Accumulator arrangement with an integrated subcooler

Abstract

An accumulator arrangement for use in a cooling system suitable for operation with two-phase refrigerant includes a condenser having a refrigerant inlet and a refrigerant outlet. The accumulator arrangement further includes an accumulator for receiving the two-phase refrigerant therein, the accumulator having a refrigerant inlet connected to the refrigerant outlet of the condenser and a refrigerant outlet. Finally, the accumulator arrangement includes a subcooler having a refrigerant inlet and a refrigerant outlet, the refrigerant inlet of the subcooler being connected to the refrigerant outlet of the accumulators, and the subcooler being arranged at least partially within the interior of the accumulator.

Claims

1. An accumulator arrangement for use in a cooling system suitable for operation with a two-phase refrigerant, the accumulator arrangement comprising: a condenser having a refrigerant inlet and a refrigerant outlet, an accumulator for receiving the two-phase refrigerant therein, the accumulator having a refrigerant inlet connected to the refrigerant outlet of the condenser a tubing forming a refrigerant outlet of the accumulator in the region of a sump of the accumulator, the tubing extending from the sump of the accumulator through the interior of the accumulator in the direction of a head of the accumulator and exiting the accumulator in a region of the head of the accumulator, the tubing connecting the formed refrigerant outlet of the accumulator to a conveying device for discharging refrigerant from the accumulator, the discharging refrigerant running in the tubing from the sump of the accumulator to the region of the head of the accumulator, and a subcooler having a refrigerant inlet and a refrigerant outlet, the refrigerant inlet of the subcooler being connected to the refrigerant outlet of the accumulator, and the subcooler being arranged at least partially within the interior of the accumulator, wherein the tubing extending from the sump of the accumulator to the region of the head of the accumulator passes through the subcooler in the interior of the accumulator.

2. The accumulator arrangement according to claim 1, wherein the subcooler comprises a heat exchanger comprising a coil heat exchanger or a double tube heat exchanger.

3. The accumulator arrangement according to claim 1, wherein the subcooler and the tubing connecting the refrigerant outlet of the accumulator to the conveying device for discharging refrigerant from the accumulator are formed as an assembly unit which is releasably connected to the accumulator.

4. The accumulator arrangement according to claim 1, wherein the subcooler and the condenser are configured to be supplied with cooling energy by a common heat sink, wherein a refrigerant provided by the heat sink first is directed to the subcooler and thereafter to the condenser or vice versa.

5. The accumulator arrangement according to claim 4, wherein the heat sink supplying cooling energy to the subcooler and the condenser comprises a chiller.

6. The accumulator arrangement according to claim 1, wherein the condenser is arranged at least partially within the interior of the accumulator.

7. The accumulator arrangement according to claim 6, wherein the accumulator, the subcooler, the condenser and the heat sink are formed as an assembly unit.

8. A method of operating an accumulator arrangement for use in a cooling system suitable for operation with a two-phase refrigerant, the method comprising the steps of: condensing the two-phase refrigerant in a condenser, receiving the refrigerant condensed in the condenser in an accumulator, discharging the refrigerant from the accumulator to a conveying device through a tubing forming a refrigerant outlet of the accumulator in the region of a sump of the accumulator, the tubing extending from the sump of the accumulator through the interior of the accumulator in the direction of a head of the accumulator and exiting the accumulator in a region of the head of the accumulator, the tubing connecting the formed refrigerant outlet of the accumulator to the conveying device, and subcooling the refrigerant discharged from the accumulator in a subcooler being arranged at least partially within the interior of the accumulator, wherein the tubing extending from the sump of the accumulator to the region of the head of the accumulator passes through the subcooler in the interior of the accumulator, wherein discharging the refrigerant includes moving the refrigerant in the tubing from the sump of the accumulator to the region of the head of the accumulator.

9. The method according to claim 8, wherein the subcooler and the condenser are supplied with cooling energy by a common heat sink, wherein a refrigerant provided by the heat sink first is directed to the subcooler and thereafter to the condenser or vice versa.

