To achieve a higher coefficient of performance in a refrigerator, the operating pressure differential between the evaporator and condenser must be____________________?
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Answer: A. small
Explanation
Keeping the operating pressure differential between evaporator and condenser small minimizes compressor work. Lower compression ratios reduce the energy required to pump refrigerant through the closed cycle. Minimizing mechanical work input directly increases the overall coefficient of performance for the system. Coefficient of performance is defined as desired cooling effect divided by net compressor work input. Thermodynamic efficiency decreases as the temperature and pressure lift across the compressor increases. Carnot refrigeration cycle efficiency depends directly on evaporator and condenser operating temperatures.
HVAC designers strive to maintain high evaporating temperatures and low condensing temperatures in chillers. Using geothermal sources for condenser cooling helps maintain a small pressure differential year-round. Optimizing operating pressures reduces electricity consumption and lowers long-term building utility costs. High pressure differentials increase compressor power consumption and degrade overall system efficiency. Equal pressure differential is a non-meaningful comparison term in refrigeration cycle analysis. Assuming performance is independent of pressure differential contradicts basic thermodynamics laws.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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