The present invention relates generally to a refrigeration system. More particularly, this invention relates to an apparatus and method for improving the overall efficiency and reliability and reducing the operating and maintenance costs, of refrigeration system compressors by using condensed refrigerant to cool the refrigeration compressor, lubricating oil, and compressor body.

Background of the Invention

Refrigeration system compressor failures are known to be associated with high compressor body temperatures. Some common attempts to cool the compressor bodies include fans circulating air over the bodies, and injecting liquid condensate into the suction or low pressure side of the refrigeration system. Both methods result in increased energy usage and have various associated problems. Air circulation is not very effective due to the amount of heat that must be removed. Injecting liquid into the suction side of the refrigeration system has the problems associated with controlling the amount of liquid injected; too much liquid and the compressor will fail due to damage to the valving system, too little refrigerant injected will result in high temperatures which will result in bearing failure. The current invention solves the problem by circulating liquid condensate through a cooling jacket surrounding the compressor body and then into the head of the compressor on the discharge or high pressure side of the compressor. Summary of the Invention The present invention provides for a refrigeration system which has in a closed loop, a compressor for compressing a refrigerant, a condenser for condensing the compressed refrigerant to a liquid refrigerant, and a condensed liquid pump for compressor body cooling. The compressor body is thermally coupled to a cooling jacket, which may be a cavity or cavities within the body for passing a cooling liquid through the cooling jacket and around the compressor body. The inlet of the condensed liquid pump is coupled to a source of condensed liquid refrigerant, which may be the condenser, and the outlet of the condensed liquid pump is coupled to the cooling jacket inlet. A cooling jacket outlet, coupled to the discharge side of the compressor cylinder head(s), is provided to discharge refrigerant from the cooling jacket into the hot compressor discharge gas in the compressor cylinder head(s). In operation, the condensed liquid pump draws liquid from the liquid refrigerant source and pumps it into and dirough the cooling jacket which cools the compressor body. The refrigerant then flows out of the cooling jacket outlet into the compressor cylinder head, cooling the cylinder head and the hot compressor discharge gas. The condensed liquid pump is driven by drive means including, for example, a fixed speed electric motor, a variable speed electric motor, or the compressor drive means.

In refrigeration systems including a lubrication oil pump for providing lubrication oil to the compressor, the condensed liquid pump may be driven by the same motor or other means used to drive the lubricating oil pump. Both the lubricating oil pump and condensed liquid pump may be driven by the compressor crankshaft or the compressor drive means. A heat exchanger is provided for cooling the lubricating oil by heat transfer from the lubricating oil to the condensed liquid coolant.

Examples of the more important features of die invention have been summarized rather broadly in order that the detailed description thereof mat follows may be better understood, and in order that the contributions to the art may be better appreciated. There are, of course, additional features of the invention d at will be described hereinafter and which will form the subject of the appended claims. These and various other characteristics and advantages of the present invention will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention and by referring to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS For a detailed description of a preferred embodiment of the invention, reference will now be made to the accompanying drawings.

Figure 1 depicts a refrigeration system embodying the invention and includes a simplified cross-section view of a compressor showing details of the cylinder head cooling apparatus of the present invention; Figure 2 depicts another refrigeration system embodying the invention:

Figure 3 depicts an embodiment of tiie invention including an alternate take-off point for condensed liquid refrigerant;

Figure 4 depicts an embodiment of me invention including anodier alternate take-off point for condensed liquid refrigerant; Figure 5 depicts an exemplary means for driving the pumps and compressors of the present invention;

Figure 6 depicts another exemplary means for driving the pumps and compressors of the present invention; and

Figure 7 depicts another exemplary means for driving the pumps and compressors of the present invention; and

