US3138004A - Entropy balancing method of refrigeration and apparatus therefor - Google Patents

Description

June 23, 1964 w. E. GIFFORD 3,133,004

ENTROPY BALANCING METHOD OF REFRIGERATION AND APPARATUS THEREFOR Filed June 11, 1962 2 Sheets-Sheet 1 Fmsr VdLl/ME a 20 l I! a Till) L I7 61 5a 1 7 3g 0 .12 j '27 F a K 1 H a E FOMW VOL/ N1 June 23. 1964 w. E. GIFFORD 3,138,004

ENTROPY BALANCING METHOD OF REFRIGERATION AND APPARATUS THEREFOR Filed June 11, 1962 2 Sheets-Sheet 2 United States Patent 3,138,004 ENTROPY BALANCING METHOD OF REFRIGER- ATION AND APPARATUS THEREFOR William E. Gifford, 829 Ostrom Ave., Syracuse, N.Y. Filed June 11, 1962, Ser. No. 201,371 15 Claims. (Cl. 62-6) This invention relates to methods and apparatus for low temperature refrigeration, i.e., in the range of and below 32 Kelvin, and more particularly the invention is concerned with an entropy balancing method of achieving refrigeration in the tempertaure range indicated.

The term entropy balancing as hereinafter employed in the specification is intended to refer to a method of refrigeration characterized by a gas displacement cycle of operation in a system in which separated portions of a constant volume of working gas undergo temperature and entropy changes with the temperature and entropy changes of some portions of the gas differing from temperature and entropy changes experienced by other portions of the gas, and with all of the changes being controlled so as to occur in a balancing relationship with respect to one another. As a result of these changes there is induced a removal of heat at several locations in the system and addition of heat at certain other locations in the system.

The temperature range of 32 K. and below has recently become of great interest to workers in the field of research especially in connection with superconductivity, maser amplification, preparation of liquid hydrogen, operations dealing with cryopumping, and various other extremely low temperature processes. In this connection there is a very real need for improved refrigeration apparatus which can provide the indicated range of refrigeration with a minimum power requirement and with a very quick cool-down period.

A chief object of the present invention is to provide an improved method and apparatus for low temperature refrigeration in a range as low as from 12-32 K. Another object is to devise a novel method of cooling by means of balancing entropy changes occuring with respect to separated portions of a constant volume of a working gas. Still another object of the invention is to provide a method of entropy balancing refrigeration in which temperatures in the range of from 12 to 14 K. may be arrived at very quickly, and in which refrigeration is accomplished without large power consumption and with a high degree of eificiency.

A still further object of the inventionv is to provide a simplified low-cost and efficient refrigeration apparatus in which the use of gascompressors is eliminated.

I have discovered that the foregoing objectives may be realized in one practical way by combining a liquid nitrogen heat sink at 78 K. with means for containing and moving separated volumes of a gas such as helium in predetermined relationship to the nitrogen heat sink during a cycle of changing temperature pressure and entropy values. As the separated volumes of gas are displaced relative to the heat sink, a heat load is continuously created at the heat sink and dissipated by boiling off the liquid nitrogen and the latent heat of vaporization of liquid nitrogen is utilized to achieve an exceedingly quick cool-down in a highly simplified refrigeration apparatus and to maintain the temperature of the gas .at 78 K.

The method is based on an increase in entropy followed by a decrease in entropy in one portion of gas; and a decrease in entropy followed by an increase in entropy in another portion of gas. These changes are controlled so as to occur in special cyclic relationship to one another so that a net cooling effect is achieved at several desired points below the initial control temperature (78 K.) of the gas portions accompanied by heat generated in some portions of the original volume of gas.

. Patented June 23, 1964 The nature of the invention and its other objects and novel features are more fully disclosed in the following description of the invention.

In the accompanying drawings,

FIGURE 1 is a view partly in cross section illustrating diagrammatically a preferred form of apparatus for carrying out the method of the invention; and

FIGURE 2 is a view partly in cross section illustrating a modified form of the invention.

