Ducted refrigeration unit

United States Patent un 3,572,052

<td> [72]</td><td> Inventor</td><td> Steven J. Toth Kendallville, Ind.</td>

<td> [21]</td><td> Appl. No.</td><td> 824,934</td>

<td> [22]</td><td> Filed</td><td> May 15,1969</td>

<td> [45]</td><td> Patented</td><td> Mar. 23,1971</td>

<td> [73]</td><td> Assignee</td><td> Streater Industries Inc. Albert Lea, Minn.</td>

[54] DUCTED REFRIGERATION UNIT 3 Claims, 1 Drawing Fig.

[52] U.S.CI.................................................. 62/278,

62/81,62/90,62/155,62/234,62/408

[51] Int. Cl.........................................................F25b 47/00

[50] Field of Search.................................... 62/81,278,

90,155,234

[56] References Cited

UNITED STATES PATENTS 1,859,427 5/1932 Bulkeley....................... 62/278

2,254,420 9/1941 Cleveland..................... 62/283

2,481,348 9/1949 Ringquist..................... 62/278

<td> 2,932,955</td><td> 4/1960</td><td> Hargrave......................</td><td> 62/526</td>

<td> 3,063,252</td><td> 11/1962</td><td> Jaunt....................</td><td></td>

<td> 3,067,592</td><td> 12/1962</td><td> McFarlan...................</td><td> 62/426</td>

<td> 3,119,239</td><td> 1/1964</td><td> Sylvan..........................</td><td> 62/90</td>

<td> 3,499,295</td><td> 3/1970</td><td> Brennan.......................</td><td> 62/256</td>

<td></td><td colspan="2"> ' FOREIGN PATENTS</td><td></td>

<td> 12,896</td><td> 6/1891</td><td> Great Britain..,.............</td><td> 62/278</td>

Primary Examiner— William J. ’Wye Attorney—Wayne B. Easton

ABSTRACT: The invention relates to a ducted refrigeration unit for continuously supplying quantities of refrigerated air to a group of refrigerated food display cases. The unit has two chambers arranged in parallel with a cooling coil disposed in each chamber. A liquid refrigerant is selectively and alternately supplied to one coil during the time a hot defrosting gas is supplied to the other coil. Damper means alternately direct circulating air through the chamber in which the coil thereof is supplied with a liquid refrigerant while bypassing the chamber m which the coil thereof is being defrosted.

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PATENTED MR 2 31971

3,572,052

CHECK VALVE

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3,572,052

-. 1 ' 2

DUCTED REFRIGERATION UNIT .

The invention relates to a new and improved ducted refrigeration unit for continuously supplying quantities of refrigerated cooling air to a group of refrigerated display cases.

One type of refrigerated display case found in supermarkets has cooling coils installed in the display case and liquid refrigerant is supplied to the coils through pipes from remotely located refrigeration apparatus. This type of refrigerated display case is distinguishable from the more common type wherein refrigeration apparatus comprising a compressor and motor unit and evaporator coils are. self-contained in the display case.

The type of refrigeration system to which the present invention pertains is referred to herein as a ducted refrigeration system. In a ducted closed circuit system cool air is supplied from a remotely located refrigeration unit through ductwork to a group of display cases. The refrigerated air supplied is warmed upon passing through the display cases and is returned through other ductwork to the refrigeration apparatus where it is recooled and the cycle is repeated. The display cases so serviced are normally of the air curtain type which provides a moving curtain of air to isolate the interior of the cases from the surrounding atmosphere.

The air curtain principle is of a nature such that a portion of the air circulating in the air circulating system is lost to the atmosphere while some atmospheric air is picked up by the curtain and is thereby drawn into the circulating system.

The atmospheric air drawn in by the air curtain is relatively humid and readily condenses on the evaporator coils in the system. The buildup of frost on the. coils causes the air circulation to be gradually restricted, with less and less air being cooled, until the temperature of the air delivered to the display cases has risen above the desired level. A defrost cycle is then required to remove the accumulated ice and frost from the coil surface. During the defrost cycle the temperature of the circulating air tends to rise above the level and cause damage to the products in the display cases being serviced, thereby shortening the shelf lives of the products.

