US2480346A - Means for defrosting cooling coils - Google Patents

Description

Aug. 30, i949. M. B. wA'rTs MEANS FOR DEFROSTING COOLING COILS Filed sept. 23, 1948 n l 1||||||IIIIl||||||||IIlllllllllllllllllllllllllllllllllli TIMER IN VENTOR.

M. B. WAT-TS ATTORNEY g f'2,4so,346

unirse sra'rEs eATENT orriee MEANS. FOR'DEFRSTING COOLING COILS Maillon B. Watts, Waynesboro, Pa., assignor to Frick Company, Wayn of Pennsylvania esboro, Pa.,l a corporation Application. September 23, 1948, Serial No. 50,800

materially impair the eiliciency of the cooling unit.

Claims. (Ci. 62,-2)

It is also imperative in order to maintain the y eiciency of the refrigeration system to remove the accumulated frost in as short a time as possible in order to maintain a relativelyv low tem'- perature in the compartment and preclude the .necessity of recooling the same after completion of the defrosting operation. ,f

Numerous systems havey been devised for accomplishing the defrosting operation, among which are the provision of a heated body adjacent the cooling unit, the passage of warm air or gas over the cooling unit, and the shutting down of the refrigeration system in order to allow theA .frost to melt.

These attempts to solve the defrosting problem have all presented several disadvantages, the most serious of which is the relatively long defrosting cycle and the "excessive raising of the temperature within the refrigerated compartment. Attempts have also been made to solve the defrosting problem by spraying a relatively warm fluid such as, water over .the cooling unit to melt the frost accumulated thereon. This system has the advantage of melting the frost in. a relatively short time without materially raising the temperature in the refrigerated compartment duit must be left open to the atmosphere or sewer and consequently, due to a reverse chimney effect, a relatively large volume of cold air will pass from the refrigerated compartment through the open supply conduit to the exterior, thus materially impairing the efficiency of the system. There is also the further disadvantage that sewer gas or other contaminating substances will be introduced into the refrigerated compartment through the' open supply conduit.

Another disadvantage arising from melting the -I frost byspraying water or other relatively warm uid thereon is the fact that this operation im-` mediately creates a considerable volume of water vapor 'in the form of fog surrounding the cooling unit. In prior devices no provision has been made for removing the fog thus produced and consequently upon completion of the defrosting operation such fog is redeposited on the cooling unit in the form of frost, thus materially increasing the load on the refrigeration system as well as insulating against heat transfer.

yIt is accordingly an object of this invention to provide a defrosting system utilizing a relatively warm fluid such as water and in which means is provided for positively removing all liquid remaining 'in the supply conduit and spray head after the completion of the defrosting operation, and also for positively removing the water vapor or fog but there are also very serious disadvantages connected with this system as it has been heretofore,

utilized.

In the first place, it is necessary to provide some sort of a spray head or ,distributing means for directing the water over all portions of the cooling unit and since this distributing means normally is provided with a plurality of relatively small 1 openings, it is imperative that uponcompletion 'of the defrosting operation all liquid be removed vtherefrom to preclude freezing of the liquid therein and the consequent clogging of the openings or other impairment of the system. This problem has been partially solved by the provision of a self-draining liquid supply conduit. However, the provision of such aconduit immediately introduces another disadvantage in that the confrom the vicinity of the cooling unit.

It is a further object of this invention to provide a defrosting system utilizing arelatively warm fluid such as water to remove the frost from a cooling unit and in which means is provided for effectively preventing the escape of cold air from the interior of the refrigerated compartment and for preventing the entrance thereto of contaminating substances. v

It is a further object of this invention to provide anautomatic defrosting system utilizing relatively warm fluid such as water to remove the frost from the cooling unit, the defrosting cycle being initiated and automatically controlled by electrical timing devices. 7

It is a further object of this invention to provide an automatic defrosting system utilizing a relatively warm fluid such as water for removing the frost from the cooling unit andin whichthe cooling unit is provided with electrical means for circulating air to be cooled therethrough wherein y the defrosting cycle is controlled by the change in load upon the air circulating means occasioned by the accumulation of frost on the cooling unit.