In carrying out one preferred form of the method of the invention, I may employ a constant volume of .gas such as helium confined in a specially constructed gas container body. The container body is combined with a liquid nitrogen bath, or heat sink, in such a way that a portion of the constant gas volume may undergo temperature and entropy changes, and another portion of the gas may undergo different temperature and entropy changes. These changes take place in a series of interconnected chambers occurring at different temperature stages.

Referring more in detail to the structure illustrated in FIGURE 1, numeral 2 denotes a sealed enclosure body which may be of cylindrical shape and which is provided with a top 4 solidly secured by fastenings as 3. At one side of the member 2 is a tubular outlet 6 which is connected to a vacuum pumping means of conventional nature for evacuating gases from the space 7 within the member 2.

Supported at the underside of the top 4, in spaced-relation to the member 2, is an inner enclosure body 8 which is designed to function as a radiation shield for excluding heat. The member 8 defines an inner space 10 which communicates with space 7 through a hooded passageway 12, and which is also adapted to be evacuated by the vacuum means noted above.

Transversely disposed in the inner enclosure body 3 is a partition 14 whose edges are sealably secured around the inner surface of the member 8. The partition 14, together with adjacent upper portions of the member 8, define a receptacle 16 in which is received a bath of a low temperature liquid, such as liquid nitrogen. The liquid nitrogen is maintained at a desired level by means of a feed member 18 passing through an inlet opening 20 in the top 4. This arrangement is designed to permit liquid nitrogen to be boiled off when heat is added to the bath N in sufiicient quantities and the vaporized nitrogen thus dissipated may be replaced through the member 18.

In accordance with the invention, I combine with the liquid nitrogen bath relatively high temperature gas chamber means at the upper side of the bath N, and relatively low temperature gas chamber means arranged at a lower side of the bath N, and interconnected with the said high temperature chamber means.

In the preferred form of the invention shown in FIG- URE l the relatively high temperature chamber means is comprised by a closed cylindrical casing 21 which may be suspended from the underside of the top 4 in a position such that a bottom part of the casing is immersed in the bath of liquid nitrogen as shown diagrammatically.

Sealably mounted in the cylindrical casing 21 is a displacer element 22 having a sealing member 24 and power-driven crank means 26 connected thereto through a sealed bearing member 27 for imparted reciprocal movement to the displacer. The displacer 22 is arranged to define upper and lower confined spaces within the cylindrical casing '21 into which a gas such as helium is supplied from a source 28. In the position of the displacer shown in FIGURE 1 there is indicated an upper confined space in which gas is contained and hereinafter referred to as a first volume. Also indicated is a lower confined space in which gas is contained and which is referred to as a second volume.

The helium gas in the first volume chamber may pass into the second volume chamber through a conduit 30 which includes a heater 32, a regenerator 34 and a heat exchanger 36 of which the latter member 36 is immersed in the nitrogen bath and is thus at the temperature of liquid nitrogen 78 Kelvin. Heat is added from the matrix material of the regenerator 34.

The relatively low temperature gas chamber means referred to above may be comprised in a preferred form by a pair of cylindrical casing members 38 and 40 which are suspended from the underside of a plate 42 which is also immersed in the bath of liquid nitrogen. A powerdriven crank mechanism 44 acts through a shaft 46 in a sealed bearing 48 to reciprocate a piston element 50 to which is solidly secured a displacer element 52 and a second displacer element 54. The two displacers, 52 and 54, define an upper confined space and two lower confined spaces as will be observed from an inspection of FIGURE 1. The upper confined space is in communication through a passageway 56 with the conduit 39 so that helium gas may be contained in the upper space and is hereinafter referred to as a third volume. The passageway 56 also communicates with a conduit 58 which is a continuation of conduit 30 and includes conduit branches 60 and 62 leading to the two lower confined spaces in the cylindrical casings 38 and 40 respectively. Helium gas may thus be conducted into these spaces to provide a fourth volume and fifth volume respectively. The conduit 58 also is provided with a heat exchanger 64, a regenerator 66, another heat exchanger 68, another regenerator 70 and a final heat exchanger 72. Heat is removed and stored in the matrix material of the regenerators.

