Salt hydrate heat pipe: Proof of concept for a breakthrough heat transfer technology

Abstract

This article introduces a novel type of thermosyphon heat pipe (THP) utilizing salt hydrates (SH) as an additive to the working medium. The study evaluates the performance of the proposed SH heat pipe concept (SH-HP) both experimentally and numerically employing MgSO₄⋅7H₂O as a sample SH additive. The MgSO₄⋅7H₂O SH-HP (in powdered and aqueous forms) was investigated and compared with a conventional HP of the same physical features and operation conditions but pure water as the medium. Effects of various concentrations and filling ratios on the performance of the SH-HP were evaluated throughout the experimental, CFD, and parametric analyses. The system performance with powdered MgSO₄⋅7H₂O showed a decrease in heat transfer efficiency due to the presence of salt crystals in the heat transfer path. Investigations on the aqueous material indicated that physical properties and crystal formation play a crucial role in the final performance of the system. The SH-HP containing aqueous MgSO₄ at a concentration of 9.8 wt% demonstrated about 33 % reduction in thermal resistance. Overall, the study with its primary results proves the effectiveness of a highly efficient passive HP concept using magnesium sulfate heptahydrate as a sample additive, which could serve as a competitive candidate for various heat transfer and even heat storage applications. The results and effectiveness of the system for practical applications are expected to be more impressive upon rigorous optimization of the operating conditions, HP geometry, and additive characteristics.