Further objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view illustrating the defrosting system of this invention applied to a conventional refrigerated compartment and with certain parts in section for greater clarity;

Fig. 2, a schematic diagram of an electrical control circuit for the defrosting system of Fig. 1; and

Fig. 3, a fragmentary diagrammatic view of control means for the defrosting system of Fig. 1 when utilized in conjunction with a cooling unit having means for circulating air therethrough.

With continued reference to the drawing, there is shown in Fig. 1 a refrigerated compartment I provided with conventional insulated walls I I, a cooling unit or evaporator I2 of any desired form being disposed within the compartment. The compartment III may be of any desired size and shape and cooling unit I2 would, of course, be proportioned and arranged in accordance with the requirementsvof the particular compartment to be refrigerated.

Immediately above the cooling unit I2 is located a spray head I3 having a plurality of relatively small apertures I4 in the lower surface thereof, there being a sufcient number of these apertures arranged in a manner to spray liquid such as water over the entire surface of the cooling unit or coil I2. A fluid supply conduit I5 is connected by a joint I6 to the spray head I3, this conduit extending through a wall of the compartment III, therebeing provided a suitable sealing means I1 in the wall of the compartment to prevent the leakage of air around the conduit I5. In order to minimize the flow of cold air from the interior of the compartment to the exterior thereof through the conduit I5 due to a reverse chimney effect in the event of an open connection this conduit is preferably inclined upwardly from the spray head I3 to approximately where it extends through the wall of the compartment.

The conduit I5 is connected to the intake 2| of ejector 22 which is provided with an elongated chamber 23 at one end. The walls of the chamber 23 converge into a relatively small outlet 24. A nozzle 25 is disposed within the chamber 23 axially of the outlet 24 and is arranged to direct a relatively high velocity stream or jet of liquid into the outlet 24. The passage of this relatively high velocity stream or jet creates a partial vacuum in the chamber 23 and the intake 2| whereupon the ejector 22 becomesessentially a pump. It is to be noted that this ejector will draw either a liquid or gas through the intake 2| with equal facility.

The nozzle 25 is supplied with liquid under relatively high pressure through a liquid supply line 26 in which is connected a valve 21. Outlet 24 of the ejector 22 is connected to a discharge conduit 28 in which there is provided a valve 29.

In installations of the type under consideration, y

it is necessary that every precaution be taken against the entry of contaminating substances into the refrigerated space. Consequently whenever` connections of any type are made to this space some provision must be made to automat'- ically prevent the entry of such substances. In the proposed structure this problem is very simply solved by providing in the discharge conduit 2l a liquid trap I9 which may be connected to this valve 29 by a suitable pipe I3. Trap I9 may be connected to the usual sewer or discharge line 20. Since regardless of the manner of using 4 this apparatus, that is, whether the valve 29 is left open or closed between defrosting periods. trap I9 will always be suiciently filled with liquid to effectively seal pipe I8, discharge conduit 28 and supply conduit I5 against the entry of any contaminating substance and consequently no further precautions in this matter are necessary.

In order to remove the defrosting liquid and water resulting from the melting frost from the compartment I0, a drip pan 3Il is located beneath the cooling unit I2. The drip pan 30 is provided with a drain 3| extending exteriorly of the compartment through a suitable sealing means 32 in one of the walls thereof. Connected to the outer end 33 of the drain 3| is a conventional U-shaped trap 34, the opposite end 35 of which may discharge to the atmosphere or be connected to a sewer pipe 36. Obviously, the trap 34 operating in a well-known manner will effectively seal the drain 3| against the passage of gas in either direction and also will effectively prevent the entry of other contaminating substances into the compartment I0. If desired, liquid supply conduit I5 and drain 3| may be formed of a relatively poor heat conducting material inorder to prevent flow of heat therethrough and maintain the eiliciency of the system.

