US3427817A

US3427817A - Device for producing cold and/or liquefying gases

Info

Publication number: US3427817A
Application number: US511044A
Authority: US
Inventors: Johan Adriaan Rietdijk
Original assignee: US Philips Corp
Current assignee: Philips North America LLC; US Philips Corp
Priority date: 1964-12-19
Filing date: 1965-12-02
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18
Also published as: SE313065B; DK123889B; GB1131418A; DE1501101A1; NL147249B; AT271403B; ES320900A1; DE1501101C3; CH444893A; BE674004A; FR1462600A; DE1501101B2; NL6414856A

Description

Feb. 18, 1969 J. A. RIETDIJK 3,427,317

DEVICE FOR PRODUCING COLD AND/OR FOR LIQUEFYING GASES Filed Dec. 2, 1965 Sheet of 5 INVENTOR. JOHAN A. RIETD/JK Feb. 18, 1969 J. A. RIETDIJK DEVICE FOR PRODUCING COLD AND/OR FOR LIQUEFYING GASES Sheet FIG.2

: INVENTOR. JOHAN A. RIETDIJK AGEN Feb. 18, 1969 J. A. RIETDIJK 3,427,817

DEVICE FOR PRODUCING COL-D AND/OR FOR LIQUEFYING GASES Filed D80. 2, 1965 Sheet 3 0f 5 INVENTOR. JOHAN A. RIETDIJK BY 2240.2. z.l-

, AGENT Feb. 18, 1969 J. A. RIETDIJK DEVICE FOR PRODUCING COLD AND/OR FOR LIQUEFYING GASES Sheet Filed Dec. 2. 1965 INVENTOR. J0 HAN A- RIETDIJK AGEN Feb. 18, 1969 J. A. RIETDIJK 3,427,317

DEVICE FOR PRODUCING COLD AND/0R FOR LIQUEFYING GASES- Filed Dec. 2. 1965 Sheet 5 of 5 INVENTOR. JOHAN A. RIETDIJK AGENT United States Patent 6414856 US. Cl. 62-113 17 Claims Int. Cl. F25b 1/10, 41/00, 5/00 ABSTRACT OF THE DISCLOSURE A gas refrigerator having a high pressure medium supply and incorporating at least two devices for cooling and pressure reduction of said medium. One of the devices is an ejector which additionally pumps up part of the medium at the lowest pressure and temperature to said ejector to mix with the cooled and pressure-reduced medium.

The invention relates to a device for producing cold and/or for liquefying gases. This device comprises at least one high-pressure medium supply, which communicates with one or with a plurality of series-connected heat exchangers in which the high-pressure medium is cooled as far as below the inversion temperature associated with the pressure concerned. The device comprises furthermore at least one member in which the high-pressure medium cooled in the heat exchanger is subjected to reduction in pressure, while there are furthermore provided one or more containers in which the medium of reduced pressure can be brought into thermal contact with a place to be cooled or can be withdrawn from the device in the liquid state. The device comprises furthermore a duct system for conducting away the medium of reduced pressure, if desired through one or more of said heat exchangers.

In known devices of the kind according to the invention, Joule-Kelvin cocks are employed for attaining the desired reduction of pressure. The high-pressure medium is choked therein to a considerably lower pressure. With correctly chosen pressure and temperature the choking process brings about a decrease in temperature of the medium or a phase transition of part of the medium or both phneomena. The medium of reduced pressure can then be brought into thermal contact with an object to be cooled or a medium to be cooled. In the event of a phase transition part of the liquid obtained may, if desired, be conducted away from the device. The low-pressure vapour produced is then conducted away to the surroundings or back to a compressor which supplies the high-pressure medium. y

