Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Refrigeration System Components > Heat Exchangers > Flashcards

Heat Exchangers Flashcards

1
Q

Three properties of an air-cooling evaporator.

A

Transfers heat from the air circulating over it to the refrigerant inside its tubing

Uses air as the primary medium for cooling the conditioned space

Conducts heat through fins, to the tubing, then to the liquid refrigerant in the tubing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

For what reason does heat transfer somewhat slowly between air and the refrigerant in an air-cooling evaporator?

A

Air has relatively low density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Air defrosting is most commonly used on evaporators in ____ applicaitons

A

low-temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A plain coil submerged and mounted inside a container filled with a liquid that provides good heat transfer is a(n) ____ evaporator.

A

immersed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why might a designer of a liquid-cooling evaporator use a brine bath rather than a sweet water bath?

A

So the bath could be could below 32 degrees F without freezing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Fin-and-tube evaporators circulating the most common types of refrigerants generally have fins made of ____.

A

aluminum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In general, the more fins an air-cooling evaporator has, ____.

A

the more its cooling ability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Dead air and hot spots in a conditioned space can often be eliminated by using ____.

A

baffles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The air-cooling evaporators that are most effective at heat transfer are ____ evaporators.

A

microchannel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Defrost timers commonly control the operation of ____.

A

Electric heating elements
Fan Motors
Solenoid Valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Defrost timers end a defrost cycle using ____.

A

Pressure
Temperature
Timers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The condition in which a defrost cycle continues too long and conditioned space temperature is raised too high is called ____.

A

overdefrosting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When melted frost cannot be directly drained by gravity alone, it must be removed using a(n) ____.

A

condensate pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The method of defrost that involves circulating a hot liquid in and around the evaporator is ____ defrosting.

A

nonfreezing solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The method of defrost that involves circulating air form the conditioned space over an evaporator after the compressor cycles off is ____ defrosting.

A

off-cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The method of defrost that involves energizing electric heating elements is ____ defrosting.

A

electric

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The method of defrost that involves removing refrigerant from the evaporator is ____ defrosting.

A

pump-down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The method of defrost that involves manually or automatically running tap water over an evaporator is ____ defrosting.

A

water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The method of defrost that involves circulating high-pressure refrigerant through an evaporator is ____ defrosting.

A

hot-gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Refrigerant entering a condenser is a hot, high-pressure vapor, but refrigeration exiting a condenser should be a ____.

A

warm, high pressure liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

A condenser that is composed of a long refrigerant cylinder filled with straight copper tubes filled with cooling water is called a(n) ____ condenser.

A

shell-and-tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

A condenser that is composed of a refrigerant cylinder filled with a winding spiral of copper tubing filled with cooling water is called a(n) ____ condenser.

A

shell-and-coil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

A condenser that is composed of a coaxial arrangement of tubing with refrigerant and water flowing in opposite directions is called a(n) ____ condenser.

A

tube-within-a-tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

The reason for head pressure control in low ambient temperature can be explained by the concepts expressed in ____ law.

A

Gay-Lussac’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The position of condenser air louvers for low ambient conditions is directly modulated by ____.

A

head pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

When head pressure control is done through fan cycling, hotter ambient temperature would result in ____.

A

more condenser fans in operation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In a suction line-liquid line heat exchanger, system capacity is increased as the suction line experiences ____.

A

more superheating

28
Q

In a suction line-liquid line heat exchanger, system capacity is increased as the liquid line experiences ____.

A

more subcooling

29
Q

In a suction line-liquid line heat exchanger, refrigerant generally flows ____.

A

in opposite directions

30
Q

The four major components of a mechanical refrigeration system are ____.

A

compressor, condenser, evaporator, and metering device

31
Q

Devices used for refrigerant flow control include ____.

A

check valves, pressure regulating valves, and any electomechanical valve that regulates flow

32
Q

A device used to maintain proper refrigerant quality is the ____.

A

filter-drier

33
Q

Install a ____ to protect a compressor after a burnout.