The operation of the defrosting system disclosed in Fig. 1 and described above is as follows: Assuming an accumulation of frost on the cooling unit I2 suflicient to require removal thereof, valve 29 in the discharge conduit 28 is closed and valve 21 in the liquid supply line 26 opened to permit liquid to flow through nozzle.25 and into ejector 22. Since the valve 29 is in closed position, liquid cannot escape through the discharge conduit 28, and consequently this liquid will fill the ejector 22 and ow through intake 2|, and liquid supply conduit I5 to the spray head I3. Upon reaching the spray head I3 the liquid will be discharged therefrom through apertures I4 in a relatively ne spray covering the outer surface of cooling unit I2 whereupon due to the relatively high temperature of the liquid, frost present on the surface of the cooling unit I2 `will be melted. The defrosting liquid as well as the liquid resulting from the melted frost will be collected in the drip pan 3U and drained therefrom through drain 3| and tra-p 34 to the atmosphere or sewer pipe 36 as the case may be. Also, during this operation due tothe relatively high temperature of the defrosting liquid a considerable volume of water vapor in the form of fog will be created in the vicinity of the cooling unitI I2.

Upon completion of the removal of frost from the cooling unit I2 of the defrosting operation, valve 29 in discharge conduit 28 is opened permitting the flow of liquid therethrough whereupon ejector 22 becomes a pump and withdraws all liquid present in the spray head I3 and supply conduit I5. Withdrawal of this liquid effectively` I precludes the subsequent freezing thereof and consequent clogging of the relatively small apertures I4 of the spray head I3. After removal of all liquid from the spray head I3 and supply conduit I5 operation of the ejector 22 is continued to withdraw the fog surrounding the cooling unit I2, the ejector 22 during this operation acting as a vacuum pump. Upon completion of the fog removal operation valve 21 is closed thus shutting off the supply of liquid to the ejector 22 and immediately thereafter valve 29 is closed to effectively seal the supply conduit I5 and spray head I3 against the entry of undesired contaminating substances. If for any reason valve 29 is not charge conduit 28 and supply conduit I5 against the entry of contaminating substances.

It will thus be seen that the above described system provides a relatlvelysimple and eflicient apparatus for defrosting a cooling unit in a refrigerated compartment by passing a relatively warm liquid thereover and for effectively and positively removing all liquid present during the defrosting operationv and in addition for removing the fog created by this operation. This system also provides means for eectively preventing the ow of cold air from the refrigerated space to' the exterior thereof and for preventing the. inflow of unde- Y sirable contaminating substances.

In many installations it is highly desirable that operation of the defrosting :system be entirely automatic' and accordingly there is illustrated in Fig. 2 an electrical control circuit which may be utilized in conjunction with the apparatus shown in Fig. 1 and described above for performing .the defrosting operation' at predetermined intervals by merely presetting a timing device for any desired number of defrosting operations within a predetermined period of time.

In this control system valves 2l and 29 are provided with operating solenoids 3l and 38 respectively, these solenoids being connected by a common lead to one side 40 of a source of electric power. The operation of solenoids 31 and 38 is controlled by switches 4I and 4i2 respectively, solenoid 3l being connected by leadl 43 to one pole t4 of switch iiiV and solenoid 38 being connected by lead 55 to one pole 46 of switch 42.v The opposite pole lil of switch 4I and pole '48 of Switch 42 are connected to a common lead 49. Switches 4I and 42 are opened and closed in the proper.

sequence by cams 50 and 5I respectively, iixed on a rotary shaft 52 driven`\at a. constant predetermined rate of speed by motor 53. Cams 50 and will be opened, thus closing thevalve 2l and stopping the flow of liquid. to ejector 22 and immediately thereafter switch 42 will be opened, thus 5I are provided with the proper surface contour to close switches 6I and 42 in the proper sequence and` to maintain these switches closed for a predetermined period of time, whereupon they are allowed to open in a predetermined sequence. Power for operation of the motor 53 is provided through a lead 54 connected to the power source 40 and through a lead 55 connected to the common lead 49 and in turn through a lead 55 to a timing device 5l. The opposite side of timer 51 is connected through a lead 58 with the power source.