10. A cooling system, in particular for use on board an aircraft, the cooling system comprising: a cooling circuit allowing circulation of a two-phase refrigerant therethrough, a condenser disposed in the cooling circuit and having a refrigerant inlet and a refrigerant outlet, an accumulator for receiving the two-phase refrigerant therein, the accumulator having a refrigerant inlet connected to the refrigerant outlet of the condenser, a tubing forming a refrigerant outlet of the accumulator in the region of a sump of the accumulator, the tubing extending from the sump of the accumulator through the interior of the accumulator in the direction of a head of the accumulator and connecting exiting the accumulator in a region of the head of the accumulator, the tubing connecting the formed refrigerant outlet of the accumulator to a conveying device for discharging refrigerant from the accumulator, the discharing refrigerant running in the tubing from the sum of the accumulator to the region of the head of the accumulator, and a subcooler having a refrigerant inlet and a refrigerant outlet, the refrigerant inlet of the subcooler being connected to the refrigerant outlet of the accumulator and the subcooler being arranged at least partially within the interior of the accumulator, wherein the tubing extending from the sump of the accumulator to the region of the head of the accumulator passes through the subcooler in the interior of the accumulator.

11. The cooling system according to claim 10, wherein a bypass line branching off from the cooling circuit downstream of a refrigerant outlet of a conveying device for discharging refrigerant from the accumulator opens into the accumulator, wherein a valve disposed in the bypass line is adapted to open the bypass line if a pressure difference between the pressure of the refrigerant in the cooling circuit downstream of the refrigerant outlet of the conveying device and the pressure of the refrigerant in the cooling circuit upstream of a refrigerant inlet of the conveying device exceeds a predetermined level.

12. The cooling system according to claim 10, further comprising: an evaporator disposed in the cooling circuit and having a refrigerant inlet and a refrigerant outlet, and a valve disposed in the cooling circuit between the refrigerant outlet of the evaporator and the refrigerant inlet of the condenser, the valve being configured to control the flow of refrigerant through the cooling circuit such that a defined pressure gradient of the refrigerant in a portion of the cooling circuit between the refrigerant outlet of the evaporator and the refrigerant inlet of the condenser is adjusted.

13. A method of operating a cooling system, in particular for use on board an aircraft, the method comprising the steps of: circulating a two-phase refrigerant through a cooling circuit by a conveying device, condensing the two-phase refrigerant in a condenser, receiving the refrigerant condensed in the condenser in an accumulator, discharging the refrigerant from the accumulator through a tubing forming a refrigerant outlet of the accumulator in the region of a sump of the accumulator, the tubing extending from the sump of the accumulator through the interior of the accumulator in the direction of a head of the accumulator and exiting the accumulator in a region of the head of the accumulator, the tubing connecting the formed refrigerant outlet of the accumulator to the conveying device, and subcooling refrigerant discharged from the accumulator in a subcooler being arranged at least partially within the interior of the accumulator, wherein the tubing extending from the sump of the accumulator in the direction of the head of the accumulator passes through the subcooler in the interior of the accumulator, wherein discharging the refrigerant includes moving the refrigerant in the tubing from the sump of the accumulator to the region of the head of the accumulator.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Preferred embodiments of the invention now are explained in more detail with reference to the enclosed schematic drawings wherein

(2) FIG. 1 shows an accumulator arrangement for use in a cooling system suitable for operation with a two-phase refrigerant, and

(3) FIG. 2 shows a cooling system suitable for operation with a two-phase refrigerant.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) FIG. 1 depicts an accumulator arrangement 10a, suitable for use in a cooling system 100, see FIG. 2, which on board an aircraft, for example, may be employed to cool food provided for supplying to the passengers. The cooling system 100 of FIG. 2 comprises a cooling circuit 12 allowing circulation of a two-phase refrigerant A therethrough. The two-phase refrigerant A may for example be CO.sub.2, or R134A. A first and a second evaporator 14a,, 14b, are disposed in the cooling circuit 12. Each evaporator 14a,, 14b, comprises a refrigerant inlet 16a,, 16b, and a refrigerant outlet 18a,, 18b. The refrigerant A flowing through the cooling circuit 12 is supplied to the refrigerant inlets 16a,, 16b, of the evaporators 14a,, 14b, in its liquid state of aggregation. Upon flowing through the evaporators 14a,, 14b,, the refrigerant A releases its cooling energy to a cooling energy consumer which in the embodiment of a cooling system 100 depicted in FIG. 2 is formed by the food to be cooled. Upon releasing its cooling energy, the refrigerant A is evaporated and hence exits the evaporators 14a,, 14b, at the refrigerant outlets 18a,, 18b, of the evaporators 14a,, 14b in its gaseous state of aggregation.

