UA Refrigeration 2 Mid Term Review
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| As refrigerant passes through the compressor | Its pressure and temperature are increased.
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| The refrigerant that exits the compressor travles to the | condenser via the discharge
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| The compressor takes a _____ pressure ______ vapor and compresses it to a _____ pressure _____ vapor | Low ,superheated High,superheated
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| Lines of constant quality applies only to the area within the saturation curve. | True
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| Lines of constant quality applies only to the areas outside the saturation curve | False
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| The horizontal lines of a pressure enthalpy diagram represent constant pressure. | True
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| Constant enthalpy is represented on a pressure enthalpy diagram by vertical lines that run from the bottem to the top of the page. | True
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| The area to the right of the saturation curve is the zone where the liqued is represented as sub-cooled | False
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| The area to the right of the saturation curve is the zone where vapor is represented as super-heated. | true
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| A sub-cooled liqued is liqued which has been cooled belowed its saturation temperature at a given pressure. | True
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| The area to the right of the saturation curve is the zone where vapor is represented as saturated refrigeran. | False
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| One key relationship shown on a pressure enthalpy diagram is between pressure and boiling temperature. | True
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| A reciprocating compressors direction of rotation is critical for oil pump operation | False
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| A crank case heater is an anti-slugging device | False
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| The pistion of a reciprocating compressor must lower cylinder pressure below suction line pressure before suction gas will enter the cylinder. | True
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| Decreased suction pressure results in increased capacity. | False
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| Compressure ratio equals discharge pressure (psig) divided by suction pressure (psig) | False
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| Volumetric efficiency of a compressor is the ratio of the actual volume of refrigerant vapor leaving the compressor compared to the volume of refrigerant vaporentering the compressor. | True
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| The piston of a reciprocating compressor must lower cylinder pressure before compressed gas leaves the cylinder. | False
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| The piston of q reciprocating compressor must lower cylinder pressure before the suction valve opens and lets new suction gas in to the cylinder. | True
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| The piston of a reciprocating compressor must raise cylinder pressure before compressed gas leaves the cylinder. | True
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| Net useful oil pressure of a reciprocating compressor is oil pump discharge pressure minus suction pressure. | True
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| The screw compressors impeller spins at high speeds (3,000 to 20,000 RPM)inside the compressor housing. | False
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| Increased compression ratio will cause the compressor to work harder. | True
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| Increased discharge pressure results in increased capacity. | False
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| The pressure enthalpy diagram has four zones to represent the differant physical conditions of the refrigerant in a refrigeration cycle. | False
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| Compliant scroll design refers to being less tolerant to liquid refrigerant. | False
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| The critical temperatureof R134A is 213 degres F the critical point represents the limiting condition for the existence of liquid. | True
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| The vertical scale of the pressure enthalpy diagram represents | Pressure
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| The horizontal scale if the pressure enthalpy diagram represents____. | Enthalpy
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| Within the saturation curve of the pressure enthalpy diagram refrigerant exusts as _____. | Liquid/Vapor
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| Lines of constant entropy extend at an angle from the saturated vapor line. Constantentropy line are used to plot_____. | Compression.
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| Motor and compressor are sealed within the same housing with removable heads and housing covers for field repairs_____. | Semi-Hermetic
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| Bith comoressor and motor are contained within the same sealed pressurized housing_______. | Hermetic
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| The motor is external of the compressor______. | Open Compressor
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| A shaft seal is required on______. | an open compressor
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| The purpose of a crank case heater is to______. | keep the refrigerant boiled out of the oil
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| Three posiable methods for reducing the capacity of a reciprocating compressor _________. | on/off control, cylinder unloading, using more than one compressor, hot gass bypass
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| In the hot gas control method< the systemcomponent that is bypassed is ________. | the condenser
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| Cylinder unloaders are usually operated by____. | oil pressure
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| The piston in a reciprocating compressor makes a compression stroke and a suction stroke, each of these strokes has two parts and make a total of four parts for each cycle of the two parts of the compression stroke are __________. | compression and discharge
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| The two parts of the suction stroke are ______. | Re-expansion and suction
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| The purpose of a cylinder unloader is to _______. | adjust compressor capacity to match the load
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| Four of the five types of compressors as to their means of compression are ______________. | Reciprocating, screw, scroll, rotary, centrifugal
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