Mechanical Theory 4 Flashcards
explain the pressure/volume relationship
- Low pressure – volume increase – less energy required
- High pressure – volume decreases – more energy required
briefly explain heat transfer
- Conduction – direct contact through solid
- Radiation – energy transfer through air
- Convection – energy transferred through fluid
breifly explain latent heat
temperature stays the same but the state changes
briefly explain sensible heat
increase of temp but state stays the same
briefly explain super heat
any temperature above the boiling point
explain the purpose of the compressor
- Raises the pressure of refrigerant
- (no liquid should enter the compressor – liquids cannot be compressed)
- Refrigerant leaving the compressor is a high-pressure hot gas
- Motive force
- Positive displacement pump
- Quadrant 1 – high pressure, hot gas
explain the purpose of the condenser
- Condenses the hot gas into a warm, high pressure liquid
- Must be a liquid on leaving the condenser
- Use sea water as a cooling medium
- Quadrant 2 – high pressure, warm liquid
explain the purpose of the evaporator
- Cold liquid refrigerant enters the evaporator
- Leaves as a gas
- Quadrant 4 – low pressure, cool gas
explain the purpose of the thermal expansion valve
- rate of flow – can increase/decrease
- Lowers the pressure
- Still stays as a fluid
- Thermometer – sense temp in refrigeration room – controls the rate of flow, to increase / decrease temp
- Quadrant 3 – low pressure, very cold liquid
what is the purpose of the moisture indicating sight glass
- Visible indication of refrigerant flow / shows presence of any moisture
- Green – indicates dry
- Yellow – indicates moisture
explain the montreal protocol agreement
Bunch of countries come together to control where refrigerants can be released
- CFC
- HCFC
- HALONS
explain the kyoto summit agreement
Reduce and limit greenhouse gases
* CO2
* HFC
* PFC
state five methods refrigeration leak detection
- Infra red leak detection system (IRLDS)
- Oil slicks
- Spectrolyne and UV lamp
- Snoop
- Halogen leak detector
state 3 oils used in a refrigeration system
- OM- 70
- SUNISO 3GS
- SW68
from what source should oil be used
fresh unopened