlet 43 from the area 41 of the interior of the gas-tight housing 37 surrounding the first refrigerant circuit 3.

[0046] It is also conceivable to have a variant of the refrigeration system 1 which, instead of the heating and / or cooling circuit 13 designed as a heating circuit and the separate cooling circuit 51, comprises only one heating and / or cooling circuit 13 designed as a heating and cooling circuit with only one pump 15.

[0047] Refrigeration system 1 is intended for a ground-based vehicle, such as a rail vehicle.

[0048] In Fig. Figure 3 schematically illustrates an embodiment of a cascade-type refrigeration system 1 for a ground-based vehicle. Within the gas-tight housing 37, the first refrigerant circuit 3, comprising a compressor 5, condenser / gas cooler 7, expansion element 9, and evaporator 11, is arranged as a circuit connected by refrigerant lines. It is operated with a toxic or flammable refrigerant, such as R-600a. The condenser / gas cooler 7 is a fluid-fluid heat exchanger for heat exchange between the refrigerant of the first refrigerant circuit 3 and the heating medium of the heating and / or cooling circuit 13. The evaporator 11 is a fluid-fluid heat exchanger for heat exchange between the refrigerant of the first refrigerant circuit 3 and the refrigerant of the second refrigerant circuit 81. The refrigerant of the second refrigerant circuit 81 is the non-flammable inert gas CO2.It comprises, connected in a circuit with refrigerant lines, the secondary compressor 83, the gas cooler 85, the hot side of the evaporator 11, the secondary expansion element 87, and the secondary evaporator 89. The gas cooler 85 is a fluid-fluid heat exchanger for heat exchange between the refrigerant of the secondary refrigerant circuit 81 and the heating medium, such as water, of the secondary heating circuit 91. The evaporator 89 is a fluid-fluid heat exchanger for heat exchange between the refrigerant of the secondary refrigerant circuit 81 and the coolant, such as a water-glycol mixture, of the cooling circuit 51. The first pump 15 is for circulating the heating medium in the heating and / or cooling circuit 13, which is configured as a heating circuit; the second pump 53 is for circulating the coolant in the cooling circuit 51; and the third pump 93 is for circulating the heating medium in the secondary heating circuit 91.The first pump 15, second pump 53, and third pump 93 are located within the gas-tight housing 37. The air supply unit 28 for cooling air is assigned to the air-fluid heat exchanger 27 of the cooling circuit 51 for cooling a section of the vehicle interior, provided the air line is configured accordingly. The air supply unit 26 for heating air in a section of the vehicle interior is assigned to the air-fluid heat exchanger 25 of the heating and / or cooling circuit 13, which is configured as a heating circuit. The air supply unit 96 for heating air in a section of the vehicle interior to a different temperature level is assigned to the air-fluid heat exchanger 95 of the further heating circuit 91, provided the air line is configured accordingly.

[0049] The three air-fluid heat exchangers 25, 27, 95 are located outside the gas-tight housing 37. The respective coolant and heating medium lines lead to the gas-tight housing 37, sealed through the housing wall. In the further heating circuit 91, the bypass 99, which can be controlled via the valve 97, runs to the gas cooler 85.

