TPC 431 Refrigeration

Question 1

Refrigeration is the process of ___ the air in a defined space

a) adding moisture to
b) cleaning
c) increasing movement of
d) lowering the temperature of

Answer 1

d) lowering the temperature of

Question 2

Temperature of the material decreases if the material ___ and nothing else happens that would have the opposite effect

a) condenses
b) contacts a cooler material
c) contacts a warmer material
d) freezes

Answer 2

b) contacts a cooler material

Question 3

Two types of air conditioning are

a) comfort and process
b) commercial and industrial
c) heat transfer and change of state
d) temperature and humidity

Answer 3

a) comfort and process

Question 4

One of the physical states of matter is

a) atom
b) element
c) gas
d) molecule

Answer 4

c) gas

Question 5

You can cause matter to change its physical state by

a) adding or removing heat
b) allowing it to age
c) chemically altering it
d) separating its atoms

Answer 5

a) adding or removing heat

Question 6

Thermal energy that is directly related to the temperature of a material is called ___ heat

a) change of state
b) latent
c) potential
d) sensible

Answer 6

d) sensible

Question 7

45 degrees F is about the same as ___ degrees C

a) 7
b) 13
c) 25
d) 58

Answer 7

a) 7

Question 8

Heat can be transferred from one place to another by the process of _____.

a) change of state
b) conduction
c) diffusion
d) insulation

Answer 8

b) conduction

Question 9

The latent heat of vaporization of a substance absorbs as it

a) condenses
b) evaporates
c) freezes
d) melts

Answer 9

b) evaporates

Question 10

A refrigeration system has been turned off for several days. It contains both liquid refrigerant and vapor. Suddenly a line containing refrigerant breaks. What happens inside the system?

a) nothing, because its off
b) the liquid refrigerant boils
c) the pressure increases
d) the refrigerant gets warmer

Answer 10

b) the liquid refrigerant boils

Question 11

From the compressor, refrigerant flows to the ____

a) condenser
b) evaporator
c) metering device
d) reservoir

Answer 11

a) condenser

Question 12

The graph below is the pressure-temperature chart for a refrigerant. Point ___ represents a condition of superheating

a) 1
b) 2
c) 3
d) 4

Answer 12

a) 1

Question 13

Compared to a dry expansion evaporator, a flooded evaporator of the same size

a) contains no refrigerant
b) is more efficient
c) leaks refrigerant
d) requires no metering device

Answer 13

b) is more efficient

Question 14

The purpose of a cooling medium is to

a) absorb excess refrigerant vapor
b) condense the water vapor in moist air
c) remove heat from compressed refrigerant vapor
d) superheat refrigerant vapor

Answer 14

c) remove heat from compressed refrigerant vapor

Question 15

An automatic expansion valve is a metering device that maintains a constant pressure in the

a) compressor
b) condenser
c) evaporator
d) surge drum

Answer 15

c) evaporator

Question 16

The properties of air that are important in psychrometrics include

a) enthalpy
b) odor
c) oxygen content
d) velocity

Answer 16

a) enthalpy

Question 17

In a sling psychrometer, the wet-bulb temp is usually lower than the dry-bulb. If the difference is very small, you know that the air is quite

a) cool
b) dry
c) humid
d) warm

Answer 17

c) humid

Question 18

Air that is saturated is air that is at the

a) desired temp
b) dewpoint temp
c) lowest possible relative humidity
d) optimum oxygen content

Answer 18

b) dewpoint temp

Question 19

Relative humidity changes if the ___ changes, but the specific humidity does not

a) barometric pressure
b) dewpoint temp
c) dry-bulb temp
d) weight of dry air

Answer 19

c) dry-bulb temp

Question 20

To calculate the enthalpy of a sample of air, you must include

a) latent heat of the air
b) latent heat of the water vapor
c) relative humidity of the air
d) specific humidity of the air

Answer 20

b) latent heat of the water vapor

Question 21

In order to remove the moisture that enters a refrigeration system during repair, you must evacuate the system by using a ___ to make all the moisture vaporize

a) charging hose
b) manometer
c) torch
d) vacuum pump

Answer 21

d) vacuum pump

Question 22

One useful method of detecting leaks in a refrigeration system involves using a(n) ___ leak detector

a) chromatographic
b) electronic
c) high frequency
d) infrared

Answer 22

b) electronic

Question 23

Relative humidity can be measured directly with a(n)

a) dewpoint thermometer
b) hydrometer
c) hygrometer
d) psychrometer

Answer 23

c) hygrometer

Question 24

Which of the following is a correct match between an electrical value and the instrument used to measure it?

a) current ; ohmmeter
b) current ; wattmeter
c) power ; ammeter
d) resistance ; ohmmeter

Answer 24

d) resistance ; ohmmeter

Question 25

Identify the answer which correctly matched the class of work area hazard to an example of that class of hazard.

a) chemical ; container of refrigerant
b) mechanical ; aluminum ladder
c) physical ; unguarded belt drive
d) temperature ; heatstroke

Answer 25

a) chemical ; container of refrigerant