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Term 3: Refrigeration and Science > Refrigeration > Flashcards

Refrigeration Flashcards

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1
Q

The amount of heat removed to lower the temperature of 15 pounds of water from 48°F to 39°F is:

A

135 BTU

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2
Q

If the pressure exerted on a refrigerant in the vapor state remains constant but its temperature above absolute zero is doubled, the volume of the vapor will be:

A

Approx. doubled

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3
Q

When an object is refrigerated:

A

Heat is removed from it

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4
Q

The boiling point of a liquid:

A

Depends on the absolute pressure

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5
Q

A ton of refrigeration is equal to ______________ Btu per hour.

A

12,000

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6
Q

Absolute zero is calculated to be ______________ degrees Fahrenheit.

A

–460

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7
Q

The unit used to measure the amount of heat removed from a substance is the ________.

A

BTU

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8
Q

The low side of a vapor compression cycle contains the:

A

Evaporator

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9
Q

The boiling point of refrigerant in a condenser is the same as:

A

Condensing temperature

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10
Q

Of the following items the largest amount in Btu for one pound of water is:

A

It’s latent of vaporization

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11
Q

If the evaporator in a vapor compression cycle is not cold enough, it can be made colder by:

A

Lowering the evaporator pressure

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12
Q

The purpose of the condenser in the vapor compression cycle is to:

A

Save the refrigerant for re-use

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13
Q

In the vapor compression cycle, the compressor:

A

Heats and compresses refrigerant vapor and reduces evaporator pressure

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14
Q

Water can be made to boil at 50F by:

A

Placing it under a high enough vacuum

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15
Q

A fluid:

A

Can be either a liquid or a gas

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16
Q

Refrigerant HCFC-22 is a:

A

Halogeneated hydrocarbon
Halocarbon
Chlorinated hydrocarbon

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17
Q

Ammonia is not used as a refrigerant in air conditioning systems because:

A

it is relatively unsafe to use.

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18
Q

List 4 desirable traits of a refrigerant

A 
Non-corrosive
Low leak tendency
Does not conduct electricity
Chemically stable
...
Chemically inert
Solvable in oil
Harmless to oil
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19
Q

In an air conditioning system using CFC-12 evaporator pressure should not be less than ______ psig if icing of the coil is to be avoided.

A

30

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20
Q

If a liquid-vapor refrigerant mixture has a quality of 75 percent, it is:

A

Mostly vapor

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21
Q

Enthalte is:

A

The heat content of substance

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22
Q

At sea level pressure, water having a temperature of 180F is:

A

Subcooled

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23
Q

In a system containing CFC-12, the temperature of the refrigerant is 120°F. The refrigerant is:

A

Saturated, superheated or subcooled depending on pressure,

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24
Q

The unit of enthaltsamem is

A

BTU per pound

25
Q

The unit of constant volume is

A

BTU per pound

26
Q

The purpose of wearing goggles when handling halocarbon refrigerants is to:

A

The possibility of freezing the eye

27
Q

Copper-plating of compressor parts is:

A

Caused by contaminants in the system

28
Q

Oil is most readily soluble in:

A

CFC-12

29
Q

The best way to put oil into a compressor is to:

A

use a pressure pump.

30
Q

A noncondensable in a refrigeration system can be:

A

Carbon dioxide, methane or air

31
Q

Air in a refrigeration system results in:

A

an increase in compressor discharge pressure.

32
Q

List four materials which are considered to be contaminants in a refrigeration system.

A
  1. air
  2. water
  3. moisture
  4. antifreeze or antifreeze agenets
  5. alcohol
  6. soldering fluz
  7. chlorinated solvents
  8. iron oxide
  9. rust
  10. copper oxide
  11. corrosion
  12. metal chips or particles
  13. dirt
33
Q

In transferring refrigerant from one cylinder to another, it is a good idea to avoid filling the cylinder more than _________ percent full.

A

80

34
Q

A capillary tube in a liquid refrigerant line is:

A

An essential component of a compression cycle

35
Q

The compressor

A

Heats the refrigerant,

increases refrigerant pressure and superheat the refrigerant

36
Q

The expansion device in a vapor compression cycle:

A

Throttles

37
Q

In a split system, the condensing unit contains the:

A

Condenser

38
Q

List the four essential components of the vapor compression cycle:

A
  1. compressor
  2. condenser
  3. evaporator
  4. expansion device (or expansion valve)
39
Q

The lowest temperature to which a direct-expansion air conditioning coil can cool the air is limited by:

A

refrigerant temperature.

40
Q

The refrigerant distributor pressure drop:

A

need not necessarily affect system capacity.

41
Q

If dirty filters in an air conditioning system reduce the quantity of air flowing over the DX coil:

A

system capacity will decrease.

42
Q

Refrigerant leaves the expansion valve as:

A

a mixture of liquid and saturated vapor

43
Q

If all other conditions in a given system remain unchanged, a decrease in condensing pressure results in:

A

a drop in evaporator temperature.

44
Q

A shaft seal is required in:

A

an open compressor.

45
Q

As compared to the speed of the prime mover, the speed of a direct-drive compressor:

A

is always the same as that of the prime mover.

46
Q

One type of compressor is the helical-rotary type; other types are the ___________________, the ________________________, and the _____________________.

A

rotary, reciprocating, centrifugal

47
Q

Of the four essential components of the vapor compression cycle, the condensing unit contains ________________________________.

A

the compressor and the condenser

48
Q

In a single-phase motor, the starting winding is

A

Out of phase with the running winding

49
Q

A split-phase motor:

A

May have a starting capacitor

50
Q

A potential relay operates from:

A

Counter-emf

51
Q

A current relay:

A

Has normally-open contacts

52
Q

An electric motor can overheat because of

A

High voltage
Low voltage
Excess current draw

53
Q

An air cooled condenser has a propeller fan driven by an air-oven motor, and the condenser has dampers for capacity control. If the dampers inadvertently remain tightly closed while the fan runs, the motor:

A

May overheat

54
Q

What doe the following abbreviation stand for: PSC

A

Permanent split capacitor

55
Q

What doe the following abbreviation stand for: CSR

A

Capacitor start

56
Q

What doe the following abbreviation stand for: CSIR

A

Capacitor start - induction run

57
Q

The part of an electric motor that rotates is called the ___ and the stationary part containing the field winding is called the ____

A

Rotor, stator

58
Q

An electric motor turns because of its rotating ____

A

Magnetic field

59
Q

A north magnetic pole attracts a ___ magnetic pole, but it repels a ____ magnetic pole.

A

South, north

Term 3: Refrigeration and Science (3 decks)

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