Unit 23 Compressors Questions and answers

Unit 23 Compressors Questions and answers Compressors are not designed to compress liquids because pumps already exist for that purpose. False The compressor in the mechanical refrigeration system is much like the heart in the human body. True At a constant RPM, a compressor is a constant displacement device and its capacity is variable. True At a constant RPM, a compressor is a constant displacement device and its capacity is constant. False The most common method(s) of capacity control for rotary compressors are motor speed control and on-off cycling. False The pattern of gas movement through a scroll compressor is from the center toward the perimeter. False The suction and discharge valves in a reciprocating compressor open and close depending on the difference in pressure across them. True Scroll compressors are becoming popular because they can handle liquid flood-back without compressor damage. False The scroll compressor is one type of reciprocating compressor. False Rotary compressors have pistons that rotate inside the cylinders. False Rotary compressors have no "clearance volume". True The sight glass on a semi-hermetic compressor is used to allow light to enter the crankcase to keep the oil warm. False The hermetic reciprocating compressor motor is essentially made of the same materials as an open type compressor motor. False A bolted together motor-compressor assembly is sometimes referred to as a semi-hermetic type. True The higher the rpm of a compressor, the higher the pumping efficiency. False All but which one of these things happens as a direct result of the compressor doing its work? the air is adequately circulated in the conditioned space. What is the compression ratio at these conditions? Discharge pressure: 282.3 Evaporator pressure: 49.3 Condenser pressure: 277.3 Suction pressure: 51.3 4.5 The piston of a reciprocating compressor must make ___ stroke(s) to complete one cycle of refrigerant compression. 2 The reciprocating compressor has a built-in problem with inefficiency which results from: its clearance volume. If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ___ will increase. If the suction valve in a reciprocating compressor is leaking slightly, the ____ cooling capacity will be reduced & compressor can overheat. The clearance volume of a compressor ____ remains the same as the compression ration decreases. What could happen if a semi-hermetic compressor is operated with the suction service valve back-seated and the discharge valve front-seated? the head of the compressor may blow off. Liquid entering the compression chamber of a reciprocating compressor can lead to ___ damaged valves & damaged piston rings Mos of the heat energy in the suction vapor entering the compressor is ___ latent heat. The temperature of the compressed gas leaving the compressor can best be described as ___ very warm. The screw-type compressor is used primarily in ___ large industrial refrigeration and air-conditioning systems. Rotary compressors are used primarily in __ domestic refrigerators. The clearance volume of a compressor cylinder is the ___ volume of the space between the bottom of the valve plate and the top of the piston at top dead-center. The discus valve design is more efficient than a flapper valve design because ___ it allows a compressor design with less clearance volume.