(5) The cooling system 100 usually is operated such that a dry evaporation of the refrigerant occurs in the evaporators 14a,, 14b. This allows an operation of the cooling system 100 with a limited amount of refrigerant A circulating in the cooling circuit 12. As a result, the static pressure of the refrigerant A prevailing in the cooling circuit 12 in the non-operating state of the cooling system 100 is low, even at high ambient temperatures. Further, negative effects of a leakage in the cooling system 100 are limited. Occurrence of a dry evaporation in the evaporators 14a,, 14b, however, can only be ensured by an appropriate control of the amount of refrigerant A supplied to the evaporators 14a,, 14b, in dependence on the operational state of the evaporators 14a,, 14b,, i.e. the cooling energy requirement of the cooling energy consumers coupled to the evaporators 14a,, 14b.

(6) The supply of refrigerant A to the evaporators 14a,, 14b, is controlled by respective valves 20a,, 20b, which are disposed in the cooling circuit 12 upstream of the first and the second evaporator 14a,, 14b,, respectively. The valves 20a,, 20b, may comprise a nozzle for spraying the refrigerant A into the evaporators 14a,, 14b, and to distribute the refrigerant A within the evaporators 14a,, 14b. The spraying of the refrigerant A into the evaporators 14a,, 14b, may be achieved, for example, by supplying refrigerant vapor from the evaporators 14a,, 14b, to the nozzles of the valves 20a,, 20b, and/or by evaporation of the refrigerant A due to a pressure decrease of the refrigerant A downstream of the valves 20a,, 20b.

(7) To ensure occurrence of a dry evaporation in the evaporators 14a,, 14b,, a predetermined amount of refrigerant A is supplied to the evaporators 14a,, 14b, by appropriately controlling the valves 20a,, 20b. Then, a temperature TK1 of the refrigerant A at the refrigerant inlets 16a,, 16b, of the evaporators 14a,, 14b, and a temperature TA2 of the fluid to be cooled by the evaporators 14a,, 14b,, for example air supplied to the cooling energy consumers, is measured, preferably while a fan conveying the fluid to be cooled to the cooling energy consumers is running. Further, the pressure of the refrigerant A in the evaporators 14a,, 14b, or at the refrigerant outlets 18a,, 18b, of the evaporators 14a,, 14b, is measured. If a temperature difference between the temperature TA2 of the fluid to be cooled by the evaporators 14a,, 14b, and the temperature TK1 of the refrigerant A at the refrigerant inlets 16a, 16b, of the evaporators 14a,, 14b, exceeds a predetermined threshold value, for example 8K, and the pressure of the refrigerant A in the evaporators 14a,, 14b, lies within a predetermined range, the refrigerant A supplied to the evaporators 14a,, 14b is thoroughly evaporated and possibly also super-heated by the evaporators 14a, 14b. Hence, the valves 20a,, 20b, again can be controlled so as to supply a further predetermined amount of refrigerant A to the evaporators 14a,, 14b.

(8) The cooling system 100 further comprises a first and a second condenser 22a,, 22b. As becomes apparent from FIG. 1, each condenser 22a,, 22b, has a refrigerant inlet 24 and a refrigerant outlet 26. The refrigerant A which is evaporated in the evaporators 14a,, 14b,, via a portion 12a, of the cooling circuit 12 downstream of the evaporators 14a,, 14b, and upstream of the condensers 22a,, 22b,, is supplied to the refrigerant inlets 24 of the condensers 22a,, 22b, in its gaseous state of aggregation. The supply of refrigerant A from the evaporators 14a,, 14b, to the condensers 22a, 22b, is controlled by means of a valve 28. The valve 28 is adapted to control the flow of refrigerant A through the portion 12a, of the cooling circuit 12 such that a defined pressure gradient of the refrigerant A in the portion 12a, of the cooling circuit 12 between the refrigerant outlets 18a,, 18b, of the evaporators 14a,, 14b, and the refrigerant inlets 24 of the condensers 22a,, 22b, is adjusted. The pressure gradient of the refrigerant A in the portion 12a, of the cooling circuit 12 between the refrigerant outlets 18a,, 18b, of the evaporators 14a,, 14b, and the refrigerant inlets 24 of the condensers 22a,, 22b, induces a flow of the refrigerant A from the evaporators 14a, 14b, to the condensers 22a,, 22b.