In order to attain very low temperatures, it is necessary to choke down to very low pressures. If, for example helium is' used as a medium, and if a temperature of 4.2 K. is wanted, it is necessary to choke down to about 1 atomsphere; 3.6 K. requires choking to about 0.5 atmosphere. Still lower temperatures require choking to even lower pressures. This means that in the case of a closed system the compressor must be very bulky, while the low-pressure side of the heat exchangers must have a low 3,427,817 Patented Feb. 18, 1969 flow resistance. Therefore, the known devices are complicated bulky and expensive. In the case of an open system, which means that the high-pressure medium is derived from some source whereas the medium of reduced pressure is conducted away to the surroundings subsequent to heat exchange with the object to be cooled, and if cold is to be supplied at temperatures associated with a subat-rnospheric pressure, the device cannot blow off automatically. Therefore, additional steps are required for conducting away the medium of reduced pressure from the device.

A further disadvantage of the known devices consists in that in the Joule-Kelvin cocks, the energy of the high-pressure medium is uselessly dissipated, which means losses.

The invention has for its object to obviate said disadvantages and is characterized in that in operation at least one of said containers has a pressure which is lower than the reduced pressure in another container which the medium is conducted away from the device, while the member in which the pressure is reduced comprises at least one ejector to which at least part of the cooledhigh-pressure medium can be supplied, the suction side of said ejector being in connection with outlet of said container of lower pressure, whereas the outlet of the reduced pressure container communicates with the duct system through which the medium of reduced pressure can be conducted away from the device.

An ejector is herein understood to mean a member in which the potential energy of a high-pressure (primary) medium is converted wholly or partly into kinetic energy, which is utilized at least partly for raising the pressure of a further (secondary) medium.

According to the invention the energy of the high-pressure medium supplied to the ejector is utilized at least partly for applying a partial vacuum to the vapour from the lower-pressure container and for bringing it to the pressure prevailing in the duct system through which the medium of reduced pressure is conducted away from the device. The cold can then be delivered at a pressure which is lower than the outlet pressure of the reduced pressure container. In the event of an open system this involves the advantage that blowing-off is performed automatically, while the cold is supplied at a pressure lower than the blowing-01f pressure.

If, according to a further aspect of the invention, there is provided a compressor, the outlet of which communicates with the high-pressure medium supply and the inlet of which communicates with the outlet for the medium of the reduced pressure container, the pressure ratio of the compressor may be considerably lower than in known devices of the kind set forth.

The difference between the known devices and the device according to the invention resides in that the pressure energy of the medium supplied to the ejector is not uselessly dissipated and is employed for pumping up the vapour from the lower-pressure container to the suction pressure of the compressor or to the pressure at which the medium leaves the device. In this way the resultant device has a higher efliciency and a much more favourable pressure ratio in the heat exchanger and the compressor. The device thus obtained is cheaper and has considerably smaller dimensions.

A further advantageous embodiment of the device according to the invention is characterized in that there are provided one or more parallel-connected ejectors, the inlet side(s) of which com-municates with the high-pressure part of the heat exchanger(s) and the outlet side(s) of which communicates with a collecting receptacle. The vapour space of each receptacle communicates with the outlet duct system for the reduced-pressure medium, and the device comprises a further container which communicates through a duct including a choke with the collecting receptacle, preferably with the liquid part of said container, the vapour space of said further container communicating with the suction side of said ejector(s). In this device the further container may have a lower pressure than the collecting receptacle, so that the cold is delivered at a lower temperature. The vapour is drawn out of the further container by the ejector and raised to the presence prevailing in the collecting receptacle.

A further advantageous embodiment of the device according to the invention is characterized in that it comprises two or more ejectors, the inlet side of each of which communicates with the high-pressure portion of the heat exchanger, and the outlet side of each ejector communicates with a reservoir. Said reservoirs have, in operation, progressively lower pressures and are connected in series with each other through ducts including chokes, the higher-pressure sides of said ducts preferably opening out in the liquid spaces of the relevant containers. The container of the lowest pressure communicates through a duct including a choke with a further container in which a still lower pressure prevails, while the vapour space of each container, with the exception of the vapour space of the container of the highest pressure, communicates with the suction side of an ejector, and the outlet side of each communicates with a container of higher pressure, while the vapour space of the container of the highest pressure joins the outlet duct system for the medium of reduced pressure. This embodiment consequently comprises a plurality of containers of different pressures so that it is possible to derive cold from this device at different temperatures.

