US2452594A - Method of refrigeration employing dry ice - Google Patents

Description

NQV. 2, 194% N. MORRIS METHOD OF REFRIGERATION EMPLOYING DRY ICE 2 Sheets-Sheet 1' Filed May 5, 1944 INVENTOR.

Xlavvv 9160M Nov. 2, 194-8.

Filed May 5, 1944 N. MORRIS 2,452,594 v METHOD OF REFRIGERATION EMPLOYING. DRY ICE 2 Sheets-Sheet 2 m m g mwsNmR. 92501.1 6% Swap/mic 7 BY Patented Nov. 2, 1943,

METHOD OF REFRIGERATION EMPLOYING nay ICE Nathan Morris, Silver Spring, Md., assignor, by mesne assignments, to American Instrument 00., Inc., a corporation of Maryland Application May 5, 1944, Serial No. 534,314

8 Claims.

My invention relates broadly to refrigeration and more particularly to a method of producing controlled sub-zero temperatures.

One of the objects of my invention is to provide a method for producing controlled temperatures of the order of 130 below zero and lower.

Another object of my invention is to provide a method of producing controlled temperatures from solid refrigerants considerably below the.

lowest temperature limit of the solid refrigerants.

Still. another object of my invention is to provide a method of producing temperatures considerably below the lowest temperature limit of solid refrigerants employed in the refrigeration system.

A further object of my invention is to provide a method of dehumidifying air, precooling the air and scrubbing the surface of a solid refrigerant with the precocled dehydrated air for continuously removing surface gases which normally enclose the solid refrigerant for producing extremely low temperatures.

A still further object of my invention is to provide a method of refrigeration utilizing Dry Ice in which the surface of the Dry Ice which is normally surrounded by an insulating blanket of CO2 gas is continuously scrubbed by a dehydrated medium at such velocity that the insulating effects of the CO2 gas are continuously removed for producing an extremely low temperature.

Other and further objects of my invention reside in a novel method of refrigerationfor producing sub-zero temperatures from Dry Ice as set forth more fully in the specification hereinafter following by reference to the accompanying drawings. in which:

Figure 1 schematically illustrates one form of apparatus for carrying out the method of my invention; Fig. 2 is a fragmentary view ,of the method of directing dehydrated air against the solid C02 in the temperature controlled cabinet;

and Fig. 3 represents a typical control circuit for the apparatus used in carrying out the method of my invention.

The lowest maximum temperature of Dry Ice, a solid refrigerant, is approximately 109 F. below zero. When Dry Ice is used as a refrigerant with ordinary methods of control it is impracticable to obta n accurate control of temperatures below -90 F. I have utilized Dry Ice 'as a refrigerant in chilling and heat treating systems in temperature control cabinets of the type set forth in my copending application Serial No.

2 rial testing for determining durability, performance, etc., at low temperatures; the conditioning of metals including the chilling of aluminum rivets to retard age hardening and to keep them soft enough for driving; in the storing of serums, blood chemicals, etc.; in the treating of tool and other steels to produce desired characteristics otherwise difllcult to obtain by ordinary methods of treatment for accelerating the ageing of metals; in food freezing and in many other commercial applications. In the course of my development I have discovered that extremely low sub-zero temperatures can be produced well below the maximum lowest temperature generally attributed to Dry Ice by utilizing the Dry Ice in special manner. I employ a refrigeration cabinet structure of the kind set forth in my copending application Serial No. 532,807, supra, which is'provided with all of the controls explained therein which will normally control temperatures to approximately F. below zero. In addition to the normal controls I employ, I provide means auxiliary to the temperature controlled cabinet for dehydrating air for removing substantially all moisture from the air; precooling the dehydrated air for lowering the air temperature before it enters the temperature controlled cabinet; and distributing the dehydrated precooled air at a predetermined velocity over Dry Ice within the temperature controlled cabinet for scrubbing the surface of .the solid carbon dioxide or Dry Ice with dry air that removes the surface of gas that normally tends to collect about the solid Dry Ice thereby causing the Dry Ice to produce lower temperatures. The CO: gas that collects around the solid carbon dioxide or Dry Ice and surrounds the Dry Ice in all directions constitutes an insulating blanket or envelope that limits the effective temperature of the.

