Midterm

Low-temperature food storage applications generally start at _____.

0°F

At standard conditions on the Celsius scale, water will boil at...

100°F

Absolute pressure at sea level under standard conditions is_____ psi.

14.696

The latent heat of fusion for a water-to-ice transformation is...

144Btu/lb.

As a rule of thumb, the temperature of the evaporator should be about _____°F colder than the box temperature.

15

The _____ of the liquid refrigerant determines the coil operating temperature.

boiling temperature

Sensible heat energy levels...

can be measured with a thermometer.

Latent heat energy levels...

cannot be measured with a thermometer

The _____ _____ is referred to as a kinetic displacement compressor.

cenfrifugal compressor

The _____ are used to change the vapor to a liquid and the liquid form back into a vapor the refrigeration cycle.

condenser and evaporator

If the application requires a coil design to operate below freezing, there must be provision for _____.

defrost

A direct expansion-type evaporator is also called a _____.

dry-type evaporator

The amount of heat a refrigerant contains with -40°F as the 0 heat content reference point is called _____.

enpalthy

The _____ in a refrigeration system is responsible for absorbing heat into the system from whatever medium is to be cooled.

evaporator

The boiling temperature and its relationship to the system exist in the ______.

evaporator

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 _____.

flooded evaporators

A refrigeration system designed for the storage of flowers or candy is considered a _____ type.

high temperature

A defrost system that pipes the compressor discharge vapor directly to the evaporator is called a(n) _____ _____ type.

hot-gas defrost

When heat transfers by convection, it...

is transported from one place to another by air of liquid.

When a refrigerant enters the compressor, it is a _____ and when it leaves the compressor, it is a _____.

low pressure low temperature superhated vapor, high pressure high temperature superheated vapor

The household of refrigerator fresh-food compartment is a good example of _____ refrigeration.

medium-temperature

The four major components of a vapor compression refrigeration system are the compressor, condenser, evaporator, and _____ _____.

metering device

When a substance is heated, the molecules...

move faster.

When heat transfers by conduction, it...

moves from molecule to molecule

When heat transfers by radiation, it...

moves through space and air and heats solid objects.

Psig indicates...

pounds per square inch of gauge pressure minus atmospheric pressure.

A Bourdon tube is often found in a...

pressure gauge.

The compressor is a refrigeration system _____.

pumps the refrigerant throughout the system

The condenser _____.

rejects the heat from the refrigerant.

98°C converted to degrees Fahrenheit equals...

208.4

70°F converted to degrees Celsius equals...

21.1

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?

25 psig

The household refrigerator fresh-food compartment typically ranges from _____.

28 to 40°F

A ton of refrigeration is equal to _____.

288,000 Btu/24-hr

The atmosphere will support a column of mercury _____ inches at sea level.

29.92

The temperature inside the refrigerator fresh food section should be about _____.

35°F

A typical evaporator operating temperature in an air-conditioning system is _____.

40°F

High-temperature refrigeration applications will normally provide box temperature of _____.

47 to 60°F

If water weighs 8.34 pounds per gallon, it will take _____ Btu to raise the temperature of 4 gallons of water from 70°F to 72°F.

66.7

A typical superheat for an evaporator operating under normal conditions would be _____.

8 to 12°F

28°C converted to degrees Fahrenheit equals...

82.4

200°F converted to degrees Celsius equals...

93.3

Ice melts in iceboxes because _____.

All of the above

_____ the air means to remove the moisture, and this is frequently desirable in refrigeration system.

Dehumidifying

T or F Every central split cooling system manufactured in the USA today must have a Seasonal Energy Efficiency Ratio (SEER) of at least 10.

False

T or F If a cylinder of R-22 is moved from a 100°F ruck body into an 80°F shop, the quantity of liquid refrigerant in the cylinder will remain the same.

False

T or F The capacity (tonnage) o the heat exchanger can vary with its height and depth.

False

T or F The only location where the refrigerant vapor is superheated is in the evaporator.

False

T or F Vapor is more dense than liquid and, as the liquid refrigerant boils, it has a tendency to sink.

False

_____-temperature refrigeration produces temperatures below the freezing point of water.

Low

_____ evaporators are used when the coil would become too long for a single circuit, percent vapor.

Multicircuit

From a performance standpoint, a substitute for R-12 is ______.

R-134A

Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure?

R-502

_____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant.

Superheat

What happens when room temperature soda is poured into a glass of ice?

The ice melts because it is absorbing heat from the soda.

T or F A stamped plate evaporator usually does not use a fan to move air across it.

True

T or F An expansion valve is the pressure reducing device that controls the flow of liquid refrigerant into the evaporator.

True

T or F Modern refrigerators have become state-of-the-art appliances and some models even include automatic beverage and ice dispensers, built in television screens and connections to the world wide we.

True

T or F Only liquid refrigerant should enter the metering device.

True

T or F The boiling point of a refrigerant should be low enough at atmospheric pressure to keep the system pressure above 0 psig when operating at low temperatures.

True

T or F The discharge gas from the compressor is a high pressure, high temperature, superheated vapor.

True

T or F The evaporator can be thought of as a "heat sponge."

True

T or F The evaporator in a refrigeration system must be colder than the refrigerated space in order to absorb heat.

True

T or F The helide leak detector should be used in well ventilated areas as the resulting blue or green frame indicates that phosgen gas is being produced.

True

T or F The refrigeration evaporator is a component that absorbs heat from the conditioned space into the refrigeration system.

True

T or F 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.

True

T or F Heat flows from a warmer substance to a cooler substance.

True

T or F The film factor is a relationship between the medium giving up heat and the heat-exchange surface

True

Reciprocating compressors have _____.

a piston and cylinder

A compound gauge measures pressures...

above and below atmospheric pressure.

The evaporator in a refrigeration system _____.

absorbs heat from the product to be cooled

The law requires technicians to recover refrigerant from all refrigeration systems so that they _____.

all of the above

High temperature refrigeration is that produced by _____.

an air-conditioning system.

Good ventilation is important when working around refrigeration equipment because modern refrigerants _____.

are heavier than air and may displace the oxygen around you

The standard atmospheric conditions for water to boil at 212°F are...

atmospheric pressure: 14.696 psi, temperature: 70°F.

The process of removing heat from a place where it is not wanted and transferring that heat to a place where it makes little of no difference is known as _____.

refrigeration

When the refrigerant vapor is saturated with heat it is known as a(n) _____ _____.

saturated vapor

The _____ _____ is another positive displacement compressor and is used for larger air conditioning and refrigeration applications.

screw compressor

The refrigerant vapor picks up additional heat as it flows from the evaporator to the compressor. The heat is picked up from the _____ _____

suction line

The _____ relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling the cooling systems temperatures.

temperature/pressure

Refrigeration can be described as _____.

the process of removing heat from a place where it is not wanted to a place where it makes little of no difference

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.

watt-hours