In a further advantageous embodiment there are provided a number of series-connected ejectors. The inlet side of the first ejector joins the last heat exchanger, whereas the last ejector joins by its outlet side the collecting receptacle. The vapour space of the receptacle communicates with the outlet duct system for the reducedpressure medium. There is furthermore provided one or more additional containers communicating with each other through appropriate ducts including chokes, the first additional container communicating with the collecting receptacle, whereas the vapour space of each of the additional containers communicates with the suction side of one or more of the ejectors. In this way a number of containers have gradually lower pressures and hence also a gradually lower temperature. It is thus possible to derive cold from this device at different temperatures. It is furthermore possible to establish a thermal contact between, for example, a medium in order of succession with the medium in the various containers, so that said medium is cooled at different temperature levels.

In a further embodiment one or more chokes are connected in parallel with the ejectors, so that part of the medium emanating from the high-pressure portion of the heat exchanger(s) passes through said chokes and then into the collecting receptacle and/or one of the further containers.

A further advantageous embodiment of the device according to the invention is characterized in that it comprises only one container, which communicates through a choke with the high-pressure portion of the heatexchanger(s), the device comprising furthermore an ejector, the inlet side of which also joins the high-pressure portion of the heat-exchanger(s), whereas the outlet side of the ejector communicates with the outlet duct system for the reduced-pressure medium, the suction side of the ejector communicating with the vapour space of the container. A lower pressure prevails in the container than the pressure at which the medium is conducted away.

In a further advantageous embodiment of the device according to the invention each of the communicating ducts (between the suction side of each of the ejectors, and a vapour space of an additional container) includes one or more heat-exchangers in which the medium flowing to the suction side of the ejectors exchanges heat with the higher-pressure medium. The efiiciency of the device is thus improved.

A further advantageous embodiment of the device according to the invention includes a control-member which governs one or more of the chokes in the ducts between the liquid spaces of the respective containers in dependence upon the liquid level in said containers. The control-member may be formed by a float which determines the position of the choke concerned.

According to a further aspect one or more of the ejectors is controllable, so that the flow of high-pressure medium passing through said ejector(s) can be controlled. The device can thus be adapted to varying conditions.

A further advantageous embodiment of the device according to the invention, which is particularly suitable for producing cold at very low temperatures, is characterized in that it comprises a machine for producing cold at low temperatures, which comprises one or more compression spaces filled with a working medium and one or more expansion spaces of variable volume, said spaces communicating with each other and having, in operation, relatively different average temperatures, the communication between each of said spaces including one or more regenerators, while the high-pressure medium flowing towards the ejector(s) or the choke(s) is in thermal contact with the working medium in the expansion space(s).

In a further advantageous embodiment the machine for producing cold at low temperatures, if required, together with an additional compression member, serves at the same time as a compressor for the medium flowing to the ejector(s) or choke(s), said machine being provided with an outlet valve and an inlet valve, said valves communicating with the heat exchanger(s) through which the medium flows 'to the ejector(s) or the choke(s) and the duct system joining the collecting recipient.

It should be noted that for the construction, the control, etc., of the device according to the invention all techniques commonly used in compression refrigerators may be employed.

In this way an extremely advantageous construction of a device producing cold is obtained.

The invention will be explained more fully with reference to the drawing.

FIGS. 1a and 1b show two known devices for producing cold in diagrammatic views.

FIGS. 2 to 7 show diagrammatically a number of embodiments of devices for producing cold, each comprising one or more ejectors.

FIG. 8 shows diagrammatically a device for producing cold, which comprises apart from an ejector a cold-gas refrigerator for cooling the compressed working medium.

