Refridgeration Flashcards
Explain conduction
Heat transfer within the material, solid transfer
Explain heat transfer
Heat will always transfer from hot to cold
Explain convention
Hotter areas of water circulate into colder areas, until all the water is the same temperature
Explain radiation
Heat transfer through the air
Explain sensible heat
The temperature increases with no change of state
Explain latent heat
The state changes but the temperature remains the same (ice cube melting)
Heat required to change the state of a substance
What is super heating
Increasing the temperature above its boiling point
IE steam that is 110’c it is 10’c super heat
A gas with a temperature rise above its boiling point
Explain Sub-cooling
A gas changes into a liquid
Cooled below a 100’c to 90’c means 10’c sub cooling
What is the fridge temperature for frozen meat
-18’c to -22’c
What are the Fridge temperatures
Cold room =-18 to -22
Cold room dairy = +4’c to +6’c
Fruit and veg store = +4’c to +6’c
Galley ready use cupboard = +5’c to +7’c
What does the compressor do in the basic refrigeration system do
Pumps the refrigerant around the system
What job does the condenser do in the refrigeration system do
Uses sea water to cool the refrigerant to achieve sub-cooling
What does TEV stand for
Thermostatic expansion valve
What job does the TEV do
Monitors the gas leaving the evaporator and adjusts the flow through the evaporator
What job does the evaporator do
To absorb heat energy, to turn refrigerant liquid into gas
What does the hp/lp cut out do
Shuts the plant down if the pressure is to high/low
What colours are in the moisture sight glass
Green indicates dry (good)
Yellow indicates moisture (bad)
3 types of defrosting
Natural defrost
Hot gas defrosting
Electrical heating coils
When do electrical heating coils used
1 hour per day
When are natural defrost done
Every 3- 6 months (normal air temp)
When are hot gas defrosting done
1 hour per day 4-15 mins slots to prevent the oil cooking off
What is used for leak detection
Infra red leak detection system (rlds)
Oil slicks
Spectrolyne dye and UV lamp
Snoop
Halogen leak detector
What is stated in the Montreal protocol 1987
Agreement to phase out the use of harmful CFC gasses and ozone depleting substances
CFC,HCFC and Halon
What is stated in the Kyoto Summit 1997
Agreement to limit and reduce greenhouse gasses
CO2, HFC’s, PFC’s greenhouse gasses