snow rapidly deposits upon the Dry Ice servingv as an effective insulator against the production of any temperatures in surrounding media lower than the lowest temperature limit'of the Dry Ice. Referring to the drawings in more detail, reference character I designates'a blower which collects and directs air to thedehydrator and precooler represented at 2. The blower is driven by motor 3 which may be connected 'to any suitable source of power such as 110 volt 60 cycle alternating current. The air delivered by blower I is forced throfigh pipe 4 into the precooler 2. For purposes of explaining the method of carrying out my invention all of this equipment is illustrated schematically and it will be understood that I am not limited tolthe particular equipment shown or arrangement of equipment shown and that the apparatus shown is to be considered in the illustrative sense and not in the limiting sense. As illustrated, the precooler comprises a cylindrical member Scontaining a multiplicity of spaced parallel plates which alternate in their efiective area so that plate 8 directs the air around the peripheraledges thereof as represented at to. The next succeeding plates repeat the arrangement heretofore explained, thereby providing a serpentine path for the air through the cylinder 5. The outlet for cylinder 5 is represented by pipe 8 connected to parts of the cylinder 5, lowering the plates 6 and I to a sub-zero temperature so that the air which is forcibly projected into cylinder 5 is dehumidlfied, that is, the moisture content in the air is substantially removed. The plates 6 and I are cooled by the Dry Ice to such a low temperature that the water vapor in th air condenses on the plates as frost or snow so that the air emerges at the outlet 81 substantially dry and free of moisture and at a sub-zero temperature which may be of the order of 109 F. which is the temperature of the solidified CO: blocks indicated at "I. The precooled dehydrated air at sub-zero temperature then enters the mani fold ll within the temperature controlled cablnet represented generally at l2; The temperature controlled cabinet is explained more fully in my copending application Serial No. 532,807, supra, as including Dry Ice compartment is and a work compartment 15 separated by partition 15. The Dry Ice compartment id contains mounting means for a multiplicity of trays that I have shown generally at i1, i8 and i9 in Fig. 2. .Each. of 'the trays containsopen work shelf-like supports as shown at 20. 2| and 22 for the blocks of solidified Dry Ice CO2 illustrated for example at 23. Boththe bottom and cover portions of the trays l1, l8 and I9 are provided with deflector members represented at No and "b, and Ila and 18b, and Illa and lab. These deflectors serve as guides to direct the air at high velocity against the surfaces of the blocks of Dry Ice 23. The high velocity air is directed against the blocks of Dry Ice and guided by the deflectors by reason of the supply of the air at high velocity through manifold I i and the multiplicity of horizontally extending distributor pipes designated, at 24, 25, 26, 21, 28 and 29 in Fig. 2. The arrangement of the trays in superimposed relation is entirely schematic and may be varied to meet necessary conditions but is intended to illustrate one method by which a relatively large surface area of solidified CO: may be scrubbed with dehumidiiied and precooled air at high velocity.

referred to more fully hereinafter.

Thescrubbing effect which is obtained by the blasts of air at high velocity against the sur-' faces of the blocks of CO2 has the eflect of removing the envelope of gas thattends to collect around the solidified block thereby producing a lowering of the sublimation temperature and'permltting the blocks of C02 to be effective for producing sub-zero temperatures that are considerably lower than the lowest temperature to which the blocks of C02 normally assume. The important feature of the method of my invention is to insure the removal of moisture from the air before it is directed against the surfaces of the blocks of C02. The removal of moisture is efiectively accomplished in the method of my invention by the precipitation of moisture through the dehydrator and precooler represented at 2.

The arrangement of the work chamber l5 and Dry Ice compartment 14 is more clearly explained in my aforesaid copending application Serial No. 532,807, supra, and is illustrated herein merely for the purpose of explaining the coopera-,

tion of the circulating fans and heater arranged within the cabinet structure.

In Fig. 1 the blower which I'provide for the intermittent circulation of gas is illustrated at 3! driven by motor 32 arranged externally of the insulated cabinet structure l2 and operative to draw gas from the blocks of C03 represented at 23 in the several superimposed trays Il, I8 and I9 and force the gas through duct system 33 into the work compartment i5. A valve 34 is located in partition l6 for controlling the volume of gas pumped from the Dry Ice compartment 14 into the work compartment I5.

In addition to the blower 3| there is the circulating fan 35 arranged beneath the Dry Ice compartment and in the work compartment and driven by the externally mounted motor 36 supplied with power from line circuit 4|- Fan 35 serves to continuously circulate the gases within the work compartment -l5 and pum the gases through the multi-section heater coils 31 and 38 which may be selectively connected in'series or parallel or isolated in a single effective section by means of selector switch 38 represented in the schematic circuit of Fig. 3. The heater coils 31-- 38 are prevented from elevating the vworl'; compartment beyond a predetermined limit of temperature by means of the thermostatic circuit breaker arranged as a-protective device 40 in the heater circuit. The power supply system for the control circuit is connected to line circuit 4| to which is connected the input circuit of transformer 42, the output circuit of which connects to rectifier system "43 through leads 54 which delivers direct current to the control circuit 55 of relay 44 which includes winding 65 connected in series with thermostat 46 which is subject to the temperatures within the work compartment [5. Relay winding 45 controls armature 41 which op-. crates mercury switches 48 and 49 in opposed relation. That is to say, when the contacts of mercury switch 48 are open the contacts of mercury switch 49 are closed. Thus the heater coils ll the air is directed througheration of thermostaticswitch 46.

and 38 are activated from the power supply circuit 4| through contacts 48 according to the op- Sets of contacts 49 control the circuit to the blower motor 32 so that when thermostat 46 calls for lower temperature in the work compartment, contacts 49 are closed, thus closing the circuit from the power line system 4| to blower motor 32. Manually operated switch 50 is provided for cutting motor 32 out of the circuit as may be desired. Switch 5| is provided and is movable to contact 5Ia for rendering switch 49 effective, or to contact 5!?) for rendering contacts 49 ineffective so that blower motor 32 may be operated continuously irrespective of temperature conditions called for by thermostat switch 4B.

