ESCO Light Commercial Refrigeration FINAL TEST.pdf file:///C:/Users/HP/Desktop/New%20fl/ESCO%20Light%20Comme
ESCO Light Commercial Refrigeration Final Test
Questions & Answers
1. How is the cooling effect in a mechanical refrigeration system produced?-
Answer Evaporation of liquid refrigerant into vapor
2. What is the primary purpose of a compressor?
Answer It circulates and pressurizesthe refrigerant vapor before the vapor Is condensed for re
use
3. Name another function that must be performed by the compressor
Answer Is raisethe pressure and temperature of the refrigerant vapor. This allows the
refrigerant tocondense into a liquid as it circulates through the condenser
4. What characteristic defines an "open" type compressor?
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,ESCO Light Commercial Refrigeration FINAL TEST.pdf file:///C:/Users/HP/Desktop/New%20fl/ESCO%20Light%20Comme
Answer Has a drive shaftprotruding from the compressor
5. What are the two main disadvantages of a hermetic compressor?
Answer If either the motor or compressor malfunctions, the entire unit must be replaced. The
motoris actually a part of the refrigerant circulation system.This means that a burnout can
contaminate the entire system
6. In a reciprocating compressor, the piston is connected to the crankshaft bya
Answer Connecting rod
7. Name the three elements of performance that are the major factors inevaluating
a compressor
Answer Efficiency, capacity, and economy of operation
8. If the suction gas superheat is too low, What could be the result?
Answer Liquid refrigerant might enter the compressor. This causes stress on the compressor
valves, wrist pins, rods, shaft, etc. It also causes excessive foaming of the oil in the crankcase
and other damaging effects.The compressor will not reach its ratedcapacity
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9. What will happen if the suction gas temperature is too high?
Answer Will cause thecompressor to run hot
10. How is compressor efficiency often judged?
Answer Btu per cubic foot (Btu/ft^3) ofdisplacement
11. When the same model of open type compressor is used with both air cooled and
water cooled condensing units, which is usually run at a slightlyhigher rpm?
Answer Water cooled
12. What is the equation for ratio of compression?
Answer The absolute discharge pressure (psig plus 14.7) divided by the absolute suction
pressure (psig plus 14.7)
13. What type of compressor is found in large applications up to 10000 tons?-
Answer Centrifugal compressors
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