The invention method for producing refrigeration using the apparatus of FIGURE 1 operates in four steps.

Step 1 .-Assuming that the displacer 22 is in its highest position and displacers 52 and 54 are in their lowest positions, the crank mechanism 26 is first actuated and moves the displacer 22 downwardly. This displaces gas from the second volume chamber through the heat exchanger 36, regenerator 34 and heater 32 into the first volume chamber. Heat is added to the gas from the matrix material of the regenerator. As this occurs the displaced gas is heated. Heating produces a rise in pressure throughout the entire closed system. Volumes of gas in the fourth and fifth volume chambers are very small at this time. The portion of gas moving from the second volume chamber to the first volume chamber undergoes an entropy increase.

Step 2.-The displacers 52 and 54 are then moved to a topmost position. This transfers gas from the third volume chamber to the fourth volume chamber and fifth volume chamber through the heat exchanger 64, regenerator 66, heat exchanger 68, conduit 60, regenerator 70, heat exchanger 72 and conduit 62. These portions of gas undergo an entropy decrease. Heat is removed and stored. It will be observed that continued motion of displacer 22 downwardly prevents the pressure from dropping in the system as the gas displaced by members 52 and 54 from the third volume chamber becomes cooled in the regenerators 66 and 78 to 35 K. and 14 K. respectively due to the expansion of gas from volume four.

Step 3.-The crank mechanism 26 begins to raise the displacer 22 which decreases the pressure in the system with displacers 52 and 54 remaining essentially stationary. Decrease in pressure is due to the fact that gas from volume one is displaced to volume two and is cooled, storing heat in the regenerator and replacing the heat earlier taken out of the regenerator. With decreasing pressure the gas portions in the fourth volume chamber and fifth volume chamber expand and produce cooling at the heat exchangers 68 and 72.

Step 4.Thereafter gas from the fourth volume chamber and fifth volume chamber is transferred to the third volume chamber by lowering displacers 52 and 54, and

in so doing heat stored in Step 2 is removed from the regenerator and put back in the gas. Pressure is prevented from rising by further upward motion of displacer 22. This completes the cycle and may be continuously repeated to produce temperatures of 35 K. at heat exchanger 68 and 14 K. at heat exchanger 72.

In FIGURE 2, I have illustrated a method of making liquid hydrogen with refrigerating means illustrated in FIGURE 1. As shown in FIGURE 2, a source of hydrogen is provided from a container and a fiow of hydrogen is conducted through a conduit 82a into the enclosure 2 and then into a counter flow heat exchanger 84 wherein the hydrogen is cooled to a temperature close to that of liquid nitrogen by heat interchanged with the nitrogen gas that is being boiled otf. Thereafter, the hydrogen gas is cooled to liquid nitrogen temperature in the heat exchanger coil 36. From the heat exchanger coil 86 the gas is conducted through another conduit 88, then to heat exchanger 90 where its temperature is cooled to about 40 K.

From heat exchanger 90 the gas is conducted through tube 92 to heat exchanger 34 where its temperature is further reduced to about 20 K. and is here liquified. The liquified product may then be drawn off through a conduit 96 in a suitable vacuum insulated transfE line.

The method of refrigerating described, based on entropy balancing, may also be employed for cooling a cold surface to be used in cryopumping. If a surface is cooled to a low enough temperature all gas which falls on it will adhere thereto and thus the surface is a pump for the gas. A temperature of 15 K. which is achievable with this invention, can pump air to very low pressures as the vapor pressure of air at 15 K. is 10 millimeters of mercury or less.

It will be evident from the foregoing description that I have disclosed a novel method of refrigeration based on a gas displacement cycle in which temperature and entropy changes are caused to take place in a balancing relationship whereby a very quick cool-down period is made possible and refrigeration in the range of 32 K. and below is realized efiiciently and with the use of only a relatively small number of operating parts.

