Performance enhancement of a dual heat pipe array based evacuated tube solar water heater for north eastern India climatic condition: A numerical approach

Heat pipes have been employed widely in solar collectors for more efficient heat transfer process. In recent times, heat pipes have been modified and micro heat pipe array has been developed with higher heat transfer characteristics. Current investigation adopted the new innovations to develop a micro heat pipe array based evacuated tube solar water heater. Outputs of solar collectors are dependent on fluctuating solar radiation, which needs to be accounted for in the analysis. To simulate the practical condition, a transient numerical study was carried out to assess the performance of such a collector with special reference to the location of Silchar, NorthEast India and hence actual solar radiation data for different months is considered for the analysis accounting the seasonal variation over the year. Results indicate that the efficiency is low in the morning session but eventually stabilized around 70-80% for the most part of the day. The output water temperature of the solar collector follows the same trend of the solar radiation curve where February month yields the highest output temperature and June month registering the lowest with approximately 5 K temperature difference between them at their respective peak points. There is unutilized heat trapped inside the evacuated tube collector, which the micro heat pipe array is unable to extract. One novel geometrical modification is adopted in the present study by incorporating two micro heat pipe arrays inside the evacuated tube collector, and the simulated results show that double micro heat pipe arrays could effectively penetrate the high temperature region to extract energy. The addition of one additional micro heat pipe array could result in 15-20% efficiency enhancement.