Refrigeration

Question 1

How it works and what we have onboard?

Answer 1

The refrigeration process operates on the principle of removing heat from a space or substance, lowering its temperature, and transferring the heat to a refrigerant gas (R-404A)

• Compressor increase pressure and temp of refrigerant vapor, forcing it into the condenser
• Condenser removes heat via SW cooling, causing it to change to a liquid state
• Expansion valve regulates the flow of refrigerant into the evaporator, causing a pressure drop, this allowing it to expand and cool rapidly.
• Evaporator absorbs the heat from the space

Question 2

Latent heat and condensation?

Answer 2

• Latent heat refers to the heat energy absorbed or released by a substance during a phase change (solid to liquid, liquid to gas, or vice versa) at constant temperature.
• Condensation is the process by which a substance changes from a gas or vapor state to a liquid state due to cooling or compression.

Question 3

Air con/refrigeration, what maintenance would I do?

Answer 3

• Flushing/ cleaning condensers
• Visual inspections
• Cleaning filters/ fan coils
• Check refrigerant/ leaks
• Build up of ice on the evaporator - turn fridge freezer off
• Compressor oil change
• Compressor bearings

Question 4

Where might you find legionella onboard and why? Precautions?

Answer 4

Legionella is found in warm stagnet water. Can be avoided by keeping hot water above 50 degrees, flush the systems regularly, disinfection via chlorination and UV.

Question 5

Refrigerant gas regulations?

Answer 5

Ozone Depleting Substances - ODS record book, monthly weighing and records.

Question 6

High fridge and freezer plant temperature in galley, what would you do?

Answer 6

• Water contamination in the refrigerant. Caused by a leak in the condenser or incorrect recharging maintenance. Change the filter dryer as this will absorb the moisture

Question 7

How would you change the filter dryer?

Answer 7

• Shut down the plant and recover all the refrigerant
• Isolate the areas as much as possible
• using a brazing touch to heat the joints and remove the dryer, ensuring you have nitrogen to purge.
• Install new dryer with the arrow in the correct direction. Brazing the connections together.
• Check the system with nitrogen, looking for leaks
• Connect a vacuum pump to remove as much moisture and air from the system
• Recharge with refrigerant
• Monitor the system
• Record all information