US2693682A - Refrigerating system with defrosting arrangement - Google Patents

Description

N63 9, 3954 M, WlNGER ET AL 2,93,582

REFRIGERATING SYSTEM WITH DEFROSTING ARRANGEMENT Filed June 25, 1952 2 Sheets-Sheet l INVENTOR, GLENN 5. KELLER y M/A TON N66? %4 Ma /2% ATTOENE? Nov. 9, 1954 ANGER ET AL 2,693,682

REFRIGERATING SYSTEM WITH DEFROSTING ARRANGEMENT 2 Sheets-Sheet 2 Filed June 25, 1952 INVENTOR. GLENN 5. K5145? y /W/[ 70M MNGEP ATTO'QNEY United States Patent REFRIGERATING SYSTEM WITH DEFROSTING ARRANGEMENT Application June 25, 1952, Serial No. 295,507

1 Claim. (Cl. 62-115) This invention relates to improved apparatus for effecting defrosting of the heat absorbing elements of mechanical refrigerators.

The primary object of this invention is to store and later utilize the heat removed from the area cooled by a mechanical refrigeration system, to periodically defrost the heat absorbing element of said system.

Another object is to provide a closed defrosting circuit that is entirely separate from its associated refrigerating system, but which derives its heat energy solely from the heat given off by the condensing unit of said refrigerating system.

A further object is to provide a method of defrosting a mechanical refrigerating system that uses a captive volume of fluid to cool the refrigerating system condenser, thereby doing away with the large volume of fluid normally necessary in conventional systems.

Still other objects are to provide a defrosting system that is simple in structure, economical in operation and easy to maintain.

These and other objects of the invention will become apparent from a reading of the following specification and claim, together with the accompanying drawings wherein like parts are referred to and indicated by like reference numerals and wherein:

Figure 1 is a schematic outline of a conventional mechanical refrigerating system and the associated defrosting system that is the subject of this invention;

Figure 2 is an end view, in perspective, of the refrigerating element showing the defrost conduit associated therewith;

Figure 3 is a front elevation of one end of the refrigerafiing element and the defrost conduit associated therewit Figure 4 is an enlarged vertical sectional view through a portion of the refrigerating element showing the defrost conduit mounted therein;

Figure 5 is a top plan view of the condenser case taken along the line and in the direction of the arrows 55 of the Figure l; and

Figure 6 is a vertical sectional view taken along the line and in the direction of the arrows 6-6 of the Figure 4.

Referring more particularly to the drawings, there is seen in the Figure 1 a schematic layout of a mechanical refrigeration system having a compression pump 10 connected on its vacuum side to the refrigerating element through the line 12 and on its compression side to the condenser through the line 13. A second pump 19 draws the liquified refrigerant from the condenser 30 through the line 14 and returns it to the refrigerating element 20 through the line 11.

The refrigerating element 20 comprises an expansion chamber formed of a plurality of tubes 15 bent back and forth upon themselves in order to occupy a minimum of cubical space. The length, diameter and number of the expansion tubes or elements 15 is dependent upon the capacity of the system which is in turn dependent upon the space or type of material to be refrigerated and the speed with which the area or materials are to be brought to the minimum temperature. In an illustrative system the refrigerating tubes 15 are A" in diameter. One end of each of the refrigerator tubes is brought out to a manifolded expansion valve 18 of the conventional type which is in turn connected to the line 11. The other end of each tube 15 is connected to a common manifold 17 which is connected to the vacuum side of the pump 10 through the line 12,

Reference numeral 16 indicates a plurality of closely spaced heat absorption fins through which the tubes 15 run and which act to increase the surface area of the refrigerating element by reason of their mechanical contact with the outside of the tubes 15.

The condenser 30 consists of a single length of tubing bent back and forth upon itself in the conventional manner and positioned within a liquid tight case 31 which is filled with a coolant fiuid 32, as shown in the Figure 1.

The refrigerating system just described is filled with any one of the well known refrigerating gases such as ammonia, sulfur dioxide, or one of the Freeon gases. The choice of the particular refrigerant being dependent upon safety factors and the lowest temperature which the system is expected to attain and maintain.

Reference numeral 40 indicates a defrost conduit of about 4" diameter which is shaped in the form of an open helix and positioned with the refrigerating tube 15 as shown in the Figures 1, 2, 3, 4 and 6. There is one of these defrost conduits in each of the tubes 15 that make up the refrigerating element 20. The diameter of the helix formed by the conduit 40 is such that the conduit will contact the interior of the tube 15 along its entire length as is shown most clearly in the Figures 4 and 6. This intimate contact assures the maximum efficiency in heat transferance between the defrost conduit 40 and the refrigerating tube 15. One end of each of the conduits 40 is connected to a common intake manifold 41 which in turn is connected through line 43 to the defrost pump 44. The other end of each conduit 40 is connected to a common exhaust manifold 42 that is connected by means of line 46 to a spray manifold 47 located near the top of the condenser case 30. Reference numeral 45 indicates a screened outlet located at the bottom of the case 30 which leads to the vacuum side of the defroster pump 44.

