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UA Refrigeration 2

UA Refrigeration 2 Mid Term Review

QuestionAnswer
As refrigerant passes through the compressor Its pressure and temperature are increased.
The refrigerant that exits the compressor travles to the condenser via the discharge
The compressor takes a _____ pressure ______ vapor and compresses it to a _____ pressure _____ vapor Low ,superheated High,superheated
Lines of constant quality applies only to the area within the saturation curve. True
Lines of constant quality applies only to the areas outside the saturation curve False
The horizontal lines of a pressure enthalpy diagram represent constant pressure. True
Constant enthalpy is represented on a pressure enthalpy diagram by vertical lines that run from the bottem to the top of the page. True
The area to the right of the saturation curve is the zone where the liqued is represented as sub-cooled False
The area to the right of the saturation curve is the zone where vapor is represented as super-heated. true
A sub-cooled liqued is liqued which has been cooled belowed its saturation temperature at a given pressure. True
The area to the right of the saturation curve is the zone where vapor is represented as saturated refrigeran. False
One key relationship shown on a pressure enthalpy diagram is between pressure and boiling temperature. True
A reciprocating compressors direction of rotation is critical for oil pump operation False
A crank case heater is an anti-slugging device False
The pistion of a reciprocating compressor must lower cylinder pressure below suction line pressure before suction gas will enter the cylinder. True
Decreased suction pressure results in increased capacity. False
Compressure ratio equals discharge pressure (psig) divided by suction pressure (psig) False
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
The piston of a reciprocating compressor must lower cylinder pressure before compressed gas leaves the cylinder. False
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
The piston of a reciprocating compressor must raise cylinder pressure before compressed gas leaves the cylinder. True
Net useful oil pressure of a reciprocating compressor is oil pump discharge pressure minus suction pressure. True
The screw compressors impeller spins at high speeds (3,000 to 20,000 RPM)inside the compressor housing. False
Increased compression ratio will cause the compressor to work harder. True
Increased discharge pressure results in increased capacity. False
The pressure enthalpy diagram has four zones to represent the differant physical conditions of the refrigerant in a refrigeration cycle. False
Compliant scroll design refers to being less tolerant to liquid refrigerant. False
The critical temperatureof R134A is 213 degres F the critical point represents the limiting condition for the existence of liquid. True
The vertical scale of the pressure enthalpy diagram represents Pressure
The horizontal scale if the pressure enthalpy diagram represents____. Enthalpy
Within the saturation curve of the pressure enthalpy diagram refrigerant exusts as _____. Liquid/Vapor
Lines of constant entropy extend at an angle from the saturated vapor line. Constantentropy line are used to plot_____. Compression.
Motor and compressor are sealed within the same housing with removable heads and housing covers for field repairs_____. Semi-Hermetic
Bith comoressor and motor are contained within the same sealed pressurized housing_______. Hermetic
The motor is external of the compressor______. Open Compressor
A shaft seal is required on______. an open compressor
The purpose of a crank case heater is to______. keep the refrigerant boiled out of the oil
Three posiable methods for reducing the capacity of a reciprocating compressor _________. on/off control, cylinder unloading, using more than one compressor, hot gass bypass
In the hot gas control method< the systemcomponent that is bypassed is ________. the condenser
Cylinder unloaders are usually operated by____. oil pressure
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
The two parts of the suction stroke are ______. Re-expansion and suction
The purpose of a cylinder unloader is to _______. adjust compressor capacity to match the load
Four of the five types of compressors as to their means of compression are ______________. Reciprocating, screw, scroll, rotary, centrifugal
Created by: mikeriv69