[0050] The second refrigerant circuit 81 is also located within the gas-tight housing 37. Non-flammable refrigerant CO2 can flow from it through the inlet 39 into the area 41 of the interior of the gas-tight housing 37 surrounding the first refrigerant circuit 3, provided the gas-tight inlet valve 38 is open. The inlet valve 38 is accessible via the Fig. The control connection shown in dashed lines is adjustable by the control unit 65 located outside the gas-tight housing 37. The control unit 65 receives the pressure values ​​measured by the pressure sensor 67 in the area 41 of the interior of the gas-tight housing 37, which surrounds the first refrigerant circuit 3. During operation, the inert gas CO2 in area 41 normally has a pressure of, for example, 3.0 bar. If the pressure is detected to be below an intermediate value of, for example, 2.3 bar but still above a lower threshold value of, for example, 1.5 bar, i.e., reduced, the control unit 65 automatically opens the adjustable inlet valve 38 once for a predetermined time interval of, for example, 2 seconds, or several times depending on the required quantity of inert gas.If, however, the pressure monitored by the pressure sensor 67 falls below the lower threshold of 1.5 bar, the fault detection device 47 contained in the control unit 65 detects a fault in the cascade refrigeration system 1. Similarly, the fault detection device 47 detects a fault if the pressure measured by the pressure sensor 67 in the area 41 of the interior of the gas-tight housing 3, located around the first refrigerant circuit 3, exceeds an upper threshold of, for example, 4.5 bar, because then at least one of the first refrigerant circuits 3 and the other refrigerant circuits 81 is likely to have a leak. The gas-tight housing 37 is designed for a maximum pressure of at least 6 bar. Higher pressure resistances are also conceivable.In the event of a detected fault, the otherwise gas-tight sealed outlet valve 42 of the outlet 43, which can be controlled via a control connection from the control unit 65, is opened in a secure environment so that the gas present in the area 41 of the interior of the gas-tight housing 37, which is located around the first refrigerant circuit 3, can be released.

[0051] Refrigeration system 1 is designed for a ground-based vehicle, such as a refrigerated truck.

[0052] In Fig. Figure 4 shows an embodiment of a vehicle 10 with a refrigeration system 1 designed as a heating and / or air conditioning system according to the invention. The vehicle 10 is designed as a bus. The refrigeration system 1 is mounted on the vehicle 10 as a roof-mounted system. It is a in Fig. 3 refrigeration system 1 shown and equipped for heating and / or cooling air for the interior 12 of the vehicle 10, in particular for the passenger compartment.

[0053] In Fig. Figure 5 in the flowchart is an embodiment of a method for the safety of a refrigeration system according to the invention, such as one in Fig. Figure 3 illustrates this process. In the first step (100), the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit is filled with an inert gas, such as CO2, through the inlet to a pressure of, for example, 2.5 bar. In the next step (110), a gas sensor monitors the refrigerant concentration, or a pressure sensor monitors the pressure in the area of ​​the interior of the gas-tight housing filled with inert gas surrounding the first refrigerant circuit, and transmits the measured values ​​to the fault detection device of the refrigeration system. The refrigerant in the first refrigerant circuit within the gas-tight housing is, for example, the flammable R-1234yf.In step 120, the fault detection device determines whether the concentration of refrigerant (monitored concentration) exceeds a predefined threshold of, for example, 5 mol%, or whether the pressure (monitored pressure) exceeds a predefined threshold of, for example, 4 bar. If "No," the system proceeds again to step 110. If "Yes," it decides to detect a fault in the refrigeration system in step 130 and, if operational, to automatically shut down the refrigeration system in step 140. In the next step, 150, the gas, which is very likely a mixture of inert gas and refrigerant, is released through the open outlet from the area surrounding the first refrigerant circuit within the gas-tight housing. The system is then moved to a secure environment, such as a fireproof room.This can be done, for example, by pumping the refrigerant into a fireproof container. Then, in step 160, the first refrigerant circuit is checked for leaks. This is done using standard, state-of-the-art methods, such as a bubble detection technique. Depending on whether a leak is found or not, step 170 determines whether, if "yes," the leak is repaired in step 180. Then, in step 190, the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit is refilled with an inert gas, such as CO2, to a pressure of, for example, 2.5 bar. If, however, no leak is found in step 160, step 170 determines whether, if "no," step 190 is immediately performed. After step 190, the process is repeated from step 110 onwards.

[0054] It is also conceivable to use a very simplified version of the procedure, which only includes steps 100 to 130.

