Oil-free liquid chiller

• US 6,564,560 B2
• Filed: 07/11/2001
• Issued: 05/20/2003
• Est. Priority Date: 10/09/1998
• Status: Expired due to Term

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: American Standard International Inc (Trane Technologies plc)
• Inventors: Vandeleest, Todd R., Butterworth, Arthur L., Eber, David H.
• Primary Examiner(s): WAYNER, WILLIAM E
• Application Number:
  US09/903,168
• Publication Number:
  US 20010037651A1
• Time in Patent Office: 678 Days
• Field of Search: 62D/IG.2, 625/05, 622/592, 62/84, 622/284
• US Class Current: 62/84
• CPC Class Codes: F04D 25/06 the pump being electrically driven F04D25/08 takes precedence
• CPC Class Codes: F04D 29/023 especially adapted for elastic fluid pumps
• CPC Class Codes: F04D 29/059 Roller bearings
• CPC Class Codes: F04D 29/063 specially adapted for elastic fluid pumps
• CPC Class Codes: F04D 29/5806 Cooling the drive system
• CPC Class Codes: F05D 2300/20 Oxide or non-oxide ceramics
• CPC Class Codes: F05D 2300/2283 of silicon
• CPC Class Codes: F05D 2300/501 Elasticity
• CPC Class Codes: F05D 2300/5021 Expansivity
• CPC Class Codes: F05D 2300/522 Density
• CPC Class Codes: F16C 2360/44 Centrifugal pumps
• CPC Class Codes: F16C 2380/26 Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators
• CPC Class Codes: F16C 33/6659 Details of supply of the liquid to the bearing, e.g. passages or nozzles
• CPC Class Codes: F16C 33/6692 Liquids other than oil, e.g. water, refrigerants, liquid metal
• CPC Class Codes: F25B 31/002 Lubrication
• CPC Class Codes: F25B 31/006 Cooling of compressor or motor
• CPC Class Codes: F25B 31/008 by injecting a liquid
• CPC Class Codes: F25B 49/025 Motor control arrangements
• CPC Class Codes: H02K 7/083 radially supporting the rotary shaft at both ends of the rotor H02K7/086, H02K7/09 take precedence
• CPC Class Codes: H02K 9/20 wherein the cooling medium vaporises within the machine casing
• CPC Class Codes: Y10S 62/02 : Refrigerant pumps

Abstract

A refrigeration chiller employs a centrifugal compressor the impellers of which are mounted on a shaft which is itself mounted for rotation using rolling element bearings lubricated only by the refrigerant which constitutes the working fluid of the chiller system. Apparatus is taught for providing liquid refrigerant to (1.) the bearings immediately upon chiller start-up, during chiller operation and during a coastdown period subsequent to shutdown of the chiller and (2.) the drive motor of the chiller'"'"'s compressor for motor cooling purposes. By use of a variable speed-driven motor to drive the compressor, optimized part load chiller performance is achieved in a chiller which does not require or employ an oil-based lubrication system.

Claims

1. A liquid chiller comprising:

a condenser, said condenser condensing refrigerant gas to the liquid state when said chiller is in operation;

a metering device, said metering device receiving refrigerant from said condenser and reducing the pressure thereof;

an evaporator, said evaporator receiving refrigerant from said metering device and causing liquid refrigerant to vaporize when said chiller is in operation;

a compressor, said compressor receiving refrigerant from said evaporator and delivering refrigerant in the gaseous state to said condenser when said chiller is in operation, said compressor having a shaft, at least one compressive element being mounted on said shaft, said shaft being rotatably supported by at least one bearing, said at least one bearing being a rolling element bearing, the rolling elements of said bearing being fabricated from a non-metallic material, said at least one bearing being lubricated by refrigerant in the absence of oil, refrigerant delivered to said at least one bearing for lubrication purposes being at least primarily in the liquid state, heat from said at least one bearing being rejected to and vaporizing a portion of the refrigerant delivered thereto at the location of said at least one bearing as a result of the bearing lubrication process; and

a source location for liquid refrigerant, discrete from said evaporator and condenser, from which liquid refrigerant is supplied to said at least one bearing for bearing lubrication purposes.