In the present invention there is provided a ducted refrigeration unit having two chambers arranged in parallel with a cooling coil disposed in each chamber. Damper means are provided so that the circulating air is selectively directed through one or the other of the chambers. During operation, either one of the coils in one chamber, through which air is being circulated, may be supplied with a condensed liquid refrigerant to provide cooling while the other coil in the other chamber is simultaneously being provided with a noncondensed hot gas refrigerant to provide defrosting for that coil. With this arrangement, cooled air may be continuously supplied to display cases in required quantities, by switching back and forth between the two chambers, with no interruptions for defrosting cycles.

A main object of the invention is to provide a new and improved ducted refrigeration unit for supplying cooled air in required quantities with no interruptions for defrosting cycles.

Other objects and advantages of the invention will become apparent from the following specification, drawings and appended claims.

The drawing shows a schematic cross-sectional view of a ducted refrigeration unit embodying the invention along with a schematic showing of refrigeration apparatus utilized in connection with the ducted refrigeration unit.

A ducted refrigeration unit 1 to which the present invention pertains has a housing which includes a cylindrically shaped middle portion 2 and frustoconically-shaped end portions 3 and 4. At the inlet end of the unit 1, adjoining housing portion 3 is attached an air moving device 6, such as an air blower or air compressor, having an air inlet pipe 7. At the opposite end of the unit 1 is attached an air outlet pipe 8.

The housing and pipe members referred to above are of sheet metal construction and, as it is only a schematic showing that is illustrated, specific shapes are referred to only for convenience of description in that a variety of other shapes could be utilized within the scope of the invention.

' ' The assembly or unit 1 described thus far is an element of a generally closed circuit refrigeration system in which cooled air is supplied through the outlet pipe 8 to one or more food display cases (not shown) and from which relatively warmer 5 and more humid air is returned to the unit 1 through the inlet pipe 7. The air moving device 6 supplies the motive power for circulating the air.

Unit 1 has in the interior thereof a partition 12, illustrated as being in a generally horizontal plane, which divides the interi10 or of unit 1 into chambers 13 and 14. Partition 12 is in spaced relation to the inlet and outlet ends of the unit 1 and, at opposite ends of the unit, dampers 16 and 17 are pivotally connected to the partition so that inlet air may be directed selectively to either the chamber 13 or the chamber 14, as desired.

Dampers 16 and 17 are illustrated in positions which would permit air to be directed from inlet pipe 7, through chamber 14, to outlet pipe 8. Unit 1 may desirably be insulated so that chambers 13 and 14 are insulated from the surrounding atmosphere and from each other.

Chambers 13 and 14 are provided with coils 20 and 21, respectively, and outlet pipe 8 is provided with a coil 22. Inlet and outlet portions of these coils extend externally of the unit 1 and outlet pipe 8, as illustrated, to allow connections with ₂₅ other refrigerating apparatus. Coils 20 and 21 have relatively wide fin spacing on the upstream sides thereof and relatively narrow fin spacing on the downstream sides thereof.

Display cases serviced by the refrigeration unit 1 have specific requirements as to the temperature of the air utilized for preserving their contents which ranges from about 50° F. for butter, cheese and eggs to —20° F. for ice cream. There are also varying requirements for the relative humidity of the air in some instances with regard to some products, as in the case of fresh vegetables, which would become dried out with too 35 little moisture in the air and would be subject to spoilage if there is too much moisture in the air.

In the operation of the system, circulating air is dehumidified, cooled, reheated and ducted to and from a group of display cases. In the operation of the unit 1, one of the coils 20 4q or 21 is supplied with a liquid cooling refrigerant during which time the other coil may be supplied with a hot gas defrosting refrigerant. Cooling and defrosting cycles are alternated between chambers 13 and 14 by an electric timer 26 which functions to control the dampers 16 and 17 and various 45 refrigeration apparatus valves for controlling the flow of cooling and hot gas defrosting refrigerants to the coils 20 and 21 and the flow of hot gas refrigerant to the coil 22.