Figure 8 illustrates a six-cylinder two-stage compressor typical in the art, in which the lubricating oil pump is driven by the crankshaft of the compressor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For purposes of illustration and not by way of limitation, tlie present invention shall be described with respect to a refrigeration system and method wherein improved compressor

maintenance, reliability, and efficiency are obtained by compressing a refrigerant to a high pressure and temperature, cooling the compressor body by circulating condensed or subcooled liquid refrigerant through a compressor body cooling jacket, and injecting liquid refrigerant into the cylinder heads. Referring now to Figure 1, an embodiment of the refrigeration system of d e present invention is shown. The system includes at least one compressor 14, with a cooling jacket 11, at least one condenser 28, at least one evaporator 54, wid an expansion device 50, a reservoir 44 for holding liquid and vapor refrigerant, a compressor body cooling system, and a control circuit 56 containing a microprocessor to control various functions of the refrigeration system including the compressor body cooling system. The compressor body cooling system includes at least one coolant temperature sensor 29 near d e outlet 12 of the compressor body cooling jacket 11 to provide a signal representative of die operating temperature of tiie refrigerant in the cooling jacket, a condensed liquid recycle line 46 coupled at one end to a condensed liquid take-off point 25 of receiver 44 and coupled at its other end to tiie cooling jacket 11 to recycle refrigerant liquid, and a condensed liquid pump 100 disposed in recycle line 46 for pumping liquid from the receiver 44 to the cooling jacket 11. Cooling jacket 11 may comprise the annular space or cooling passages created by enclosing tiie compressor body in a cooling jacket. The refrigeration system may also contain a control valve 49 disposed in die liquid recycle line 46 to vary the flow rate of recycled cooling liquid for compressor body cooling. A cylinder head temperature sensor 39 may optionally be disposed near tiie outlet line discharging coolant from die compressor cylinder heads to provide a signal representative of die cylinder head operating temperature. A coolant flowmeter 19, or odier flow measuring and/or indicating device as is known in die art, may be disposed near recycle line 46 to provide a signal representative of d e coolant flow rate. Coolant temperature sensor 29, cylinder head temperature sensor 39, and coolant flowmeter may be electrically connected to microcontroller 56.

The microcontroller circuit 56 contains a microprocessor and odier circuitry which enables it to access information from various sensors used in ie refrigerator system, to process tiiese signals, and to control a variety of functions of the refrigeration system. Referring now to

Figure 2, tiie embodiment of die refrigeration system of die present invention depicted d erein is a closed loop, commonly connected, multiple-stage refrigeration system. A vapor refrigerant at a low pressure is passed dirough a refrigerant line 10 into manifold 20 and into parallel compressors 14 and 18. The compressors 14 and 18 compress die refrigerant to a high pressure gaseous state and discharge it through refrigerant lines 22 and 24 which communicate wi i a condenser 28. The condensed refrigerant leaves tiie condenser 28 through liquid line 38 as a liquid, and is discharged into a main fluid reservoir 44 dirough a main line 58. The liquid from

tiie reservoir 44 flows dirough line 58 into a liquid manifold system 57, where it enters a liquid line diat is connected to expansion valves 50 and 52. Each expansion valve 50 and 52 is connected to separate parallel evaporators 54 and 55 respectively. These evaporators form a refrigeration system wherein die expansion valves 50 and 52 meter ie liquid refrigerant into evaporators 54 and 55 respectively. Similarly, odier evaporator systems (not shown) may be connected to die liquid manifold system 57 via lines 62 and die like. When die liquid refrigerant is metered dirough die expansion valves 50 or 52, it evaporates into a gaseous state widi in its respective evaporator at a low pressure and a low temperature. The low pressure vapor refrigerant is passed to die compressors 14 and 18 dirough die suction line 10 and suction manifold 20. Compressors 14 and 18 compress me refrigerant vapor and discharge die compressed vapor into discharge line 22. The compressed vapor then passes dirough condenser inlet line 24 to condenser 28. Condenser 28 causes die refrigerant vapor to be cooled and condensed into a liquid phase by cooling die condenser coils widi air at ambient temperature. The liquid refrigerant may also be subcooled in condenser 28. In any case, liquid refrigerant is discharged from condenser via liquid line 38, which completes a refrigeration cycle mat is continuously repeated during operation.