2. The chiller according to claim 1 wherein said chiller is a centrifugal chiller, wherein said non-metallic bearing material is a ceramic material, wherein said compressive element is an impeller and wherein the refrigerant used to lubricate said at least one bearing is primarily in the liquid state.

3. The chiller according to claim 2 wherein said source location is a reservoir for refrigerant.

4. The chiller according to claim 2 further comprising a refrigerant sump, liquid refrigerant being delivered to said sump from said evaporator while said chiller is shutdown.

5. The chiller according to claim 4 wherein said source location is a reservoir for refrigerant, said reservoir being in selective flow communication with said sump, said sump being the location from which liquid refrigerant is initially provided to said reservoir for bearing lubrication purposes when said chiller starts up.

6. The chiller according to claim 5 wherein said sump is isolated from said evaporator when said chiller starts up.

7. The chiller according to claim 6 further comprising means for delivering liquid refrigerant to said reservoir so as to replenish the supply of liquid refrigerant available for bearing lubrication purposes therein while said chiller is in operation.

8. The chiller according to claim 7 wherein said means for delivering liquid refrigerant initially delivers liquid refrigerant from said sump to said reservoir as said chiller starts up and subsequently delivers liquid refrigerant from said condenser to said reservoir.

9. The chiller according to claim 8 wherein said means for delivering liquid refrigerant is a pump, said pump being in flow communication with and disposed (i) upstream of said reservoir and (ii) downstream of both said condenser and said sump.

10. The chiller according to claim 5 further comprising means for isolating said reservoir upon shutdown of said chiller so as to retain a residual pressure therein for a period of time after chiller shutdown, said residual pressure being the driving force by which liquid refrigerant in said reservoir at the time of chiller shutdown is driven to said at least one bearing so as to provide for the lubrication thereof while said shaft coasts to a stop.

11. The chiller according to claim 5 wherein said chiller further comprises a motor and a pump, said pump pumping liquid refrigerant from said sump to both said reservoir and said motor when said chiller starts up and from said condenser to both said reservoir and said motor when said chiller is in operation, liquid refrigerant pumped to said reservoir by said pump being used to lubricate said at least one bearing and liquid refrigerant pumped to said motor by said pump being used to cool said motor.

12. The chiller according to claim 2 further comprising a motor for driving said compressor and means for delivering liquid refrigerant to both said source location for bearing lubrication purposes and to said motor for motor cooling purposes while said chiller is in operation.

13. The chiller according to claim 12 further comprising a variable speed drive, said motor being an induction motor capable of being driven at variable speeds substantially higher than 3600 RPM in order for said chiller to operate at its maximum capacity.

14. The chiller according to claim 12 further comprising a pump, said pump pumping liquid refrigerant to said source location and to said motor both during start-up and during normal operation of said chiller.

15. The chiller according to claim 12 further comprising a reservoir, a pump and a sump, said reservoir being said source location for liquid refrigerant for bearing lubrication purposes, said pump pumping liquid refrigerant from said sump to both said reservoir and said motor when said chiller initially starts up and said pump pumping liquid refrigerant from said condenser to both said reservoir and said motor subsequent to start-up of said chiller when liquid refrigerant comes to be available in said condenser for such purposes.

16. The chiller according to claim 12 further comprising an economizer, refrigerant used for cooling said motor and the refrigerant used for lubricating said at least one bearing being delivered to said economizer subsequent to such uses.

17. The chiller according to claim 12 further comprising a drive for said motor and means for delivering liquid refrigerant to said motor drive for purposes of cooling heat generating components therein.

18. The chiller according to claim 17 wherein refrigerant used for bearing lubrication purposes, for motor cooling purposes and for motor drive cooling purposes is returned to said condenser.

19. The chiller according to claim 17 further comprising an economizer, refrigerant used for cooling said motor and said motor drive being returned to said economizer.

20. The chiller according to claim 2 further comprising means for delivering liquid refrigerant sourced from one of said evaporator and said condenser to said source location while said chiller is in operation.

21. The chiller according to claim 20 wherein said means for delivering refrigerant from one of said condenser and said evaporator comprises a pump.

