Cooling system using chiller and thermally coupled cooling circuit

Abstract

A cooling system suitable for cooling food on board an aircraft is provided which includes a chiller device and a first cooling circuit which is adapted to feed cooling energy generated by the chiller device to at least one cooling station, the chiller device includes a second cooling circuit formed separately from the first cooling circuit and is thermally coupled to the first cooling circuit.

Claims

1. An aircraft cooling system for cooling food on board an aircraft, comprising: a chiller device; a first cooling circuit adapted to feed cooling energy generated by the chiller device to at least one cooling station, wherein a first refrigerant circulating in the first cooling circuit is a two-phase, liquid gas, refrigerant, wherein the chiller device comprises a second cooling circuit formed separately from the first cooling circuit and is thermally coupled to the first cooling circuit via a first heat exchanger, wherein a second refrigerant circulating in the second cooling circuit is a two-phase, liquid-gas, refrigerant; at least one throttle valve; at least one evaporation device associated with the at least one cooling station, the at least one evaporation device arranged serially with the at least one throttle valve; and a first delivery device for circulating the first refrigerant in the first cooling circuit, wherein the first refrigerant flowing into the first delivery device is in the liquid state, wherein the first delivery device is arranged serially with the at least one throttle valve and the at least one cooling station, wherein the first delivery device circulates the first refrigerant in its liquid state to each of the at least one throttle valve solely through one or more duct lines, wherein the at least one throttle valve regulates a pressure of the first refrigerant upstream of the at least one cooling station and regulates an evaporation temperature of the first refrigerant in the at least one evaporation device converting the first refrigerant from the liquid to gaseous state when cooling energy is delivered to the at least one cooling station, and wherein the first refrigerant emerging from the at least one evaporation device returns to the liquid state again through appropriate pressure and temperature control in the first cooling circuit.

2. The aircraft cooling system according to claim 1, wherein the first delivery device is a pump.

3. The aircraft cooling system according to claim 1, further comprising a first reservoir for temporarily storing the first refrigerant disposed in the first cooling circuit.

4. The aircraft cooling system according to claim 1, further comprising a second delivery device for circulating the second refrigerant in the second cooling circuit disposed in the second cooling circuit.

5. The aircraft cooling system according to claim 1, wherein a cooling device is disposed in the second cooling circuit.

6. The aircraft cooling system according to claim 5, further comprising a second heat exchanger disposed in the second cooling circuit, wherein the second heat exchanger thermally couples a portion of the second cooling circuit which extends upstream of the cooling device to a portion of the second cooling circuit which extends downstream of the cooling device.

7. The aircraft cooling system according to claim 1, wherein a second reservoir for temporarily storing the second refrigerant is disposed in the second cooling circuit.

8. The aircraft cooling system according to claim 1, wherein the cooling station includes a third cooling circuit which is formed separately from the first cooling circuit and is thermally coupled to the first cooling circuit.

9. The aircraft cooling system according to claim 8, wherein the third cooling circuit is thermally coupled to the first cooling circuit via a third heat exchanger formed by the evaporation device.

10. An aircraft cooling system for cooling food on board an aircraft, comprising: a chiller device; a first cooling circuit adapted to feed cooling energy generated by the chiller device to a plurality of cooling stations, wherein a first refrigerant circulating in the first cooling circuit is a two-phase, liquid gas, refrigerant, wherein the chiller device comprises a second cooling circuit formed separately from the first cooling circuit and is thermally coupled to the first cooling circuit via a first heat exchanger, wherein a second refrigerant circulating in the second cooling circuit is a two-phase, liquid-gas, refrigerant, and wherein the first cooling circuit comprises a feed line, a withdrawal line and a plurality of branch lines, each branch line connecting one of the plurality of cooling stations to the feed line and the withdrawal line; a throttle valve arranged in each branch line and upstream of the cooling station arranged in the respective branch line; an evaporation device associated with the cooling station and arranged in each branch line serially with the throttle valve; and a first delivery device for circulating the first refrigerant in the first cooling circuit, wherein the first delivery device is arranged in the feed line downstream of the first heat exchanger and upstream of a first of the plurality of branch lines, and wherein the first refrigerant flowing into the first delivery device is in the liquid state, wherein the first delivery device circulates the first refrigerant in its liquid state to each throttle valve solely through the feed line and the respective branch line, wherein each throttle valve regulates a pressure of the first refrigerant upstream of the respective cooling station and regulates an evaporation temperature of the first refrigerant in the respective evaporation device converting the first refrigerant from the liquid to the gaseous state when cooling energy is delivered to the respective cooling station, and wherein the first refrigerant emerging from the evaporation device returns to the liquid state again through appropriate pressure and temperature control in the first cooling circuit.

