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Flashcards in Refrigeration and Air Conditioning Deck (102)
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1

What are refrigerants primarily classified into ?

Primary and Secondary Refrigerants

2

What is a primary refrigerant ?

It directly takes part in the refrigeration system

3

What is a secondary refrigerant ?

It is first cooled and then used

4

What is used to cool a secondary refrigerant ?

A primary refrigerant

5

What are primary refrigerants classified into ?

Halocarbon
Azeotrope
Inorganic
Hydrocarbon

6

What are the three types of properties refrigerants are checked for before use ?

Physical, Chemical and Thermodynamic

7

Why should a refrigerant have a low boiling point at atmospheric pressure ?

It provides for lower refrigeration temperature

8

How low should it be, generally ?

Lower than the required refrigeration temperature

9

What should be the condensing pressure of a refrigerant at normal temperature ?

Low

10

Why should a refrigerant have high critical temperature ?

Easy to provide refrigeration, even at room temperature

11

What is critical temperature ?

the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied.

12

Why should refrigerants have low freezing point ?

Easy to circulate even at room temperature

13

What kind of a coefficient of performance (COP), is desired (high or low) ?

High

14

What is coefficient of performance (COP) ?

Ratio of refrigeration effect to work input

15

What is a desirable horsepower/ ton of refrigeration ?

Low

16

What is ton of refrigeration ?

Amount of ice melted in 24 hours from 0 degree centigrade water

17

What is the required flammability of a refrigerant ?

Low flammability

18

Why should refrigerants have low water dissolvity ?

Reduces moisture chocking of expansion devices with narrow passages

19

What affect should refrigerants have on metals ?

They should be non corrosive to metals

20

How should refrigerants mix with lubricating oil ?

Should mix well

21

What kind of a dielectric strength in required for a refrigerant ?

Strong dielectric strength, especially for hermetically sealed units

22

What is the property of a hermetic seal ?

It is air tight

23

Why should refrigerants have high thermal conductivity ?

It increases heat transfer rates

24

What is the desired viscosity of a refrigerant ?

Low viscosity

25

What should be the thermal capacity of a refrigerant at evaporating temperature ?

High thermal capacity at evaporating temperature

26

What should be the thermal capacity of a refrigerant at condensing temperature ?

Low thermal capacity at condensing temperature

27

What is thermal capacity ?

Measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change

28

What are some common refrigeration systems ?

Vapour Compression
Vapour Absorption
Air Refrigeration

29

What are some special refrigeration systems ?

Thermoelectric Refrigeration
Steam Jet Refrigeration
Vortex tube Refrigeration
Passive Refrigeration

30

What are the four main parts of a vapour compression refrigeration system ?

Compressor
Condensor
Expansion Device
Evaporator