A

suction line filter-drier

34
Q

The main task of a drier is to ____.

A

adsorb moisture and other contaminants that could mix to create acids

35
Q

(T/F) Suction line filet-driers can hinder the return of oil to the compressor.

A

True

36
Q

(T/F) There should not be a measurable pressure difference in pressure measurements taken before and after the filter-drier.

A

True

37
Q

A liquid receiver is a tank connected between the ____ that is used for refrigerant storage.

A

condenser and liquid line

38
Q

In a commercial refrigeration system that pumps down during the Off cycle, ____ controls the liquid line solenoid valve.

A

cooling thermostat

39
Q

Using Off-cycle pump-down on a commercial refrigeration system is a good method of ____.

A

preventing compressor flooding

40
Q

The sizing of a filter-drier is primarily based on a systems’s ____.

A

capacity rating

41
Q

(T/F) A filter-drier should be replace whenever the system is opened for service.

A

True

42
Q

(T/F) If a moisture indicator is hot, it may produce an inaccurate reading on the amount of moisture in a system.

A

True

43
Q

(T/F) Shutoff valves are made so that only refrigeration service valve wrench can be used on them.

A

True

**Some have handwheels on them

44
Q

Systems that include manifold valves usually have multiple ____.

A

evaporators

45
Q

Refrigerant line valves are used to accomplish ____.

A

blocking of refrigerant when flow reverses, isolation of flow, or restriction of flow.

46
Q

A shutoff valve controlling refrigerant flow through a vertical length of refrigerant line is a ____ valve.

A

riser

47
Q

A valve that allows fluid flow in only on direction is a ____ valve.

A

check

48
Q

The inefficient operation of a check valve may cause a(n) ____ noise.

A

hammering

49
Q

To prevent a TXV from opening intermittently during the Off cycly, a(n) ____ can most easily be used to automatically divert high-side pressure to the underside of the TXV’s diaphragm during the Off cycle.

A

three-way solenoid valve

50
Q

A hot-gas defrost valve directs refrigerant into the low-side form the ____.

A

discharge line

51
Q

A hot-gas bypass valve is primarily used for ____.

A

controlling low-level conditions

52
Q

The two values on which hot-gas bypass valves operate is ____.

A

low-side pressure and low-side temperature

53
Q

The value on which liquid injection valves operate is ____.

A

superheat

54
Q

A liquid injection vave is used in conjunction with a(n) ____.

A

hot-gas bypass valve

55
Q

A liquid injection valve’s primary purpose is to ____.

A

reduce the temperature of bypass hot-gas

56
Q

As crankcase pressure rises, a crankcase pressure regulator ____.

A

closes

57
Q

The purpose of a CPR (Crank Case Pressure Regulator) is to prevent ____.

A

compressor overload

58
Q

The calibration screw on a crankcase pressure regulator (CPR) is adjusted according to which compressor rating?

A

Rated load amperage (RLA)

59
Q

The primary purpose of evaporator pressure regulators (EPRs) on multiple-evaporator systems is to ____.

A

maintain different evaporator temperatures

60
Q

EPRs are applied to refrigeration systems primarily based on the principle of ____ law.

A

Gay-Lussac’s

61
Q

An electric evaporator pressure regulator differs from a standard EPR in that it uses a stepper motor to control its valve position and also measures and reacts to ____.

A

evaporator temerature

62
Q

Relief valves are generally used to protect against high ____.

A

head pressure

63
Q

A relief valve with a metal core that melts at a low temperature is a ____.

A

fusible plug

64
Q

A relief valve with an element that burst before system pressure exceeds an unsafe level is a ____.

A

rupture disk

65
Q

A condenser pressure regulator is a(n) ____ valve.

A

open on rise of inlet pressure (ORI)

66
Q

A receiver pressure regulator is a(n) ____ valve.

A

open on rise of differential pressure (ORD)

67
Q

A low-ambient control valve is a combination of which two pressure regulators?

A

Condenser and receiver

Refrigeration System Components (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions