US3131548A

US3131548A - Refrigeration purge control

Info

Publication number: US3131548A
Application number: US234638A
Authority: US
Inventors: Donald E Chubb; Wilbur C Smith
Original assignee: Worthington Corp
Current assignee: Worthington Corp
Priority date: 1962-11-01
Filing date: 1962-11-01
Publication date: 1964-05-05
Anticipated expiration: 1981-05-05

Description

May 5, 1964 5 :H ETAL 3,131,548

REFRIGERATION PURSE CONTROL Filed NOV. 1, 1962 SEPARATOR FIG.I

TO PURGE MECHANISM COMPRESSOR DRIVG MOTOR DONALD E. CHUBB WILBUR C. SMITH IN VENTORS H62 I Z 7 United States Patent 3,131,548 REFRIGERATION PURGE CONTROL Donald E. Chubb, Caldwell, and Wilbur C. Smith, Rutherford, N .J., assignors to Worthington Corporation, Harrison, N.J., a corporation of Delaware Filed Nov. 1, 1962, Ser. No. 234,638 7 Claims. (Cl. 62-159) This invention relates in general to an improved refrigeration system. It relates more particularly to a control means for automatically operating a purge arrangement for removing non-condensible gases from the system.

Closed systems in which a vaporizable refrigerant such as those in the Freon class is normally circulated, depend in large for their efiiciency on the ability of the system to maintain the refrigerant substantially free of non-condensible gases. Ordinarily, it is impossible to completely eliminate air leakage into a closed system operated below atmospheric pressure so means is provided for purging the entire system continuously or intermittently to remove undesirable gases and maintain the purity of the refrigerant.

As a feature of economy it is advantageous to purge the system intermittently rather than continuously. However, to be practical, the purger must be characterized by simplicity of operation and also be automatic to avoid the need for continuous monitoring.

It is therefore an object of the present invention to provide an automatic control means governing operation of a refrigerant purge system.

Another object is to provide a closed refrigeration system circulating a vaporizable refrigerant and having means for automatically removing non-condensible gases.

A further object is to provide a method for automatically controlling the amount of non-condensible gases contained in a closed refrigeration system to a minimum.

A still further object is to provide means to automatically operate a refrigeration system purging arrangement responsive to the degree of superheat contained in saturated liquid refrigerant.

These and other objects of the invention will become apparent to one skilled in the art from the following description made in conjunction with the drawings, in which:

FIGURE 1 is a diagrammatic representation of the present closed refrigeration system including a purge arrangement cooperative with the system, and a novel control means for operating the purger.

FIGURE 2 is a diagrammatic representation of the refrigeration system condenser shown in FIGURE 1 including an alternate purger control.

The aforementioned objectives are carried out according to the invention by providing control means cooperative with a first portion of the system main condenser holding vaporous refrigerant, together with variable amounts of non-condensible gases; and a second portion of the system holding saturated condensate in contact with its vapor. The pressure differential between the stated first and second mentioned portions of the system is normally substantially constant. Thus, a variation in the predetermined normal pressure differential, indicating a pressure build-up attributable to non-condensible gases, will initiate operation of the purger compressor whereby vapor may be removed from the main condenser and directed to the purging system for separation into the refrigerant and non-condensibles.

Briefly stated, the invention is hereinafter described in conjunction with a refrigeration system holding and circulating a charge of a volatile refrigerant such as CCLBF, and includes a purging means cooperative with the system for removing non-condensible gases and for discharging the same to the atmosphere. The basic refrigeration system consists of main components including essentially a condenser, a compressor, and an evaporator serially connected by the required valving to circulate refrigerant at a suificient flow rate to achieve a desired cooling.

The main condenser, following accepted manufacturing practice, is characterized by a vapor holding high pressure chamber, and a hot well or high pressure receiver which together with the compressor, define the high pressure side of the refrigeration system. The normal function of the receiver is to accumulate and hold a supply of liquid refrigerant at saturated condition in a flow chamber substantially at main condenser head pressure, which liquid is metered to the low pressure main evaporator through a float controlled mechanism.