FIG. 9 shows diagrammatically a device for producing cold, which comprises an ejector and a cold-gas refrigerator serving as a compressor and as a cooling aggregate for the medium to be expanded.

FIG. 1a shows a known device for producing cold, comprising a compressor 1. The outlet 2 of the compressor communicates with the high-pressure portion 3 of a heat exchanger. The medium cooled in the heat-exchanger is choked in a choking cock 4, which joins a collecting receptacle 5. To the recipient 5 a quantity of heat can be supplied, for example by passing the medium to be cooled through a helix 6. Instead of a medium passed through the helix, an object to be cooled may be brought into thermal contact with the container 5 and the liquid contained therein. The vapour in the container 5 is passed through the low-pressure portion 7, of the heat exchanger to the inlet 8 of the compressor 1.

The temperature at which the cold is supplied (temperature of the liquid in the container 5) depends upon the pressure in said container. The lower the pressure, the lower is the temperature. If, for example, helium is the Working medium, a pressure of about 1 atmosphere in the container 5 will correspond to a temperature of 4.2" K. It is often desirable to attain lower temperatures. This may be achieved by choosing a lower pressure in the container 5. At a pressure of 0.5 atmosphere a temperature of 3.6 K. prevails, and so on. At these low pressures in the container 5 the gas flowing through the portion 7 of the heat-exchanger will have a particularly large volume, so that the heat-exchangers must have a large passage in order to ensure low flow resistance. Since a closed system is concerned here, the compressor must be very large owing to the high pressure ratio.

An improved known construction of the aforesaid device is shown in FIG. lb. The device comprises a compressor 1, the outlet 2 of which communicates with the high-pressure portion 3 of a heat-exchanger. The medium is chocked in the choking member 4. The choke medium is collected in a receptacle 9, in which an average pressure prevails. The vapour space of the receptacle 9 communicates through a portion 10 of the heatexchanger with the inlet 8 of the compressor 1. The receptacle 9 communicates through a duct 11 including a choking member 12 with a container 5 having lower pressure. In this container there is arranged a helix 6 to be cooled. The vapour space of container 5 communicates through the portion 7 of the heat exchanger with the surroundings. In this device choking is performed stepwise, which is conducive to the efficiency. Since the duct 7 opens out in the atmosphere, the pressure in the container 5 cannot be lower than the atmospheric pressure. The vapour formed in the container 5 is blown off and must be raised in pressure in some way or other. Particularly, if it is desired to produce cold at gradually lower temperatures, this involves a very complicated heat exchanger and a bulky compressor.

The devices according to the invention shown in the figures to be described hereinafter obviate the disadvantages of the known devices described above, while all advantages thereof are maintained.

FIG. 2 shows a device which comprises a compressor 1. The outlet 2 of this compressor communicates with the high-pressure portion 3 of a heat exchanger. The portion 3 joins the supply side of an ejector 21. The outlet 22 of the ejector 21 is connected with a collecting receptacle 23. The vapour space of the receptacle 23 communicates through the portion 7 of the heat exchanger with the inlet 8 of the compressor. The collecting receptacle 23 communicates through a duct 24 including a choke 25 with an additional container 26. The vapour space of the container 26 communicates through a duct 27 including

heat exchangers

110 and 111 with the suction side 28 of the ejector 21. The container 26 accommodates a helix 29, through which the medium to be cooled can be conducted. There is furthermore provided a control-member 30, which controls the choke 25 in dependence upon the liquid level in the

containers

23 and 26. If necessary, the ejector may be provided with a control-member 120. By varying the position of the member 120, the high-pressure medium flow passing through the ejectors can be adjusted.

This device operates as follows.

