Heat transfer enhancement in a thermosyphon using TiO2 nanofluid through natural convection

Performance of thermosyphon can be improved by using nanofluid where the colloidal suspension of nanosized TiO2 (1-100 nm) particle in the basefluid enhances the heat transfer characteristics of the base fluid. Therefore, a systematic study is made to characterise thermal conductivity of water based TiO2 nanofluid and then use in a circular finned thermosyphon to measure its thermal performance. The main novelty of the experimental investigation is that cooling in the condensing section of the thermosyphon is achieved through free convection unlike forced convection. Moreover, concerning higher stability of the prepared nanofluid, lower concentration of TiO2 nanofluid is varied within 0.10 to 0.30 vol.% with ethylene glycol as a surfactant. Variation of thermal conductivity with varying concentration and temperature is compared with theoretical models available in the literature. Results of different heat input (5, 10, 15 and 20W), different inclination (30º, 45º, 60º and 90º) and at different concentration of TiO2 nanofluid are compared with deionised water. It is noticed that use of nanofluid reduces the wall temperature distribution as well as thermal resistance of thermosyphon compared to deionised water.