Performance Evaluation of Phase Change Material Based Free Cooling System /

Abstract

Greenhouse emissions around the world are increasing day by day due to increase in demand of global energy utilization in buildings for different purposes. Large portion of energy is used for heating, cooling, and air conditioning purposes in buildings. Phase change material (PCM) can be used to store cold during night time which can be used during day time for lowering the temperature of buildings also known as free cooling. This paper presents the mathematical modelling under real time weather conditions (Islamabad) of PCM based free cooling system. Mathematical model was developed using MATLAB with Lauryl Alcohol as PCM. To analyze the performance of free cooling system three other PCMs were selected under suitable melting point range (22 to 28 ˚C) i.e., RT22HC, RT25HC & RT27. The performance evaluation of this system was done on two factors, varying air inlet velocity and air inlet temperature. The charging time for all PCMs can be reduced by 50 to 55% at higher air inlet velocity (3 m/s) and discharging time can be improved by 55 to 60 % at lower air inlet velocity (1 m/s). The optimum air inlet velocity was selected for charging and discharging process on the basis of above results. The effect of varying air temperature was analyzed for the selection of best suitable PCM for free cooling. Cost comparative analysis with conventional air conditioning system was also done to establish the setup for standard room.