The compressor 1 compresses a medium, for example, helium to a pressure 12 This high-pressure medium is cooled in the heat exchanger 3 and then supplied to the ejector, in which it is subjected to a reduction of pressure, while the potential energy is partly converted into kinetic energy, which is partly employed for obtaining the pressure of the high-pressure medium. The medium leaving the ejector with a pressure p is collected in a receptacle 23. The vapour at a pressure p can then flow through a portion 7 of the heat-exchanger back to the compressor. The liquid obtained is choked in the choking member ,25 to a pressure 12 which is associated with the temperature at which cold has to be delivered. The vapour in the receptacle 26, having a pressure 12 is drawn by the ejector 21 and brought to the pressure p of the collecting receptacle 23. Before entering the ejector 21, the vapour of the container 26 exchanges in heat exchangers and 111 heat with a medium of higher pressure. In the ejector 21 the energy of the high-pressure medium (17 is partly used for applying a partial vacuum to the container 26 and pumping up the vapour therein to a pressure p The pressure p prevailing in the vessel 26, and corresponding to the desired low temperature, may be considerably lower than the pressure p in the receptacle 23. In this device the compressor is operative between the pressures p and 17 so that it may be structurally much more simple than in the known devices, in which the compressors operate between the pressures p and 17 FIG. 3 shows a modification of the device of FIG. 2.

This device comprises three series-connected

ejectors

31, 32 and 33. The supply side 34 of the ejector 31 communicates with the portion 3 of the heat exchanger. The

outlets

35, 37, and 39 of the

ejectors

31, 32 and 33 respectively communicate with the inlet sides 36, 38 of the

ejectors

32 and 33 respectively and with the collecting receptacle 40. The device comprises three

additional containers

41, 42 and 43, which communicate with each other through ducts including choking

members

44, 45 and 46 respectively. The vapour spaces of the

additional containers

41, 42 and 43 communicate through

ducts

49, 48, 47 respectively including

heat exchangers

112, 113, 114 and 115, 116, 117 respectively with the suction sides 50, 51 and 52 of the

ejectors

33, 32 and 31 respectively. The container 43 includes a helix 29, through which a medium to be cooled can be passed. If desired, the

containers

40, 41 and 42 may be provided with such helices, so that the device is capable of supplying cold at different temperatures. If desired, a medium to be cooled may be brought into thermal contact with the medium in the

containers

40, 41, 42 and 43. The high-pressure medium from the compressor 1 is subjected in the

ejectors

31, 32 and 33 stepwise to a reduction in pressure. After the ejectors the medium is collected in the container 40. The vapour can flow out of this container back to the compressor. The liquid from the container 40 is also subjected stepwise to a reduction in pressure, so that a progressively lower pressure prevails in the

container

41, 42 and 43. The low-pressure vapour from the

containers

41, 42 and 43 is drawn by the

ejectors

33, 32 and 31 respectively and brought to the pressure prevailing in the container 40. In this way an extremely simple structure is obtained for a device which is capable of supplying cold at diflerent temperatures. Although the drawing shows only three ejectors and three additional containers, it will be obvious that this number may be enlarged or diminished at will. Moreover, as is shown in FIG. 3a, a number of series-connected ejectors may be connected by their suction sides with one additional container.

Although, as shown in the drawing, the additional containers are connected in a given order of succession, with the respective suction sides of the ejectors, it will be obvious that this order may be changed, if desired, while the device is nevertheless capable of supplying cold.

FIG. 4 shows diagrammatically a device for producing cold, which comprises three

ejectors

121, 122 and 123. These ejectors communicate by their

inlet sides

124, 125 and 126 respectively, with the high-pressure portion 3 of the heat-exchanger. The ejector 121 communicates by its outlet 127 with a container 128, in which a pressure p prevails. The ejector 122 communicates by its outlet 129 with the container 130 having a pressure 11 The ejector 123 communicates by its outlet 131 with a container 132, in which a pressure p, prevails. The

containers

128, 130 and 132 communicate through ducts including choking

cocks

133 and 134 with each other and the container 132 communicates through a duct including a choking cock 135 with an additional container 136, in which a pressure 1 prevails. The vapour spaces of the

containers

136, 132 and 130 communicate with the suction sides 137, 138 and 139 respectively of the

ejectors

123, 122 and 121 respectively. The device comprises furthermore a number of heat-