Condensed liquid pump 100 increases tiie pressure in lines 46 and 60, but may also be used to increase me pressure in liquid line 60 alone, in embodiments of me present invention where die compressor body is not cooled.

Referring back to Figure 1, diere is shown in greatly simplified cross section a reciprocating compressor exemplary of a type which may be used widi die present invention.

While die invention is described widi respect to reciprocating compressor for simplicity, it is understood mat one experienced in die art may easily apply die invention to all sorts of compressors, such as reciprocating, rotary, rotary vane, screw, scroll, and centrifugal compressors, as well as hermetically sealed motor-compressor units. It is intended that die present invention apply to all sorts of compressors. Compressor 14 comprises a compressor body 79, containing one or more cylinder bores 76. Piston 75 reciprocates widiin cylinder bore 76, by die rotation of crankshaft 77 and connecting rod 78. Compressor cylinder head 71 is disposed at one end of compressor body 79, perpendicular to the direction of travel of piston 75. Cylinder head 71 contains passages connected to and communicating widi refrigerant suction manifold 20 and refrigerant oudet line 22, and valves controlling die flow of refrigerant being compressed, such as intake valve 72 and exhaust valve 73. Cylinder head 71 also includes cooling jacket outlet 12, dirough which cooling liquid is passed from cooling jacket 11 into exhaust manifold 74 and mixed widi hot compressed refrigerant vapor discharged from die cylinder dirough exhaust valve 73.

An oil separator 80 is preferably disposed in refrigerant outlet line 22 to remove lubricating oil carried over into refrigerant outlet line 22 wid die compressed discharge refrigerant. A

lubricating oil return line 83 is coupled to d e oil outlet of oil separator 80 and to oil injection point 86, disposed in die compressor body 79. An oil level sensor 93 is disposed widiin compressor body 79 to provide a signal representative of die oil level witiiin compressor body 79. Control valve 88 and level sensor 93, are preferably electrically coupled to microcontroller circuit 56 for control of die lubricating oil level widiin compressor body 79, as is further described in copending application 08/467,604, filed June 6, 1995, incorporated herein by reference in its entirety.

A lubricating oil suction line 215 is preferably coupled at one end to die compressor body 79 at a point below die level of lubricating oil in body 79. Lubricating oil suction line 215 is coupled at its odier end to a lubricating oil circulating pump 200, to supply lubricating oil to pump 200. An oudet of lubricating oil circulating pump 200 is coupled to one end of lubricating oil supply line 210. Oil supply line 210 is coupled at its odier end to oil passages 211 for providing lubricating oil to bearings in crankshaft 77 and connecting rod 78. Oil passages 211 may be holes drilled in crankshaft 77 and connecting rod 78 as is known in die art.

In anodier embodiment of die invention, the coolant discharged from condensed liquid pump 100 into liquid recycle line 46 passes in heat exchange relationship widi die lubricating oil circulated by lubricating oil circulating pump 200 irough oil supply line 210. In this embodiment, heat exchanger 300 transfers heat from die lubricating oil in line 210 to tiie liquid coolant in liquid recycle line 46. The lubricating oil and liquid coolant in heat exchanger 300 may be in co-current, counter-current, or cross-current heat exchange relationship as is known in ie heat transfer art. The flow of compressor body coolant is preferably effected by a pressurization member such as condensed liquid pump 100. The coolant flow rate may require no control means but may optionally be controlled by microcontroller circuit 56. In any event d e coolant flow rate may be measured by coolant flowmeter 19 or similar flow measuring means, such as pulse modulated solenoid supply, as described in copending application 08/467,604, filed June 6, 1995, and incorporated herein by reference in its entirety. Condensed liquid pump 100 may be a variable speed pump, as is known in die art. A control valve 49 may also be used in recycle line 46 to vary die flow of cooling liquid, in which case die position of die control valve may be controlled by microcontroller 56, and condensed liquid pump 100 may be a constant speed pump. Microcontroller 56 varies die position of control valve 49 to control the flow of coolant in response to d e coolant temperature sensor 29 to maintain a predetermined coolant operating temperature, or to maintain a coolant temperature just above die condensing temperature. In d e latter case, microcontroller 56 controls die position of control valve 49 to maintain uie temperature of me coolant a few degrees above diat of die liquid line, sensed by temperature sensor 36. When die difference between d e coolant temperature and die liquid line temperature exceeds a predetermined amount, microcontroller 56 increases die flow dirough control valve 49. Similarly, when me

difference between die coolant temperature and die liquid line temperature is less man a predetermined amount, microcontroller 56 decreases die flow dirough control valve 49. Coolant flow may be similarly controlled to maintain a predetermined cylinder head operating temperature using temperature sensor 39. In uie case of multiple compressors (Figure 2), separate control valves (not shown) may be placed in each of die cooling liquid injection lines 47 to individually control d e flow of coolant to each compressor body individually, as described widi respect to a system using a single compressor 14 in Figure 1.

The present invention provides a condensed liquid pump 100 in die liquid line 58 disposed between die reservoir 44 and die coolant recycle line 46. In die embodiment illustrated in Figure

1, d e liquid pump 100, when in operation, recycles refrigerant liquid from the reservoir 44, dirough control valve 49, via recycle line 46 and heat exchanger 300, as coolant for injection into uie compressor body cooling jacket 11. The coolant injected into cooling jacket 11 cools die walls surrounding cylinder bore 76 of die compressor body 79 and reduces die cylinder operating temperature.

In die multiple compressor embodiment illustrated in Figure 2, condensed liquid pump 100 draws refrigerant from reservoir 44 dirough line 58. Liquid refrigerant is then supplied to manifold system 57 which includes take-offs for line 60 feeding evaporators 54 and 55, as well as coolant recycle line 46. Eidier arrangement of condensed liquid pump 100 and coolant line 46 may be used for boui single compressor and multiple compressor systems. For example, condensed liquid pump

100 may be disposed to supply refrigerant to evaporator 54 as well as cooling jacket 11 in a single compressor system, and condensed liquid pump 100 may be disposed to supply only cooling jacket 11 in a multiple compressor system.

In all of die above embodiments, die temperature of cylinder bore 76, compressor body 79, and parts disposed dierein is reduced due to heat removal by uie coolant passing through cooling jacket(s) 11. The temperature of die refrigerant vapor compressed widiin cylinder bore 76 is consequently reduced.

As best illustrated by reference to Figure 1, e coolant dien passes from cooling jacket 11 dirough outlet 12 into exhaust manifold 74, which is disposed widiin cylinder head 71. Relatively hot refrigerant vapor, compressed by piston 75, leaves uie compressor cylinder 76 dirough exhaust valve 73 and enters exhaust manifold 74. In exhaust manifold 74, die hot compressed refrigerant vapor leaving uie cylinder 76 mixes widi die coolant leaving cooling jacket 11 dirough outlet 12. The mixture of diese two fluids has a temperature which is relatively lower ian die temperature of uie compressed vapor passing dirough exhaust valve 73. The temperature of ie surfaces of exhaust manifold 74 is dierefore reduced by die injection of die coolant. The temperature of

cylinder head 71 and odier parts disposed dierein is in turn reduced by die conduction of heat dirough die walls of cylinder head 71.