The intermittently operated purging arrangement connected to receive air and other non-condensible vapors from the main system, includes a motor driven auxiliary compressor connected to the main condenser vapor holding portion for receiving water, refrigerant, and non-con densibles in vapor phase. An auxiliary condenser receives hot vapors from the purge compressor which vapors are condensed and forwarded to an element in which the liquid is separated from the non-condensibles. Water is further separated from the refrigerant, the latter being returned to the system for circulation and the water being rejected. Non-condensible gases are accumulated to a predetermined pressure greater than the system pressure and periodically vented to the atmosphere.

The instant control contemplates means whereby the purge compressor is actuated intermittently at such times as the accumulation of non-condensibles exceeds a prede termined level. The control means is so communicated with the main system as to monitor and detect superheat in the main condenser liquid and to react in response to variations thereof.

One embodiment of the novel control arrangement includes a conduit means communicated with the high side liquid holding portion of the main condenser and main evaporator respectively. Flow control means interposed in the conduit affords means for varying the flow rate of saturated liquid in accordance with main condenser partial pressure attributable to non-condensibles which liquid is subsequently recirculated to the evaporator. Actuating means also disposed in the conduit means is connected for governing operation of the auxiliary purge compressor motor in response to the increase in partial pressure of non-condensibles in the main condenser vapor holding portion.

Referring to FIGURE 1, a typical refrigeration system is illustrated into which is incorporated the features of the novel purge control arrangement. It should be mentioned in passing that the prior art has dealt considerably with refrigeration systems including gas purging arrangements. We therefore do not profess to claim novelty in the present system of itself, but rather in the novel arrangement and benefits afforded through use of the automatic control device disposed to be effected by both above mentioned phases of the refrigeration system. Also, although the invention has been shown and described as being embodied in a particular arrangement of components, it is not intended to so limit the scope of the basic concept which is readily applicable to other similarly arranged systems.

Referring more particularly to the figures, the refrigera tion system and purging arrangement comprise generally: a main refrigerant compressor ltl connected to and driven by a motor 12. A main condenser 14 is communicated with the discharge outlet of compressor 10 through conduit 15 for introducing hot compressed superheated gas to the condenser. Condenser 14 includes a hot well 16 or other high pressure receiver for holding a supply of saturated liquid refrigerant within a flow chamber 17 un- J3 der condenser pressure. Means communicated with the liquid holding side of high pressure chamber 17 through a float valve 19, directs condensed refrigerant through conduit 18 into main evaporator 21. The closed refrigeration cycle is completed by conduit 22 communicating the upper or vapor holding portion of the evaporator with the inlet of compressor 10.

These main refrigeration elements are standard items in the commercial market as is the means for connecting the same to define the closed refrigeration cycle. Main condenser 14, for example, is provided with a coil 23 circulating a cooling medium such as water for the purpose of condensing superheated vapor entering the condenser. The main evaporator 21 is similarly provided with a coil 24 through which water is circulated in heat exchange contact with a bath of liquid refrigerant held at low pressure in the evaporator to absorb heat upon being vaporized. This well known arrangement of refrigeration elements in a system as previously mentioned is old in the art. a purge device in a refrigeration system has similarly been known and utilized for many years.

Cooperative with and interconnected to the main refrigeration system is the purge arrangement. The purger, as shown in FIGURE 1, is constituted of basic units connected to define a flow circuit including; an auxiliary compressor 26 having a suction inlet 31, a discharge outlet 32, and powered by a prime mover 27 such as an electric motor or an internal combustion engine. Compressor Z6 is connected at inlet 31 through an elongated conduit 29 to the upper or vapor'holding portion of main condenser 14. This upper portion of the condenser in normal operation holds refrigerant and water vapors together with the vaporized non-condensibles which pollute the system. Auxiliary compressor dischargeoutlet 32 is communicated through conduit 33 to inlet 35 of an auxiliary condenser 36 shown for the immediate description as being of the shell type having an internal coil 34 receiving superheated compressed vapors including the aforementioned air which is to be purged from the system.

Compressor motor 27 may be adapted and controlled to run at a suitable speed to achieve a desired purge rate, alternatively, it may merely run at selected speeds within a particular range. Regulation of motor 27 for driving the compressor constitutes an important part of the invention and will be described more thoroughly hereinafter with relation to control of the entire purge system.