exchangers

140, 141, 142 and 143, in which the various flows of medium exchange heat. The vapour space of the container 128 communicates with the low-pressure portion 7 of the heat-exchanger. In this device a number of containers is available, in which different pressures prevail, so that if desired the cold can be derived at different temperatures. The ejectors of this device receive the primary medium at the same pressure p FIG. 5 shows a device for producing cold, in which the compressed and cooled medium emanating from the high-pressure portion 3 of the heat-exchanger is split up in two portions. A suitably chosen portion is supplied to an ejector 60 and the other portion to a choking member 61. The outlets of the ejector and the choking member both open out in the container 62. The vapour space of this container 62 communicates with the inlet 8 of the compressor 1, while the container communicates furthermore through a choking member 63 with an additional container 64. The container 64 accommodates a heat-exchange helix 29. The vapour space of container 64 communicates with the suction side 65 of the ejector 60. This ejector draws the low-pressure vapour out of the container 64 and raises it to the pressure prevailing in the container 62. A control-member provides constant liquid levels in the

containers

62 and 64. In this case the pressure ratio between inlet and outlet of the ejector 60 and the choking member 61 is the same. However, the outlet of the choking cock may be connected with the container 64 of lower pressure. This alternative is illustrated in the drawing by broken lines.

FIG. 6 shows a device for producing cold in a diagrammatic view, in which only one container 70 is provided, in which the desired low pressure corresponding to the temperature of the cold supply prevails. The high-pressure portion 3 of the heat-exchanger communicates with a choking member 71, in which part of the compressed medium is choked. The device comprises furthermore an ejector 72, the inlet side 73 of which communicates with the high-pressure portion of the heat-exchanger. The suction side 74 of the ejector communicates with the vapour space of the container 70-. The outlet 75 of the ejector communicates with the portion 7 of the heat-exchanger. From the foregoing the operation method of this device will be obvious.

FIG. 7 shows a device corresponding with that of FIG. 6. The ejector 72 is arranged here in the heat-

exchanger

3, 7, which means that the vapour of the container 70 exchanges heat in the portion 7' with the medium flowing towards the choking cock 71, after which it is supplied to the suction side 74 of the ejector 72. The outlet 75 of the ejector 72 communicates with a second portion 7 of the heat-exchanger. The ejector 72 receives the primary medium from a place 76 of the portion 3 of the heat-exchanger.

FIG. 8 shows a device for producing cold at low temperatures, which comprises a cold-gas refrigerator 80 of the multi-space type. This refrigerator comprises a compression piston 81, which is adapted to move in a cylinder 82. The cold-gas refrigerator comprises furthermore a displacer piston, which consists of two

portions

83 and 84 of different diameters. The compression piston 81 and the displacer piston are movable with phase difference and they vary the volume of a compression space 85 and of the

expansion spaces

86 and 87. The compression space 85 and the expansion space 86 communicate with each other through a cooler 88, a regenerator 89 and a first freezer 90. The

expansion spaces

86 and 87 communicate with each other through a regenerator 91 and a second freezer 92. In operation the first freezer has a temperature of about 80 K. whereas the second freezer has a temperature of about 15 K.

A compressor 1 compresses a medium, for example, helium. The compressed medium first passes through a portion 3 of a heat-exchanger. Then the medium exchanges heat in a heat-exchanger 95 with the first freezer 90. It then flows through a portion 3" of a heat-exchanger and exchanges heat in the heat-exchanger 96 with the second freezer 92 and finally it passes through a further portion 3" of a heat-exchanger, after which the cooled medium is supplied to an ejector 21, the outlet of which communicates with a collecting receptacle 23. The receptacle communicates through a duct 24 including a choking member 25, controlled by a float 97, with a container 26. The vapour space of the container 26 communicates through the duct 27, including heat-exchangers, with the suction side of the ejector 21. The vapour space of the container 23 communicates through the heat-exchangers 7", 7" and 7 with the inlet 8 of the compressor 1. In this way an extremely efficient device for producing cold at low temperatures is obtained.