22. The chiller according to claim 21 wherein said source location is a reservoir for liquid refrigerant, liquid refrigerant in said reservoir being the refrigerant by which said at least one bearing is lubricated.

23. The chiller according to claim 22 further comprising a sump, said sump being the location from which said reservoir is replenished with liquid refrigerant during chiller start-up, said pump pumping liquid refrigerant from said sump to said reservoir during chiller start-up and from said condenser to said reservoir when said chiller is in operation.

24. The chiller according to claim 22 wherein refrigerant used for bearing lubrication purposes is returned to said condenser subsequent to such use.

25. The chiller according to claim 22 wherein the rate of flow of liquid refrigerant from said reservoir to said at least one bearing is such that at least 80% of the liquid refrigerant delivered to said at least one bearing for bearing lubrication purposes remains in the liquid state subsequent to having been used to lubricate said at least one bearing.

26. The chiller according to claim 22 wherein said pump has an impeller, a motor and a shaft, said pump shaft being mounted for rotation in a pump bearing, said pump bearing having rolling elements fabricated from a ceramic material, said pump motor being cooled and said pump bearing being lubricated by liquid refrigerant, said pump impeller pumping liquid refrigerant from said sump to said reservoir as said chiller starts up and from said condenser to said reservoir when said chiller is in operation.

27. A liquid chiller comprising:

a condenser, said condenser condensing refrigerant gas to the liquid state when said chiller is in operation;

a metering device, said metering device receiving refrigerant from said condenser;

an evaporator, said evaporator receiving refrigerant from said metering device;

a compressor, said compressor receiving refrigerant from said evaporator and delivering refrigerant in the gaseous state to said condenser when said chiller is in operation;

a motor, said motor driving said compressor and being cooled by refrigerant sourced from said condenser;

a variable speed drive, said variable speed drive being electrically connected to said compressor drive motor for varying the speeds thereof, refrigerant being delivered from said condenser to said variable speed drive so as to cool said variable speed drive.

28. The chiller according to claim 27 further comprising a pump, said pump pumping refrigerant from said condenser to said variable speed drive so as to cool said variable speed drive.

29. The chiller according to claim 28 wherein refrigerant delivered by said pump to said variable speed drive is returned therefrom to said condenser.

30. The chiller according to claim 29 wherein refrigerant pumped from said condenser by said pump is pumped in parallel to both said compressor drive motor and to said variable speed drive.

31. The chiller according to claim 29 wherein refrigerant pumped by said pump from said condenser is pumped in series to both said compressor drive motor and to said variable speed drive.

32. The chiller according to claim 29 wherein said compressor includes at least one bearing, said at least one bearing being a rolling element bearing, the rolling elements of said bearing being fabricated from a non-metallic material, said at least one bearing being lubricated by refrigerant in the absence of oil, refrigerant delivered to said at least one bearing for lubrication purposes being at least primarily in the liquid state and a portion of the refrigerant used in the lubrication of said at least one bearing vaporizing at the location of said at least one bearing as a result of the bearing lubrication process, said pump pumping refrigerant from said condenser to said at least one bearing for bearing lubrication purposes.

33. The chiller according to claim 32 further comprising a reservoir, refrigerant pumped by said pump from said at least one bearing being pumped to said reservoir prior to flowing to said at least one bearing.

34. The chiller according to claim 33 wherein refrigerant pumped by said pump from said condenser is additionally pumped to said compressor drive motor, the refrigerant pumped to said variable speed drive being pumped to said reservoir prior to flowing to said variable speed drive.

35. The chiller according to claim 34 wherein refrigerant to said at least one bearing for bearing lubrication purposes drains, subsequent to being used for lubrication purposes to a location in said compressor drive motor and is returned therefrom, together with refrigerant used for motor cooling purposes, to said condenser.

36. The chiller according to claim 29 wherein said pump pumps refrigerant to said compressor drive motor so as to cool said motor and further comprising apparatus for regulating the flow of refrigerant pumped by said pump to said compressor drive motor and to said variable speed drive in accordance with the conditions under which said chiller is operating.

