US 3379033 A
Description (OCR text may contain errors)
April 23, 1968 w. l. GRANT REFRIGERATION SYSTEM AND APPARATUS Filed Aug. 10, 1966 United States Patent 3,379,033 REFRIGERATION SYSTEM AND APPARATUS Whitney I. Grant, Muskego, Wis., assignor to Vilter Manufacturing Corporation, Milwaukee, Wis., a corporation of Wisconsin Filed Aug. 10, 1966, Ser. No. 571,475 13 Claims. (Cl. 62-505) ABTRACT OF THE DISCLOSURE A refrigerating system wherein the refrigerant employed in the system is utilized for maintaining the compressor lubricating oil at proper temperatures and for cooling the compression cylinders.
Background It is a Well-known and accepted fact that the temperature of the suction gas in a refrigeration system should be kept as low as possible for efficient operation. Since there is considerable difference between the temperature of the gas entering the compression chamber of a compressor and the temperature of the surrounding cylinder Walls due principally to the atmospheric temperature surrounding the compressor and the frictional heat resulting from the compression operation, it has become common practice to provide various means for effecting a reduction in the temperature increase of the gas within the compression cylinders in order to maintain the gas at a low temperature for most efficient operation.
In prior attempts to maintain the suction gas at a low temperature, it has heretofore been proposed to cool the compressor cylinders by air, or by providing a water cooling jacket surrounding the end of the cylinder or cylinders. Since the temperature of the ambient air in the region of the compressor is generally considerably higher than the suction gas temperature, the air cooling methods have proven relatively ineffectual. Likewise, the refrigeration systems which have embodied water cooling of the compressor cylinders have not proven entirely satisfactory because of the restrictions which must necessarily be imposed in maintaining the cooling water at operating temperatures above freezing and below or in the vicinity of the temperatures of the suction gases.
Accordingly, while such prior methods of cooling have aided in preventing the cylinders of the compressors from deterioration due to the heat generated during the compression operations, they have proven relatively ineffectual in preventing excessive heating of the suction gases. The problem of maintaining the suction gases at relatively low temperatures through air or water cooling of the cylinders has, therefore, left considerable to be desired and the capacity of the compressor in such cases has been unduly and undesirably restricted.
In efforts to overcome the foregoing disadvantages, it has also been heretofore proposed to utilize the refrigerating medium for the cooling of the compression cylinders of the compressors, the refrigerant being returned to the compressor from the evaporator being used for such purpose. However, in these prior systems wherein it has been proposed to utilize the refrigerant circulating in the system for cooling the compressor cylinders, proper controls to compensate for load conditions imposed on the compressor have been lacking, and such systems have accordingly not been generally accepted.
In addition to the cooling of the compression cylinders, it is also highly desirable to maintain the lubricating oil of refrigeration compressors at certain temperatures for most e ncient operation of the compressor or compressors. If the oil is chilled to too low a temperature, the efliciency of the compressor is impaired under light loads, and the oil pump horsepower requirements increase due to the viscous nature of the oil. When the operating conditions change so that relatively high loads are imposed on the compressor or compressors, the compressor beings to overheat and the oil temperature rises. Thus, unless precautionary measures are taken, the temperature of the oil will become dangerously high.
Summary It is a object of this invention to provide a system which obviates the aforementioned disadvantages and objections to prior systems in a simple and highly efficient manner.
Another object of the present invention is to provide an improved refrigeration system wherein the compressor lubricating oil is effectively maintained at most efficient operating temperatures through utilization of the refrigerant circulating in the system.
A further object of the invention is to provide an improved refrigerating system wherein the compression cylinders are cooled to most eiTective operating conditions by means of the refrigerant circulating within the refrigeration system and being returned to the suction side of the compressor.
Still another object of the invention is to provide an improved refrigeration system wherein liquid refrigerant in the system is used for the dual purpose of maintaining the lubricating oil at predetermined temperatures and for cooling of the compressor cylinders, the refrigerant thus used being returned to the suction side of the compressor in gaseous condition.
These and other more specific objects and advantages will become apparent from the following detailed description.
The drawings A clear conception of the features constituting the present improvement and of the construction and mode of operation of a typical refrigeration system utilizing the invention may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference characters have been used to identify corresponding or similar parts in the several views.
