US2559095A - Refrigeration system - Google Patents

Description

ET'AL 2,559,095

July 3, 1951 F. K. STORM, JR.,

REFRIGERATION SYSTEM Filed Feb. 24, 1947 Patented July 3, 1951 REFRIGERATION SYSTEM Frederick K. Storm, Jr., Los Angeles, and Eldridge H. Smiley, Hermosa Beach, Calif., assignors to C. Van King, West Los Angeles, Calif.

Application February 24, 1947 Serial N o. 730,264

3 Claims. 1

Our invention relates to refrigeration systems and more particularly to systems having no mechanical pumps and actuated solely by heat absorption by a precooled mass.

One of the perplexing problems in the shipment of perishable food, for example, is cooling en route to prevent spoilage. Two methods are used at present. First, heat absorption by mechanical refrigeration can be utilized Which, however, requires a source of positive energy; and second, the direct use of the heat absorbing power of a precooled mass such as, for example, an ice and salt mixture or, for lower temperatures, a mass of solid carbon dioxide, known as Dry Ice. Both of these methods have definite disadvantages. Y

In shipment by rail, for example, in special cars or reefers, the first method mentioned above has not been found practical because of the number of such cars in use and the requirement for a constant source of power. The average refrigerator car on a ooast-to-coast journey may be stationary about half the time during the trip so that the axle-driven generators, for example, will not deliver energy in a satisfactory manner to run refrigeration systems. Car strings are often broken up, and cars are shifted from train to train so that a central power system has not found favor. In consequence, the

second method is more commonly used, with refrigerator cars carrying perishables being cooled by air circulating by thermosiphon action only over ice and salt masses in bunkers. Forced circulation is much better but that again requires a power source, or if blowers driven from the car axle are used, circulation ceases when the car stops. 1

For frozen foods, air temperatures produced by ice and salt are usually not sufliciently low, and solid carbon dioxide has sometimes been used directly in an attempt to keep such cars at zero degrees F. However, difficulties have arisen because of the too low base temperature of the Dry Ice, and vapor circulation problems. Also,

inmany cases it may be objectionable to circulate the CO2 vapor directly over the food.

The main object of the present invention is to provide a simple means and method of circulating a refrigerant through a space to be cooled, this circulation being preferably accomplished by a lnon-mechanical pump actuated by internal pressures developed by the absorbed heat, this heat then being taken up by a mass of material at a lower temperature than that obtained in the cooled space, without necessity of drawing (Cl. (i2-91.5)

on an outside power source. Thus, for example, refrigerator cars or the like can be continuously cooled whether travelling or standing still.

Other objects and/advantages of our invention can be more readily understood by reference to the figure which shows diagrammatically one preferred embodiment of our invention.

The method of the present invention will be described as applied to a system adapted for cooling a space such as the interior of a refrigerator car used for the transportation of frozen foods. As it is desirable that frozen foods be held at zero degrees F., the system for this purpose utilizes solid carbon dioxide, Dry Ice, as a source of negative heat, with Freon 12 used as the refrigerant.

The temperature level of Dry Ice is between 109 and 156 F. when at atmospheric pressure in its own vapor. Freon 12 (dichlorodiiiuoromethane-CCl2F2) has a vapor pressure of about 110 p. s. i. at 80 F. and about 12 p. s. i, at 0 F.

Referring to the diagram, a bunker I is provided to hold Dry Ice 2 in block form. Preferably, the bunker is provided with insulating walls 3v and an upper loading door 4. A gas release vent 5 is installed to maintain the bunker substantially at atmospheric pressure.

Gn an offset shoulder G inside the bunker l is positioned an economizer tank l connected to a liquid refrigerant storage tank 8 by pipe 9. Thus, both of these latter tanks 'I and 8 are cooled by CO2 vapor escaping through vent 5, The Frech 12 for the system is initially placed in storage tank 8, which should be large enough to hold all of the refrigerant when liquid.