Return air enters either the chamber 13 or 14 depending on the positions of dampers 16 and 17. The air is first dehu50 midified by its traversing the wide fin portion of the 20 or 21 and then cooled by its traversing the narrow fin portion of the same coil. Heat may be added to the air as it traverses coil 22 in outlet pipe 8, if desired or necessary, to provide a high degree of control relative to the temperature and humidity of 55 the air.

The refrigeration apparatus utilized in connection with the unit 1 included a compressor 30, a condenser 31, and a liquid refrigerant receiver 32. A conduit 33 conriects compressor 30 with condenser 31 and a conduit 34 connects condenser 31 to 60 receiver 32. A refrigerant liquid supply line 38 has one end thereof connected to the receiver 32 and is connected through parallel branches 39 and 40 thereof, respectively, to the inlets of coils 20 and 21 in chambers 13 and 14. The suction fine of compressor 30 is provided with a suction header 42 to which 65 the outlets of coils 20 and 21 are connected respectively through parallel conduits 43 and 44.

Each of the coils 20 and 21 has the usual thermostatic expansion-type valve 47 associated therewith for regulating the amount of liquid refrigerant to be admitted to the coils during 70 the normal refrigeration cycle for the respective coil. Conduits 43 and 44 have solenoid controlled valves 45 and 46 disposed respectively therein, each of which valve is open during the normal refrigeration cycle for the respective coil. Valves 4S and 46 are also regulator valves which perform the functions 75 of regulating the pressures and the corresponding tempera3,572,052 tures in coils 20 and 21 but these functions of these valves have no bearing on the invention. Refrigerant liquid supply line 38 has a solenoid controlled valve 48 disposed therein which is open during the normal refrigeration cycle.

With the apparatus described, a conventional refrigeration cycle may be performed relative to each coil 20 and 21. Compressor 30 compresses a gaseous refrigerant which flows to the condenser 31 where the refrigerant is condensed to a liquid and flows through the liquid supply line 34 to the receiver 32. Assuming that coil 21 is to be cooled and that coil 20 is to be defrosted, the timer 26 causes dampers 16 and 17 to move to the positions illustrated and causes the opening of valve 46 and the closing of valve 45. Liquid refrigerant then flows from the receiver 32 through the normally open solenoid valve 48 to the coil 21 through the liquid supply line branch 40 and the thermostatic expansion valve 47 therein. The liquid refrigerant is expanded through the expansion valve 46 and enters the coil 21. The expanded and evaporated refrigerant then leaves the coil 21 and is drawn through the return conduit 44, in gaseous form, to the suction header 42 and the suction inlet of the compressor 30.

The defrosting cycle for alternately defrosting the coils 20 and 21 requires certain additional apparatus as will be described. The cycling involved is controlled by the timing mechanism 26 and the timing programming will of course vary for different installations. An example of the programming would be to have the dampers 16 and 17 change at 30 minute intervals such that the cooling function would be performed by each coil 20 and 21 during alternate 30 minute intervals. During each 30 minute period the other coil would be defrosted for a period of time up to 30 minutes. As a practical matter for the purpose of efficiency, the programming relative to defrosting would be set for a lesser period such as 10 or 15 minutes which would be the actual time needed to complete the defrosting of a coil.

With regard to additional apparatus for defrosting, each of the conduits 39 and 40 is provided with a bypass around the thermostatic expansion valve 46 therein. These are bypass conduits 50 and 51 with each conduit having a check valve 52 disposed therein. Compressor discharge line 33 has two hot gas conduits 53 and 54 individually connected thereto and the opposite ends of these hot gas conduits are connected respectively to conduits 43 and 44 at points between the coils 20 and 21 and the valves 45 and 46. Respectively disposed in the hot gas conduits 53 and 54 are solenoid operated valves 56 and 57.

