Abstract
Various types of solar collectors are used to harness solar energy for different purposes, such as heating water. One example is a solar collector with evacuated tube heat pipes, which is employed in both residential and industrial environments. The efficiency of this type of solar collector is affected by several factors, including the performance of the heat pipe, the type of fluid used, the design of the geometric inserts, and the tilt angle. The primary aim of this study was to perform a simulation-based analysis of heat transfer enhancement in an evacuated tube heat pipe solar collector that is improved with nanofluids and internal geometric inserts.
Experiment was carried out to examine the thermal performance of evacuated heat-pipe solar collectors by employing different traditional fluids in combination with insert geometries as a method for data collection. The collected data were used to develop a multivariable linear regression model using response surface methodology (RSM) to simulate the thermal efficiency of heat pipes enhanced with a combination of various nanofluids and geometric inserts.
The results revealed several key trends in the efficiency (%) of various fluids. Among traditional base fluids, water demonstrated the greatest efficiency, reaching a maximum efficiency of 64% when paired with a square insert. However, it underperformed compared to nanofluids enhanced with inserts, making it less suitable for high-efficiency applications. Titanium oxide and aluminium oxide demonstrated moderate efficiencies of 64% and 79%, respectively, with square insert. The copper oxide with a volume fraction of 2% achieved a higher efficiency of 81% with square insert. Notably, copper oxide with 8% volume fraction attained the highest efficiency, ranging from 73% without an insert to 92% with a square insert. Interestingly, the larger the insert area, the greater the efficiency. This indicates that a larger contact area of the insert increases the contact between the materials and the working fluid, which in turn decreases the thermal resistance and boosts the effectiveness of heat transfer.
This study is significant as it demonstrates how the integration of nanofluids with optimized geometric inserts in evacuated tube heat pipe solar collectors can substantially enhance thermal efficiency, offering a promising pathway for more sustainable and cost-effective solar energy applications in both residential and industrial contexts.