(9) Each of the condensers 22a,, 22b, is thermally coupled to a heat sink 29a,, 29b designed in the form of a chiller. The cooling energy provided by the heat sinks 29a, 29b, in the condensers 22a,, 22b, is used to condense the refrigerant A. Thus, the refrigerant A exits the condensers 22a,, 22b, at respective refrigerant outlets 26, see FIG. 1, in its liquid state of aggregation. Liquid refrigerant A from each of the condensers 22a,, 22b, is supplied to an accumulator 30a,, 30b. Within the accumulators 30a,, 30b, the refrigerant A is stored in the form of a boiling liquid. In the embodiment of an accumulator arrangement 10a, shown FIG. 1 the condenser 22a, is disposed outside of the accumulator 30a. As depicted in FIG. 2, it is, however, also conceivable to arrange the condensers 22a,, 22b, within the interior of the accumulators 30a,, 30b.

(10) In the cooling circuit 12, the condensers 22a,, 22b, form a “low-temperature location” where the refrigerant A, after being converted into its gaseous state of aggregation in the evaporators 14a,, 14b,, is converted back into its liquid state of aggregation. A particularly energy efficient operation of the cooling system 100 is possible, if the condensers 22a,, 22b, are installed at a location where heating of the condensers 22a, 22b, by ambient heat is avoided as far as possible. When the cooling system 100 is employed on board an aircraft, the condensers 22a,, 22b, preferably are installed outside of the heated aircraft cabin behind the secondary aircraft structure, for example in the wing fairing, the belly fairing or the tail cone. The same applies to the accumulators 30a,, 30b. Further, the condensers 22a,, 22b, and/or the accumulators 30a,, 30b, may be insulated to maintain the heat input from the ambient as low as possible.

(11) As becomes apparent from FIG. 1, each of the accumulators 30a,, 30b, has a refrigerant inlet 32 connected to the refrigerant outlet 24 of one of the condensers 22a,, 22b, and a refrigerant outlet 34. The refrigerant outlet 34 of the accumulator 30a, shown in FIG. 1 is disposed in the region of a sump 36 of the accumulator 30a. A tubing 38 which connects the refrigerant outlet 34 of the accumulator 30a, to a conveying device 40 (see FIG. 2) for discharging refrigerant A from the accumulator 30a, extends from the sump 36 of the accumulator 30a, in the direction of a head 42 of the accumulator 30a. The accumulator 30b, shown in FIG. 2 may have the same design as the accumulator 30a, of FIG. 1.

(12) As shown in FIG. 2, a subcooler 44a,, 44b, is arranged at least partially within the interior of each of the accumulators 30a,, 30b. In the accumulator arrangement 10a of FIG. 1 a refrigerant inlet 46 of the subcooler 44a, is connected to the refrigerant outlet 34 of the accumulator 30a. In particular, the tubing 38 connecting the refrigerant outlet 34 of the accumulator 30a, to the conveying device 40 passes through the subcooler 44a, to a refrigerant outlet 48 of the subcooler 44a, which is disposed downstream of the head 42 of the accumulator 30a. Refrigerant A which is discharged from the sump 36 of the accumulator 30a, through the tubing 38 thus is subcooled upon flowing through the portion of the tubing 38 extending through the subcooler 44a. Thus, unintended evaporation of the refrigerant A and hence cavitation in the conveying device 40 which may, for example, be designed in the form of a pump is avoided.

(13) In the accumulator arrangement 10a, of FIG. 1 the subcooler 44a, comprises a heat-exchanger designed in the form of a double tube heat-exchanger. It is, however, also conceivable to employ a heat-exchanger in the form of a coil heat-exchanger extending around a circumferential wall of the tubing 38. The subcooler 44b, depicted in FIG. 2 may have the same design as the subcooler 44a, depicted in FIG. 1.

(14) The heat sinks 29a,, 29b, which serve to supply cooling energy to the condensers 22a, 22b, also serve to supply cooling energy to the subcoolers 44a,, 44b. In other words, the heat sink 29a, serves as a common heat sink for the condenser 22a, and the subcooler 44a,, while the heat sink 29b, serves as a common heat sink for the condenser 22b, and the subcooler 44b. Each of the heat sinks 29a,, 29b, supplies a refrigerant B, which may be a gaseous or liquid refrigerant or also a two-phase refrigerant, to the condensers 22a,, 22b, and the subcoolers 44a,, 44b. In the configuration of an accumulator arrangement 10a, according to FIG. 1 refrigerant B provided by the heat sink 29a,, after flowing through the subcooler 44a,, is guided to the condenser 22a, where it releases its residual cooling energy so as to cool and hence liquefy the gaseous refrigerant A supplied to the refrigerant inlet 24a, of the condenser 22a, from the evaporators 14a,, 14b. It is, however, also conceivable to supply the refrigerant B provided by the heat sink 29a, first to the condenser 22a, and only thereafter to the subcooler 44a, or to control the order in which the condenser 22a, and the subcooler 44a, are provided with refrigerant B from the heat sink 29a, in a variable manner as desired. The thermal coupling of the heat sink 29b,, the condenser 22b, and the subcooler 44b, may be designed as described above in connection with the heat sink 29a,, the condenser 22a, and the subcooler 44a.

