US3460354A - Refrigeration system and method - Google Patents

Description

Aug. 12, 1969 Filed March 7. 1968 H. P. PETERSON 3,460,354

REFRIGERATION SYSTEM AND METHOD 2 Sheets-Sheet 1 r 1,1? d u L- LI I II * I I! F -32 I i I I I I UH; l

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REFRIGERATION SYSTEM AND METHOD Filed March 7, 1968 2 Sheets-Sheet 2 U u u m n n u CONTROLLER Fig. 3

46 INVENTOR.

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ATTORNEYS nited States Patent Office 3,460,354 Patented Aug. 12, 1969 3,460,354 REFRIGERATION SYSTEM AND METHOD Hans P. Peterson, Simsbury, Conn, assignor to Dunham- Bush, Inc., West Hartford, Conn., a corporation of Delaware Filed Mar. 7, 1968, Ser. No. 711,243 Int. Cl. F25b 39/04 U.S. Cl. 62-184 8 Claims ABSTRACT OF THE DISCLOSURE There are many refrigeration systems of the type which have the evaporator positioned within a building and an air-cooled condensing unit positioned upon the roof of the building or adjacent the building. An arrangement is disclosed for controlling the cooling effect of the air on the condenser of such a refrigeration system. The condensing unit is enclosed within a housing which has an air inlet at the bottom and an air outlet near the bottom, and the condenser is positioned near the top of the casing. Fans are provided which are operative to circulate air through the housing and thereby cool the condenser in a very efficient manner. When the ambient air temperature drops sufiiciently to cause the condenser to be cooled excessively, the fans are stopped so that there is no longer a positive circulation of the air into and out of the housing. The air within the housing continues to be heated by the condenser and the housing provides an inverted pocket in which the heated air tends to accumulate. The fans also may be operated to circulate the air through the condenser but without causing fresh air to be circulated through the housing.

This invention relates to refrigeration systems, and more in particular to refrigeration systems of the type where the entire condensing unit is mounted outside of a building and has an air-cooled condenser which is exposed to wide variations in the temperature of the air.

An object of this invention is to provide an improved refrigeration system of the above character. A further object is to provide simple and efficient arrangements providing variable cooling of air-cooled condensers. A further object is to overcome the difiiculties which are ncountered with air-cooled refrigerant condensing units as a result of excessive cooling of the condenser. These and other objects will be in part obvious and in part pointed out below.

Condensing units of the above type are exposed to wide variations in the outside air temperature and there have been resultant problems and difficulties which have interfered with eilicient and dependable operation. When the temperature of the outside air drops, particularly near or below the temperature of the refrigerated space, the liquid refrigerant tends to accumulate in the condenser, and the evaporator does not receive liquid refrigerant in the normal manner. A great deal of effort has been expended in overcoming that condition, and many different arrangements have been proposed and used. It is a further object of the present invention to solve such problems. Another object is to provide simple and efficient arrangements for controlling precisely the amount of cooling of the refrigerant in systems of the character referred to above.

In the drawings:

FIGURE 1 is a side elevation with parts broken away showing one embodiment of the invention;

FIGURE 2 is a reduced scale representation of the condenser and fan assembly of the system of FIGURE 1; and

FIGURE 3 is a schematic representation of the electrical control system for the illustrative embodiment.

Referring to FIGURE 1 of the drawings, a refrigeration system 1 has a condensing unit 2 positioned upon the roof of the building and comprising, a compressor 4, an air-cooled condenser 6, a receiver 8 and standard auxiliaries and controls, all enclosed within a sheet metal housing 10. The refrigeration system also has an evaporator 12 and an expansion valve 13 which are positioned within a refrigerated space in the building, and which are represented schematically in FIGURE 1. Housing 10 has a rigid frame construction and sheet metal walls at the top, bottom and sides, and the housing is closed except for a rectangular air inlet opening 16 in the front of the bottom wall 25, and an air outlet opening 18 beneath the front wall 20. A slanting wall 22 extends between the bottom edge of opening 18 and the left-hand edge of opening 16 and upwardly toward the center of the housing to a horizontal plate 24. Bottom wall 25 extends beneath compressor 4 to the rear wall 26. Condenser 6 is a finned coil assembly of standard construction with parallel vertical faces between the side walls 29 and directly below the top wall 28. Two fans 30 and 32 (see also FIGURE 2) are positioned side-by-side horizontally at the left of the condenser, and cowls 34 close off the left-hand face of the condenser around the fans. A vertical wall 31 extends upwardly from plate 24 to the bottom of the cowls 34. Hence, housing 10 is divided by wall 22, plate 24 and wall 31 to provide a vertical air inlet passageway extending upwardly from opening 16 past the motor compressor and the other components and thence between the walls 31 and 26 to the rear face of the condenser. An air discharge passageway is also provided from the left-hand face of the condenser and the fans 30 and 32 downwardly between front Wall 20 and wall 31 to opening 18.

