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Refrigeration System Components and Operation, Exams of Nursing

University of CambridgeNursing

A comprehensive overview of the key components and operating principles of refrigeration systems. It covers topics such as the refrigeration cycle, evaporators, condensers, compressors, and expansion devices like thermostatic expansion valves (txvs) and electronic expansion valves (eevs). The document delves into the specific functions, characteristics, and performance considerations of these critical refrigeration system elements. It also addresses concepts like superheat, subcooling, head pressure control, and system efficiency. This information would be highly relevant for students and professionals studying hvac, refrigeration, or related engineering disciplines.

Typology: Exams

2023/2024

Available from 09/16/2024

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Commercial Refrigeration > Units 21, 22,
23, 24
The process of removing heat from a place where it is not wanted and transferring that
heat to a place where it makes little or no difference is known as ____. - Question and
answersrefrigeration
The household refrigerator fresh-food compartment is a good example of ____
refrigeration. - Question and answersmedium-temperature
The household refrigerator fresh-food compartment typically ranges from ____. -
Question and answers28 to 40°F
Low-temperature food storage applications generally start at ____. - Question and
answers0°F
High-temperature refrigeration applications will normally provide box temperatures of
____. - Question and answers47 to 60°F
A refrigeration system designed for the storage of flowers or candy is considered a ____
type. - Question and answershigh temperature
The ____ in a refrigeration system is responsible for absorbing heat into the system
from whatever medium is to be cooled. - Question and answersevaporator
The boiling temperature and its relationship to the system exist in the ____. - Question
and answersevaporator
A typical evaporator operating temperature in an air-conditioning system is ____. -
Question and answers40°F
The ____ of the liquid refrigerant determines the coil operating temperature. - Question
and answersboiling temperature
If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig,
what is the pressure at the inlet of the evaporator? - Question and answers25 psig
Evaporators that are operated full of liquid and are equipped with a device to keep the
liquid refrigerant from passing to the compressor are known as ____. - Question and
answersflooded evaporators
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Commercial Refrigeration > Units 21, 22,

The process of removing heat from a place where it is not wanted and transferring that heat to a place where it makes little or no difference is known as ____. - Question and answersrefrigeration The household refrigerator fresh-food compartment is a good example of ____ refrigeration. - Question and answersmedium-temperature The household refrigerator fresh-food compartment typically ranges from ____. - Question and answers28 to 40°F Low-temperature food storage applications generally start at ____. - Question and answers0°F High-temperature refrigeration applications will normally provide box temperatures of ____. - Question and answers47 to 60°F A refrigeration system designed for the storage of flowers or candy is considered a ____ type. - Question and answershigh temperature The ____ in a refrigeration system is responsible for absorbing heat into the system from whatever medium is to be cooled. - Question and answersevaporator The boiling temperature and its relationship to the system exist in the ____. - Question and answersevaporator A typical evaporator operating temperature in an air-conditioning system is ____. - Question and answers40°F The ____ of the liquid refrigerant determines the coil operating temperature. - Question and answersboiling temperature If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator? - Question and answers25 psig Evaporators that are operated full of liquid and are equipped with a device to keep the liquid refrigerant from passing to the compressor are known as ____. - Question and answersflooded evaporators

A direct expansion-type evaporator is also called a ____. - Question and answersdry- type evaporator ____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant. - Question and answersSuperheat A typical superheat for an evaporator operating under normal conditions would be ____.

  • Question and answers8 to 12°F If the application requires a coil design to operate below freezing, there must be provision for ____. - Question and answersdefrost The refrigeration evaporator is a component that absorbs heat from the conditioned space into the refrigeration system. - Question and answerstrue The film factor is a relationship between the medium giving up heat and the heat- exchange surface. - Question and answerstrue A stamped plate evaporator usually does not use a fan to move air across it. - Question and answerstrue The capacity (tonnage) of the heat exchanger can vary with its height and depth. - Question and answerstrue Every central split cooling system manufactured in the USA today must have a Seasonal Energy Efficiency Ratio (SEER) of at least 10. - Question and answersfalse To check the performance of a dry-type evaporator, the service technician would first make sure that the refrigerant coil is operating with enough liquid inside. - Question and answerstrue ____________________-temperature refrigeration produces temperatures below the freezing point of water. - Question and answersLow As a rule of thumb, the temperature of the evaporator should be about ____________________°F colder than the box temperature. - Question and answers ___________________ the air means to remove the moisture, and this is frequently desirable in refrigeration systems. - Question and answersDehumidifying SEER is calculated based on the total amount of cooling the system will provide over the entire season, divided by the total number of ____________________ it will consume. - Question and answersWatt-Hours When the refrigerant vapor is saturated with heat it is known as a(n) ____________________. - Question and answerssaturated-vapor

