Thermal performance of a thermosyphon heat pipe evacuated tube solar collector using silver-water nanofluid for commercial applications

An experimental study was performed to determine the thermal efficiency of thermosyphon heat pipe (THP) evacuated tube solar collector using silver-water nanofluid for commercial applications. Firstly, the synthesis of silver-water nanofluid was carried out which can maintain its long-term stability. The identification of nanofluid was determined by X-ray diffraction, scanning electron microscopy, UV-visible spectroscopy and thermophysical analysis. Secondly, the heat transfer properties of cylindrical copper THPs charged with silver-water nanofluid and pure water was investigated experimentally. Experiments of THP charged with silver-water nanofluid were repeated four times at intervals of two weeks in order to observe changes in the performance of THP. It was observed that the THP charged with silver-water nanofluid maintained its improved heat transfer characteristic in the THP experiments. Nanofluid working fluid increased the efficiency of solar collector between 20.7% and 40% compared with the pure water. In conclusion, the experimental results show the use of silver-water nanofluid provides a significant improvement in the THP evacuated tube solar collector.