FIGURE 1 is a diagrammatic view of a typical refrigerating system embodying the present invention;
FIGURE 2 is a fragmentary part sectional view of a typical modulating temperature pilot valve which is interposed in the conduit leading from the cooling jacket or jackets of the compression cylinder back to the compressor suction line; i
FIGURE 3 is a fragmentary part sectional view of a typical therrno valve which is interposed in the refrigerant line from the evaporator to the oil cooler; and
FIGURE 4 is a schematic perspective view of a compressor embodying an alternate and somewhat modified cooling system.
Detailed description Referring to the drawing, the invention is shown as being embodied in a typical refrigerating system which includes a compressor 10 driven by a motor, not shown, in a Well known manner. The compressor 10 has one or more compression cylinders 11 and has its suction and discharge ports connected to a refrigerant circuit. The discharge conduit 12 receives high pressure gaseous refriger ant from the compressor 10 and conducts the same to a condenser 13 wherein it is liquified or condensed. From the condenser, the refrigerant is conducted through a conduit 14 to a receiver 15. In turn, the refrigerant stored in the receiver 15 is conducted by way of a conduit 16 to an evaporator 17 where it performs its useful work, and a conduit 18 then returns the low pressure gaseous refrigerant to the suction side of the compressor 10. The compressor is operated in a well known manner according to the demand on the evaporator 17, thus varying the load imposed on the compressor.
The compressor 10 may be of the well known reciprocating piston type in which oil is supplied to the crankcase wherein it is splashed about to lubricate the working parts. Since the oil becomes heated during the performance of its work, it is common practice to circulate the same, and this is accomplished by means of a pump 21 customarily driven by the same motor which drives the compressor, it being understood that the pump 21 may be driven directly from the compressor crankshaft 22 rather than being located remote from the compressor as schematically shown in FEGURE l. The pump 21 draws oil from the compressor crankcase 20 via a conduit 23 and returns the oil to a sump 25 via conduit 24. Attempts are generally made to cool the oil in sump 25, and the cool oil is then returned to the compressor crankcase 20 by way of a conduit 26.
All of the apparatus thus described is old and well known, and it is apparent that heat is generated to varying degrees within the compression cylinders 11 according to the load imposed on the compressor 10. The heat in the areas of the compression cylinders is, of course, undesirable and impairs the operating efficiency of the compressor. Also, the lubricating oil is subject to temperature variations dependent upon compressor operation, and if the oil temperature is not maintained within predetermined desired ranges, its eniciency is likewise impaired. While various attempts have heretofore been made to cool the areas of the compression cylinders and to also maintain the lubricating oil within certain temperature ranges, all of the prior proposals have generally left something to be desired, particularly in the control of the temperatures according to variances in compressor operation. It is these problems which are obviated by the present invention.
In accordance with the present invention, liquid refrigerant is conducted through a conduit 3% from the line 16 between the receiver 15 and evaporator 17 to the oil sump 25. The refrigerant thus by-passed through the sump 25 cools the warm oil contained therein and is caused to expand. The expanding refrigerant which includes a mixture of liquid and vapor is then conducted from the oil sump or cooler 25 through a conduit 31 to a cooling chamber 32 formed by a jacket 33 surrounding and spaced from the compression cylinder 11. Due to the heat existing within the area of the compression cylinder 11, further evaporation of the liquid which remains with the gas takes place and cools the area surrounding the compression cylinder. The finally evaporated cooling refrigerant is then conducted to the compressor suction line 18 via a conduit 34.
The flow of cooling refrigerant through the oil sump or cooler 25 and the cylinder cooling chamber 32 is controlled according to load conditions. To accomplish this control, a special temperature pilot valve 4% is interposed in the line 34 between the cylinder cooling chamber 32 and the low pressure suction line 18. Operation of this valve 44; is controlled by a bulb 41 connected thereto by a tube 42, the bulb being attached to the oil line 26 and which senses the oil temperature in this line.
Thus, when the oil temperature in line 26 is reduced to a predetermined set point, the control bulb 41 actuates the valve to reduce the flow of cooling refrigerant past the valve and thus through the line 36, oil sump 25, line 31 and cylinder cooling chamber 32. This is essential so that under light load conditions the oil will not be chilled to too low a temperature which would not be desirable for efficient operation of the compressor 1% Additionally, the oil pump horsepower requirements would increase substantially when the oil becomes viscous at low temperatures, and the controls thus described will control at light loads and low oil temperatures.