[0055] In Fig. Figure 6 in the flowchart shows a further embodiment of a method for the safety of a refrigeration system according to the invention, such as one in Fig.Figure 3 illustrates this process. In the first step (200), the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit is filled with an inert gas, such as CO2, through the inlet to a pressure of, for example, 2.2 bar. In the next step (210), a pressure sensor monitors the pressure in the inert gas-filled area surrounding the first refrigerant circuit and transmits the measured pressure values ​​to the control unit with fault detection for the refrigeration system. The refrigerant in the first refrigerant circuit within the gas-tight housing is, for example, the flammable R-600a. In step 220, the control unit determines whether the pressure value, at the monitored pressure, is below an intermediate value of, for example, 1.9 bar and above a lower threshold of 1.5 bar, which would indicate reduced pressure.

[0056] If "No," the system proceeds to step 230. In step 230, the fault detection device determines whether the pressure reading monitored by the pressure sensor is above an upper threshold of, for example, 3.5 bar, or below a lower threshold of 1.5 bar. If neither is true, the result is "No," and the system proceeds again to step 210. However, if either of the conditions in step 230 is true, the result is "Yes," and a fault in the refrigeration system is detected in step 240.

[0057] However, if a reduced pressure is detected in step 220—in this example, between the intermediate value of 1.9 bar and the lower threshold of 1.5 bar—the result is "Yes," and the process continues to step 250. In step 250, the inlet valve for inert gas is opened by the controller into the area of ​​the interior of the gas-tight housing surrounding the first refrigerant circuit. The inlet valve remains open for a time interval of, for example, one second, so that only a defined quantity of inert gas flows through the inlet. Other time intervals are also conceivable, depending on the desired quantity of inert gas. Furthermore, a variant is also conceivable in which the lower the detected reduced pressure, the longer the time interval for opening the inlet valve is automatically selected.If, in step 260, it is detected that the monitored pressure value lies within the range between a predefined setpoint and the lower threshold value, as in this example between 2.2 bar and 1.5 bar (i.e., "Yes"), the procedure returns to step 250. However, if the result in step 260 is "No", the process continues with step 230 as described above. Alternatively, in step 250, the inlet valve could remain open until the result in step 260 is "No". In this case, the opening of the inlet valve would be limited so that, in the event of a dangerously large leak in the gas-tight housing, the inflow of inert gas through the inlet would not be sufficient to stop the pressure drop, thus ensuring that a fault is detected quickly enough in step 240.