The operation of the control system illustrated in Fig. 2 is initiated by the timer 5l which may be present to close the circuit from Ipower line 59 to motor 53 and poles l and 4t of switches 4I and 42 respectively at predetermined intervals. Energizing of the motor 53 will cause rotation of cams and 5I and the configuration of the surface of these cams are such that switch 4I will be closed, thus energizing solenoid 3l and opening valve 2l to permit the flow of liquid to ejector 22 and spray head I3. During the defrosting operation initiated by opening of valve 21, switch 42 will remain open and consequently valve 29 will remain closed. Upon completion of the defrosting operation the time of which has been predetermined, cam 5I will close switch 42 thus energizing solenoid 38 and opening valve 29, whereupon ejector 22 will withdraw the liquid present in supply conduit I5 and spray head I3 together with the fog present around the cooling unit I2, thus completing the defrosting operation. After operation of the ejector for a predetermined time to remove the fog, switch 4I- 75 precluded any possibility of clogging of the sys- I closing valve 29 to prevent flow through the sup- /Dly conduit I5 of contaminating or other undesirable substances into the compartment I0.

It willI thus be seen that' by the above described control circuit a relatively simple and eillcient means has been provided whereby the refrigeration equipment may be defrosted at predetermined intervals, the defrosting cycle being predetermined in accordance with the normal time required for such operation.v

In certain refrigeration installations means ie provided usually in the formof an electrically driven fan for circulating air within the revfrigerated compartment and over the cooling unit to more elliciently cool the compartmentand in installations such as these the motor for driving the circulatingfan and the power supply therefor may be conveniently utilized as a vcontrol means for a defrosting system such as that shown in Fig. l and described above.

Such a control system is illustrated in detail infFig. 3 in which a cooling unit 59 is appropriately located in a compartment of the rerigerator and a fan or blower 60 driven .by motor 6l is provided to circulate air through or over the cooling unit 59. Motor 6I may be of any desired type but for illustrative purposes only is supplied with S-phase current through lines 62, 63, and 5t. In order to take advantage of this particular arrangement for controlling a defrosting apparatus, a solenoid operated switch 65 is connected in the line 64 to the motor 6I, the coil 66 of switch 65 being so proportioned as to operate the movable contact 61 upon a predetermined change in current flowing in line 64.

This particular control system is designed to take advantage of the fact that as frost accumulates on the cooling unit 59 the passage of air therethrough will be impeded, thus increasing the load on the fan 60 and the motor' 6i so that the current ilowing in line 64 will be increased.

45 This increase in current results in movement of the contact 6l, thus closing the circuit'between contacts 68 and 69 to initiate operation ofthe defrosting apparatus. In adapting this control means to the circuit shown in Fig. 2 for control- 60 ling the defrosting system, switch 65 may be substituted for the timer 5l, contact 68 being connected to a line 56 leading to motor 53 and contact 69 being connected to the power source 55.

The control system shown in Fig. 3 is fully dis- 05 based on a predetermined cycle of operation, and

a predetermined period of time between cycles of operation and also which may be conveniently controlled by the degree of accumulation of frost on the cooling unit. This defrosting system com- 70 pletely and rapidly removes the accumulated frost from the cooling unit while maintaining a relatively low temperature in the refrigerated compartment. Also by removing all liquid used to ,accomplish the defrosting operation there is tem by formation of ice, and leakage of cold air into or fromthe compartment is prevented and removes any possibility of contamination of the interior of the compartment by the influx of gas or other substance.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown in the drawings and described in the specication but only as indicated in the appended claims.

What is claimed is:

1. A refrigeration system comprising a refrigeration compartment, a cooling unit disposed in said compartment, a defrosting system for removing accumulated frost from said cooling unit, said defrosting system comprising a spray head disposed above said cooling unit, a drip pan disposed beneath said cooling unit, .a drain connected to said drip pan and extending exteriorly of said compartment, a liquid trap in said drain, a liquid supply conduit connected to said spray head extending` upwardly therefrom and exteriorly of said compartment, said liquid supply conduit being connected to the intake of an ejector, a liquid supply line having a valve thereinl connected to said ejector, a discharge conduit havingl a valve therein and a liquid trap connected to the outlet of said ejector whereby upon closing of the valve in said discharge conduit and opening of the valve in said supply line liquid will flow through said ejector and into said spray head and be sprayed over said cooling-unit, thus melting the frost accumulated thereon, the liquid and melted frost being collected in said drip pan and removed from said compartment through said drain and whereby upon openingof the valve in said discharge conduit said ejector will operate to produce a partial vacuum in said liquid supply conduit and said spray head thereby removing all liquid present therein and upon continued operation of said ejector to thereby remove any water vapor present in the vicinity of said cooling unit. thus rapidly defrosting said cooling unit while maintaining a relatively low temperature in said compartment. y