Finally, FIG. 9 shows a device for producing cold at low temperatures, in which the compressor 1 is replaced by a cold-gas refrigerator 100, having an outlet valve 101 and an inlet valve 102. The outlet valve 101 is constructed so that it opens when the pressure in the refrigerator attains a given value exceeding the minimum pressure. The refrigerator thus operates as a compressor and it is proportioned so that it supplies, in addition, a quantity of cold so that the medium emanating from the refrigerator is at a lower temperature than the incoming medium.

Although in the embodiments shown the device cools a medium or an object, it is possible to withdraw a given quantity of liquid from one of the containers. The liquid withdrawn from the device must of course be replenished in the form of a gas to the compressor.

The drawing shows the compressor diagrammatically as a one-stage member. It will be obvious that under certain conditions use will be made of a multi-stage compressor. It is furthermore possible to obtain the highpressure medium from a different source and to blow off the medium of reduced pressure.

As will be apparent from the foregoing the invention provides a surprisingly effective construction of a device for producing cold and/or for liquefying gases, in which a lower pressure ratio prevails in the compression member than in the known devices. The energy of the compressed medium is not dissipated uselessly, but it is used for raising the pressure of the vapour of a container, in which a lower pressure prevails and in which the medium is brought into thermal contact with a place to be cooled or is withdrawn in the liquid state from the device.

The device according to the invention is capable of producing cold at any desired temperature.

I claim:

1. A gas refrigerator [for use with a medium dischargeable at a first high pressure from a source, comprising:

(a) a first heat exchanger for receiving and cooling the high pressure medium to a first temperature below its inversion temperature and above its critical temperature;

(b) a first ejector having ('1) a first inlet for receiving from the heat exchanger at least some of the cooled medium in a gaseous state, which medium is expandable in the ejector to a second intermediate tempera- 9 ture and pressure below that in said heat exchanger, (2.) an outlet through which expanded medium is dischargeable, and (3) a suction inlet for pumping medium therein;

(c) a first container having an inlet for receiving said expanded medium, and first and second outlets,

(d) a choke means through which medium (from the first containers first outlet) is further expandable to a third pressure below that of the second pressure, and

(e) a second container having an inlet for receiving the further expanded medium, and an outlet through which medium in vapor state is pumped to the suction inlet of the ejector, medium in the second con tainer providing cold for cooling a substance brought into thermal contact therewith, and the second outlet of the first container being a dischange means for gaseous medium therein.

2. A gas refrigerator as claimed in claim 1 further comprising means in said ejector for adjustably controlling the fiow of high pressure medium passing through said ejector.

3. Apparatus as defined in claim 1 further comprising: (a) at least one additional container connected in series between said choke and second container for medium to flow progressively between them;

(b) at least one additional choke means connected after each additional container for expanding the medium entering said containers to progressively lower pres sures and temperatures;

(c) at least one additional ejector connected in parallel with the first ejector, each additional ejector having (1) its first inlet in communication with high pressure supply medium, (2) its outlet in communication with one of said containers, and (3) its suction inlet in communication with the outlet of a container discharging at a lower pressure than the outlet of said ejector.

4. Apparatus as defined in claim 1 further comprising:

(a) at least one additional container connected in series between said choke and second container for medium to flow progressively between them;

(b) at least one additional choke means connected after each additional container for expanding the medium entering said containers to progressively lower pressures and temperatures;

(c) at least one additional ejector connected in series with the first ejector, the ejectors operable at progressively descending pressures with the outlet of one ejector discharging into the inlet of the subse-, quent ejector, the containers (in ascending order of pressure) each discharging into a suction inlet of one of the ejectors (in descending order of pressure), the container at highest pressure discharging vapor to the high pressure medium source.

5. Apparatus as defined in claim 1 further comprising at least one additional ejector connected in series between said first ejector and said first container, and each ejector having its suction inlet in communication with the outlet of the second container.