From the bottom of storage tank 8 a refrigerant pipe Hl passes through a wall 6 of bunker I to enter a space II to be cooled, this latter space also being provided with heat insulating walls I2. Refrigerant pipe l0 is directed downwardly through an evaporator check valve I4 to enter the bottom of evaporator I5 which is of sufcient area and of proper shape to absorb heat from the space II to cool it to zero degrees F. in this case or any other desired temperature within the range of the system. Generally used temperatures are 0 to 5 for frozen lfoods, and 35 to 40 for perishables such as vegetables.

After evaporation by the absorbed hea-t, Freon vapor from the top of evaporator I5 is led downwardly by evaporator pipe I6 through thermostat valve I'I to the bottom of the space II, to enter thev top of a smaller valve tank I9. This tank should be as small as possible, within the limit of pipe accommodation. Close to this latter tank and somewhat above it is a larger valve tank 20. The tops of these latter tanks are connected to equalize the pressure therein by equalizing pipe 2|. These two valve tanks are also connected by siphon pipe 22 leading from close to the bottom of smaller valve tank I9 to enter large valve tank below the top thereof and then terminating adjacent the bottom of this larger tank.

The two valve tanks are again interconnected by a valve pipe 24 terminating near the bottom of each tank and extending outside both tanks. The valve pipe 24 is connected by a discharge pipe 25 to storage tank 8 discharging near the top thereof. Tanks I9 and 20 and pipes 2|, 22, and 24 form a gas pressure operated, intermittent cycling valve whose action will later be described.

Larger Valve tank 20 is fed with Freon by gravity through a condenser discharge pipe 26 having a condenser check valve 21 therein and passing through the bottom of the bunker I to enter a condenser 29-positioned on the oor thereof. The economizer tank I is connected with the condenser 29 by a vapor line 30.

In operation, bunker I is filled with Dry Ice. In case of a railroad car, about two tons are loaded, lasting for about 240 to 300 hours with a normal complement of frozen food in space II. Usually the car is about two-thirds full.

Starting with storagetank 8, the Freon flows by gravity through check valve I4 into the bottom of the evaporator I5. Here heat is absorbed to 4cool space II and its contents to about zero degrees F. or other desired temperature. During this cooling the refrigerant boils, producing vapor at about 12 p. s. i. This vapor passes from the top of the evaporator I5 through thermostatic valve II and then moves downwardly through pipe I6 to enter smaller valve tank I9, by virtue of the pressure developed by the difference in liquid levels in tank 8 and evaporator I5. Without liquid in small valve tank I9, the vapor then passes upwardly through pipes 24 and 25 to the top of storage tank 8, then to economizer 'I- for precooling by escaping gas, and then into condenser 29 through vapor pipe 39. Here the refrigerant vapor is condensed by the low temperature of the Dry Ice, the liquid passing through condenser discharge pipe 26 and check valve 2'I to enter larger valve tank 20 which gradually fills with liquid. As soon as the liquid level tops siphon pipe 22, siphoning starts, and liquid flows into small valve tank I9 to cover the bottom of valve pipe 24 which then has both ends covered. This action equalizes the liquid level in both tanks I9 and 20 and isolates the evaporator I5 from the storage tank 8 and the condenser 29 by a liquid refrigerant seal in both large and small valve tanks I9 and 20. When this happens, the pressure in the evaporator builds up, as liquid refrigerant remaining in the evaporator keeps onboiling by absorbing heat from the space II. At. the same time, the pressure in storage tank 8 is being reduced due to continued condensation of vapor remaining in tank 8. The first effect of the increase in evaporator pressure and the decrease in tank 8 pressure is the closure of check Valves I4 and 21, thus leaving no path open for the liquid refrigerant in small valve tank I9 and large valve tank 20 except that path between the tanks I9, 20 and storage tank 8 through pipe 24 and discharge pipe 25. As the differential pressure between the evaporator I5 and storage tank 8 increases, the liquid in the tanks I9 and 20 is CII forced upwardly through pipe 24 and discharge pipe 25 into storage tank 8.

No boiling of the refrigerant takes place in either valve tank I9 or 2D, or during the passage of the refrigerant from the tanks I9 and 20 to the storage tank 8, as the liquid refrigerant received in the Valve tanks 20 and I9 from the condenser is supercooled. When the liquid refrigerant in tanks I9 and 20 has been sufficiently removed to uncover the lower ends of pipe 24, vapor from the evaporator can again pass through small valve tank I9, pipe 24, pipe 25, storage tank 8, and economizer 'I to the condenser, the pressure is substantially equalized, and the check valves open. As the end of pipe 24 in tank 20 will be quickly closed by condensate entering valve tank 26, the vapor path is through the end of pipe 24 in small valve tank I9 and discharge pipe 25.

The vapor phase continues until large valve tank 2U fills with condensed refrigerant to the point where the refrigerant therein siphons over into small valve tank I9 to cause the lift cycle to be repeated. In the meantime, the liquid refrigerant lifted into storage tank 8 is flowing'by gravity into the evaporator and is being boiled therein to cool space II. The hydrostatic head between storage tank 8 and the evaporator I5 need not be great, as the top of tankv 8 and the: top of the evaporator are connected during vaporA flow and only a small differential pressure is required to maintain the vapor flow. Thus, vapor and liquid are alternately passed into storage tank 8, the vapor for condensation, the liquid for storage and evaporation. When the proper tem. perature has been reached in space II, the thermostatic valve I'I closes, pressure. builds up in evaporator I5, and evaporation ceases to stop system operation.

Thus, we are able to cool space II by theyrefrigerant at its higher temperature level without' thev use of mechanical parts, utilizing only the energy stored in the Dry Ice. In this way the,` system operates irrespective of whether or not the car is moving and without application of any energy other than that of the Dry Ice. The-space to be cooled is kept at the ideal temperature for' the frozen food therein in spite of the fact that the Dry Ice temperature is far lower than that required for this purpose. Except for normal evaporation caused by heat input through the bunker walls, the heat from space II is absorbed by the Dry Ice only as desired and the system is highly economical. Bunker I can be placed wholly or partly within space I I and thus drain heat therefrom instead of from outside; 'Ihe system also operates at relatively low internal pressures resulting in a relatively low cost for the system. Many other advantages will be apparent to those skilled in the art.

Several points should be noted. One of the problems of a non-mechanical system as shown herein is the problem of starting. In the present system, with all portions of the car and bunker at substantially the same temperature as for eX- ample 60-'70 F. Substantially all of the refrigerant remaining in liquid phase will beat the bottom of the system. Then, when the Dry Ice is loaded into the bunker, sufcient refrigerant vapor is held within the bunker space in tank i),v economizer 'I and the condenser 2'I, to be con-Y densed to produce the differential pressure necessary to set the system into operation and raise liquid into tank 8. At below zero car and bunker temperatures, most of the refrigerant will be in liquid phase in storageA tank 8 and therefore in; condition to run into evaporator I5 as soon as the car has heated to the point where thermostatic valve I1 opens. Thus the system will start automatically, irrespective of car and bunker temperature obtaining when the bunker is lled with Dry Ice.

It should also be noted that the system just described may be adjusted to maintain space Il at temperatures higher than zero degrees F. This is readily done by adjusting thermostat Il, andthe system will function at higher pressures throughout, but the differential pressure required for the liquid lift Will still be present.

While we have described our invention as applied for the purpose of cooling a space by the use of Dry Ice, other primary cooling masses and other refrigerants can be utilized. For example, a mixture of ice and salt in bunker l will cool condenser 29 to about 0 to 6 F. A refrigerant such as methylene chloride will be condensed at that temperature and will provide the necessary differential lifting pressure. This latter type of system is ideal for cooling fruits and vegetables While being transported to market as by rail or truck Where only ice is available. Thus we do not desire to be limited by specific choice of either the primary coolant, the refrigerant, or the construction of the system shown, as various modifications can be combined as desired to obtain heat absorption at a desired upper temperature level, and condensation at the lower temperature level as set by the primary coolant.

Furthermore, while We prefer to use the siphon cycling valve described, other valve arrangements have proved satisfactory, such as, for example, a float actuated valve operating to place the diiferential pressure on the liquid in tank 20 as it is filled from condenser 2l so that the liquid will be forced upwardly into tank 8.

We claim:

l. A refrigerating system operated solely by the negative heat of a mass of material capable of maintaining itself for a period at a predetermined low temperature comprising a storage tank for a volatile refrigerant condensible at said temperature, an evaporator connected to receive liquid refrigerant from said storage tank by gravity, a check valve in said connection, a rst vapor line connected to the top of said evaporator, a small valve tank, a large valve tank positioned higher than said small valve tank, a pressure equalizing connection between said valve tanks, said pressure equalizing connection being connected to said vapor line, a liquid siphon connection between said valve tanks, a second vapor line terminating adjacent the bottoms of both of said valve tanks connected together and to the top of said storage tank to form an intermittent Siphon cycling valve delivering liquid in said valve tanks to said storage tank by gas pressure, a condenser receiving vapor from said storage tank, a line delivering condensate to said larger valve tank by gravity, and a check valve in said line, said condenser being cooled by said mass.

2. A refrigerating system operated solely by the negative heat of a mass of material capable of maintaining itself for a period at a predetermined low temperature comprising a storage tank for a volatile refrigerant condensible at said temperature, an evaporator connected to receive liquid refrigerant from said storage tank by gravity, a check valve in said connection, a rst vapor line connected to the top of said evaporator, a thermostatic liquid valve in said vapor line, a small valve tank, a large valve tank positioned higher than said small valve tank, a pressure equalizing connection between said valve tanks, said pressure equalizing connection being connected to said vapor line, a liquid Siphon connection between said valve tanks, a second vapor line terminating adjacent the bottoms of both of said valve tanks connected together and to the top of said storage tank to form an intermittent sip'hon cycling valve delivering liquid in said valve tanks to said storage tank by gas pressure, a condenser receiving vapor from said storage tank, a line delivering condensate to said larger valve tank by gravity, and a check valve in said line, said condenser being cooled by said mass.

3. A space cooling refrigerating system operated solely by the negative heat of a mass of material capable of maintaining itself for a period at a predetermined low temperature comprising a container for said mass, a storage tank for a volatile refrigerant condensible at said temperature positioned within said container, an evaporator connected to receive liquid refrigerant from said storage tank by gravity positioned in said space, a check valve in said connection, a first vapor line connected to the top of said evaporator, a thermostatic liquid valve in said vapor line, a small valve tank, a, large valve tank positioned higher than said small valve tank, a pressure equalizing connection between said Valve tanks, said pressure equalizing connection being connected to said vapor line, a liquid siphon connection between said valve tanks, a Second vapor line terminating adjacent the bottoms of both of said valve tanks connected together and to the top of said storage tank to form an intermittent Siphon cycling valve delivering liquid in said valve tanks to said storage tank by gas pressure, a condenser receiving vapor from said storage tank and positioned at the bottom of said container, a line delivering condensate to said larger valve tank by gravity, and a check valve in said line.

FREDERICK K. STORM, JR. ELDRIDGE H. SMILEY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,195,293 Andersson Mar. 26, 1940 2,210,511 Taylor Aug. 6, 1940 2,226,797 Andersson Dec. 3l, 1940 2,285,131 Ullstrand June 2, 1942 2,354,496 Brizzolara July 25, l1944

Images