US 2217702 A
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Description (OCR text may contain errors)
Oct. 15, 1940. H. w. KLElsT COOLING METHOD AND APPARATUS Filed Jan. 2, 1956 Patented Oct. 15, 1940 PATENT- oFFlcE COOLING METHOD AND Herman. W. Kleist, Chicago, lll., signor to Dole Befrigerating Company, Chicago, lli., a cor- Nporation of Iliinois V appunti@ January z, 193s, sei-m No. 51.118
zo claim. (ci. zz- 126) This invention relates to coolingmethod and apparatus and has for its object to provide a new and improved device of this description.
The invention has as a furtherV object to provide a cooling method and apparatus wherein a liquid refrigerant can. be congealed without injury to the container.
'Ih invention has as a further object to provide -means for satisfactorily using-a liquid relo frigerant in a thin container.
The invention has as a further object to provide a container for a liquid refrigerant consisting of plates of heat conducting material, preferably metal, with the cooling coil between them, with a liquid refrigerant between the plates, and with means for permitting the refrigerant when congealed to expand without injuring the plates. The invention has other objects whichare more particularly pointed out in the accompanying 9g description.
Referring now to the drawing, Fig. 1 is a view showing one form of device embodying the invention, with parts broken away;
Fig. 24s a sectional view taken on line l2--2 of Fig. l, on an enlarged scale;
' Fig. 3 is a sectional view showing one form of vacuum nipple;
Fig. 4 is a view showing a modified construc- 30 tion; and
Fig. 5 is a view showing a further modified construction.
Like numerals refer to like parts throughout the several figures.
One of the diiilcult problems in refrigeration has been to provide a refrigerating device which contains a liquid refrigerant, which liquid refrlgerant is to be congealed at a very low item perature and held at this low temperature. In o such devices heretofore it has not been possible to get a uniform temperature on the outside and it has been difllcuit to hold the liquid refrigerant and to keep the sides from bulging out and when the liquid refrigerant congeals it has been pracitlcally impossible to prevent injury to the device by the expansion. Another problem has been the difficulty of securing an efilcient heat trans-- fer relationship between the contacting metal parts of the apparatus. This present device obvi- 50 ates all these dimculties.
In carrying out my invention, I provide a tank i made up of two separatedplates 2, 3 of heat conducting material, such as metal. which are connected together at the edges so as to form u a hermetically sealed compartment between them.
Within thisv compartment are provided pipes 4 i and 5 having at intervals spacers 6 .between them, the pipes being in contact with the plates 2 and 3. The pipes may be arranged in coils or in any other form and maybe placed as close together as desired, or a distance apart, depending upon the conditions presented. A cooling fluid is passed through these pipes so as to cool them and any suitable cooling uid may be used. The pipes 4 and 5 are connected to the source of lo fluid supply in any desired manner, as by means of the nipple 1. In the construction illustrated a continuous pipe is used and is bent back and forth between the plates, and the cooling medium passes in through one nipple 1 and out u through the other nipple 1. In the space between the plates 2 and 3 is placed a liquid refrigerant 8. All of the known eutectic solutions which I contemplate using have an appreciable vapor pressure at the temperature of the containing unit and of the eutectic contained therein. This liquid refrigerant does not entirely fill the space between the plates 2 and 3, but there is left a space 9 free of the refrigerant. When liquid refrigerant is placed -between the two plates Wltha cooling coil between them, it pushes out the plates, causing them to bulge and when the liquid congeals the plates are often ruptured.
Air is exhausted from between the plates 2 30 and 3 in any desired manner, as by connecting the nipple i0 with a vacuum producing device. This withdraws the air from the space 9. 'I'he amount of air withdrawn from between the platesv will depend upon the result desired, but it should be sufdcient to provide such a dif-y ference in pressure between the interior and the exterior of the plates as to cause the plates to be pressed against the coils of the pipe and to be properly held when the liquid between the plates congeals. There is also air intermingled with the liquid refrigerant 8 which causes an uneven temperature on the face of the plates 2 and3. The vacuum in the space between the plates, withdraws the air .from the liquid refrigerant so that it is substantially free of air, so that thzere will be even temperatures over the face of the plates. In the preferred form the space 9 is substantially free of air, a vacuum plate being thus produced. Thus vacuum causes the plates 2 and 3 to be tightly pressed against the pipes 4 and 5.
When the liquid refrigerant or cryohydrate is congealed it expands up into the space 9. If there -wereA air at atmospheric pressure in this space,
the air would be compressed and the pressure inside of the device would be greatly increased, and this'pressure often causes injury or rupture of the parts. With this vacuum arrangement when the liquid refrigerant is congealed it smply expands up into4 the vacuum, that is the space 9, and since there is no air in this space there is no increase in pressure and danger of rupture or injury to the parts 'by congealing of the liquid refrigerant is thereby avoided. Flirthermore, by removing the air from the liquid refrigerant a uniform temperature throughout the surface of the plate is secured.
