Guideline for efficient chiller operation

Ensure correct utility for process:  If a process is capable to run on 5 Deg C never use 1 Deg C Chilled water, lowering every 1 Deg C will increase power consumption from 2.5 to 4% in compressor power.

During Design insure proper IPLV / NPLV selection : Chillers/ refrigeration system never operates on  full load capacity throughout year, hence it is important to check IPLV/ NPLV of chiller for energy efficient selection.

Use corrugated / finned HE for condenser and evaporation: use of corrugated / finned type HE will improve heat transfer and reduce approach across evaporator and condenser. Reduced approach will save power.

Monitor SPC of refrigeration system on continuous basis : It is important to monitor SPC of refrigeration system on continuous basis to find abnormality and attending it on shorter possible time.

Monitor and eliminate excess distribution and insulation losses: loss in distribution network will increase capacity requirement of generation system, Distribution system should be monitored on regular interval and corrected if damaged.

Consider eliminating primary circuit (if load is constant) : Primary circuit not only add power but heating load to chilling system, if load is constant and it can be managed with secondary circuit return line. Primary circuit may be avoided.

Avoid shock load by building capacity of hot and cold well: Chillers are designed to be operated on consistent load, excess load fluctuation will disturb pressure across system and system Specific power may increase.

Use Thermal storage system : Thermal Storage system may be used to get benefit of tariff schedule. In peak hours power cost is high while in non peak hours cost is low, with thermal storage system refrigeration system can be operated on low cost.

Minimize Temp difference of refrigerant condensation and cooling tower outlet (Approch): lowering every 1 Deg C of condenser approach will reduce power consumption from 2.5 to 4% in compressor power. Clean condenser if approach is higher, normally it varies from manufacturer to manufacture but generally kept at 3 deg C.

Online condenser cleaning system: online cleaning system can be used to maintain consistent lower approach.

Use Evaporative condenser : use of evaporative condenser not only eliminates cooling water pumping cost but it also help in reducing condenser pressure if properly designed.

Air cooled condenser to be avoided: air cooled condenser may be avoided if water availability is not an issue to site. In air cooled condensers power requirement is high at both condenser and compressor motor.

Non Condensable gases: non condensable gases need to be removed from system for eliminating excess power consumption due to lower heat transfer.

Use condenser heat (Heat Pump) : condenser heat can be used for various application, may be for generating hot water for process application, Using condenser heat is can also be harness by properly designed heat pump.

Minimize evaporator approach: lowering every 1 Deg C of evaporator approach will reduce power consumption from 2.5 to 4% in compressor power. Clean evaporator if approach is higher, normally it varies from manufacturer to manufacture but generally kept at 3 deg C. Evaporator approach can also be increased by oil fouling in the evaporator tubes. Oil fouling in evaporator to be checked and eliminated time to time.

Use of PHE in evaporator: with plate type heat exchanger lower evaporator approach of approx 1 Deg C can also be possible.

Eliminate secondary circuit (use direct refrigeration) : Direct refrigeration not only eliminate primary and secondary circuit but it will also minimize heat exchanger requirement.

Ensure correct concentration of brine: Correct brine concentration helps in running chillers efficiency.

Ensure correct expansion valve operation:  Proper and steady flow of refrigerant in the evaporator will help in maintaining steady state condition and ensure chillers operation on better specific power requirement.

Energy efficient compressor, with better turndown ratio: use energy efficient compressor for better turndown ratio for varying load requirement.

Multiple compressor system: Multiple compressors can be checked for load variation for better IPLV/ NPLV.

Oil Free compressors: oil free compressor may be selected for avoiding oil fouling related problems in evaporator.

Use of VFD can be explored : VFD can also be used for better IPLV or NPLV requirement

Ensure liquid sub cooling: Liquid sub cooling not only help in reducing size but help in efficient heat transfer in evaporator.  Ensure proper pressure in flash sub cooler.

Avoid liquid entering in compressor: Compressor suction should be slightly superheated for trouble free operation of refrigerant compressor.

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