Modeling of the thermal behaviour of reverse thermosyphon, utilizing solar energy and different working fluids

Abstract

In solar collectors, the most important challenge is the low performance in off-peak hours of sunlight. Thermal performance of the bubble pump enabled reverse thermosyphon integrated with a U-tube solar collector is evaluated numerically concerning the average temperature along the length of the thermosyphon, thermal resistance, and efficiency. The proposed system is equipped with different nanoparticles and phase change materials at specific concentrations as two working media for passive downward heat transfer. The influences of actual variable heat flux, different fill ratios, and flow rate on thermal processes are analysed along with condensation and evaporation processes of phase change material. The results show a significant enhancement in thermal efficiency of 71% and a high operating temperature up to 98𝐶. The investigated parameters were found to have a large impact on thermal performance. The best phase change material and the nanoparticle at lower and higher heat flux and the best fill ratio for various heat fluxes are adjudged. Temperature distribution profiles, heat transfer, and thermal performances along with a multi-phase flow visualization of the reverse thermosyphon by CFD simulations are summarised. Quantitative estimation of the performance analysis under the high sink as well as the anti-gravity operating attributes of critical nature is highlighted.

Keywords

• thermal efficiency
• cfd
• anti-gravity
• nanofluid
• boiling
• condensation
• evaporation