Condensing temperatures in an air-cooled condensing unit can be reduced by ____. - Question and answersall of the above An air-cooled condenser that is operating in a climate that has four distinct seasons must ____. - Question and answershave some type of head pressure control Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser? - Question and answersall of the above A water regulating valve helps to maintain a system's head pressure by modulating the flow of refrigerant through the condenser. - Question and answersfalse The desired water flow through a condenser connected to a recirculating water system is 3 gallons per minute. - Question and answerstrue When the evaporative condenser is used in colder climates, freeze protection must be provided in winter. - Question and answerstrue If the spring pressure of a water regulating valve is increased, the system head pressure will also increase. - Question and answerstrue One large problem designer's face when designing air-cooled refrigeration and air conditioning equipment is a changing ambient from the changing seasons. - Question and answerstrue High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators. - Question and answersfalse Low suction pressures, iced coils, short-cycling, and inefficient cooling can also result from low head pressures. - Question and answerstrue Hard starting may also occur in a low ambient condition causing low head pressures. - Question and answerstrue The heat in the vicinity of the discharge gas has a tendency to cause any minerals in the water to deposit onto the ____________________. - Question and answerstube- surface In a water-cooled condenser, the leaving water temperature is normally ____________________°F lower than the condensing temperature of the refrigerant. - Question and answers An evaporative condenser uses air and ____________________ as the transfer medium for system heat. - Question and answerswater

If an air-cooled condenser's fan motor stops running, the head pressure will increase and the amount of subcooling will decrease. - Question and answerstrue In order for a flooded condenser type head pressure control system to operate, a device called a(n) ____________________ holds the extra refrigerant. - Question and answersreceiver If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____. - Question and answerswill increase Most of the heat energy in the suction vapor entering the compressor is ____. - Question and answerssuperheated from the evaporator The temperature of the compressed gas leaving the compressor can best be described as ____. - Question and answersvery warm The screw compressor is used primarily in ____. - Question and answerslarge industrial refrigeration and air-conditioning systems Rotary compressors are used primarily in ____. - Question and answersresidential air conditioning The clearance volume of a compressor cylinder is the ____. - Question and answersvolume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke The discus valve design is more efficient than a flapper valve design because ____. - Question and answersit allows a compressor design with less clearance volume Liquid entering the compression chamber of a reciprocating compressor can lead to ____. - Question and answersboth a and b Rotary compressors have pistons that rotate inside the cylinders. - Question and answersfalse The rotary screw compressor uses an open motor instead of the hermetic design. - Question and answerstrue The sight glass on a semi-hermetic compressor is used to allow light to enter the crankcase to keep the oil warm. - Question and answersfalse The shell of a hermetic type reciprocating compressor is generally considered to be on the low pressure side of the system. - Question and answerstrue

The Internal Pressure Relief valve opens at approximately 400 +/- 50 psi differential between high and low side pressures for R-22, and 500 to 625 psi differential for R- 410A. - Question and answerstrue The thermostatic expansion valve regulates refrigerant flow to the evaporator based on

  • Question and answerssuction-line superheat. The capillary tube is A type of - Question and answersmetering device. The TXV sensing bulb is mounted - Question and answerson the suction line between the evaporator and compressor. An external equalizer is used when - Question and answersthe pressure drop across the evaporator is excessive. When the load on the evaporator increases, the TXV - Question and answersincreases the flow of refrigerant The liquid charge bulb is - Question and answersA TXV-sensing bulb charged with A fluid similar to that of the system refrigerant. Superheat is - Question and answersthe sensible heat absorbed by the refrigerant after it has boiled to A vapor. The sensing bulb and transmission tube are A part of the - Question and answersTXV. A small amount of superheat in the suction line is desirable with A TXV to - Question and answersensure that no liquid refrigerant enters the compressor. The thin metal disc connected to the needle in the TXV is called the - Question and answersdiaphragm. Liquid refrigerant should be completely boiled to A vapor - Question and answersnear the outlet of the evaporator. The cross liquid charge bulb at the TXV contains fluid that - Question and answershas characteristics different from the system fluid and helps prevent liquid refrigerant from flooding over to the compressor. Balanced-port TXVs are used - Question and answersto feed refrigerant at A normal rate with low ambient temperatures. The pressure-limiting TXV - Question and answersshuts off the refrigerant flow to the evaporator when it has reached A predetermined pressure.

The automatic expansion valve was designed to - Question and answersmaintain A constant pressure in the evaporator. What force is cancelled out when using a balanced-port TXV? - Question and answersLiquid force What type of TXV can handle large varying head pressures, widely varying evaporator loads and very low liquid-line temperatures? - Question and answersBalanced-port Which type of valve uses A control board, transistors, thermistors, and A stepper motor controlled by an algorithm? - Question and answersElectronic expansion valve The difference between the superheat set point of an electronic expansion valve and the actual super heat is called a(n) - Question and answerserror. The terms "offset" and "error" are one and the same. - Question and answerstrue