The tank is filled up to any desired height, preferably about nine-tenths of its total capacity, with any of the refrigerant liquids desired. This liquid refrigerant is then frozen solid in order to increase its latent heat over the regular solution. This solution without freezing, for example, might have a latent heat of 12 to 15 B. t. u.s per pound and when frozen into a solid mass and then thawed, the latent heat per pound will be as high as 105 B. t. u.s. These liquid refrigerants often have intermingled with them, in addition to air, different kinds of gases and by exhausting the air these gases are also exhausted. These gases and the air decrease the eiiiciency of the refrigerant and when they are removed its eiiciency is increased. By elimihating these diierent gases corrosion of the' tank is prevented. This corrosion has been quite a problem heretofore. This device is exceedingly effective with a brine solution as heretofore in the tanks used it has been impossible to keep the brine solution free from air. I have found by numerous tests that one advantage of having the two sets of coils 4 and 5 in the tank is that the plates 2 and 3 may be spaced farther apart and a larger tank thus provided, and therefore more eutectic solution can be used than is the case where a single coil is used with the plate 2 engaging one side of the pipe and the plate 3 engaging the other side of the pipe. By using the greater amount of eutectic solution, the efficiency of each tank is increased. When a single coil is used, the size may be varied, depending upon the conditions presented. I have secured satisfactory results with pipe ranging from three-eighths inch to one inch in diameter.
Any desired form of vacuum nipple may be used. I have shown a vacuum nipple I0 which has an enlarged recess II and a check valve I2 in said recess and normally closing the passageway I3. Each time the vacuum withdrawing device is operated, the valve lifts so as to let air and gas pass out and then drops to close passageway I3 against re-entrance of air. When the desired vacuum is produced, the plug I4 is then placed in position to further prevent the entrance of air. ably a high vacuum, the preferred form being a vacuum of about twenty-eight inches.
In Fig. 4 there is shown a modified construction where there is a hermetically sealed tank having the plates 2a and 3a joined together to form a hermetically sealed tank and the pipe or coil I5 placed in the -center and the spacers I6 and I'l on each side, which engage the pipe and which also engage the plates 2a and 3a. The liquid refrigerant I8 is placed in the tank leaving a space I9 at the top and the air is then exhausted as hereinbefore set out.
In Fig. 5 I have shown a modied construction where there is a vacuum tank 20 in the middle and it is surrounded by the vacuum tank The vacuum used is prefer- 2I, there being the spacers 22 and 23 between the vacuum tank 20 and the walls of the vacuum tank 2l. The vacuum tank 2li simply has the air exhausted and the vacuum tank 2l is partially lled with the liquid refrigerant 24 and has the space 25 which is free from liquid refrigerant and the air is exhausted from this space and from the liquid refrigerant as hereinbefore set out.
The tight pressing of the plates against the pipes or the spacers due to the vacuum inside the tank provides a smooth surface on each side of the tank. In view of the fact that the temperature of this tank is often very low and may be kept at about thirty degrees below zero for long periods, frost may accumulate on -the plates, but it can be easily scraped off as it only loosely adheres to the surface and any slight brushing dislodges it. In all cases there is a vapor present and in all cases a lfilm of condensed vapor lies against all surfaces of metal within the unit, covering all surfaces of the pipe coils and all surfaces of the intermediate metal members and the inner surfaces of the plates and the end sections. This film is very hard and when two of the films on the two surfaces are brought together the two films under pressure partially coalesce and form what is called the wringing film. Such films are very hard, having high compressionstrength and because of their extreme thinness and other physical characteristics possess a much higher coeicient of heat conductivity than the free liquid of which they are composed. There is therefore provided between the metal parts of the refrigerating unit a direct thermal contact which in `every way is one having capabilities of heat conduction approaching if not actually equaling the heat conduction of integral metal construction. This film between two members of the unit has been measuredand has a thickness of approximately two times the radius of molecular attraction. In other words, its thickness is approximately one and two-tenths of a millionth of an inch.
This device can be used wherever desired. One of the important uses is for use in trucks and in connection with the storage and sale of ice cream and in any other place where it is desired to have low temperatures and to maintain a low temperature for a long period. For example, when the device is used in trucks, the liquid refrigerant may be frozen at night and then the truck used to deliver ice cream or any other material, the frozen liquid refrigerant maintaining the temperature for many hours, as for example through the entire day, the refrigerant gradually melting and then being again frozen and the same operation repeated.
l. A cooling apparatus comprising two separated plates, cooling means between said plates, the plates being hermetically sealed so as to provide a tank, said tank being partially filled with a liquid refrigerant so as to leave a space above it, the air being substantially all exhausted from said tank when the liquid refrigerant is therein, so as to tightly press the sides of the tank against said cooling means and remove air from the liquid refrigerant and provide a high vacuum above the liquid refrigerant into which it can expand when congealed.