When the operating conditions change such that high loads are encountered, the compressor begins to overheat .4 and the oil temperature begins to rise. At this point, the special temperature pilot 4%) senses the warming oil by means of the bulb 41 and will be actuated to open to its fullest extent, thus allowing full flow of refrigeration past the valve 40 and through the line 30, oil sump 25, line 31, cylinder cooling chamber 32 and the line 34 to the low pressure suction line 18. Due to the heat of the oil and the high temperature existing within the area of the compression cylinder 11 during periods of high loads, complete evaporation of the cooling refrigerant will occur so that the refrigerant returning to the low pressure suction line will be in gaseous condition.
It is, of course, essential that when the oil is very warm the refrigerant cooling system will not allow 'an excessive flow of refrigerant such that slugs of liquid refrigerant will enter the inlet of the compressor thus creating the possibility of serious resulting damage. Accordingly, to control refrigerant flow during high load conditions, a thermo valve 45 is installed in the liquid line 30 leading from the line 16 of the refrigerant system to the oil sump or cooler 25. The valve 45 has its control bulb 46 attached to the line 34 leading from the cylinder cooling chamber 32 to the low pressure suction line 18. A tube 47 connects the bulb 46 and the valve 45. The control bulb 46 accordingly responds to the temperatures existing in the line 34 to control operation of the valve 45 which is adjustable to maintain a fixed predetermined superheat condition in the refrigerant leaving the compression cylinder cooling chamber 32. Thus, the amount of refrigerant conducted past the valve 45 through the line 39, oil sump 25, line 3 1 and cylinder cooling chamber 32 is varied in accordance with the superheat condition in line 34 and prevents the possibility of refrigerant liquid entering the compressor under light load conditions. At the same time, the special temperature pilot valve 40 will control the light load conditions to prevent overcooling of the oil. At load conditions varying between minimum and maximum, the controls will modulate to maintain proper oil temperature without overfeeding the liquid refrigerant through the cooling line, thus avoiding the possibility of having slugs of refrigerant reach the compressor.
The modulating temperature pilot valve 40 may be of a type which is available from Alco Valve Company, identified by the number 937, and this valve is shown in FIGURE 2 of the drawing, the direction of flow being reversed from that of FIGURE 1. This valve comprises a valve body 40 which has an inlet fitting 5%} connecting the line 34 with a port 51 which is normally closed under a predetermined set pressure by a disc 53 seated against the seat 52. The disc 53 carries an adjusting stem 54 surrounded by a spring 55 which urges the disc 53 to seated condition. The control bulb 41 connects through tube 42 with a diaphragm disc 57 carrying lift posts or push rods 56, and when the sensing bulb calls for increased flow through the valve 46, the member 57 and push rods 56 act to lift the disc 53 from its seat 52 and permit flow through the port 58 which is attached to the discharge side of the line 34 by means of fitting 59. This valve is, however, merely shown herein for purpose of illustration and can be replaced by any other type of modulating temperature control valve adapted to perform the same function.
In FIGURE 3, a typical thermo valve 45 is shown, and this valve is also available from Alco Valve Company and is identified as types TIL and THL. The valve shown in FIGURE 3 has its inlet end 60 attached to the line 39 and the inlet communicates with the interior 61 of a spool type valve member 63 normally seated against seats 62, 62'. The spool 63 carries a stem 64 seated against diaphragm 66 at its upper end, and a spring 65 surrounding the stem 64 normally urges the spool to seated condition. The diaphragm chamber above the diaphragm 66 is connected by the tube 47 to the bulb 46, and in response to demands by the control pump, the
diaphragm 66 is deflected downwardly and causes the spool 63 to unseat and permit full flow through the inlet end 60, chamber 61 and out of the outlet end 67 which discharges into line 30. Again, it should be appreciated that the valve shown in FIGURE 3 is merely for purposes of illustration and this valve may be replaced by any other suitable valve adapted to perform the same function.
An alternate arrangement of the cooling system is shown in FIGURE 4 wherein the compressor is identified by the numeral 70 and is shown as including three compression cylinders 71, 71', 71". The high pressure discharge line 72 of the compressor is connected in the refrigeration system as described with reference to FIG- U-RE l, and the low pressure suction line 78 receives refrigerant from the evaporator as also heretofore described. In this case, the pump 81 is shown as attached directly to the compressor housing within the area of the compressor crankcase 80 and the pump circulates oil through conduit 84 to the oil sump or cooler 85 and then back to the compressor crankcase by way of conduit 86. In this case, only a single thermo valve is utilized, the thermo valve 100 being connected by a pair of control bulbs 101, 106 through tubing 102, 107, respectively, to the oil line 36 and to the conduit 94 returning cooling refrigerant from the cooling chamber of the cylinder 71' back to the low pressure suction line '73. Again, refrigerant flow through the oil cooler 85 cools the oil contained therein while partially evaporating. The mixture of liquid and vapor is then circulated to the cooling covers of the cylinders 71, 71, 71" via the conduits '91, 91', 9.1", and the remaining liquid is evaporated within the cylinder cooling chambers. Control bulb 106 senses the superheat of the refrigerant vapor entering the compressor suction line 78 via the line 94 and regulates the flow of cooling refrigerant by modulating the thermo expansion valve 100. Under light load conditions during which less heat is generated in the compressor and the oil is at a lower temperature, the control valve 101 senses the oil outlet temperature and will override the control bulb 106 and throttle the expansion valve 100 to maintain a constant oil temperature.