The condenser case or tank 30 is filled with a liquid fluid such as a light oil whose solidification point is a safe distance below the minimum temperature expected to be developed within the refrigerating element tubes 15. The fluid capacity of the case 30 is dependent upon the use to which the refrigerating system is to be put. In the case of a system that is intended to hold approximately 2000 lbs. of meat at a constant freezing temperature in a 6 x 8 foot freezer, a one horse-power installation will be required, in which case approximately 10 gallons of oil will be needed. The quantity of fluid will of course vary with the capacity of the system, the amount of heat to be extracted and the heat storing factor of the oil or other fluid mixture that is used.

In operation, the refrigerating system acts in the conventional manner, the liquified refrigerant being delivered by the pump 19 to the expansion valve 18 through which it enters the refrigerating tubes 15 which are kept under partial vacuum by the pump 10. The expanding refrigerant draws heat from the area surrounding the finned tubes 15. The presence of the helical defrost conduit 40 Within the refrigerating tube 15 causes the expanding refrigerant to be swirled around inside the tube 15 thereby making for more uniform and speedier cooling action the full length of the tube than occurs in conventional installations having unobstructed tube bores.

The expanded refrigerant, now in gaseous form, is drawn through the manifold 17 and line 12 by the pump 10 which then compresses the gas and sends it through the line 13 to the oil cooled condenser 30. The refrigeraut now contains both the heat of expansion and compression which is absorbed by the oil bath 32. At the pressure under which the refrigerant is held in the condenser, the lowering of the temperature of the refrigerant due to the absorption of its heat by the oil 32 causes the refrigerant to become liquid. The liquid refrigerant is then returned to the expansion valve through the line 14 and pump 19 to repeat the cycle. As the cycles are continuously repeated, the heat absorbed by the condenser oil 32 accumulates until the temperature of the oil 32 may rise as high as F. or more. At the same time, Water vapor within the refrigerated area condenses upon the fins and tubes 16 and 15 respectively in the form of frost which eventually acts to insulate the tubes which seriously reduces the efficiency of the system.

The refrigerating elementv is defrosted by stopping the refrigeration cycle and activating the defroster pump 44. Hot oil is drawn from the bottom of the case through the screened outlet by the pump 44 and delivered to the defrost conduit 40 through the line 43 and manifold 41. The hot oil then passes through the conduit 40 and is returned to the case 30 through the exhaust manifold 42 and line 46. The oil which has given up a part of its heat by passage through the conduit 40 is sprayed back into the bulk of hot oil in the case, through the manifold 47 which has a number of small spray holes along the lower face thereof. The cooled oil then mixes with the oil remaining in the case to equalize the average temperature of the defrost oil as a whole. The oil is then re-circulated through the defrost system until the frost on the tubes 15 is melted. Inasmuch as the oil is at a temperature of approximately F. to begin with and the refrigerating tubes 15 may be at 30 or 40 F., there is an instantaneous rise in the temperature of the tubes 15 which quickly defrosts them. Since it is only necessary to raise the tem perature of the tubes 15 to 32 F. to assure'compleie defrosting, the starting temperature of 100 F. of the hot oil is more than adequate to do this and especially so since the oil is kept circulating in the defrost system. As soon as the frost is melted, the defrost pump 44 is stopped and the refrigerating compressor 10 is started again. The action of the refrigerating cycle then causes heat to be re-accumulated in the defrost oil 32 in preparation for the next defrosting cycle. Since the defrost system is a closed one, the same oil is used over and over again to both cool the condenser and defrost the system. The cost of operating the defrost system is negligible since the only expense is that of periodically operating the pump 44. Furthermore, a defrost system of this type will not run out of heat since the volume of the oil can be regulated to store more heat than will ever be needed to defrost the heaviest accumulation of ice. The length of time between defrost cycles is dependent upon the type of work being done. If materials having a high water content are being frozen, more frost will accumulate within a given time than if the system were only performing a holding operation. 4

A defrost system of this type is most economical in operation because 1t not only uses the heat derived from 4 the freezing cycle to do the defrosting, but also because the use of a fixed volume of fluid to coolthe condenser of the refrigerating unit saves the cost of the great quantity of water which is necessary to operate the conventional commercial refrigerating system.

Furthermore, if this defrost system is used with an air-cooled refrigerating unit, a much smaller volume of air need be handled to provide efficient operation of the system since the excess. heat is stored in the defrost oil and put to useful Work during the defrost period.

It will now be clear that there is provided a device which accomplishes the objectives heretofore set forth. While the invention has been disclosed in its preferred form, it is to be understood that the specific embodiment thereof as described and illustrated herein is not to be considered in a limited sense; as there may be other forms or modifications of the invention which should also be construed to come within the scope of the appended claim.

We claim:

In a refrigerant system, the combination of a tubular refrigerating element normally subject toaccumulation of frost thereon, a compressor for circulating refrigerant vapor, a condenser for normally supplying the refrigerant after condensation to the refrigerating element to vaporize therein and cool the same, a case surrounding the condenser, the said case having fluid therein adapted to cool said condenser by receiving the heat of condensation therefrom, a helically wound conduit positioned within the said tubular refrigerating element in continuous contact with the inner wall thereof and extending the full length thereof, a. closed conduit circuit including a pump connecting the ends of said conduit with the said fluid filled case, and means for periodically operating the said conduit circuit pump to circulate hot fluid from the case through the conduit to raise the temperature of the refrigerating element sufficient to rapidly defrost the same.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,121,253 McGuffey June-21, 1938 2,245,454 Baker June 10, 1941 2,526,032 La Porte Oct. 17, 1950 2,538,660 Shreve Jan. 16, 1951

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