The downstream side or outlet 50 of auxiliary condenser 36 is connected through line 37 to the inlet of separator 38 which includes primarily means for simultaneously receiving condensed flows of refrigerant and water from the condenser 36. The separator also receives noncondensibles from the compressor 26 which are dis charged to the atmosphere at an elevated pressure. Discharge of air from separator 33 is ordinarily controlled by a pressure sensitive valve 41 or by other means operable in accordance with conditions within the system for maintaining operating pressure.

Auxiliary compressor 26 may be of a reciprocating or centrifugal type and suitably coupled to the drive motor 27 which as previously mentioned may be a constant or variable speed electric motor connected to a power source, or an internal combustion engine. Compressor 26 normally functions when operated, to compress vapors carried from the vapor holding portion of main condenser 14, which vapors include the undesirable non-condensibles. The auxiliary compressor according to the invention is started and driven periodically by motor 27 responsive to the amount of non-condensible gas accumulated in the condenser 14 exceeding a minimum predetermined amount. Likewise, this compressor is halted when purging of the system becomes necessary.

A vaporous stream discharged from compressor 26 is passed through coil 34 of auxiliary condenser 36 in which a portion of the vapors received is condensed into liquid,

Furthermore, provision of purging means or the non-condensible portion remaining in the vapor phase. Both liquid and vapors are then passed through conduit 37 for condenser 36 to separator 38.

The function of the separator is two-fold. Primarily, this element bifurcates the combined liquid and vaporous stream such that the vaporous air and other gases are accumulated to a predetermined pressure to maintain the pressure within the system, and then vented to the atmosphere through a valve 41. Water and liquid refrigerant are caused to overflow and thus become separated permitting removal of the water through line 42 and recycling of the refrigerant back into the main system. To this end, conduit 43 communicates the liquid holding portion of the separator with the low pressure side of the system at the main evaporator inlet 44.

An embodiment of control means whereby the instant purger is actuated for removing non-condensibles from the system is illustrated in FIGURE 1 and consists of the following: conduit 45 communicates the liquid holding high pressure side of main condenser 14 such as the hot well or flow chamber 17 for circulating refrigerant prior to reintroduction into the low pressure evaporator 21 through conduits 4t), 41 and 46. Conduit 45 is provided with a flow constricting orifice 47 having an inlet connected to the downstream end of conduit 45 for passing a restricted fiow of liquid. Flow control means including a dilferential pressure regulating device 48 positioned downstream of orifice 47 regulates the flow rate of liquid and consequently the pressure in conduit 40 com municating the orifice with the flow control means 48.

Differential pressure element 48 is of standard construction embodying characteristics well known in the art and functions in response to a differential of at least two pressures applied on a movable element. One tap 49 is communicated through a fluid holding conduit means 51 connected to the vapor containing portion of condenser 14 for transmitting condenser head pressure. Thus, pressure in this portion of the main condenser is normally registered on one side of the differential pressure device .-8 urging the flow control element toward one of its operable limits, causing liquid flow through line 4 3 to be increased in proportion to the increase in pressure in condenser 14. A second pressure is communicated with the fiow control element to transmit a force in proportion to the temperature of saturated liquid in hot well 17.

The second actuating pressure is connected to a sensing means 52 positioned within the hot well or in the liquid holding flow chamber of receiver 17 in which saturated liquid is maintained at a predetermined level prior to passage into evaporator 21.

The sensing means adapted to the present function may suitably be of the type including a bulb containing expandible liquid, preferably the same as system refrigerant. Increase in hot well condensate temperature will thus expand the contained liquid eifecting a pressure increase transmittable to flow control regulator 48.

Under ordinary conditions, when the system operates with a lack of non-condensible vapor in condenser 14, there will be only a slight pressure differential between the vapor holding portion of the condenser and the pressure of saturated fluid within the hot well 17. For example, condenser head pressure may normally be on the order of magnitude of about 10 to 15 pounds per square inch. The saturated temperature of liquid in flow chamer 17 under these conditions is within the range of about 104 to 113 degrees F. Thus, under varying atmospheric conditions, although the high and low pressures within the vaporized fluid containing portion of condenser 14 will vary, the actual pressure differential between the vapor portion of the condenser and the liquid holding portion will be substantially constant.