Claims

[1] Refrigeration system (1) for a ground-based vehicle (10) comprising at least one heating and / or cooling circuit (13) equipped with a first pump (15) and a first refrigerant circuit (3) with at least one compressor (5), at least one condenser / gas cooler (7), at least one expansion element (9) and at least one evaporator (11), wherein at least one condenser / gas cooler (7) and at least one evaporator (11) are each designed as a fluid-fluid heat exchanger, wherein - the first refrigerant circuit (3) is arranged within a gas-tight housing (37), - an area (41) of an interior of the gas-tight housing (37) located around the first refrigerant circuit (3) can be filled with an inert gas through a gas-tight sealable inlet (39), and - the gas-tight housing (37) is designed for a higher maximum pressure of the inert gas than the normal pressure, characterized by , that at least partially inside the gas-tight housing (37) a further refrigerant circuit (81) for the inert gas, such as CO2 in particular, as a refrigerant of the further refrigerant circuit (81) is arranged, and from the further refrigerant circuit (81) the inlet (39) for the refrigerant, which can be closed gas-tight with a controllable inlet valve (38), exists in the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3). [2] Refrigeration system (1) according to claim 1 characterized by , that the heating and / or cooling circuit (13) is designed as a heating circuit and a cooling circuit (51) with a second pump (53) is arranged separately from it. [3] Refrigeration system (1) according to claim 1 or 2, characterized by, that the first refrigerant circuit (3) is designed for a flammable refrigerant and that a gaseous fire retardant is provided as an inert gas for the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3). [4] Refrigeration system (1) according to any one of claims 1 to 3 characterized by, that in the refrigeration system (1) at least one of the at least one condenser / gas cooler (7) designed as a fluid-fluid heat exchanger is arranged for heat exchange of refrigerant of the first refrigerant circuit (3) with heating medium in a heating and / or cooling circuit (13) designed as a heating circuit and at least one of the at least one evaporator (11) designed as a fluid-fluid heat exchanger is arranged for heat exchange of refrigerant of the first refrigerant circuit (3) with coolant of the cooling circuit (51) or both the at least one condenser / gas cooler (7) and the at least one evaporator (11) are arranged for heat exchange of the refrigerant of the first refrigerant circuit (3) with coolant in a heating and / or cooling circuit (13) designed as a heating and cooling circuit. [5] Refrigeration system (1) according to any one of claims 1 to 4 characterized by, that it includes a pressure sensor (67) for detecting pressure values ​​of the pressure in the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3). [6] Refrigeration system (1) according to claim 5 characterized by , that it includes a fault detection device (47) designed to detect a fault in the refrigeration system (1) when the pressure value detected by the pressure sensor (67) exceeds a predetermined upper threshold. [7] Refrigeration system (1) according to any one of claims 1 to 6 characterized by , that the gas-tight housing (37) is designed for a maximum pressure of at least 6 bar. [8] Refrigeration system (1) according to any one of claims 1 to 7 characterized by, that it comprises a gas sensor (45) for detecting refrigerant escaping from the first refrigerant circuit (3) in the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3) and that it comprises a fault detection device (47) designed to detect a fault in the refrigeration system (1) when the concentration of refrigerant from the first refrigerant circuit (3) detected by the gas sensor (45) exceeds a predetermined threshold value. [9] Refrigeration system (1) according to any one of claims 1 to 8 characterized by that the first pump (15) and / or the second pump (53) is / are arranged inside the gas-tight housing (37). [10] Refrigeration system (1) according to any one of claims 1 to 9 characterized by , that the gas-tight housing (37) is made of metal, such as in particular aluminium or sheet steel. [11] Refrigeration system (1) according to any one of claims 5 to 10 characterized by, that it includes a control (65) which is configured to control the adjustable inlet valve (38) depending on the pressure detected by the pressure sensor (67) in the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3). [12] Ground-based vehicle (10), such as in particular a rail or road vehicle, characterized by , that it comprises a refrigeration system (1) according to any one of claims 1 to 11. [13] Method for the safety of a refrigeration system (1) according to any one of claims 1 to 11 characterized by the steps a) of the filling (100, 200) of the area (41) of the interior of the gas-tight housing (37) located around the first refrigerant circuit (3) with inert gas up to a predetermined setpoint pressure through the inlet (39), b) monitoring (110, 210) the concentration of refrigerant and / or the pressure in the inert gas-filled area (41) of the interior of the gas-tight housing (37) surrounding the first refrigerant circuit (3), and c) detecting (130, 240) a disturbance when a pressure value at monitored pressure is above a predetermined upper threshold or the concentration at monitored concentration of the refrigerant is above a predetermined concentration threshold. [14] Method according to claim 13 characterized by , that in step c) (130, 240) a fault is also detected if a pressure value under monitored pressure is below a specified lower threshold. [15] Method according to claim 13 or 14 characterized by the next steps d) of switching off (140) the operation of the refrigeration system (1), if it is in operation, in the event of a fault detected in step c) (130, 240, e) of the release (150) of the gas from the area (41) of the interior of the gas-tight housing (37) surrounding the first refrigerant circuit (3) into a safe environment in the event of a fault detected in step c) (130, 240, f) checking (160) the first refrigerant circuit (3) for a leak, g) of repairing (180) any leak(s) found, and h) of refilling (190) the area (41) of the interior of the gas-tight housing (37) surrounding the first refrigerant circuit (3) with inert gas up to the specified target pressure. [16] Method according to claim 14 or 15, characterized by the intermediate steps after step b) (110, 210) (aa) detecting (220) a reduced pressure when a pressure value at monitored pressure is in a range between a specified intermediate value and the lower threshold value below that value, and then bb) of the opening (250) of the inlet valve (38) of the inlet (39) of inert gas into the area (41) of the interior of the gas-tight housing (37) surrounding the first refrigerant circuit (3) for at least a time interval.

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