2. In a refrigeration system including a compartment and a cooling unit therein, a spray head above said cooling unit, a liquid supply conduit connected to said spray head and having a portion located exteriorly of said compartment, a drip pan in said compartment beneath said cooling unit, a drain connected tov said drip panv including a liquid trap disposed externally of said compartment, an ejector having its intake connected to said liquid supply conduit, a liquid supply line having a valve therein connected to said ejector, a discharge conduit having a valve therein connected to the outlet of said ejector, whereby upon closing the valve in said discharge conduit and opening the valve in said supply line liquid will ow through said liquid supply conduit into said spray head and be sprayed over said cooling unit to melt frost accumulated thereon with the resultant liquid collected in said drip pan and drainable therefrom through said trap, and whereby upon opening of the valve in said discharge conduit said ejector will operate to produce a partial vacuum in said liquid supply conduit and all liquid removed therefrom and water vapor removed from the vicinity of said cooling unit whereby said cooling unit may be rapidly defrosted while maintaining a relatively low temperature in said compartment.

3. In a refrigeration system having a compartment and a cooling unit therein, a spray head disposed above said cooling unit, a liquid supply conduit connected to said spray head and extending externally of said compartment. a drip pan in said compartment disposed beneath said cooling unit,`a drain connected to said drip pan and having a liquid trap disposed therein externally of said compartment, an ejector having its intake connected to said liquid supply conduit, a liquid supply line having a valve therein connected to said ejector, a discharge conduit having a valve therein connected to the outlet of said ejector whereby upon closing of the valve in said discharge conduit and opening of the valve in said 4supply line liquid will flow through said liquid supply conduit into said spray head and be sprayed over said cooling unit thus melting frost accumulated thereon, the resultant liquid being collected in said drip pan and draining therefrom through said trap and whereby upon opening cf the valve in said discharge conduit said ejector will operate to produce a partial vacuum in said liquid supply conduit thus removing all liquid therefrom and serving to remove water vapor present in said compartment in the vicinity of said cooling unit whereby said cooling unit may be rapidly defrosted while maintaining a relatively low temperature in said compartment.

4. In a refrigeration system having a compartment and a cooling unit therein, a spray head disposed 'above said cooling unit, a liquid supply conduit connected to said spray head, a drip pan in said compartment disposed beneath said cooling unit, a drain connected to said drip pan, an ejector connected to said liquid supply conduit, a liquid supply line connected to said ejector. a discharge conduit having a Valve therein connected to the outlet of said ejector whereby upon closing of the valve in said discharge line liquid will flow through said ejector and said liquid supply conduit into said spray head and be sprayed over said cooling unit thus melting frost accumulated thereon and whereby upon opening of the valve in said discharge conduit said ejector will operate to produce a partial vacuum in said liquid supply conduit thus removing all liquid therefrom, whereby said cooling unit will be rapidly defrosted while maintaining a relatively low temperature in said compartment.

5. In a refrigeration system having a compartment and a. cooling unit therein, a spray head disposed above said cooling unit, a liquid supply conduit connected to said spray head, a drip pan in said compartment disposed beneath said cooling unit, a drain connected to said drip pan, an ejector connected to said liquid supply conduit, a liquid supply line connected to said ejector, a discharge conduit connected to said ejector, and means for controlling the supply of liquid to said ejector and the disharge of liquid therefrom whereby during one cycle of operation liquid will be supplied to said spray head thus melting frost accumulated on said cooling unit and during another cycle of operation said ejector will operate to produce a partial vacuum in said liquid supply conduit thus removing all liquid therefrom whereby said cooling unit may be rapidly defrosted while maintaining a relatively low temperature in said compartment.