Description

(1) A preferred embodiment of a cooling system according to the invention is now illustrated in detail on the basis of the accompanying schematic drawings, of which:

(2) FIG. 1 shows a cooling system according to the invention,

(3) FIG. 2 is an enlarged representation of a chiller device which is used in the cooling system according to the invention as shown in FIG. 1,

(4) FIG. 3 is a representation of the refrigeration process control in a cooling system known from the prior art in a pressure-enthalpy diagram using CO.sub.2 as the first refrigerant and

(5) FIG. 4 is a representation of the refrigeration process control in a cooling system according to the invention in a pressure-enthalpy diagram using CO.sub.2 as the first refrigerant.

(6) FIG. 1 shows a cooling system 10 which is provided to cool food provided on board a passenger aircraft for distribution to the passengers and stored in mobile transport containers. The cooling system 10 comprises a central chiller device 12 as well as a plurality of cooling stations 14 which are distributed in the region of the on-board kitchens at respective deposit locations of the transport containers in the passenger compartment of the aircraft. In order to supply the cooling stations 14 with cooling energy, a first cooling circuit 16 is provided, through which a first refrigerant, as indicated by the arrow P, flows anticlockwise. CO.sub.2 is used as the first refrigerant.

(7) The first cooling circuit 16 of the cooling system 10 is thermally coupled to a second cooling circuit 20 of the chiller device 12 via a first heat exchanger 18. Otherwise the first and the second cooling circuit 16, 20 are formed separately from one another, so that the first cooling circuit 16 is not subjected to the pressure prevailing in the second cooling circuit 20, which may be very high, during operation of the cooling system 10.

(8) The first cooling circuit 16 comprises a feed line 22, a withdrawal line 24 as well as a plurality of branch lines 26, the branch lines 26 in each case serving to connect the individual cooling stations 14 to the feed or the withdrawal line 22, 24 of the first cooling circuit 16.

(9) A first delivery device 28, which is in the form of a pump, is disposed in the feed line 22 of the first cooling circuit 16 and serves to deliver the first refrigerant from a first reservoir 30, which is disposed upstream of the delivery device 28 in the first cooling circuit 16, and to circulate it in the first cooling circuit 16. The first reservoir 30 is provided with appropriate insulation, so that the first refrigerant which is temporarily stored in the first reservoir 30 can be maintained at the desired low temperature.

(10) A throttle valve 31 is disposed in each branch line 26 connecting the feed line 22 of the first cooling circuit 16 to the individual cooling stations 14, which valve 31 serves to control the flow rate of the first refrigerant in the direction of each cooling station 14 as well as the pressure in the first refrigerant upstream of each cooling station 14. If required, each throttle valve 31 is capable of completely interrupting the flow of the first refrigerant through the corresponding branch line 26 and therefore stopping the feed of the first refrigerant to the cooling station 14 disposed downstream of the throttle valve 31. Individual cooling stations 14 can thereby be isolated from the first cooling circuit 16 in a simple manner, while other cooling stations 14 continue to be fed with cooling energy.

(11) Each cooling station 14 has a third cooling circuit 32 which is formed separately from the first cooling circuit 16 and is thermally coupled to the first cooling circuit 16 via a heat exchanger 33. The heat exchanger 33 is formed as an evaporation device, so that the first refrigerant flowing through the first cooling circuit 16 is converted from the liquid to the gaseous state when its cooling energy is delivered to the cooling station 14. After emerging from the heat exchanger 33, the first refrigerant is returned to the liquid state again through appropriate temperature and pressure control in the first cooling circuit 16.

(12) As can be seen from FIG. 2 of the accompanying drawings, a second delivery device 34 in the form of a compressor is disposed in the second cooling circuit 20 of the chiller device 12, this serving to circulate a second refrigerant in the second cooling circuit 20. CO.sub.2 is used as the second refrigerant. A cooling device 36, which is formed as a gas cooler, is disposed in the second cooling circuit 20 of the chiller device 12 downstream of the second delivery device 34. The cooling device 36, in which ambient dynamic air is used as the heat sink, serves to cool the second refrigerant circulating in the second cooling circuit 20 to the required low temperature.