Fans 30 and 32 are operative to draw air from right to left through the condenser, and that causes air to flow into the bottom of the housing, to the left through the condenser, and thence downwardly out through opening 18. Hence, a simple air-flow path is provided which cools the components of the system and the refrigerant in the condenser.

As indicated above, the present invention provides for controlled cooling of the refrigerant in condenser 6. In accomplishing that purpose, housing 10 provides an inverted pocket above the bottom edge 21 of front wall 20 which is totally closed by the rear, side, top and front walls. Hence, while fans 30 and 32 may be operated to pass air through the housing to provide maximum cooling, there is no substantial flue effect to cause a natural flow of heated air from the housing when the fanas arenot operating. If the fans are stopped, the air in the top of the housing, which has been heated by the condenser is lighter than the cold outside air surrounding the housing, and that heated air remains in the inverted pocket in the top of the housing so that the condenser is surrounded by the heated air. Assuming that the operating conditions are such that the circulation of the air by the fans has caused over-cooling of the condenser, the stopping of the fans will immediately relieve that condition.

In the illustrative embodiment there is also an arrangement for providing a controlled amount of air cooling for the condenser. Referring to FIGURE 2, fans 30 and 32 may be operated to draw the air through the condenser from the rear of the housing toward the front as discussed above. However, the direction of fan 32 may be reversed so as to direct air from the front of the housing toward the rear through the condenser. When operating in that the manner, the air in the top of the housing is circulated back and forth through the condenser, but there is no positive discharge of air from housing. The air being circulated by the fans in that manner is subjected to a limited amount of cooling by conduction through the sheet metal walls of the housing. Also, when the fans are stopped and when they are operating in opposite directions to merely circulate air within the housing, the air in the vicinity of the motor compressor may be heated sufficiently to cause an upward flow in the rear of the housing with a corresponding natural discharge of air through opening 18.

With the arrangement of the illustrative embodiment, there is a wide range in the amount of actual cooling of the refrigerant. Sequence controller 40 is operative to gradually reduce the cooling effect by first stopping motor 32, then operating motor 32 in the reverse direction, and then stopping both of the motors; and the motors may be two-speed. In addition, the invention contemplates the use of a fan speed controller which operates in response to the temperature or pressure of the refrigerant in the condenser to govern the power input into the fan motor or motors, and with a fan motor or motors which operate at a speed proportional to the power input. That provides an uninterrupted modulation in the air circulation. The invention also contemplates the possible use of a damper to close the air outlet opening 18, thus to provide a positive shutting off of the air discharge. Openings 16 and 18 may be covered with suitable screens so that the housing is kept free from the entry of foreign materials and items and the housing gives very adequate protection for components of the condensing unit.

In FIGURE 3 there is represented schematically the control system for the operation of fans 30 and 32. Electrical current is supplied to a sequence controller 40 from which lines 42 and 44 extend to both windings of the motor for fan 30, and line 42 also extends on one side of the field winding 46 of the motor for fan 32. The other side of field winding 46 is connected through a line 48, a switch unit 50 of a relay 52 and a line 54 to line 44. The starting winding 56 of the motor for fan 32 is connected at one side through a line 58 and a switch unit 60 to line 48, and the other side is connected through a line 64, a switch unit 66, and a line 68 to line 42. Hence, with relays 52 and 62 positioned as shown, both of the fan motors are operated when controller 40 supplies current to lines 42 and 44.

Controller 40 is also connected to the solenoids 70 and 72 of relay 52. It has been indicated above that fan 32 may be stopped while fan 30 continues to operate. That is accomplished by energizing solenoid 72 which raises the armature of switch unit 50 through which line 44 is connected to the motor for fan 32, and fan 32 is stopped. Controller 40 may then operate fan 32 in the reverse direction by energizing solenoid 70 which closes a switch unit 74 so as to connect line 54 through a line 76 to a switch unit 78. Switch unit 78 is closed by the lifting of the armature of switch unit 50 by solenoid 72. Hence, with switch units 74 and 78 closed, line 44 is connected to line 48 and thence to the field winding of the motor for fan 32.

