CARNOT REFRIGERATION CYCLE
The Carnot cycle refrigeration performs the reverse effect of the heat engine because it transfers energy from a low level of temperature to a high level of temperature. The refrigeration cycle requires the addition of external work for its operation. The diagram of the equipment and the temperature entropy diagram of the refrigeration cycle. The process which constitute the cycle are:
1-2 Adiabatic compression.
2-3 Isothermal rejection of heat.
3-4 Adiabatic expansion.
4-1 Isothermal addition of heat.
All the process in the Carnot cycle are thermodynamically reversible .Process 1-2 and 3-4 isentropic. The withdrawal of heat from low temperature source in process 4-1is the refrigeration step and is the entire purpose of the cycle. All the other processes in the cycle function so that the low temperature energy can be discharged to some convenient high temperature sink. VAPOUR COMPRESSION CYCLE
The vapour compression cycle is the most widely used refrigeration cycle in practice. In this cycle vapour is compressed, then condensed to a liquid, following which the pressure so that fluid can evaporate at low pressure. The standard vapour compression cycle is shown in temperature enthalpy diagram. The process constituting the standard vapour compression cycle are: 1-2 Reversible and adiabatic compression from saturated vapour to condenser pressure. 2-3 Reversible rejection of heat at constant pressure, causing de-superheating and condensation of refrigerants; 3-4 Irreversible expansion at constant enthalpy from saturated liquid to the evaporated pressure; 4-1 Reversible addition of heat at constant pressure causing evaporation to saturated vapour.
PERFORMANCE OF THE STANDARD VAPOUR COMPRESSION CYCLE
With the help of pressure-enthalpy diagram, the significant quantities of the standard vapour compression cycle will be determined. These quantities are the work of compression, heat...