Understandably then, as long as this constant pressure differential is maintained between the stated points the passage opening of the differential pressure valve 48 will be maintained constant. However, as the amount of noncondensible vapor Within the condenser 14 increases due, for example, to air leakage into the system, the partial pressure effected by such vapor increases the pressure differential at valve 48, increasing liquid flow through line 45, orifice 47 and regulator 48 respectively, thus establishing a pressure variable in line 40 from the norm.

Actuating means 54 positioned in line 40 may be a commercially available electrical switch 56, as shown in the figure, normally held in an open position by pressure within a column 53 communicated with line 40. Pressure in line 40 is thus registered on a diaphragm linked to switch 56 for operating the latter. Switch 56 is in turn electrically connected through a suitable relay or starting means, not presently shown, to the power supply feeding motor 27 whereby the latter is actuated by regulating the electrical input.

The actuating element in its simplest form may embody an electrical switch, or simply an appropriate mechanical means such as a motion transmitting linkage controlled by pressure on column 53 when an engine is the prime mover. The linkage is in turn cooperative with the internal combustion engine through throttle control means for varying the speed of the engine and thus varying the speed of compressor 26. Although the mentioned devices as well as other embodiments of the purge control means fall within the broadest concept of the present invention, the principle for operating the purger upon the basis of a pressure differential at the noted points within a refrigerating system remains the same.

For example, while regulating device 48 and actuating mechanism 54 are described as being two distinct elements, it is within the ambit of one skilled in the art that said elements may be incorporated into a single unit whereby opening and closing of the liquid passage defined by valve 48 may occur simultaneously with the functioning of actuating means 54.

Still another embodiment of the differential sensing means constituting the basic function as herein described may consist of a pair of suitably cooperative arms. At least one arm is stationary and carrying one or more switches while the other arm is movable responsive to conditions in the circuit, into engagement with the respective switches to control operation of the purger and compressor motor between the operating limits of the movable arm.

Under particular circumstances the main condenser 14 may operate such that condensate in the lower portion or in the hot well is at a subcooled condition. This would of course tend to provide an erroneous pressure differential than expected from the refrigerant vapor pressure in the condenser upper or vapor containing portion. With proper condenser design however subcooling of liquid in the hot well may be avoided that a true pressure differential reading is assured.

An alternate arrangement for effecting system purging through measurement of condensate superheat is accomplished in the following manner. Referring to FIGURE 2, condenser 14 is provided with a condensate collector 58 supported in the condenser vapor holding portion to receive at least a part of the liquid condensed. Collector 58 may be an open-sided trough, tray or similar receptacle positioned relative to coil 23 as to catch liquid falling from the coil surface.

Because this liquid pool is positioned in the condenser upper section, saturated liquid will always be subjected to direct condenser pressure. Conduit 60 communicates collector 58 with the condenser hot well 17 through a float valve 62 in order that there will always be some liquid stored upon which a superheat measurement might be made. A sensing means or element 61 is positioned relative collector 58, in contact with the liquid pool held in the latter.

For convenience of manufacture and assembly, conduit 66 may be terminally connected as mentioned but disposed external to the condenser shell. When the latter arrangement is employed, the liquid holding means and sensing element 61 are readily accommodated in a hermetic enclosure.

The sensing element 61 consists of a bulb containing an expandible fluid. Thus, whether positioned inside or outside of the condenser confines, the sensing element is always subject to condenser pressure. Element 61 is connected to the purge compressor drive motor through a suitable mechanical or electrical intermediary.

The slightly greater condenser pressure at tray 58 above the pressure of hot well 17, will promote a steady flow of condensate through line 60 and assure a greater accuracy of superheat determination and efficient utilization of the purger.

It is understood that while the present invention is described as comprising an integral part of a particular refrigeration system, the purging arrangement and its novel control may be similarly incorporated into other forms of refrigeration systems. It is further understood that certain modifications and changes may be effected in the control system Without departing from the spirit and scope of the invention.