In association with liquid supply valve 48 there is provided a pressure sensing and responsive switch 60. A sensing tube 61 is connected to and extends from switch 60 to liquid supply line 39 on the downstream side of valve 48. The switch 60 in turn is electrically connected to valve 48 with a wire 62 for operating valve 48.

Timing or clock unit 26 has electrical connections (not shown) with the solenoid operated valves 45 and 46, the solenoid operated valves 56 and 57, the solenoid operated valve 48 and valve regulator 60. The defrosting operations in the il-. lustrated embodiment of the invention are based on predetermined time intervals although other known methods for determining defrosting times could also be used within the scope of the invention. It may be assumed for purposes of illustration that the timing unit 26 is set to allow the refrigeration cycle described above with respect to coil 21 to operate for a period of 30 minutes and then effect defrosting of the coil 21 while allowing previously defrosted coil 20 to provide cooling for the system. It is further assumed that the refrigerant used is R-12 which has a condensing pressure of about 117 p.s.i.g. at a condensing temperature of 100° F., and that the compressor pressure in the discharge line 33 is about 117 p.s.i.g. Refrigerant R-12 is only referred to by way of example as other refrigerants would also be suitable.

At a predetermined time when the coil 21 is to be defrosted, the timing unit 26 simultaneously effects the opening of the normally closed valve 56, the closing of the normally open valve 46, the closing of the normally open valve 48, and shifting of the dampers 16 and 17 to their dotted line positions shown in the drawing. In the defrosting operation relative to coil 21, the closing of valve 48 in the liquid supply line 38 causes the pressure developed by the compressor 2 to be directed from the condenser 31 to the hot gas line 53. The hot gas flows from line 53, through line 44, into coil 21. While traversing the evaporator 21 the hot gas loses heat to the coil to cause defrosting thereof and, in the process, condenses and becomes a cold liquid. The liquified refrigerant flows out of coil 21 through line 51 and the check valve 52 thereof, and into the branch liquid supply line 39. Keeping in mind that the valve 48 is closed during the defrosting operation, except under certain conditions as noted hereinafter, the condensed refrigerant resulting from the defrosting of coil 21 is available to provide cooling for coil 20 in the same manner as the liquid refrigerant supplied through valve 48 during the part of the cycle during which time there is no defrosting operation of either coil 20 or 21. The liquid refrigerant from coil 21 thus flows to coil 20 where the refrigerant is vaporized and returned to the suction header 42 through line 43 in the same manner as during the normal refrigeration cycle.

The purpose in having the main liquid supply valve 48 closed during the above-described defrosting operation is that the condensed liquid may be removed quickly from the coil being defrosted so that the defrosting can be accomplished very efficiently. At the same time, the condensed refrigerant from the coil being defrosted is utilized to provide cooling for the other coil.

With regard to the operation of valve 48, the refrigerant R-12, for example, has a normal condensing pressure of about 117 p.s.i.g. and, if that is the refrigerant to be used, the pressure in the liquid supply line should not be allowed to drop below 117 p.s.i.g. during a defrosting operation. In the system of the present invention the pressure of the refrigerant in the liquid supply line 38 during a defrosting operation, when the valve 48 is closed, is dependent upon a number of variables such as the sizes of the coils and the lengths of the piping runs, for example. It is contemplated that in some installations the defrosting cycle described above would always operate with the pressure in the line 38 being higher than the condensing pressure of the refrigerant being used. In other installations, however, the pressure in the line 38 may at times fall below the desired pressure of the liquid refrigerant and, in order to provide an antidote for that type of operating condition, the valve regulator 60 is provided. The sensing tube 61 senses the pressure in the line 38 and the regulator 60, which is devised to override the effect of the timing unit 26 on the valve 48, is adjusted to open the valve 48 whenever the pressure in line 38 drops below the preset pressure of the refrigerant being used. In particular installations the regulating feature performed by the regulator 60 may not be needed and in such instances that feature may be omitted.