Optimization of Cooling Systems

Transcription

1 Optimization of Cooling Systems Basic principles Compressors and other power consumers The simple refrigeration system - refrigerants Svenn Hansen Refrigeration and Heat Pump Technology sha@teknologisk.dk

2 Biography Svenn Ole Kjøller Hansen Position: Technology Manager Heat Pumps Education: B. Sc. (mechanical engineer) in 1979 Employments: Sabroe Refrigeration Industrial refrigeration Development - screw compressors and units Danish Technological Institute since 1989 Courses: Basic refrigeration, ammonia safety, energy savings, natural refrigerants, quality scheme for refrigeration companies, quality scheme for heat pump installers Projects: Small ammonia systems, guideline for cold stores, energy efficient controls, small systems with R723, guidance on renewable energy, Consultancy: Industrial plants, trouble shooting, oil/water in ammonia systems, Secretariats: Information Center for Refrigeration without HFC, Quality schemes for refrigeration and heat pump installers (KKO and VPO) Boards: Society of Refrigeration Engineers a part of Danish Society of Engineers IDA (former)

3 The refrigerator Evaporator Suction accumulator Condenser Heat exchanger Drier Capillary tube Discharge pipe Suction pipe Service connection

4 A basic refrigeration system Q C = Q E + W Subcooling Condenser Refrigerant As liquid and gas Expansion valve W Evaporator Superheat Compressor Q E

5 The evaporator Evaporator Superheat Liquid Q E Gas

6 The compressor W Compressor Gas

7 The condenser Q C = Q E + W Subcooling Liquid Condenser Gas

8 The expansion valve Liquid Expansion valve Liquid and gas

9 Temperatures and pressures Condensing temperature: +35 C Air inlet temperature: +20 C Air outlet temperature: +24 C Liquid temperature: +32 C Subcooling Condenser Discharge gas temperature: +75 C Discharge pressure: 7,9 bar,o Expansion valve Refrigerant R134a Evaporator Compressor Superheat Suction pressure: 1,4 bar,o Suction gas temperature: +3 C Air inlet temperature: +5 C Air outlet temperature: +2 C Evaporating temperature: 5 C

10 Refrigerants

11 Small simple cooling system Cap. tube inlet evaporator Cap. tube outlet condenser

12 Large complex cooling system M+P Tiefkühlkost GmbH, Germany NH 3 -compressors: Cooling capacity approx. 580 kw at 11/+40 C 2 x SMC 108 CO 2 -compressors: Cooling capacity approx. 475 kw at 52/-8 C HPC 104, HPC 106 NH 3 -conderser: Capacity approx. 880 kw at t c +40 C, t dry 30 C Air cooled condensere CO 2 -condenser: Capacity approx. 640 kw at t c 8 C, t NH3 11 C Plate heat exchanger Freezer: Freezing capacity approx. 350 kw at t c 50 C, t air 45 C Frigoscandia FMC Evaporators: Capacity 5 x 25 kw at t o 40 C, t room 28 C 5 air evaporators ceiling mounted Reference: Job report from York Refrigeration: M+P Tiefkühlkost GmbH

13 Basic cooling and heating systems Heat pump Primary use of heat from condensing Refrigeration system Primary use of refrigeration effect Heat recovery system Refrigeration system with use of heat from condensing

14 Energy consumption for cooling in Denmark In Denmark, approx. 11% of all electrical power is used for cooling purpose. Cooling applications varies from very small domestic refrigerators in large numbers and very big industrial systems for cooling and freezing in small numbers.

15 Main energy consuming components Compressors Fans Pumps Example: Cold storage facility, AM-Transport A/S, Horsens, Denmark

16 Compressor is most important power consumer In general the energy optimization in cooling systems can be expressed by following formula: Minimum (Σ W compressors + Σ W fans + Σ W pumps ) Power consumption for compressors is mainly dependent on Inverter efficiency (full load and part load) Motor efficiency (full load and part load) Compressor effciency (full load and part load) Pressure differential from suction to discharge (refrigerant and operating conditions) Operation time (running hours) In principle the same story for fans and pumps

17 Example of compressor data Observations: Energy Efficiency Ration EER decreases a lot, when evaporating temperature (suction pressure) is decreased or condensing temperature (discharge pressure) is increased. Efficiency is only limited affected, when superheat og subcooling is changed. Important conclusion: Efficiency changes 2-3% per ºC change in evaporating or condensing temperature Reference: Bock

18 Avoid use of pressure regulation valves Capacity regulator Evaporating pressure regulator Condensing pressure regulator All pressure regulating valves increase energy consumption

19 Min. power consumption by intelligent control Primary setpoints Secondary setpoints Cooling system Wanted primary temperatures System intelligent calculation of secondary setpoints Evaporating temperature Condensing temperature Brine temperature (flow or differential pressure) Compressors, fans, pumps Measurements

20 ESO-project: Optimal temperatures Optimal evaporating temperature Optimal condensing temperature Point in the system with maximal load Point in the system with maximal load on valve

21 End of presentation