US3408826A

US3408826A - Refrigeration system and systems for cooling and controlling compressors

Info

Publication number: US3408826A
Application number: US612222A
Authority: US
Inventors: Soumerai Henri; Clark B Hamilton; James R Blatt
Original assignee: Dunham Bush Inc
Current assignee: Dunham Bush Inc
Priority date: 1967-01-27
Filing date: 1967-01-27
Publication date: 1968-11-05
Anticipated expiration: 1985-11-05
Also published as: GB1220132A; DE1728619A1; SE342501B; BE709704A; GB1220133A; DE1601058A1; CH483607A; NL6801229A; GB1220131A; DK122415B; FR1553294A; DE1601058C2

Description

Nov. 5, 1963 H. SOUMERAI ETAL 3,408,826

REFRIGERATION SYSTEM AND SYSTEMS FOR COOLING AND CONTROLLING COMPRESSORS Filed Jan. 27, 1967 mm Q 9m, g 3 g mw I uu F H m w ww r R ATTORNEYS United States Patent 3,408,826 REFRIGERATION SYSTEM AND SYSTEMS FOR COOLING AND CONTROLLING COMPRESSORS Henri Soumerai, West Hartford, Harold Moody, Farmington, Clark B. Hamilton, Wether'sfield, and James R. Blatt, Coventry, 'Conn., assignors to Dunham-Bush, Inc.,

West Hartford, Conn., a corporation of Connecticut Filed Jan. 27,1967, Sei'.- No. 612,222"

- .13 Claims. (Cl. 62-193) ABSTRACT OF THE' DISCLOSURE ,A refrigeration. system isadisclosed in the form.of a liquid chiller. The compressor is 0f.the screw type, and a stream of compressed gas and .oi l mist is used to cool the compressor and the motor. Variations in load are accommodated by an unloader on the compressor.

Specification is in the form of a liquid chiller. 4

An object of thisinvention is to provide an improved refrigeration system. Another object is to provide an improved method and means for operating compressors of the screw type. Another object is to provide. improved means for maintaining desirable operating conditions: in a screw compressor. under varyingv loads andextreme conditions of use. A further object is to provide for the above in a manner which avoids the ditficulties'which have been encountered in the past with similar constructions. These and other objects will'be in part obvious and in part pointed out below.

In the drawings:

FIGURE 1 is a schematic representation of one embodiment of the invention; and,

FIGURE 2 is an enlarged vertical section of the lower left-hand portion of the evaporator-chiller shown at the bottom of FIGURE 1.

Referring to FIGURE 1 of the drawings, a refrigeration system 2 includes: a screw compressor 4 having an unloader 5 and driven byan electric motor 6; an oil separator 8; a refrigerant discharge li ne 10; a watercooled condenser 12; a liquid refrigerant line 14 extending to a heat exchanger 16 which acts as a superheater unit; a liquid refrigerant dryer-filter 18;'-a liquid supply control assembly 20 through which the liquid refrigerant flows'to a distributor header 22 for aplurality of liquid distributor tubes 24; an evaporator-chiller 26 having a refrigerant inlet header28 and a refrigerant outlet tube plate 30; and, a gas refrigerant return line 32 through which the gas refrigerant returns to compressor 4.

The system also includes an oil circulating system including the following in series: an oil sump 34; an oil pump 36 driven by an electric motor 37; an oil cooler 38 through which water flows from a water' inlet 40.t0 a water outlet 42 and which cools the oil flowing from the pump; and, an oil filter 44. An oil supply line 46 delivers oil under controlled pressure through distributor lines 48 to the motor bearings 50 and through lines 52 and 54 and 56' to compressor 4. Oil is also delivered from line 46 through a line 58 to the unloader 5,'and through a line 59 to a load control unit 60.

During operation; the dense high-pressure oil-gas mix ture is discharged from compressor 4 into a chamber 62 and thence through the motor where it is discharged axially against a bafile 64. This gas-oil mixture uniform ly blankets and cools the stator and rotor of the motor,

3,408,826 Patented Nov. 5, 1968 and themotor! also serves as -a first-stage oil-separator and-removes, by centrifugal action, the-'bulk'ofthe oil entrained in. the gas. It has been-found-that something of the ordersof 9.5% .of the oil is. removed by the motor, and the. oil'accumulates at 66 in the-bottom of the lion's.- ing-from-which it flows through a line 35 .to oil sump 342 The remaining fine oil'mist is then separated. from the gas by the action of battle 64 and oil separator 8.