(13) A second heat exchanger 38 is also disposed in the second cooling circuit 20 of the chiller device 12. The second heat exchanger 38 thermally couples a portion of the second cooling circuit 20 which extends upstream of the second delivery device 34 to a portion of the second cooling circuit 20 which extends downstream of the cooling device 36. As a result of disposing the second heat exchanger 38 in the second cooling circuit 20, the second refrigerant which is heated by the cooling energy transfer from the second cooling circuit 20 to the first cooling circuit 16 in the first heat exchanger 18 firstly flows through the second heat exchanger 38 before it enters the second delivery device 34 and the cooling device 36. As it passes through the second heat exchanger 38 the second refrigerant, which flows through the portion of the second cooling circuit 20 which extends upstream of the second delivery device 34, absorbs heat and therefore undergoes a rise in temperature. This ensures that the CO.sub.2 which is used as the second refrigerant is fed to the second delivery device 34, which is formed as a compressor, in the gaseous state.

(14) The second refrigerant flowing through the portion of the second cooling circuit 20 which extends upstream of the second delivery device 34 is brought in the second heat exchanger 38 into thermal contact with the second refrigerant flowing through the portion of the second cooling circuit 20 which extends downstream of the cooling device 36. The refrigerant flowing through the portion of the second cooling circuit 20 which extends downstream of the cooling device 36 is therefore further cooled in the second heat exchanger 38 through heat transfer to the second refrigerant flowing through the portion of the second cooling circuit 20 which extends upstream of the second delivery device 34. The second refrigerant is therefore at the desired low temperature downstream of the second heat exchanger 38 in order to obtain in the first heat exchanger 18 the required cooling of the first refrigerant flowing through the first cooling circuit 16 of the cooling system 10.

(15) Finally, a second reservoir 40 for temporarily storing the second refrigerant as well as a throttle valve 42 are disposed in the second cooling circuit 20 of the chiller device 12. The second reservoir 40 is positioned upstream of the second delivery device 34 in the second cooling circuit 20, while the throttle valve 42 is disposed downstream of the second heat exchanger 38. The second delivery device 34 can therefore deliver the second refrigerant which is temporarily stored in the second reservoir 40 from the second reservoir 40. The throttle valve 42 regulates the flow of the second refrigerant through the second cooling circuit 20. Moreover, the throttle valve 42 may also be used to control the pressure and therefore the evaporation temperature of the second refrigerant in the second cooling circuit 20.

(16) FIG. 3 shows the refrigeration process control in a cooling system known from the prior art, for example DE 43 403 17 A1, in a pressure-enthalpy diagram using CO.sub.2 as the first refrigerant. In the case of this cooling system known from the prior art a first cooling circuit is directly coupled to a central chiller device, so that the high pressure of approximately 95 bar occurring in the chiller device at an ambient temperature of approximately 30 C. is applied directly to a feed line of the first cooling circuit (points A, B). It is only in the region of a branch line which connects the feed line of the first cooling circuit to a corresponding cooling station that the pressure in the first refrigerant is reduced to a pressure of approximately 30 bar by the action of a throttle valve positioned in the branch line. Between a point C directly upstream of the cooling station and points D and E in the branch line downstream of the cooling station or the withdrawal line of the first cooling circuit the first refrigerant is converted to the gaseous state by a heat exchanger, which is formed as an evaporation device, of the cooling station. Finally, a rise in pressure to approximately 95 bar takes place in the first refrigerant upon flowing through the chiller device.

(17) FIG. 4 is a representation of the refrigeration process control in a cooling system illustrated in FIGS. 1 and 2 in a pressure-enthalpy diagram using CO.sub.2 as the first refrigerant. As is evident from a comparison of the diagrams in FIGS. 3 and 4, the pressure level in the first cooling circuit in the cooling system according to FIGS. 1 and 2 is distinctly lower than in the system known from the prior art. In addition, the process control in the system according to FIGS. 1 and 2 differs from the process control in the system known from the prior art in that the first cooling circuit of the system according to FIGS. 1 and 2 represents a right-hand cyclic process, i.e. a cyclic process running clockwise, whereas the cooling circuit in the system known from the prior art represents a left-hand cyclic process, i.e. a cyclic process running anticlockwise.