What is claimed is:

1. In a closed refrigeration system circulating a volatile refrigerant and having a main compressor, a main condenser including a cooling coil and having an upper vapor holding portion connected to the main compressor discharge receiving vaporized refrigerant and non-condensable gases, and having a hot well in the condenser lower portion holding saturated refrigerant condensate at condenser pressure:

(a) a purge mechanism connected to and operable with said refrigeration system to remove non-condensable gases therefrom,

(b) said purge mechanism including a motor driven auxiliary compressor having an inlet communicated with the refrigeration system to receive a flow of both vaporized refrigerant and non-condensable vapors,

(c) a refrigerant condensate collector positioned in the main condenser vapor holding pontion, holding a pool of said condensate under condenser pressure,

(d) control means connected to the system to regulate operation of the auxiliary compressor motor and activate said purge mechanism in response to the volume of non-condensable vapors contained in the refrigeration system in excess of a predetermined amount,

(e) said control means including:

(1) sensing means positioned in the condensate collector in contact with the condensate pool therein,

(2) said sensing means being connected to the purge mechanism auxiliary compressor motor to regulate operation thereof in response to a variation in pressure in the main condenser vapor holding portion.

2. In a closed refrigeration system substantially as defined in claim 1 wherein said refrigerant collector positioned in the main condenser vapor holding portion includes:

(a) a tray having an open side disposed downwardly adjacent at least a portion of the main condenser cooling coil to receive condensate falling from the latter.

3. In a closed refrigeration system substantially as defined in claim 1 including:

(a) conduit means in communication with the condensate collector carrying excessive refrigerant condensate therefrom to maintain a condensate pool in said collector at a predetermined level.

4. In a closed refrigeration system substantially as defined in claim 1 wherein the sensing means connected to the purge compressor motor includes:

(a) a sensing element,

(b) a switch operable in response to actuation of the sensing element,

(c) said switch being connected to a source of power and to said auxiliary compressor motor for operating the latter in response to conditions in said condensate collector.

5. In a closed refrigeration system having a main evaporator, a main compressor arranged to receive vapors refrigerant from the main evaporator, and a main condenser connected to the compressor and having a high pressure section holding refrigerant vapor and non-con densable gases, said condenser functioning to condense refrigerant vapor for passage of condensate to the evaporator, a high pressure receiver connected downstream of the main condenser holding a supply of said refrigerant condensate at saturated conditions under main condenser head pressure;

(a) a purge mechanism cooperative with the refrigeration system and including a motor driven auxiliary compressor having its suction connected to the main condenser high pressure vapor holding section for intermittently receiving said refrigerant and noncondensable gases,

(b) an auxiliary condenser connected to the auxiliary compressor discharge,

(c) conduit means in communication with the supply of condensate in the high pressure receiver and passing a stream of said condensate to the main evaporator,

(d) flow control means interposed in said conduit means and being automatically adjustable to vary the rate of liquid flow therethrough in response to a pressure change in the main condenser high pressure section, said pressure change being indicative of the presence of excessive mon-condensable vapors in the condenser,

(e) sensing means connected to said flow control means to simultaneously transmit pressure of said vapor in the condenser vapor holding portion, and the pressure of saturated refrigerant in the high pressure receiver, to the flow control means for effecting automatic adjustment thereof,

(f) a pressure sensitive switch operable by fluid pressure in said conduits and being movable between first and second positions, said switch being connected in respective first and second positions to control operation of the auxiliary compressor motor,

(3) means communicating said switch to pressurized liquid in said conduit means at a point upstream of the flow control means whereby pressure in said conduit means will effect movement of the switch between the first and second positions.

6. In a refrigeration system as defined in claim 5 includi'ng:

(a) means forming a constricted orifice positioned in said conduit means and being disposed to a position upstream of the flow control means and the pressure sensative switch respectively.

