1. C oncerns Ltd ool Energy Efficient Refrigeration Jane Gartshore, Cool Concerns Ltd

2. C oncerns Ltd ool Outline Revision - the basics Component operation Factors effecting efficiency –load reduction –operating conditions The low hanging fruit

3. C oncerns Ltd ool Revision Common principles How a system works Importance of operating conditions: –evaporating temperature –condensing temperature –superheat –subcooling

4. C oncerns Ltd ool A Simple System

5. C oncerns Ltd ool A Simple System COSP = capacity / total power input

6. C oncerns Ltd ool COSP What do you expect the COSP to be?

7. C oncerns Ltd ool COSP What do you expect the COSP to be? Typically … LT ~ 0.5 to 1.5 HT ~ 2 to 4 AC ~ 4 to 6

8. C oncerns Ltd ool A Simple System Saturated mixture low pressure Superheated gas low pressure Superheated gas high pressure Saturated liquid high pressure Saturated mixture high pressure Subcooled liquid high pressure

9. C oncerns Ltd ool How Many Times Round the Circuit?

10. C oncerns Ltd ool 20,000 How Many Times Round the Circuit?

11. C oncerns Ltd ool Compressor Most efficient if: compression ratio low suction superheat low cooling adequate

12. C oncerns Ltd ool Evaporator Evaporator effectiveness depends on... evaporating temperature / pressure –size / condition of evaporator –temperature of cooled space / fluid degree of useful superheat degree of subcooling

13. C oncerns Ltd ool Condenser Condenser effectiveness depends on... condensing temperature / pressure –size / condition of condenser –cooling medium –temperature of cooling medium head pressure control

14. C oncerns Ltd ool Superheat Useful superheat in evaporator aim for ~ 5K Non useful superheat in suction line minimise Refrigerant arriving at compressor must be superheated (but not too much!)

15. C oncerns Ltd ool Subcooling 10K subcooling ~ 7% capacity increase –natural cooling or by subcooler –insulate liquid line when using a subcooler No subcooling ~ ??% capacity reduction –condensing temperature too low –liquid line passes through hot area –loss of refrigerant

16. C oncerns Ltd ool Expansion Valve Subcooled liquid at entry Useful superheat setting important TEV, minimum 6 bar pressure drop EEV, minimum 4 bar pressure drop

17. C oncerns Ltd ool Central Plant Systems Several smaller compressors for better capacity matching to load Can be unevenly sized Controlled on suction pressure

18. C oncerns Ltd ool Central Plant Systems

19. C oncerns Ltd ool Central Plant Control EV S S S S

20. C oncerns Ltd ool Evaporator Temperatures EV S S S S -12 -8 -6

21. C oncerns Ltd ool An Efficient System... …has minimum load …has minimum temperature lift …uses an efficient combination of components …is well controlled

22. C oncerns Ltd ool Keeping the Load Low

23. C oncerns Ltd ool Load - Door Management Open door: Freezer, £6/h Chiller, £3/h

24. C oncerns Ltd ool Load - Product Loading

25. C oncerns Ltd ool Load - Defrost Does the defrost work? Is it controlled correctly Defrost on demand can improve efficiency

26. C oncerns Ltd ool Load - Auxiliaries Switching off fans can save up to 14%

27. C oncerns Ltd ool Load - Sec. Ref. Pumps Contribute twice to energy use –direct electricity consumption –heat into secondary fluid Variable Speed Drive –will reduce pump power, e.g. by 25% –will reduce heat load

28. C oncerns Ltd ool Load - Insulation Cold store / cabinet insulation Secondary fluid pipe work insulation ensure in good condition ensure sufficient thickness ensure well joined / sealed Suction line Liquid line

29. C oncerns Ltd ool Temperature Lift Evaporating temperature Condensing temperature Control 1°C = 2% to 4%

30. C oncerns Ltd ool Evaporating Temperature Cooled space / fluid temperature - as high as possible e.g. increasing frozen food store temperature from -25°C to -20°C saves over 10% (and reduces breakdown)

31. C oncerns Ltd ool Evaporating Temperature

32. C oncerns Ltd ool Evaporating Temperature Ensure evaporator is clean Ensure evaporator is clear of frost

33. C oncerns Ltd ool Evaporating Temperature Refrigerant charge is critical –leak test –repair –re-charge

34. C oncerns Ltd ool Reduce Leak Potential Brazed joints Minimum charge Minimum pressures Charge monitoring Effective leak testing

35. C oncerns Ltd ool Condensing Temperature Ensure condensers are clean

36. C oncerns Ltd ool Condensing Temperature What’s the problem here?

37. C oncerns Ltd ool Condensing Temperature

38. C oncerns Ltd ool Condensing Temperature

39. C oncerns Ltd ool Condensing Temperature Recommend replacement –take opportunity to fit larger condenser

40. C oncerns Ltd ool Condensing Temperature Non condensable gases increase condensing temperature Purge air / nitrogen –use an automatic (refrigerated) air purger –portable versions available

41. C oncerns Ltd ool Control Highest possible evaporating temperature –thermostat / controller (LP) setting Lowest possible condensing temperature –minimum head pressure control Appropriate useful superheat –TEV / EEV adjustment Optimum compressor strategy

42. C oncerns Ltd ool Low Hanging Fruit Cold store air change load reduction Auxiliary load reduction Reducing refrigerant leaks System control Re commissioning Maintenance

43. C oncerns Ltd ool Air Change Reduction Heat and moisture Door management Strip curtains / air lock Try dehumidification –e.g. 8% reduction

44. C oncerns Ltd ool Aux Load Reduction Double impact / saving Evaporator fan motors –E.g. 14% reduction on HT area Process fluid pump control

45. C oncerns Ltd ool Leak Reduction 15% leakage doubles power input Maintenance –Leak test method –Regime Fixed leak detection Charge monitoring Tuesday 05/02/2002 39152161812 Wednesday 06/02/2002 39152161812 Thursday 07/02/2002 39152161812 Friday 08/02/2002 39152161812 PPM 0 50 100 150 200 250 300

46. C oncerns Ltd ool Control Suction and discharge pressure optimisation –~10% savings Defrost on demand –~2.5% savings Floating head pressure –~ 7% savings

47. C oncerns Ltd ool Re Commissioning Re set suction & discharge set points Example savings: 21.2% on HT pack 13.6% saving on LT pack 6.9% on total site energy

48. C oncerns Ltd ool Maintenance is Vital Ensure there is a maintenance regime which at least … …cleans condensers and evaporators …checks for leaks (and repairs them!) …does an eyes & ears system check

49. C oncerns Ltd ool Energy Efficient Refrigeration Jane Gartshore, Cool Concerns Ltd