(15) As shown in FIG. 2, the refrigerant A exiting the subcoolers 44a,, 44b,, by means of the conveying device 40, is supplied to the evaporators 14a,, 14b,, wherein a valve 50 controls the supply of refrigerant A from the subcoolers 44a,, 44b, to a refrigerant inlet 52 of the conveying device 40. A bypass line 54 branches off from the cooling circuit 12 downstream from a refrigerant outlet 56 of the conveying device 40 and opens into the accumulator 30b. A valve 58 disposed in the bypass line 54 is adapted to open the bypass line 54 if a pressure difference between the pressure of the refrigerant A in the cooling circuit 12 downstream of the refrigerant outlet 56 of the conveying device 40 and the pressure of the refrigerant A in the cooling circuit 12 upstream of the refrigerant inlet 52 of the conveying device 40 exceeds a predetermined level. In particular, the valve 58 opens the bypass line 54 if the evaporators 14a,, 14b, during operation consume less refrigerant A resulting in a pressure increase in the cooling circuit 12 downstream of the refrigerant outlet 56 of the conveying device 40. By draining refrigerant A from the cooling circuit 12 downstream of the refrigerant outlet 56 of the conveying device 40 into the accumulator 30b,, the conveying device 40 can be protected from excess pressure and the pressure within the cooling circuit 12 can be maintained within a certain range without it being necessary to adjust the operation of the conveying device 40.

(16) For controlling the start-up of the cooling system 100 there are different options. As a first option, upon start-up of the cooling system 100, all evaporators 14a,, 14b, are simultaneously supplied with cooling energy. Typically the cooling system 100 will be designed for this start-up mode of operation. It is, however, also conceivable to control the supply of cooling energy to the evaporators 14a,, 14b, upon start-up of the cooling system 100 such that at first only selected ones of the evaporators 14a,, 14b are supplied with cooling energy until a predetermined target temperature of the selected evaporators 14a,, 14b, supplied with cooling energy is reached, Only then also the remaining evaporators 14a,, 14b, may be supplied with cooling energy. In this start-up mode of operation the amount of heat to be discharged by means of the cooling system 100 is smaller than in a mode of operation wherein all evaporators 14a,, 14b, are simultaneously supplied with cooling energy. Hence, heat sinks 29a, 29b, designed in the form of chillers can be operated at lower temperatures allowing heat to be discharged from the cooling energy consumers rather quickly due to the large temperature difference between the operating temperature of the heat sinks 29a,, 29b, and the temperature of the cooling energy consumers.

(17) Finally, it is also conceivable to control the supply of cooling energy to the evaporators 14a,, 14b, upon start-up of the cooling system 100 such that at first all evaporators 14a,, 14b, are simultaneously supplied with cooling energy until a predetermined intermediate temperature of the evaporators 14a,, 14b, is reached. Immediately after start-up of the cooling system 100 the temperature difference between the operating temperature of heat sinks 29a,, 29b, designed in the form of chillers and the temperature of the cooling energy consumers still is high allowing a quick removal of heat from the cooling energy consumers. After reaching the predetermined intermediate temperature of the evaporators 14a,, 14b, the operating temperature of the heat sinks 29a,, 29b, may be reduced and further cooling energy may be supplied only to selected ones of the evaporators 14a,, 14b, until a predetermined target temperature of the selected evaporators 14a,, 14b, supplied with cooling energy is reached. Finally, the remaining evaporators 14a,, 14b, may be supplied with cooling energy until a predetermined target temperature is reached. also for these evaporators 14a,, 14b. Again a quick removal of heat from the cooling energy consumers may be achieved due to the large temperature difference between the operating temperature of the heat sinks 29a,, 29b, and the temperature of the cooling energy consumers.