Experimental performance evaluation of a novel designed phase change material integrated manifold heat pipe evacuated tube solar collector system

In this study, the thermal performance of a novel solar collector integrated with stearic acid as phase change material has been investigated. In this design, the solar radiation was collected by heat pipe equipped evacuated tubes and then stored in manifold integrated with phase change material. The stored thermal energy of phase change material then transferred to water flowing through bundle of finned copper pipes placed inside the manifold. In present study, the design, the operating principle and the experimental investigation of the developed system have been presented. The developed system was investigated with different mass flow rates and also discussed the influence of varying mass flow rate on the thermal performance of system. The experimental investigation of designed and developed system has been carried out for two modes i.e. mid-day charging mode and full-day charging mode. It has been observed that for considered mass flow rates, thermal efficiency of the system was varied in the range of approximately 52-62% for full-day charging mode while for mid-day charging mode, it was varied between 55 and 72%. The maximum value of thermal efficiency was approximately 72.52% at mass flow rate of 24 LPH for mid-day charging mode. The efficiency of phase change material for both modes was varied in the range of approximately 61-64%. The annual cost and annual fuel cost of the developed system are much lower than conventional system. Also, the initial capital cost for the developed system can be recovered after 6 years of operation. However, there is no recovery of initial investment for electricity based water heating system. The proposed system overcomes two problems associated with conventional heat pipe evacuated tube solar collector: elimination of heat pipe overheating problem and low thermal conductivity of phase change materials. By this novel design of manifold, the influence of thermal stratification on the thermal performance of solar collectors can be completely eradicated.