The cooling of die compressor cylinder 76 and body 79 will reduce die temperature of die discharge gas compressed by piston 75 into die exhaust manifold 74 of cylinder head 71. Compressor body cooling and die mixing of die coolant widi die hot compressed discharge gas, as described above, will further reduce e temperature of die discharge gas. By reducing die discharge gas temperature, die extent to which die refrigerant entering d e condenser is superheated above its condensing temperature is decreased. Decreasing die level of superheat in die vapor entering die condenser 28 reduces die condenser heat transfer surface used to desuperheat die vapor, and dierefore increases die condenser heat transfer surfaces available for condensing and subcooling service. By dius increasing die subcooling taking place in die condenser 28 die refrigeration system efficiency and refrigerating effect are increased. In anodier embodiment, me present invention is also applicable in combination widi enhanced subcooling of die refrigerant, such as is described in U.S. Pat. No. 5,115,664, which is incoφorated herein by reference. In anotfier embodiment, only a portion of uie coolant flowing through cooling jacket 11 is discharged dirough cooling jacket outlet 12 into exhaust manifold 74. The coolant is ien discharged from cooling jacket 11 into line 24 for desuperheating die hot compressor discharge gas in accordance widi die apparatus and metiiod described in copending application Serial No. 08/430,637, filed April 28, 1995, incoφorated herein by reference in its entirety. Figures 3 and 4 show die take-off of recycle liquid, as coolant for cooling die compressor body and cylinder heads, from die liquid line 38 between condenser 28 and reservoir 44, ratiier man from reservoir 44 itself. The liquid leaving die condenser may be maintained at a constant level by an inverted trap 82 (Figure 3) or trap leg 83 (Figure 4), if die condenser is at a higher level d an die compressor. This eliminates die need for die condensed liquid pump 100 shown in Figure 2, and allows die liquid to be subcooled before leaving die condenser 28, as is further described in copending application Serial No. 08/480,773, filed June 7, 1995, incoφorated herein by reference in its entirety.

The embodiments of Figures 3 and 4 also provide a column of liquid refrigerant of sufficient height to overcome die pressure drop dirough condenser 28. This ensures diat liquid refrigerant will flow, due to uie weight of die liquid from condenser 28, to d e compressor body

79. A control valve such as valve 49 or a restriction (not shown) may be placed in line 46 (or in lines 47 where two or more compressors are used) to assist in forming and controlling a liquid column in trap 82 or trap leg 83.

Referring now to Figures 5, 6, and 7, means for driving condensed liquid pump 100 and/or lubricating oil circulating pump 200 are described. Figure 5 illustrates an embodiment of tiie

invention in which compressor drive motor 401 for driving a compressor such as compressor 14, is mechanically coupled to the compressor and is also mechanically coupled to lubricating oil circulating pump 200. Alternatively, motor 401 may drive compressor 14, widi lubricating oil circulating pump 200 being coupled to the crankshaft of compressor 14. Condensed liquid pump 100 is mechanically coupled to motor 405, which may be a fixed speed electric motor, a variable speed electric motor, or other drive member. Motor 405 is preferably electrically coupled to, and controlled by, microcontroller circuit 56. Motor 401 and compressor 14 may togetiier comprise a hermetic motor-compressor unit 15, as is known in die art, which may include pump 200 or odier lubrication means. Figure 6 illustrates an embodiment of die invention in which compressor 14, lubricating oil circulating pump 200, and condensed liquid pump 100 are all mechanically coupled to, and driven by, compressor motor 401 or anotiier single drive member. It should be understood diat die embodiments of the invention illustrated by Figure 5 and 6 may also include suitable gear reduction members (not shown) as are known in die art, and whose application to drive die compressor 14 and pumps 100, 200 at different speeds would be obvious to one skilled in die art.

Figure 7 illustrates an embodiment of d e invention in which motor 401 drives compressor

