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Energy audit for chiller plant

Article By MG Cooling Solutions In Energy Audit - July 27, 2017

MGCS-Energy audit company

    Case Study- Performance of Chiller:

Existing Conditions-Two chillers are installed at one of our client site with the operating principle of vapor compression.
Mostly two chillers are in running condition due to climatic condition. Cooling tower is Natural air cooling.

energy audit for chiller plant
energy audit for chiller plant

Chiller Details

a) Rated Capacity in TR for Chiller 250 TR
b) Sr. No. of Chiller — SHMM-035670
c) Model No KWF195.12
d) Make of Compressor — YRWDWBT1555A
e) Type of Compressor — Screw Compressor
f) No. of Stages — Single Stage
g) Other Relevant Number Plate Refrigerant 134a, Oil Flooded, RPM of compressor 2950 RPM, Direct Drive type, step less capacity control.

Motor Details

a) Make of Electric Motor — York maxe
b) Sr. No. of Motor — F00580SG03
c) Connected Motor Kw — 170 kW
d) Rated RPM — NA rpm
e) Rated Efficiency of Electric Motor 92 %
f) With or Without VFD / Type of Starter Without VFD
g) Type of Transmission in Motor & Comp. Directly Coupled

The performance assessment of the chiller SPC, COP & EER Calculations from Condenser Circulation Data

Measured Data & Analysis Chiller-1
Compressor Speed
Ambient dry bulb temperature — °C 29 29
Ambient wet bulb temperature — °C 26 26
Water Flow rate through condenser, m3/hr 180 202
Cooling Water density kg/cm3 1000 1000
Specific heat of Cooling Water kcal/kg°C 1 1
Water temperature at inlet to Condenser °C 28 30.5
Water temperature at outlet to Condenser °C 33 32.83
Heat Rejected Through Condenser Kcal/hr 900000 470660
Heat Rejected Through Condenser TR 297.619 155.64
Condenser pressure kg/cm2 9.37 9.56
Condenser saturation temperature °C 40.16 40.8
Sub cooling temperature °C -11.3 -15
Power input to motor kW 87 89.00
Likely motor efficiency % 90.6 90.60
Likely drive transmission efficiency % 98 98.00
Estimated Compressor shaft power kW 77.24556 79.02
Coefficient of Performance, COP 12.007 6.138
Energy Efficiency Ratio, EER Btu/h-W 40.945 20.931
Specific power consumption, SPC — kW/TR 0.292 0.572

SPC, COP & EER Calculations from Evaporator Circulation Data
Measured Data & Analysis-CHILLER 2

Compressor Speed — RPM
Ambient dry bulb temperature — °C 29.0 29
Ambient wet bulb temperature — °C 26.0 26
Water Flow Rate through Evaporator m3/hr 292.0 305
Density of Water kg/cm3 1000.0 1000
Specific heat of Water kcal/kg°C 1.0 1
Water temperature at inlet to Evaporator °C 16.4 13.05
Water temperature at outlet to Evaporator °C 14.2 11.7
Refrigeration Effect kcal/hr 642400.0 411750
Refrigeration Effect TR 212.4 136.161
Evaporator pressure kg/cm3 4.07 3.3
Saturation temperature °C 11 15.7
Power input to motor kW 87.00 89.00
Likely motor efficiency % 90.60 90.60
Likely drive transmission efficiency % 98.00 98.00
Estimated Compressor shaft power kW 77.25 79.02
Coefficient of Performance, COP 8.571 5.370
Energy Efficiency Ratio, EER Btu/h-W 29.226 18.311
Specific power consumption, SPC kW/TR 0.410 0.654
Evaporator to Condenser TR Ratio kW/TR 0.714 0.875

Technical Evaluation

OUTCOME 1: Lift is difference between the evaporator pressure and condenser pressure.Greater the pressure, more energy for given load.
Lift for Chiller 1 is 5.3
Lift for Chiller 2 is 6.26

It shows that condenser in chiller 2 condensers is fouled as it requires more energy to do the work.

OUTCOME 2: Condenser approach should be between 0-2 (Liquid refringent temperature – Condenser outlet temperature)
Condenser approach for Chiller-1 1.44
Condenser approach for Chiller-2: 4.47
so it can conclude that condenser in chiller-2 is fouled.

OUTCOME 3: Most chillers are designed with max condenser inlet temperature of 28°C. if it exceeds efficiency of chiller will decrease by 2% for every one degree in raise.

OUTCOME 4: Condenser Inlet temperature for Chiller-1: 28°C and 30.5°. It can be either instrument problem or cooling tower problem.

OUTCOME 5: Evaporator approach for chiller -1 & 2 is 3.22 and 4 respectively. As design data is not available auditors can’t command on it.

Energy Saving Recommendation:
Chiller-2 condenser need to cleaned.
Result of the outcome:
Chiller-2 efficiency will improve and approach too.
Present Scenario: Condenser approach=4.47
After technical recommendation: Condenser approach = < 2
Proposed Energy/Electricity Saving
Saving Calculation:
Consumption = 87 kW
Energy Saving @ improving 4% of efficiency = 3.48 kW
Energy saving per annum = 3.48 X10 X 240 ( 10 hours ,240 days of working)
= 8352 kWh
Monetary Saving = Rs 93125/-
Expected Pay back = Immediate

This way, we helped our client in saving money by taking the corrective action through our detailed auditing for the chiller plants.

Note: The above information is only for knowledge sharing and MGCS has its sole right and proprietorship of above technical data.

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