Performance analysis of liquified petroleum gas (LPG) driven half-cycle air conditioning system

Liquified petroleum gas (LPG) is one of the potential refrigerants to be used in half-cycle air conditioning systems. After evaporation to get air-conditioning, LPG may be further used in combustion applications such as electric-generators, auto-motives and cooking stoves. Expansion device (or a flow control valve) is usually used before the evaporator to make sure that the refrigerant vaporizes in evaporator and provides cooling. The present study reports the investigation of an experimental study to determine the performance of three in-house designed and manufactured evaporators for an air conditioning system using LPG as refrigerant. The evaporators used are finned-tube evaporators having difference in tube arrangements, fin materials, fin spacing and tube dimensions. The thermal energy to evaporate LPG is obtained from air driven by a fan attached to one side of the evaporator. Cold air exiting from the evaporator is then supplied to a cabin having the similar dimensions of an automotive rickshaw. The performance parameters determined for a fixed time duration for different fan speeds include; the cooling effect, contact factor and rate of condensation. The investigations were conducted for different LPG flow rates and evaporative pressures. The test results show that for each flow condition; the cooling effect, contact factor and rate of condensation are also the function of air flow rate passing through the evaporator. Experimentally determined cooling effects were then analytically validated by using the Nusselt number correlations of Grimison model, modified Grimison model and Zhukauskas model for each of the evaporators used.