The rate of release and storage of heat from a refrigerator depends on the characteristics of the refrigerant and its properties. The use of phase change material (PCM) improves the rate of heat transfer and thus improves the COP (Coefficient of Performance) of the refrigeration. The experiment analysis exemplifies considerably the improvement of a COP (Coefficient of Performance) of the conventional refrigeration system. Using water as PCM and for a certain thermal load it is observed that the COP (coefficient of yield) of the conventional refrigerator increased by 18-26% on average. Here the phase change material (PCM) used in a manually constructed chamber surrounding the evaporator chamber of a conventional refrigerator. All heat transfer from the load given to the refrigerator box to evaporator, evaporator to phase change material (PCM) by conduction.
A refrigerator is a common household appliance that consists of a thermally insulated compartment and that when it works, it transfers heat from the inside of the compartment to its external environment. It usually works in the steam compression cycle which uses a circulating liquid refrigerant that absorbs heat from the space to be cooled and subsequently rejects that heat elsewhere. All these systems have four components: - A compressor, a condenser, an evaporator and an expansion valve. The circulating refrigerant enters the compressor in the thermodynamic state known as saturated vapor and is compressed to a higher pressure, resulting in a higher temperature. The hot compressed steam is then in the thermodynamic state known as superheated steam and is at a temperature and pressure at which it can be condensed with the cooling water or cooling air typically available. This hot vapor is routed through a condenser where it cools and condenses in liquid by flowing through a coil or tubes with cold water or cool air flowing through the coil or tubes. This is where the circulating refrigerant rejects the heat of the system and the rejected heat is drawn by the air. The condensed liquid refrigerant, in the thermodynamic state known as a saturated liquid, is then conducted through an expansion valve where it undergoes an abrupt reduction of pressure. This pressure reduction results in the adiabatic evaporation of a portion of the liquid refrigerant. The self-cooling effect of adiabatic flash evaporation decreases the temperature of the mixture of liquid refrigerant and vapor to where it is colder than the temperature of the enclosed space to be cooled. The cold mixture is then routed through the coil or tubes in the evaporator. A fan circulates the hot air in the enclosed space through the coil or the tubes carrying the coolant and the vapor mixture. This hot air evaporates the liquid part of the cold refrigerant mixture. At the same time, the circulating air cools and therefore lowers the temperature of the enclosed space to the desired temperature. The evaporator is where the circulating refrigerant absorbs and removes the heat that is later rejected in the condenser and transferred elsewhere by the water or air used in the condenser. To complete the refrigeration cycle, the evaporator refrigerant vapor is again a saturation vapor and is returned to the compressor. And the cycle is continued. In the project, the condenser tube is divided into two sections: one is for cooling purpose while the other is for the purpose of heating. The residual heat from the compressor is supplied to the hot box and, therefore, the hot temperature is maintained within the heating chamber. The hot box is made of galvanized iron in which copper tubes are rolled. The glass wool is used as an insulation for this hot box so that the temperature inside the hot box is more than the ambient temperature.