37. The chiller according to claim 29 wherein said motor is an induction motor, wherein, in addition to pumping refrigerant to said variable speed drive, said pump pumps refrigerant to said compressor drive motor so as to cool said motor, said pump increasing the pressure of refrigerant pumped by it from said condenser to a pressure which is higher than condenser pressure, and wherein heat rejected to refrigerant pumped by said pump to said compressor drive motor and to said variable speed drive is carried therein back to said condenser, said condenser transferring such heat, which has a parasitic effect on the efficiency of said chiller, to the cooling medium which flows through said condenser.

38. The liquid chiller according to claim 27 further comprising a pump, wherein refrigerant is pumped by said pump from said condenser to both said compressor drive motor and to said variable speed drive so as to cool said compressor drive motor and said variable speed drive, said pump increasing the pressure of refrigerant pumped by it from said condenser to a pressure which is higher than condenser pressure, and wherein heat rejected to refrigerant pumped by said pump to said compressor drive motor and said variable speed drive is carried therein back to said condenser, said condenser transferring such heat, which has a parasitic effect on the efficiency of said chiller, to the cooling medium which flows through said condenser.

39. The liquid chiller according to claim 38 wherein said compressor includes at least one bearing, said bearing being lubricated by refrigerant in the absence of oil, the refrigerant used to lubricate said at least one bearing in the absence of oil being refrigerant pumped thereto from said condenser by said pump.

40. The liquid chiller according to claim 39 wherein said pump pumps liquid refrigerant from said condenser, in parallel, to said at least one bearing and to said compressor drive motor, the liquid refrigerant pumped to said variable speed drive by said pump being pumped thereto in parallel with refrigerant pumped by said pump to said compressor drive motor.

41. A method of operating the liquid chiller comprising the steps of:

connecting a condenser, a metering device, an evaporator and a compressor for flow so as to form a refrigeration circuit;

flowing a cooling medium through said condenser so as to carry heat thereoutof;

driving said compressor by the use of a motor;

controlling the speed of said motor by the use of a variable speed drive which includes heat generating components;

delivering refrigerant from said condenser to said at least one of said compressor drive motor and said variable speed drive;

rejecting heat from said at least one of said compressor drive motor and said variable speed drive to the refrigerant delivered in said delivering step;

returning refrigerant to which heat has been rejected in said rejecting step to said condenser; and

transferring heat carried back to said condenser in said returning step to the cooling medium which flows through said condenser.

42. The method according to claim 41 wherein said delivering step includes the step of pumping refrigerant from said condenser to said at least one of said motor and said variable speed drive.

43. The chiller according to claim 42 wherein said pumping step includes the step of pumping refrigerant in parallel from said condenser to both of said motor and said variable speed drive.

44. The method according to claim 42 wherein said pumping step includes the step of pumping refrigerant in series from said condenser to both of said compressor drive motor and variable speed drive.

45. The method according to claim 42 wherein said compressor includes a bearing and wherein said pumping step includes the step of pumping refrigerant from said condenser to said bearing so as to lubricate said bearing.

46. The method according to claim 45 wherein said chiller includes a reservoir and wherein said pumping step includes the step of delivering refrigerant to said reservoir prior to its delivery to said bearing for bearing lubrication purposes.

47. The method according to claim 46 comprising the further step of isolating refrigerant in said reservoir from a drop in pressure upstream thereof so that pressurized refrigerant continues to be available from said reservoir to lubricate said bearing for a predetermined period of time in the event of a pressure drop upstream of said reservoir.

48. The method according to claim 47 comprising the further step of delivering refrigerant from said reservoir to said variable speed drive so as to cool said variable speed drive.

49. The method according to claim 45 comprising the further step of defining a flow path from said bearing to said motor so that refrigerant used to lubricate said bearing flows to said motor and returns to said condenser, in said returning step, with refrigerant used to cool said drive motor.

50. The method according to claim 42 comprising the further step of regulating the flow of refrigerant pumped in said pumping step in accordance with chiller operating conditions.

51. The method according to claim 41 wherein said driving step includes the step of driving said compressor directly so that said compressor is driven at the same rotational speed as the rotor of said drive motor.