2.- A cooling apparatus comprising two separated plates, two separated sets of cooling coils between the plates, one engaging one plate and the other the other plate, separating devices beto form a tank which is partially filled with llq uid refrigerant so as to leave a space above it,
.the air being substantially exhausted from said space and from the liquid refrigerant, so as to provide a high vacuum in the space above the liquid refrigerant into which it can expand when congealed. Y
3. A cooling apparatus comprising two separated plates, a pipe bent back and forth between said plates, through which cooling medium is received, the plates being hermetically sealed so as to provide a tank, the distance between the opposed faces of the tank being greater than the diameter of the pipe, said tank being partially filled with a liquid refrigerant, the pressure inside of the tank being below atmospheric pressure so as to cause the sides of the tank to be pressed toward the pipe, and resisting means inside of the tank, in addition to the pipe and the liquid, for resisting the atmospheric pressure on the outside of the tank, so as to hold the sides of the tank apart and maintain the distance between them greater than the diameter of the pipe.
4. The method of heat transfer from one member to another which consists in pressing the members toward each other in the presence of a liquid which forms a surface nlm on each of said members, said surface nlm being compressed between the members, `as specied.
5. The method of securing heat transfer from one metallic member to another not in direct contact with each other which consistslin placing said members in the presence of a liquid having a vapor pressure whereby a lm of condensed vapor collects on the surfaces of said metallic members and between the same, and forcing said metallic members toward each other to coalesce the surface lms between the same, as specified.
6. The method of heat transfer from one member to a second member which consists of enclosing one of the members within the other, partially filling the enclosure member with a liquid having a vapor pressure, and exhausting air to reduce the pressure within the enclosure member below that of atmospheric pressure whereby the sides of said enclosing member are pressed toward and against the other member thereby bringing surface films ofcondensed vapor on the adjacent contacting surface of said members together to form an intimate heat transfer bond between the same.
7. The method of producing and maintaining thin lms of high thermal conductivity between two members not in actual contact which consists in providing one member in the form of an enclosure, `locating the other member'y within said enclosure between the sides thereof so as to substantially bridge the distance between said sides, partly lling the enclosure with a liquid having a vapor pressure under the conditions of use thereof, and exhausting air from the enclosure and sealing the same to thereby decrease the pressure within said enclosure below that of atmospheric pressure whereby the sides of said enclosing member are pressed toward the coil located within said' container, the pipes of said coil extending between opposite sides of the container, said container having a cryohydrate therein which has an appreciable vapor pressure under the temperatures at which the refrigerating unit is used, said container and the cryohydrate therein -being at a less pressure than the pressure of surrounding atmosphere whereby atmospheric pressure `forces the side of the container inwardly toward the pipes or tubes of said coil, substantially as and for the purposes described.
9. 'I'he herein ldescribed method,'consisting of providing an enclosing container having opposed sides and with a coil located within said container between said opposed sides and substantlally bridging across between said sides, filling said container partly with a liquid having an appreciable vapor pressure under the temperature conditions at which used, and removing air from the container to reduce the pressure therein below atmospheric pressure, as speciied.
10. The method o f transferring heat from one metallic member to a second metallic member' surface film, whereby said surface lms are compressed between the members, as specified.
" 12. The method of providing a heat transfer structure which consists in providing an enclosing member partially lling said member with a liquidlhaving a -vapor pressure' located within said member, a second member which extends between opposed walls of the first member and exhausting air to reduce the pressure within the enclosing member below atmospheric pressure, whereby air pressure from the outside forcesv the sides of the enclosing member inwardly, as and for the purposes specified.
13. The process of producing a wringing film which consists in bringing two surfaces, having liquid films thereon, together under pressure.
14. The process of producing a wringing lm vfrom a medium which is capable of changing from solid to liquid phase which consists in providing a first surface having said mediumY thereagainst, then forcing a second surface, likewise having said medium thereagainst, against the rst surface, one of the said surfaces being restricted to a predetermined degree whereby unit pressure is increased as desired.
15. The method of producing and maintaining thin films of high thermal conductivity between two members not in actual contact by the utilization of pressure.
16. The method of transferring heat from one member to a second member not in actualcontact with the rst member by placing between the two members a thin nlm whose thickness is approximately two times the radius of molecular attraction.
17. The method of transferring heat from one metallic member to a second metallic member not in metallic contact with the rst member by placing between the metal members a film of condensed vapor whose thickness is approximately one and two-tenths of a millionth of an inch. f
18. The method of transferring heat from one metallic member to a second metallic member not in metallic contact' with the iirst member by placing between the metal members a thin liquid lm 19. The method of forming av thermal conductor of high efficiency which consists in compressing two liquid barrier lms together under a predetermined pressure to form a "wringing nlm."
HERMAN; W. KLEIS'III.