Refrigeration

Question 1

What is the definition of refrigeration?

Answer 1

The process of absorbing energy from a substance thus lowering its temperature.

Question 2

What are the applications of refrigeration on ships?

Answer 2

Preservation of food.
Chilled water plants (provides cooling for air conditioning, magazines, and weapon systems).
Manufacture of ice.

Question 3

Describe Sensible Heat

Answer 3

Heat added to, or subtracted from, a substance causing a change in temperature but not a change in state.

Question 4

Describe latent heat.

Answer 4

This is the amount of heat which when added to or removed from a substance produces a change of state.

Question 5

What is specific heat?

Answer 5

The amount of heat required to raise 1kg of a substance 1°C + 273°K. Measured in kJ/kg°K

Question 6

Define saturation temperature (T-sat)

Answer 6

Means boiling point. The saturation temperature is the temperature for a corresponding saturation pressure at which liquid boils into its vapour phase. A saturated liquid contains as much thermal energy as it can without boiling.

Question 7

Define Saturation Pressure

Answer 7

Saturation pressure is the pressure for a corresponding saturation temperature at which a liquid boils into its vapour phase.

Question 8

What is the relationship between saturation pressure and saturation temperature.

Answer 8

They have a direct relationship. As one increases, so does the other. For example, water at a low pressure requires less temperature to boil.

Question 9

Define Superheat

Answer 9

This is the heat energy added to a substance to raise its temperature after its saturation temperature has been reached.

Question 10

Starting with the compressor, list the order of components in the refrigeration cycle (9 components)

Answer 10

Compressor
Oil Separator
Condenser
Liquid Reciever
Liquid Stop Valve
Filter Dryer
Sight Glass / Moisture Detector
TEV (Thermal Expansion Valve)
Evaporator

Question 11

Define ‘Crital point’

Answer 11

The point at which, under specific conditions, the vapour and liquid are indistinguishable / identical. The substance fluctuates between liquid and gas.

Question 12

What is Boyle’s law?

Answer 12

Describes the inversely proportional relationship between the absolute pressure and volume of a gas if the temperature is kept constant within a closed system.

Question 13

Describe the state of the refrigerant between the following components:
a) compressor - condenser
b) condenser - TEV
c) TEV - evaporator
d) evaporator - compressor

Answer 13

a) HP Superheated Gas
b) HP Subcooled Liquid
c) LP Saturated Liquid
d) LP superheated Gas