The blower I which forces air into the precooltor 3 may not be operated at the same time that motor 32 is operated. Thermostat 46 may thus be set for sub-zero temperatures of approximately the order of 109 F. which may be attained within work compartment 15 by intermittent operation of blower 3|. If, however, extremely low sub-zero temperatures are required of the order, for example. of l39 F. then with thermostat 43 set for such sub-zero temperatures switch 53 is closed so that blower motor 3 is also operated simultaneously with blower motor 32. thus driving blower I and forcing air through the dehydrator and recooler 2 to the distributor system I l and through the distributing nozzles over the blocks of Dry Ice for scrubbing the insulating blanket of CO2 gas that surrounds the blocks of CO: away from the surfaces, thereby permitting the production of lower sublimation temperatures. This forces the temperature of the work compartment to a very low sub-zero temperature achieving the production of temperatures lower than the normal operating temperature of solidified CO2.

While I have described my invention in one of its preferred embodiments I realize that changes in details of the method and arrangement of apparatus for carrying out the method may be employed and I intend no limitations upon my invention other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. The method of effecting refrigeration with solidified CO2 at sub-zero temperatures which comprises dehydrating air, precooling the dehydrated air and blowing the precooled dehydrated air over the surface of solidified CO2 in a confined temperature controlled area at a velocity sufficient to maintain the solidified CO2 free from the collection of gas over the surface area thereof.

2. In a system of refrigeration employing solidified CO2 in a confined temperature controlled cabinet, the method of maintaining sub-zero temperatures within a temperature controlled cabinet which comprises forcibly flowing dehy drated air into a confined temperature controlled cabinet, precooling the air before entry into the temperature controlled cabinet and distributing the dehydrated precooled air within the temperature controlled cabinet over the surface of solidified CO2 for preventing the accumulation of a blanket of insulating gas around the surface ofthe solidified CO2 and creating asubiimation temperature lower than the lowest temperature limit of the solidified C02.

3. In a, system for producing sub-zero temperatures in a temperature controlled confining cabinet employing solidified CO: as a refrigeration medium, the method of producin sub-zero temperatures which comprises forcibly flowing air into the temperature controlled cabinet, removing moisture from the air and precooling the air to sub-zero temperatures before the air enters the temperature controlled cabinet, and directing the air at high velocity over the surface of solidified CO2 within the temperature cont-rolled cabinet at a velocity sufficient to eliminate the formation of blankets of insulating gas around the solidified CO2 for creating extremely low sublimation temperatures.

4. In a refrigeration system employing solidified CO2 as a refrigerating medium within a temperature controlled cabinet, the method of producing sub-zero temperatures within the cabinet which comprises forcibly flowing air into the temperature controlled cabinet, dehydrating the air and lowering the temperature of the air to sub-zero temperatures before entry into'the temperature controlled cabinet and forcibly flowing the dehydrated precooled air over the surface of the solidified CO2 within the temperature controlled cabinet for continuously preventing the formation of blankets of insulating gas around the solidified CO2.

5. In a refrigeration system employing solidified CO2 as a refrigerating medium within a temperature controlled cabinet, the method of producing sub-zero temperatures within the cabinet which comprises forcibly flowing air into the temperature controlled cabinet, dehydrating the air and lowering the temperature of the air to sub-zero temperatures before entry into the temperature controlled cabinet and forcibly flowing the dehydrated precooled air at predetermined velocity over the surface of the solidified CO2 within the temperature controlled cabinet. scrubbing the surface of the solidified CO2 within the temperature controlled cabinet for continuously removing the insulating blanket of CO2 gas that tends to collect around the solidified CO2 whereby the solidified CO2 is effective to produce subzero sublimation temperatures within the temperature controlled cabinet.

6. The method of effectin refrigeration with solidified gas at sub-zero temperatures which comprises dehydrating air, precooling the dehydrated air and blowing the precooled dehydrated air over the surface of solidified gas in a confined temperature controlled area at a velocity sufficient to maintain the solidified gas free from an insulating envelope of gas over the surface thereof.

7. In the art of refrigeration employing solidilower than the lowest temperature limit or the solidified gas.

8. In a system for producing sub-zero temperatures in a temperature controlled confiningcabinet employing solidified gas as a refrigeration medium, the method of producing sub-zero temperatures which comprises forcibly flowing air into the temperaturecontrolled cabinet, removlug-moisture from the air and precooiing the air to sub-zero temperatures before the air enters the temperature controlled cabinet, and directing the air at high velocity over the surface of solidified gas within the temperature controlled cabinet at a velocity sumcient to eliminate the formation of blankets of insulating gas around the solidified gas for creating extremely low sublimation temperatures.

NATHAN MORRIS.

REFERENCES man The following references are of record in the file of this patent! V i UNITED STATES PATENTS

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