While I have disclosed preferred embodiments of the invention, it is intended that changes and modifications may be resorted to within the scope of the appended claims.

I claim:

1. Method of entropy balancing refrigeration which comprises (a) containing a constant volume of gas in a closed container body which is supported in a bath of liquid nitrogen and which body includes relatively high temperature chamber means occurring at one side of the bath of liquid nitrogen and relatively low temperature chamber means arranged at an opposite side of the liquid nitrogen bath and interconnected with the said relatively high temperature chamber means,

(b) displacing a portion of said constant volume of gas into the relatively high temperature chamber means and causing an increase in pressure in the constant gas volume system,

(c) displacing another portion of gas maintained at the said increased pressure, into the said low temperature chamber means,

(d) then decreasing pressure and causing the gas portion in the said low temperature chamber means to expand and produce cooling.

2. A method according to claim 1 in which the constant volume of gas consists of helium.

3. A method according to claim 1 in which the liquid nitrogen is replaced by liquid hydrogen.

4. A method according to claim 1 in which the liquid nitrogen is replaced by liquid oxygen.

5. A method according to claim 1 in which the volumes of gas are displaced along heat regenerative paths where by heat is added to the gas during its travel along the heat regenerative paths in some directions and whereby heat is released from the gas during its travel along the said heat regenerative paths in certain other directions.

6. A method of refrigeration which comprises containing a constant volume of gas in a closed container body which is divided into a plurality of enclosed spaces some of which are maintained at the temperature of 78 K., displacing a portion of the gas from one of the said relatively cold chambers to another relatively hotter chamber to increase pressure through the constant volume of gas, displacing another portion of said gas to a relatively colder enclosed space with maintenance of said increased pressure, then decreasing pressure by movement of said first displaced portion of gas and causing the said second displaced volume of gas to expand and produce cooling whereby the different portions of gas are largely heated or cooled by removal or addition of heat from matrices in transit between the said spaces at different temperatures.

7. A method of refrigeration which comprises containing a constant volume of gas in a confined space which is divided into a plurality of chambers, at least two of which chambers are maintained at a temperature of 78 K. in a bath of liquid nitrogen and which chambers are interconnected through heat exchangers and regenerators to provide for pressure being substantially the same in all of the chambers,

(a) displacing a portion of the gas into a relatively hot first chamber from a relatively cold second chamber in the said nitrogen bath whereby the displaced gas portion is regeneratively heated and the gas system undergoes an increase in pressure,

(b) then displacing another portion of the constant volume of gas at the said increased pressure from a relatively cold third chamber in the nitrogen bath into relatively colder fourth and fifth chambers and regeneratively removing heat from said last displaced portion of gas,

() thereafter moving gas from the said first hotter chamber to the said second chamber in the nitrogen bath while releasing regenerative heat thereby to decrease the pressure throughout the constant volume of gas in the system and to cause the gas portions in the said fourth and fifth chambers to expand and produce useful refrigeration,

(d) and then returning expanded gas in the said fourth and fifth chambers to the said third chamber in the nitrogen bath and regeneratively heating the expanded gas.

8. A method according to claim 7 in which a heat load is periodically delivered from gas portions in the said second chamber and said third chamber to the nitrogen bath in which each of these chamber sections is immersed whereby nitrogen is caused to vaporize and the latent heat of vaporization is drawn from the heat load.

9. A refrigeration apparatus which comprises the following components (a) a gas container body having a constant volume of gas contained therewithin, a first cylinder mounted in the container, a movable displacer in said cylinder defining a pair of variable chambers therein, a second cylinder, a displacer in said second cylinder defining a pair of variable chambers, conduit means connecting the pairs of chamber in each cylinder (b) container means for supporting a body of liquid nitrogen around the bottom of one displacer unit and around the top of the other displacer unit,

(0) means for reciprocately moving the first and second displacer units in timed relation with one another thereby to cause the said constant volume of gas in the containers to be moved from one end of the respective cylinders to the other, and

(d) said conduit means including a plurality of regenerators and heat exchangers so that gas can flow from volumes at either end of any cylinder to volumes at either end of the other cylinders.

