Commercial Refrigeration FINAL TEST Questions with Verified Answers

Commercial Refrigeration FINAL TEST Questions with Verified Answers A SORIT, BEPR, or CDA valve may be used as a ____ valve Evaporator pressure regulating (EPR) A typical low temperature rack maintains a suction temperature of ____ -25 degrees F ARI Standard 710-86 specifies flow rates through a filter drier at a pressure drop of _____ 1 Psig How are the disadvantages overcome in compressors that are employed in low temperature applications? Use supplementary cooling How are the disadvantages overcome in water cooled hermetic compressor systems? Have water jackets, or water coils around the compressor/motor shell or housing How far away from the inlet air wall should the air opening for condensers be when condensing units are place in position? Why? They should be located side by side, facing the wall, with the air openings at a distance of 24 to 36 inches This ensures that all units get a sufficient supply of outside air How is compressor efficiency often judged? Btu per cubic foot (Btu/ft^3) of displacement How is the cooling effect in a mechanical refrigeration system produced? Evaporation of liquid refrigerant into vapor How many sources of heat have to be rejected from the vapor in the condenser? Three, the heat absorbed in the evaporator, the heat picked up in the suction line, the additional heat of compression caused by compressor operation If a choice is available, should a drier be installed in a vertical position or horizontal position? Vertical If an air cooled condensing unit room has an exhaust capability of 1000 cfm per unit horsepower and 2 1/2 ft^2 of inlet louver per unit horsepower, what will the average inlet air velocity be in feet per minute? Less than 500 ft/min If condensing pressure is higher than the corresponding condensing temperature, what is normally the cause? Non condensable gases If the suction gas superheat is too low, What could be the result? 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 rated capacity In a reciprocating compressor, the piston is connected to the crankshaft by a _____ Connecting rod Is refrigerant gas more soluble in oil at low temperatures or high temperatures? Low Is the condenser load greater or less for compressors designed for low temperature applications than for compressors designed for high temperature applications? The condenser load is less for the low temperature applications Name another function that must be performed by the compressor Is raise the pressure and temperature of the refrigerant vapor. This allows the refrigerant to condense into a liquid as it circulates through the condenser