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UA Refrigeration 2
UA Refrigeration 2 Mid Term Review
| Question | Answer |
|---|---|
| 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
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