Refrigeration and AC Flashcards
What is Refrigeration?
Refrigeration is defined as a method of reducing the temperature of a system below that of the surroundings and maintain it at a low temperature by continuously abstracting heat from it.
What is a refrigerant?
In a refrigerator, a medium called refrigerant continuously extracts the heat from the space within the refrigerator which is to be kept cool at temperatures less than the atmosphere and finally rejects to it.
What are the first two Refrigeration concepts?
1) Heat flows from a system at higher temperature to another at lower temperature. (high to low, cold objects absorb.)
2) Fluids by absorbing the heat, change from liquid phase to vapor phase and subsequently condense by giving off heat. (change of phase- vapor back to liquid.)
What are the second two refrigeration concepts?
3) The B & F temperatures of a fluid depend on its pressure. When a certain fluid at a very low pressure and temperature are compressed, even though its pressure increases it may still be in the condensed state if its temp is not increased to the saturation temperature at the increased pressure.
4) Heat can flow from a system of low temperature to that of a higher temperature by external work according to the 2nd law of Thermodynamics.
What are the parts of a refrigerator?
There are four parts:
1) Evaporator 2) Circulating system 3) Condenser
4) Expansion device
Explain the function of the evaporator.
Evaporator: ->It is the heart of the refrigerator where the liquid refrigerant is evaporated by the absorption of heat from the refrigerator cabinet.
- > It consists of simply a metal tubing which surrounds around the freezing and cooling compartments to produce the cooling effect required for freezing ice or lowering the temperature of the perishables.
- > Since it produces the cooling effect, it is also sometimes called cooling coil or freezer coil.
Another name for evaporator?
cooling coil or freezing coil.
What is refrigerating effect?
The rate at which the heat is absorbed in a cycle from the interior space to be cooled is called refrigeration effect.
What is a ton of refrigeration?
A ton of refrigeration is defined as the quantity of heat absorbed in order to form one ton of ice in 24 hours when the initial temperature of the water is 0 C.
What is ice making capacity? Give the unit.
An Ice making Machine is normally specified by its ice making capacity. Ice making capacity is defined as the capacity of the refrigerating system to make ice beginning from water (at room temperature) to solid ice. -> Kg/hr
What are two types of refrigeration systems?
VCR and VCR and air refrigerator.
What is used in vapour compression refrigerator?
Vapour is used as a refrigerant.
It is circulated through the system in which it [alternatively evaporates and condenses thus undergoing a change of phase from vapour to liquid and again liquid to vapour]
What happens during evaporation?
During evaporation it absorbs the latent heat from the refrigerated space and subsequently gives off heat while condensing. A vapour system makes use of [mechanical energy energy supplied to the compressor to run the refrigerator.]
Name four refrigerants.
Ammonia, Freon and carbon dioxide.
What does a VCR consist of? [Write4VCR]
It consists of :
1) an evaporator made up of coiled tubes installed in
2) freezing compartment of the refrigerator and connected to the
3) suction side of the compressor and
4) throttle valve.
- >Delivery side of the compressor is connected tot the condenser which in turn is connected to throttle valve.
