Numerical Analysis of Evacuated Tube Solar Collector with Heat Pipe Containing an I-section Insert

Evacuated tube collectors can achieve a much high efficiency and temperature for a much longer period compared to conventional single flat plate collector systems. However, they can be a lot more expensive compared to flat panel collectors. Hence, the building of a suitable model would make the analysis of the configuration of the systems more insightful to achieve higher efficiencies. In this paper, a thermal resistance network model of an evacuated tube heat pipe was developed. An analysis of its performance was done to understand the effect of adding an I-section geometry insert on the total thermal resistance, the heat transfer and the efficiency considering several working fluids such as water, ethanol, methanol, acetone and toluene. The proposed model was validated using data collected on a cloudy day from the SAURAN STATION located in UMLAZI, SOUTH AFRICA. This study reveals that the addition of an insert decreases the total thermal resistance, which results in improved efficiencies. Water exhibited higher efficiency compared to other working fluids with the efficiency of 62.24% and 54.27% corresponding to the configuration with and without a geometry insert. An improvement in the rate of heat transfer from 530 to 605 KW when introducing an insert into the heat pipe was observed. Interestingly, the solar collector exhibited better results, even on a cloudy day. The thermal resistance network model proposed in this paper was deemed appropriate to be used for the performance prediction of the heat pipe with an insert.