In this system, we select any suitable gas/liquid matter (known as refrigerant) whose saturation point at atmospheric pressure is very low, i.e., less than the required low temperature of refrigeration. (Saturation point of a liquid is such value of temperature at which if heat energy is given to liquid at constant pressure, its temperature will not change but it will evaporate from liquid phase to vapour phase in the same way as water changes into steam at 100 o C at the atmospheric pressure).
During evaporation, it will absorb its latent heat. If this latent heat is again taken back, it will again convert to liquid at same temperature as steam if cooled at 100 0 C, changes into water. (Saturation point or temperature is different for different substances and directly proportional to pressure). Thus when such type of liquid is allowed to flow inside the bundle of tubes going through refrigerated space, it will start evaporating, absorbing its latent heat from the space around tubes and produce cooling. After absorbing latent heat the liquid will convert into vapours. For continuous cooling, these low pressure and low temperature vapours are again required to be converted to low-pressure low temperature liquid and made to flow through refrigerated space. For that these vapours are first compressed in a mechanical compressor to such a high pressure where the saturation point becomes more than the atmospheric temperature. Being at higher pressure and temperature, these vapours will reject their latent heat to the atmosphere and condense i.e. convert to liquid at the same high pressure in a condenser.
After condensation this high-pressure liquid is allowed to pass through an expansion valve and expand to low pressure. As soon as the pressure of refrigerant liquid is reduced, the saturation point also reduces to a very low value. So, some of the liquid evaporates, i.e., converts into vapour taking latent heat from the rest of the liquid and thus cooing it. Now this low pressure, low temperature partially vapourized liquid is again ready to flow through the refrigerated space to extract heat energy and produce cooling by fully evaporating in tubes.
In this way, the refrigerant is made to flow continuously through the closed system from one component to the other connected through pipes with the help of compressor. It absorbs heat while flowing through the evaporator coil in refrigerated space and rejects it to the atmosphere while flowing through the condenser. The condition of refrigerant keeps on changing while flowing through different components of the system and it continuously produces cooling in refrigerated space.
i. Tons of Refrigeration
The capacity of any refrigerating machine is given in terms of its capacity of cooling. And one ton refrigeration capacity of a machine means, it can convert one ton of water at 0 0 C into ice at 0 0 C in 24 hours. Mathematically, it means 50 Kcal/min, i.e., a refrigerating machine of 1 ton can extract 50 Kcal of heat from the refrigerated space in one minute.
ii. Co-efficient of Performance (C.O.P.)
C.O.P. of a refrigerating machine is the ratio of heat extraction rate to the power consumption. Higher C.O.P. means better is the performance of refrigerating machine.
In the coming pages we will study the construction of different components. How they work, how they perform different processes on refrigerant and in what sequence they are arranged.
During evaporation, it will absorb its latent heat. If this latent heat is again taken back, it will again convert to liquid at same temperature as steam if cooled at 100 0 C, changes into water. (Saturation point or temperature is different for different substances and directly proportional to pressure). Thus when such type of liquid is allowed to flow inside the bundle of tubes going through refrigerated space, it will start evaporating, absorbing its latent heat from the space around tubes and produce cooling. After absorbing latent heat the liquid will convert into vapours. For continuous cooling, these low pressure and low temperature vapours are again required to be converted to low-pressure low temperature liquid and made to flow through refrigerated space. For that these vapours are first compressed in a mechanical compressor to such a high pressure where the saturation point becomes more than the atmospheric temperature. Being at higher pressure and temperature, these vapours will reject their latent heat to the atmosphere and condense i.e. convert to liquid at the same high pressure in a condenser.
After condensation this high-pressure liquid is allowed to pass through an expansion valve and expand to low pressure. As soon as the pressure of refrigerant liquid is reduced, the saturation point also reduces to a very low value. So, some of the liquid evaporates, i.e., converts into vapour taking latent heat from the rest of the liquid and thus cooing it. Now this low pressure, low temperature partially vapourized liquid is again ready to flow through the refrigerated space to extract heat energy and produce cooling by fully evaporating in tubes.
In this way, the refrigerant is made to flow continuously through the closed system from one component to the other connected through pipes with the help of compressor. It absorbs heat while flowing through the evaporator coil in refrigerated space and rejects it to the atmosphere while flowing through the condenser. The condition of refrigerant keeps on changing while flowing through different components of the system and it continuously produces cooling in refrigerated space.
i. Tons of Refrigeration
The capacity of any refrigerating machine is given in terms of its capacity of cooling. And one ton refrigeration capacity of a machine means, it can convert one ton of water at 0 0 C into ice at 0 0 C in 24 hours. Mathematically, it means 50 Kcal/min, i.e., a refrigerating machine of 1 ton can extract 50 Kcal of heat from the refrigerated space in one minute.
ii. Co-efficient of Performance (C.O.P.)
C.O.P. of a refrigerating machine is the ratio of heat extraction rate to the power consumption. Higher C.O.P. means better is the performance of refrigerating machine.
In the coming pages we will study the construction of different components. How they work, how they perform different processes on refrigerant and in what sequence they are arranged.
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