7. In a closed refrigeration system having a main evaporator, a main compressor arranged to receive vapor refrigerants from the main evaporator, and a main condenser connected to the main compressor and having a high pressure section holding refrigerant vapor and noncondensable gases and a first supply of refrigerant condensate in the upper section thereof, said condenser normally functioning to condense refrigerant vapor for passage of condensate thereof to the evaporator, a high pressure receiver downstream of the main condenser and holding a second supply of refrigerant condensate at saturated conditions under said condenser head pressure;

(a) conduit means communicating the second refrigerant supply with the main condenser,

(b) a purge mechanism cooperative with the refrigeration system and including a motor driven auxiliary compressor having its suction connected to the main condenser high pressure vapor holding section for intermittently receiving said condensed refrigerant and non-condensable gases,

(0) second conduit means communicating the high pressure receiver holding said second condensate supply with the evaporator,

(d) flow control means interposed in said second conduit means and being automatically adjustable to vary liquid fiow therethrough in response to a pressure change in the condenser vapor holding high pressure section, said pressure change being indicative of the presence of an excessive non-condensable vapor in the condenser,

(c) sensing means operably connected with said flow control means and having a sensing element positioned in contact with the first condensate supply to effect adjustment of the flow control means, to simultaneously transmit the pressure of vapor in said condenser,

(f) switching means disclosed in said conduit means being movable between first and second positions and connected in said respective positions to control operation of the auxiliary compressor motor to on and off positions,

(g) said switching means being sensitive to fluid pressure in the second conduit means at a point upstream of the fiow control means, whereby pressure in said conduit means will effectuate movement of the switching means between said first and second positions for controlling operations of the compressor motor.

References Cited in the tile of this patent UNITED STATES PATENTS 2,298,924 Bichowsky Oct. 13, 1942 2,321,964 Zieber June 15, 1943 2,577,598 Zwickl Dec. 4, 1951 2,940,274 McGrath June 14, 1960 2,986,894 Endress et al June 6, 1961 2,986,905 Kosher et a1 June 6, 1961 3,013,404 Endress et a1 Dec. 19, 1961

Claims

1. IN A CLOSED REFRIGERATION SYSTEM CIRCULATING A VOLATILE REFRIGERANT AND HAVING A MAIN COMPRESSOR, A MAIN CONDENSER INCLUDING A COOLING COIL AND HAVING AN UPPER VAPOR HOLDING PORTION CONNECTED TO THE MAIN COMPRESSOR DISCHARGE RECEIVING VAPORIZED REFRIGERANT AND NON-CONDENSABLE GASES, AND HAVING A HOT WELL IN THE CONDENSER LOWER PORTION HOLDING SATURATED REFRIGERANT CONDENSATE AT CONDENSER PRESSURE: (A) A PURGE MECHANISM CONNECTED TO AND OPERABLE WITH SAID REFRIGERATION SYSTEM TO REMOVE NON-CONDENSABLE GASES THEREFROM, (B) SAID PURGE MECHANISM INCLUDING A MOTOR DRIVEN AUXILIARY COMPRESSOR HAVING AN INLET COMMUNICATED WITH THE REFRIGERATION SYSTEM TO RECEIVE A FLOW OF BOTH VAPORIZED REFRIGERANT AND NON-CONDENSABLE VAPORS, (C) A REFRIGERANT CONDENSATE COLLECTOR POSITIONED IN THE MAIN CONDENSER VAPOR HOLDING PORTION, HOLDING A POOL OF SAID CONDENSATE UNDER CONDENSER PRESSURE, (D) CONTROL MEANS CONNECTED TO THE SYSTEM TO REGULATE OPERATION OF THE AUXILIARY COMPRESSOR MOTOR AND ACTIVATE SAID PURGE MECHANISM IN RESPONSE TO THE VOLUME OF NON-CONDENSABLE VAPORS CONTAINED IN THE REFRIGERATION SYSTEM IN EXCESS OF A PREDETERMINED AMOUNT, (E) SAID CONTROL MEANS INCLUDING: (1) SENSING MEANS POSITIONED IN THE CONDENSATE COLLECTOR IN CONTACT WITH THE CONDENSATE POOL THEREIN, (2) SAID SENSING MEANS BEING CONNECTED TO THE PURGE MECHANISM AUXILIARY COMPRESSOR MOTOR TO REGULATE OPERATION THEREOF IN RESPONSE TO A VARIATION IN PRESSURE IN THE MAIN CONDENSER VAPOR HOLDING PORTION.