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Flashcards in Heat Exchangers Deck (67)
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1

Three properties of an air-cooling evaporator.

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

2

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

Air has relatively low density

3

Air defrosting is most commonly used on evaporators in ____ applicaitons

low-temperature

4

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

immersed

5

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

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

6

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

aluminum

7

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

the more its cooling ability

8

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

baffles

9

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

microchannel

10

Defrost timers commonly control the operation of ____.

Electric heating elements
Fan Motors
Solenoid Valves

11

Defrost timers end a defrost cycle using ____.

Pressure
Temperature
Timers

12

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

overdefrosting

13

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

condensate pump

14

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

nonfreezing solution

15

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

off-cycle

16

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

electric

17

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

pump-down

18

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

water

19

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

hot-gas

20

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

warm, high pressure liquid

21

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

shell-and-tube

22

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.

shell-and-coil

23

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

tube-within-a-tube

24

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

Gay-Lussac's

25

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

head pressure

26

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

more condenser fans in operation

27

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

more superheating

28

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

more subcooling

29

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

in opposite directions

30

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

compressor, condenser, evaporator, and metering device