The disk-like bafile:- 64 deflects the stream" of gas radially outwardly toward the outer-wall and the oil then flows axiallypast the edge of the-battle through a passage- 1 way 68. Positioned in. axial alignment with passageway 58 is an annular separatorunit 70 which -effectively removes the oil-.from-the gas passing. through 'it. Unit 70 is a..loosely-formed ring': of: woven rnetal mesh "which is wound upon a perforated tubular-mandrel 72.'-Mandrel 72 forms acentralgas discharge'passageway 74-throu-gh which the gas flows-to a gas discharge tube 73 and thence pasta check valve 75 to. line .10. E

Unit 70 is spaced. axially. from bafile 64 so as to provide a radial passageway 76 through=which-= the gas is free. to flow radiallyinwardly to passageway 74 without passing through unit 70. Hence, the gas flowing axially through passageway 68 may proceed in the axial-direction and fiow into and through unit 70, or it may flow radially inwardly through passageway- 76 without restriction into the central passageway 74. However, there is a tendency for there to 'be two-phase fluid flow, with the heavier mixture of gas and oil mist flowing along the outer casing wall and with the oil-free gas flowing adjacent the outer edge of baflle 64. Hence, as the stream flows past bafile 64, the oil-laden gas impinges against and enters unit 70, whereas the lighter oil-free gas makes the sharp turn around the edge of the batile and flows radially inwardly through passageway 76 to passageway 74. The gas and oil mist entering unit 70 are. slowed down, and the free gas migrates radially inwardly to passageway 74.

The oil from unit 70 adheres to the exposed surfaces of the wire mesh and fiows downwardly and it collects at the bottom of unit 70 in the body of oil 66. It then flows to sump 34 through line 35. During operation there may be a tendency for the oil to bridge some of the passageways between the adjacent lmesh portions in unit 70. Such bridging of the passageways could be expected to cause the oil to be re-entrained in the gas so as to reduce the effectiveness of the oil separator. However, I

with the present arrangement which permits the oil-free trainment does not occur, apparently because of the reduced gas velocity within unit 70. Also, the gas is readily.

diverted around any plugged passageways or portions without building up back pressure. At light loads there is a tendency for a high percentage of the refrigerant gas to fiow through unit 70,.whereas at increased loads an increased amount of the gas is free of oil and passes radially inwardly through passageway 68. The concentric discharge tube 73 insures that only oil-free gas flows to line 10.

It has been indicated above that the liquid refrigerant is delivered through distributor tubes 24 to the inlet header 28 of the evaporator-chiller 26. Chiller 26 has refrigerant tubes 80 which are supported within the shell between their ends and are mounted at their ends in

tube plates

82 and 84, respectively (see also FIGURE 2). Mounted upo n tube plate 82 is an orifice plate 86 which is held in place beneath a header 88. Orifice plate 86 has a plurality of small round openings or orifices 90 which are so positioned that one of them is in axial alignment with the end of each of the evaporator tubes 80. Header 88 has a plurality of ribs 92 which rest against orifice plate 86 and divide the area of the orifice plate into a number of header through one -of-thedistributor tubes The-pattern 'of' ribs 92 is such that substantially the same number of orifices 90 is in each of the header chambers 94. Hence, the refrigerant supplied to-each of tubes 24 is delivered through one of the headers and its orifices 90 to a specific group of evaporator tubes 80. Each of the orifices 90 acts as an expansion unit to provide the desired pressure drop, so that each of the evaporator tubes is in effect a separate evaporator.- Also,-lsubstantially the same amount of the refrigerant flows to each chamber 94, and it is then distributed substantially evenly toa'relatively small number of evaporator'tubes. Hence, a highlyefiicient and depend able arrangement is provided for distributing the 're valve 140 and a restrictor in a line 144 which extends --'-'-=between--'thesuction inlet of thecoin'pressor housing and 5 142, line 144, and valve 140 to the compressor casing. As

indicated above, when the compressor is operating, the pressure 'o f -the comp'r e ssed gas at the discharge side of theco'mprssor il'jrges sliding "valve 1211 toward its full-load 'p ositioh. Hence wheri valve 140 is, open, the pressure equalizes ori t he' twosides of the piston because of the iiow of oil from chamber. 130, and the discharge pressure acting on slidevalve 120 moves the slide and piston 126 back to the position shown. R'estrictor 142 controls the rate of flow of oil from chamber 130 and therefore frigerant substantially equally to all of the evaporator Controls the rate f movemeht 0f the Piston from a mh i partial-loadposition to the full-load position.

"."As indicated above, the discharge ends of the evaporator T Oil Pressure in line-46 is cohtreiied y a Control tubes are supported in "a tube plate 84,'and the tubes open unit 146 which it Vaivc 148 iii a line 150 extending i i thesshe" 95 of theheat an er '1 'wa or from line 46 to'suinp-34. A control line 152 extends from other hhuid to he-cooled hows to n m w-93 unit 146 to thedischarge chamber 162 of the compressor through a'pair f lines oo- 102' e f i f as so that unit 146 is responsive to the compressor discharge flowi g h 11. '9 of heat a g -1 cools h pressure. Unit 146 and its valve 148 act as a relief valve liquid refrigerant in coil 104, and the gas then fiows to maintain a p i l e 146 which is a predeterthrough a filt 106 a o h '32 k to mined amount above the pressure in chamber 62. Illuspressor 4. Positioned in the path of the returning refrigtratively, When the Compressed gas'pressufe in chamber 62 erant gasare two control bulbs 108'and 110 which control is 200 Pounds P Square inch, the Pressure in line 46 is liquid supply or

regulator valves

112 and 114, respectively 240 Pounds Pef'Square ihch- Hence, the Oil delivered to through

controllers

116 and 118. Valves 112 and 114' are the compressor through the Various lines 54 and in parallel. Valve 114 is fully' closed at low loads, for 56, and thr0ugh'1ineS'58 an 59 o the unloader is maincham'ple, below 35% f fullload, and valve 112 defeptained at a predetermined value above the compressor dismines the supply ofliquid refrigerant to header 22 below charge Pressure This insures 3 P p and vadequate of full load. At loads above 35% of full load valve PP Y l t0 the motor hearings and t0 the compressor- 112 is fully open and the'control is exerted by valve 114. I also insures that the uhioadei wiii Op P y- Asindicated above, unloader 5 controls the operation T Opening of Valve 132wheh the cohiliressor is P f the compresspr so h i compresses the amount of 35 tially or fully loaded will unload it at a rapid rate. The refrigerant required for the load at all times, Accordingly, Opening of valve when the compressor is Partially compressor 4 has a capacity control slide valve 120 01" completely unloaded will fully load it at a controlled which is shown in the'full-load position wherein it'forms Tatei a portion of the compressor-rotor casing 122. Slide valve It has been Pointed out above that the heavy mixture 120 is mounted to slide to the left from the position shown of compressed gas and l mist provides y satisfactory to thereby expose an opening in the bottom f the rotor cooling of the motor. The oil mist produces a scrubbing casing through which the suction gas can pass back from action which mp the heat cXchahgef l and the central portion of the compressor to the suction inlet. creases the cooling of the mOtOr- The Oil which is P- n this way the amount of gas pumped is h plied to the compressor may contain some refrigerant and Sliding valve 120 is connected through an operated that refrigerant tends to flash and to aid in the cooling spindle 124 to a piston 126 which i slidable in a cylinder effect of the oil. It is thus seen that the refrigerant and the 128. Piston 126 is moved to the left from the position Oil are circulated through Separate Cycles, but tht inter- Show by supplying 11 at a Controlled pressure to h relationshipis maintained which provides an improved chamber 130 in the cylinder at the right of the piston. {node f ep p 36 started Prior to the Start- Cylinder 128 is open at its left-hand end to the suction e of or 6 so that the oil pressure builds p and D pressure of the compressor, but the sliding valve 120 is V1 deS Oil for the motor a d Compressor, ahd the desired cxposed to the ressure of the compressed refrigerant at 011 pressure is provided for the unloader. The controls the discharge side of the compressor. Therefore, when the also provide automatic unloading at start-up. compressor is operating the sliding valve 120 is urged I A hot gas bypass line 11 is connected between the gas toward the fully loaded position against the action of the f ig rant discharge line 10 and the liquid supply line 21 oil hd Pressure in h b 130 H h oil i through which liquid refrigerant flows from valves 112 su to h b 139 at a ressure greater than the and 114 todistributor header 22. Line 11 includes a cutdischarge pressure, piston 126 is moved to the left; and, ofii'valve 23 and a restrictor 15. When desirable, valve when the pressure of the oil in chamber 130 is less than 23 is opened to supply hot gas under the control of rethe" discharge pressure, piston 126 moves to the right. Oil strictor 15 to" prevent Stratification of the liquid phase supply line 58 is connected to chamber 130 through'a and unstable operation of the refrigerant controls. shut-off valve 132 and a line 134. Hence, when valve 132 The inventioncontemplates that some of the evaporator is open the oil at the full pressure in

lines

46 and 58 is tubes 80 may be supplied with more refrigerant than supplied at once to chamber 130. Also, a flow circuit is others. Such arrangements permit variations in the heat provided in parallel with valve 132 by line 59 and a retransfer or cooling'effect in various zones, Accordingly, strictor valve 136 and a shut-off valve 138. Hence, when the orifices SN may be of different sizes in any chamber valve 132 is closed and valve 138 is opened, the oil at the 94 and from one chamber to another. Also, various of pressure of line 46 flows through line 59, restrictor 136, the chambers may have different numbers of tubes convalve 138'and line 134 to chamber 130. However, ren'e'cted to them, with or without variations in the orifice strictor 136 limits the rate of, flow so that piston 126 is size. Hence, great freedom of design is provided while moved at a reduced but controlled rate, whereas when valve 132 is open the piston moves at a rapid rate. This permits unloading rapidly by opening valve 132, or unloading at a slower rate by opening valve 138.

An additional control circuit is provided by a shut-olf permitting dependableand accurately controlled operation.

The system of FIGURE l includes standard components and controls. It is also understood that the embodiment herein disclosed is illustrative, and it is contemplated that f ,5 changesand modifications .may be made within the scope of thexinvention, H v I I ,lNzhat -isclaimed is: ,v v v 1. In a refrigeration system, the combinationof, a compressor: having .an unloader means and connectormeans by which it is moved between a fully-loadedposition and fullyeunloaded position, aacylinder and piston assembly operatively connected to said connector means .to move said-unloader: means throughout itspperating range, said compressor and unloader means including means, utilizing force produced bypompressed gas :on the discharge side of the compressor to move said unloader means toward the fully-loaded position against-the unloading-action of said cylinder and piston assembly, an. oil supply means, control means for said cylinder and piston ,assembly including means providing twoparallel flow. paths for oil flowing from fsaid.,oil supply means to: .one endof ,the. cylinder of said cylinder and piston assembly, oneof said flow paths providing for the free flow, of oil and the other of said flow paths including restrictor means providing for the restricted flow of oil to said one end of said cylinder thereby to produce a force acting through, said connector means and urging said unloader means toward, the fullyunloaded position, said control means also including means providing for the restricted flow of oil from one end of said cylinder to the other, thereby to equalize the pressures on the opposite sides of said piston within said cylinder and permit the force produced by the compressed gas to move said unloader means to the fully-loaded. position, said control means includingval ve means to control the flow of oil along each of said flow paths.

2'." Apparatus as described in claim 1 wherein said com p'ressor' is a screw-type compressor and wherein said unloader means comprises an unloader sliding valve and wherein said connector means comprisesa spindle connected at one end to said .piston and at.t he other end to said sliding valve, and whereinsaid-one end of said cylinder is closed and the other end is open to the suction inlet for refrigerant gas being compressed by the compressor.