From the foregoing detailed description, it is apparent that the present system provides a dual control for refrigerant cooling of compressors which may be adjusted to closely control the oil temperature under varying operating conditions while also effectively cooling the areas surrounding the compression cylinders under varying compression loads. The improved arrangement also insures complete evaporation of the liquid refrigerant used for cooling purposes before it is returned to the low pressure side of the compressor.
Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter that is regarded as the invention.
1. In a refrigerating system including a compressor having at least one compression cylinder, a condenser communicating with the compressor through a high pressure discharge line to receive gaseous refrigerant therefrom, and an evaporator communicating at one end with the condenser through a liquid refrigerant conduit and communicating at its other end with the compressor through a low pressure suction line to supply gaseous refrigerant to the compressor: an oil cooler connected to the compressor so that oil passes from the compressor to the oil cooler and back to the compressor, means forming a cooling chamber in heat exchange relation with the compression cylinder of the compressor, a conduit placing said oil cooler in communication with the liquid refrigerant conduit between the condenser and the evaporator, means for conducting refrigerant from said oil cooler to said cooling chamber, and a conduit placing said chamber in communication with the low pressure suction line to return the refrigerant to the system.
2. A refrigerating system according to claim 1, wherein the compressor has a plurality of compression cylinders each of which is formed with an adjacent cooling chamber, and means are provided for interconnecting said cooling chambers.
3. A refrigerating system according to claim 1, wherein a valve is interposed in the conduit between the compression cylinder cooling chamber and the low pressure suction line for regulating flow of refrigerant through the oil cooler and said cooling chamber.
4. A refrigerating system according to claim 3, wherein the valve is automatically operated in response to conditions prevailing in the compressor oil supply conduit.
5. A refrigerating system according to claim 3, wherein a temperature responsive bulb is secured to the oil supply conduit between the oil cooler and the compressor, said bulb being connected to the valve to automatically operate the same within predetermined set limits according to temperature conditions existing in said oil supply conduit.
6. A refrigerating system according to claim 1, wherein a valve is interposed in the conduit between the oil cooler I and the liquid refrigerant conduit for regulating flow of refrigerant to said oil cooler.
7. A refrigerating system according to claim 6, wherein the valve is automatically operated in response to con-ditions prevailing in the compressor oil supply conduit.
8. A refrigerating system according to claim 7, wherein the valve is also responsive to conditions prevailing in the conduit between the compression cylinder cooling chamber and the low pressure suction line.
9. A refrigerating system according to claim 6, wherein a temperature responsive bulb is secured to the oil supply conduit between the oil cooler and the compressor, said bulb being connected to the valve to automatically operate the same within predetermined set limits according to temperature conditions existing in said oil supply conduit.
10. A refrigerating system according to claim 9, Wherein a second temperature responsive bulb is secured to the conduit between the compression cylinder cooling chamher and the low pressure suction line, said second bulb also being connected to the valve to automatically operate the same within predtermined set limits according to temperature conditions existing in said conduit.
11. A refrigerating system according to claim '3, wherein a second valve is interposed in the conduit between the oil cooler and the liquid refrigerant conduit for regulating flow of refrigerant to said oil cooler.
12. A refrigerating system according to claim 11, wherein the first valve is automatically operated in response to conditions prevailing in the compressor oil supply conduit and the second valve is automatically operated in response to conditions prevailing in the conduit between the compression cylinder cooling chamber and the low pressure suction line.
13. A refrigerating system according to claim 12, wherein the means for automatically operating the first valve is a temperature responsive bulb secured to the compressor oil supply conduit for communicating with said first valve, and the means for automatically operating the second valve is a bulb secured to the conduit between the compression cylinder cooling chamber and the low pressure suction line and communicating with said second valve.
ROBERT A. OLEARY, Primary Examiner.