10. A refrigeration apparatus comprising an enclosure body formed with a plurality of interconnected chamber sections having a susbtantially constant volume of gas contained therewithin, a liquid nitrogen bath surrounding a part of said enclosure body, vacuum pump means for maintaining a vacuum in the enclosure body at one side of the liquid nitrogen bath means for supplying heat to an enclosure body chamber located at an opposite side of the liquid nitrogen bath, upper and lower displacer units mounted for reciprocal movement in the enclosure body at points above and below the liquid nitrogen bath and conduit means arranged between the various chamber sections and having included therein heat exchanger element that exchange elements and regenerator devices.

11. An apparatus according to claim 10, including a source of hydrogen gas and means for conducting the hydrogen into the enclosure body and causing it to liquify.

12. An apparatus according to claim 10, including means for conducting a flow of hydrogen gas along a counter flow path within the enclosure body whereby nitrogen cooling of the hydrogen is accomplished and means for conducting the cooled hydrogen through the said regenerator and heat exchanger bodies to produce liquid hydrogen.

13. A refrigeration apparatus comprising a first enclosure casing for containing a substantially constant volume of gas therein, a displacer member mounted for movement in said enclosure body and defining a plurality of chambers of variable volume in accordance with the movement of said displacer member, a conduit connecting said chambers and including a heater, a heat exchanger means and regenerator means, means for cooling the heat exchanger, a second constant volume enclosure casing having a movable displacer means therein defining a pair of variable volume chambers, a conduit connectingsaid chambers and including a heat exchanger, means for supplying a liquid nitrogen bath to portions of the constant gas volume in said first enclosure casing to provide temperature and entropy changes, additional means for subjecting other portions of the constant gas volume in said second enclosures to different temperature and entropy charges, and means for positively operating said displacer members for varying the volume in said chambers by movement of the gas through said conduits.

14. The substance of claim 13, characterized in that a conduit connection is provided between one chamber of the first enclosure casing and one chamber of the second disclosure casing.

15. The structure of claim 13, characterized in that means are provided for supplying gas to all variable chambers from a common source.

Kohler Oct. 6, 1959 Gifford Dec. 27, 1960

Claims (1)

1. METHOD OF ENTROPY BALANCING REFRIGERATION WHICH COMPRISES (A) CONTAINING A CONSTANT VOLUME OF GAS IN A CLOSED CONTAINER BODY WHICH IS SUPPORTED IN A BATH OF LIQUID NITROGEN AND WHICH BODY INCLUDES RELATIVELY HIGH TEMPERATURE CHAMBER MEANS OCCURRING AT ONE SIDE OF THE BATH OF LIQUID NITROGEN AND RELATIVELY LOW TEMPERATURE CHAMBER MEANS ARRANGED AT AN OPPOSITE SIDE OF THE LIQUID NITROGEN BATH AND INTERCONNECTED WITH THE SAID RELATIVELY HIGH TEMPERATURE CHAMBER MEANS, (B) DISPLACING A PORTION OF SAID CONSTANT VOLUME OF GAS INTO THE RELATIVELY HIGH TEMPERATURE CHAMBER MEANS AND CAUSING AN INCREASE IN PRESSURE IN THE CONSTANT GAS VOLUME SYSTEM, (C) DISPLACING ANOTHER PORTION OF GAS MAINTAINED AT THE SAID INCREASED PRESSURE, INTO THE SAID LOW TEMPERATURE CHAMBER MEANS, (D) THEN DECREASING PRESSURE AND CAUSING THE GAS PORTION IN SAID LOW TEMPERATURE CHAMBER MEANS TO EXPAND AND PRODUCE COOLING.

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