3. The combination as described in claim 1 which includes, an electric motor connected directly to said compressor," and a common casing enclosin-g'said compressor andsaidimotor with said compressorpositioned to 'dischargeamixture or compressed gas and oil mist through said-motor; and wherein said oil supply system includes an oil'pump and an oil cooler which cools the oil flowing to said compressor.

"4. The combination asdescribed in claim 3 wherein said motor separates a substantial portion of the oil from the refrigerant, and which includes an oil separator positioned in axial alignment with the path of gas flow from said motor and including a central bafiie which deflects the gas radially outwardly to an axially directed flow path, said oil separator also including an annular separator-unit positioned in alignment with said annular flow path whereby the-gas impinges against said separator unit, said separator unit being'spaced from said bafiie upon the opposite side-of said motor to provide a free flow path radially inwardly between said separator unit and said baflie and then axially through said unit.

'SIThecOmbination as described claim 4 which includes; means to direct oil "from said motor and said separator unit to said oil supply system.

6. The combination as described in claim 5 which includes, a condenser and an evaporator, said evaporator being a'chiller of the shell and tube type and having a plurality of refrigerant distributor circuits to supply re fri'gerant to said evaporator.

7. In a system of the character described, the combination of, a'screw-type compressor having an unloader slide which is moved from and tea full-load position to control the operating capacity, operatingmeans to move said unloader slide throughout its operating range and comprisinga cylinder and piston assembly operatively conh 6 V d I nected to said unloader slide, oil supply means to cool and lubricate said compressor and toprovide oil under pressure to operate said cylindefand piston assembly, and control means to controlthesupplying'of oilj't'o said cylinder and piston assembly including a firsf'valve which is opened to movesaid unloader slide to its fully-unloadd position and a second vane which is opened to provide a fluid flow path from one end to the other ofth'e cylinder of s'aidcylinder and piston-assembly. i

8; The combination as"des'cribed 'in claim 7 wherein a fluid connection is' provided'b'etween said cylinder and the inlet'sidfe of saidcornpre'ss'or and said 'unloaderyslide" is subject to the discharge pressure' of said cdmpressorjand which includes means fbr'minga fluid flow path in parallel with said first valve and havinga third-valve" and restrictor' means therein, and wherein either said first valve or said third valvemay be opened to supply oil to? ove said unloader valve 'tow-ard'its fully-unloaded pbsition."""'

9. Asystem'as described in claim" 7*-whichincludes, an electricmotor connected to drive said'compressbrand positioned the path'along' which the compressed gas'an'd oil are discharged from said compressoig a shellconstruc tion enclosing said compressor and said motor and including means forming a passageway through 'which'the compressed gas flows from said'compressor and through said motor, and means to deliver oil from said oil supply means to the inlet of said compressor in suflicient quantity to cool the compressor and the refrigerant.

10. In a refrigeration system, the combination of, a screw-type compressor having an unloader slide which is moved to and from a full-load position to control the compressing of refrigerant, said unloader slide being urged 'to its full-load position by the action of the compressed refrigerant, aicylinder and piston assembly operati-vely connected to move said unloader slide away from said fullload position under the action of fluid supplied to said cylinder, and oil supply means connnected to circulate oil through said compressor and also connected to supply oil under pressure to said cylinder, to move said unloader slide away from said full-load position.

11. In a refrigeration system, the combination of, an electric motor, a compressor connected to said motor and operative to compress the refrigerant in the system, ashell construction enclosing said motor and said compressor and including means forming a passageway through which the compressed refrigerant flows directly from said compressor through said motor, means constituting a con tinuous supply of oil, means to deliver oil from said supply to said compressor with the refrigerant which is being compressed, means to cool said oil prior to passing to said compressor to a temperature which is sufficiently low to permit said motor to be cooled by the refrigerant and accompanying oil flowing therethrough, and means to return the oil passing from said motor to said means constitut- References Cited UNITED STATES PATENTS 2,762,204 9/ 1956 Hanson 62-193 3,041,847 7/1962 Hatter et a1 62193 3,081,604 3/1963 Namisnia-k et al. 62192 X 3,200,603 8/1965 Wake et al 62193 X 3,280,576 10/1966 Endress 62--193 X 3,299,655 1/ 1967 Rayner et al. 62-193 LLOYD KING, Primary Examiner.