14 but does not drive pumps 100, 200. Pumps 100 and/or 200 are mechanically coupled to, and driven by, motor 406. Motor 406 may be a fixed speed electric motor, a variable speed electric motor, or another type of drive member. This embodiment provides additional flexibility in controlling die speeds of pumps 100 and/or 200 independently of the speed of compressor 14, and diereby ensures adequate lubricating oil flow at all speeds of compressor 14. Pumps 100 and/or 200 may also each be individually driven by motors such as motor 406. This provides additional flexibility which is particularly important for variable speed compressors. As discussed in my U.S. Patent No. 5,067,326, incoφorated herein by reference in its entirety, d e minimum speed of a variable speed compressor may be determined by safe oil pressure limits. Independent control of die speeds of motors 401 and 406 tiius eliminates die need to increase compressor speed simply to raise oil pressure. All of die above motor drive arrangements are applicable to embodiments in which die condensed liquid pump is used to increase die pressure in liquid line 60, but where no compressor body cooling jacket is employed. Figure 8 illustrates a six-cylinder two-stage compressor 14', typical in die art, in which oil pump 200' is driven by die crankshaft of compressor 14'. Such a compressor may be retrofit in accordance widi an embodiment of d e present invention such as tiiat illustrated in Figure 6, in which compressor 14, lubricating oil circulating pump 200, and condensed liquid pump 100 are all driven by compressor motor 401, witii pumps 100 and 200 being coupled to die crankshaft of compressor 14. The retrofit of an existing compressor-oil pump combination such as 14' and 200'

where die oil pump is driven by die compressor crankshaft, is accomplished by insertion of a condensed liquid pump (such as pump 100 in Figure 6) between die compressor 14' and oil pump 200'. Internal connections may en be made from die pump to die cylinder head(s). This arrangement facilitates cooling of the lubricating oil by the proximity of die condensed liquid pump to die oil pump 200' and compressor crankcase. Cooling may be further enhanced by use of a heat exchanger as discussed above.

The retrofit of an existing compressor-oil pump combination such as 14' and 200' may also be accomplished by die addition of a separately driven condensed liquid pump (such as pump 100 in Figure 5). In this case, condensed liquid pump 100 is external to die compressor-oil pump combination, and d e condensed liquid pump may be driven by an electric motor as described above.

The signals provided by sensors such as oil pressure sensor 94 and/or oil level sensor 93 (Figure 2) may be used by microcontroller circuit 56 to detect faults such as a failure of lubricating oil circulating pump 200, an oil leak, a blockage of oil lines 210 or 215, or die like. Microcontroller 56 may then sound an alarm or shut down compressor 14 to avoid compressor damage due to inadequate lubrication. It should be understood d at in all die above embodiments, the motors may be electrically coupled to microcontroller 56, which men controls tiieir speeds.

While the embodiment of die invention illustrated in Figure 1 has been described widi respect to a single compressor (14), any number of compressors may be used. In single compressor and multiple compressor embodiments utilizing an individual condensed liquid pump

100 for each compressor, additional diagnostic capabilities are realized. For example, because microcontroller circuit 56 may control the operation of each condensed liquid pump, die operating time and coolant flow rates may be monitored and compared for each of die compressors. Also, die coolant flow for any individual compressor may be cumulated and the variation in coolant flow rate over time may be analyzed. The coolant flow may be calculated by microcontroller circuit 56 or measured directly by a sensor such as coolant flowmeter 19. An increase in coolant flow for a compressor may indicate a problem such as an exhaust valve failure. Similarly, die flow rate may be compared to a previously measured flow rate and a substantial difference for a single compressor, or for one compressor in a multiple compressor system, may be indicative of a service problem for at compressor. This information can be used by microcontroller circuit 56 or a remote computer (noy shown) to sound an alarm (not shown), call out via a modem (not shown) to notify service personnel of an impending problem, to shut down d e compressor(s), or to take odier corrective action. The present invention tiius provides a substantial savings in the operation and maintenance costs of refrigeration compressors relative to die current state of die art, and is indicative of a development tiiat will be welcomed by die refrigeration field.

While die invention has been described in accordance widi reciprocating compressors and air cooled condensers, one experienced in die art may easily apply die invention to compressors of all types, including multiple-stage and multiple-compressor systems, and water or fluid cooled condensers of all sorts. It is intended tiiat the current patent shall apply to all sorts of compressors and condensers. These embodiments have not been specifically described because they are considered redundant in application of die invention in view of die above description.

Further, die present invention is equally applicable to condenser systems employing modulation of multiple condenser cooling fans or water flow modulation in die case of water cooled condensers. As would be obvious to one skilled in the art, many other applications of the present invention are possible and die description provided herein is intended to be limited only by die claims appended hereto.