6. Apparatus as defined in claim 1 further comprising a choke means connected in parallel with the ejector and discharging into the first container.

7. Apparatus as defined in claim 1 wherein at least some of the medium in each container is in liquid state and at progressively lower temperature, for providing refrigeration at different temperatures.

8. Apparatus as defined in claim 7 further comprising a control member responsive to the liquid levels in said containers for governing the choke between said containers.

9. Apparatus as defined in claim 1 further comprising an additional heat exchanger comprising first and second freezers of a Stirling cycle cold gas refrigerator through which the high pressure medium is flowed and progressively cooled before entering said first heat exchanger.

10. Apparatus as defined in claim 1 wherein said choke is combined with-a float valve for automatically controlling the flow of medium between said containers.

11. Apparatus as defined in claim 1 in combination with a cold gas refrigerator which is said source of cooled high pressure medium.

. 12. Apparatus as defined in claim 1 wherein cold from said medium discharged from the first container is transferred to medium flowing to said ejector in counterflow heat exchange. 1

13. Apparatus as defined in claim 1 further comprising a second heat exchanger wherein cold from the medium discharged from the second container is transferred to medium flowing to said choke.

14. A gas refrigerator for use with a high pressure medium dischargeable from a source which also includes an inlet, comprising:

(a) a heat exchanger for receiving and cooling the high pressure medium to a first temperature below its inversion temperature and above its critical temperature;

(b) a choke means through which medium, (from the heat exchanger) flows and is expanded to a pressure below that of the source;

(c) a container for receiving medium discharged from the choke and for providing cold for cooling an article brought into thermal contact therewith, and

(d) an ejector having its inlet in communication with high pressure medium from the heat exchanger, its suction inlet in communication with and for pumping medium from an outlet of the container, and its outlet in communication with the heat exchanger which is then communicated to an inlet of the medium source.

15. Apparatus as defined in claim 14 wherein the medium dischargeable from the ejector provides-cold for said heat exchanger and the medium flowable from the container to the ejectors suction inlet also provides cold for the heat exchanger.

16. A refrigerating method using a fluid medium having initial high pressure and temperature comprising the steps:

(a) cooling the medium in its gaseous state to a first temperature below its inversion temperature and above its critical temperature;

(b) expanding the cooled medium in an ejector to a second temperature and pressure below that in its initial state;

(0) collecting the cooled medium in a first container with vapor therefrom being dischargeable;

((1) further expanding at least some of the collected medium to a third temperature and pressure below that of the medium in the first container;

(e) collecting the further expanded medium in a second container and (f) pumping vapor of said further expanded medium to a suction inlet of said ejector by using the kinetic energy developed during said expansion in the ejector, whereby cold is provided in said first and second containers for refrigerating at progressively lower temperatures.

17. A refrigerating method using a fluid medium having initial high pressure and temperature, comprising the steps:

' (a) cooling the medium in its gaseous state to a first temperature below its inversion temperature and above its critical temperature;

(b) expanding some of the cooled medium in an ejector to a second temperature and pressure below that in its initial state;

(c) expanding the remainder of the cooled medium through a choke to a third temperature and pressure below that in its initial state;

1 1 1 2 (d) collecting in a container the medium expanded in References Cited the choke, some of the collected medium being in a UNITED STATES PATENTS liquefied state for refrigerating matter brought into 2,014,701 9 1 5 seligmann 62 500 XR thermal contact therewith, the remainder of the col- 2,146,797 2/1939 Dasher 62500 XR lected medium being vapor, 5 2,513,361 7/ 1950 Rausch 62-50O XR (e) drawing at least some of said vapor into the suctlon 1nlet of the e ector by the k1net1c energy developed during said expansion in said ejector, and MEYER PERLIN, Primary Examiner. (f) discharging the expanded medium from the ejector 10 u CL to a heat exchanger for said cooling step (a). 62117, 191, 500