If the starting winding 56 were to remain connected as before, fan 32 woulld be operated in the same direction as before. However, relay 62 has a solenoid 80 which is connected at one side through line 68 to line 42, and the closing of switch unit 74 connects the other side of solenoid through a line 88, switch unit 74 and line 54 to line 44, so that solenoid 80 becomes energized. The ener gization of solenoid 80 lifts the armatures of switch units 60 so as to reverse the connection of lines 42 and 44 to field winding 56, so that fan 32 operates in the opposite direction. At that time, one side of winding 56 is connected through line 58, switch unit 66 and line 68 to line 42, and the other side of winding 56 is connected through line 64, switch unit 60, line 48, switch unit 78, line 76, switch unit 74 and line 54 to line 44.

During operation, controller 40 acts in response to a drop in the head pressure of the compressed refrigerant passing to the condenser. Controller 4%) then carries on a sequence of steps as that head pressure drops through a relatively narrow range. When the head pressure is above that range both of the condenser fans 30 and 32 operate whenever the compressor operates. A drop in the head pressure to that range indicates that there is over-cooling of the condenser, and the first control step is to stop fan 32. That reduces the amount of air circulation through the condenser, but fan 30 continues to operate and provides a reduced amount of cooling of the refrigerant. If the over-cooling condition continues, there is a further drop in the head pressure and controller 40 then starts fan 32 in the reverse direction so as to provide the air circulation solely in the top of the housing. If the overcooling condition then continues, the next step of controller 40 is to stop both fan motors by cutting off the power to lines 42 and 44. It is thus seen that controller 40 modulates the amount of cooling which is performed upon the refrigerant in condenser 6 to maintain the proper condition.

In this embodiment, compressor 4 is driven by an electric motor which is enclosed within the same housing. The particular control arrangement illustrated in the drawing provides a very practical mode of modulating the cooling. The invention contemplates that other control arrangements may-be provided and that the apparatus and the mode of operation may be modified.

What is claimed is:

1. In a refrigeration system, the combination of, an evaporator positioned to perform a cooling function by the evaporation of refrigerant therein, a condensing unit to supply liquid refrigerant to said evaporator and to withdraw and condense the evaporated refrigerant, said condensing unit including an air cooling condenser, a housing enclosing said condenser and providing an inverted air pocket for air to cool said condenser, said housing being closed from its top downwardly to a level substantially below the bottom of said condenser and having structure therebelow which provides for the entry of air into said pocket and the discharge of air therefrom, fan means to circulate air through said pocket in heat exchange relationship with said condenser, and control means to modulate the air flow between a condition wherein said fan means directs a maximum amount of air therethrough and a condition wherein there is substantially no air flow therethrough.

2. A system as described in claim 1, wherein said fan means comprises a plurality of electric fans, and said control means comprises a sequence controller.

3. A system as described in claim 2, wherein said condenser has vertical faces transverse to the flow of air therethrough and wherein said fans comprise two fans in side-by-side relationship horizontally spaced along one of said faces, and wherein said controller operates in response to the pressure of the condensed refrigerant.

4. A system as described in claim 3, wherein said fans operate in parallel to draw air through said condenser when the refrigerant pressure is above a predetermined value and upon successive decreases in said refrigerant pressure, said fans are operated to successively decrease the air flow.

5. A system as described in claim 1, wherein said housing has a bottom wall with an air inlet opening therein and a side wall with an air outlet opening therein, and partition means providing air passageways to and from the opposite faces of said condenser. v

6. A system described in claim 5, wherein said compressor is mounted on said bottom wall in the path of the air entering said inlet opening.

7. A condensing unit for a refrigeration system comprising a compressor having an electric motor which drives it, a receiver, a condenser, refrigerant lines providing a refrigerant flow path to and from said compressor, said condenser, and said receiver, a housing providing an inverted air pocket and air inlet and discharge paths for said pocket, said condenser being positioned within said pocket whereby it is surrounded by air which tends to become stratified within said pocket when heated above the temperature of the air surrounding said housing and control means to provide controlled air circulation to cool said condenser.

8. Apparatus as described in claim 7, wherein said control means comprises fan means and a controller responsive to a drop in the pressure-temperature condition of the refrigerant in the condenser.

References Cited UNITED STATES PATENTS 15 WILLIAM J. WYE, Primary Examiner US. Cl. X.R. 62507

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