6. In a refrigeration system having a compartment and a cooling unit therein. a spray head disposed adjacent said cooling unit, a liquid supply conduit connected to said spray head, an ejector connected to said liquid supply conduit,

a liquid supply line connected to said ejector, a discharge conduit connected to said ejector, means for controlling the supply of liquid to said ejector and the discharge of liquid therefrom whereby during one-cycle of operation liquid will be supplied tdY said spray head and during another cycle of operation said ejector will operate to produce a partial vacuum in said liquid supply conduit thus removing all liquid therefrom whereby said cooling unit may be rapidly defrosted while maintaining a relatively low temperature in said compartment.

7. In a refrigeration system having a compartment and a cooling unit therein, a spray head disposed adjacent to said cooling unit, means for supplying liquid to said spray head whereby frost accumulated on said cooling unit is melted therefrom and pump m'eans for positively removing all liquid present in said spray head upon completion of the defrosting operation and for removing water vapor present in said compartment in the vicinity of said cooling unit whereby said cooling unit may be rapidly defrosted While maintaining a relatively low temperature in said compartment.

8. In a refrigeration system including a compartment and a cooling unit therein, that improvement which consists in providing a defrosting system having means for spraying a fluid of relatively high temperature over said cooling unit to melt frost accumulated thereon, means for collecting said uid and the melted frost and draining the same from said compartment,

means for sealing said spray means and said drainmeans against the flow of cold air from said compartment and against the entry of foreign substances thereto, and means operatively connected to said spray means for creating a partial vacuum whereby fluid therein is positively removed.

9. In a refrigeration system including a compartment and a cooling unit therein, that improvement which consists in providing a defrosting system including means for directing uid over said cooling unit to melt frost accumulated thereon, means for collecting said uid and the melted frost and draining the same from said compartment, and means operatively connected to said spray means for creating a partial vacuum whereby fluid therein is positively removed.

10. In a refrigeration system including a compartment and a cooling unit therein, that improvement which consists in providing a defrosting system having means for spraying iluid over said cooling unit to mselt frost accumulated thereon, and means operatively connected to said spray means for creating a partial vacuum whereby uid therein is positively removed.

11. In a refrigeration system including a compartment anda cooling unit therein, that improvement which consists in providing an automatic defrosting system having means for spraying uid of relatively high temperature over said cooling unit to melt frost-accumulated thereon, means for collecting said fluid and melted frost and draining the same from said compartment, means operatively connected to said spray means for creating a partial vacuum whereby fluid therein is positively removed, electrical control means operatively associated with said spray means and said vacuum creating means whereby the same is operated through a predetermined cycle, and means associated with said control meansl for initiating operation thereof at predetermined intervals.

12. In a refrigeration system including a compartment and a cooling unit therein, that improvement which consists in providing an automatic defrosting system having means for spraying fluid over said cooling unit to melt frost accumulated thereon, means for collecting said uld and the melted frost and draining the same from said compartment, means operatively connected to said spray means for creating a partial vacuum whereby uid collected therein is positively removed, electrical control means for said defrosting system comprising electrically operated valve means associated with said spray means and said vacuum creating means, means for actuating said valve means in accordance with a predetermined cycle and means automatically responsive to the accumulation of frost on said cooling unit for initiating operation of said valve actuating means. 1

13. An apparatus as dened in claim l2 in which said valves are each operated by a solenoid, each solenoid being controlled by a switch actuated by a motor driven cam timing device controlling the period of operation of said motor and capable of being preset for a predetermined cycle of operation.

14. Anapparatus as dened in claim 412 in which a motor driven fan is provided for circulating air through said cooling unit and in which electrical control means is provided in the power circuit for said motor, said control means initiat- I ing the actuation of said valves in response to a changel in load on said motor due to an accumulation of frost on said cooling unit.

15. An apparatus as defined in claim 12 in which said valves are each operated by a solenoid, each solenoid being controlled by a switch actuated by a motor driven cam and means responsive to the accumulation of frost on said cooling unit fo'r controlling the operation of said motor.

MAHLON B. WATTS.

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

UNITED STATES PATENTS Number Name Date 2,001,027 Kitzmiller May 14, 1935 2,001,028 Kitzmiller May 14, 1935 2,025,456 Kage Dec. 24, 1935 2,219,393 McAdam Oct. 29, 1940 2,300,085 Yunker Oct. 27, 1942 2,323,511 Baker July 6, 1943L

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