Fluid flow and thermal performance of the pulsating heat pipes facilitated with solar collectors: Experiments, theories and GABPNN machine learning

Abstract

Listen

Translate article

Solar energy could be effectively exploited and transferred by the solar collectors, where thermal transport efficiency was inhibited by actual operations and applications. In present research, solar collector combined with pulsating heat pipes (PHP) was proposed to enhance solar energy conversion and management. Fluid temperature oscillation, flow patterns and motions, heat transfer mechanisms inside present facility were comprehensively investigated, which aimed to suitably determine the flow stability of working fluid for PHPs, such that the whole system performance could be fully optimized. Firstly, an experimental investigation was comprehensively conducted to obtain the flow motions, temperature oscillation, and thermal resistance of PHPs, under multi-parameter conditions. Our results indicated that heat transfer performance was promoted with an increase in thermally driven force, accompanied by which low frequency with “small amplitude” transformed to high frequency with “bulk amplitude”. In addition, filling ratio of 25% even a minimum input power generally results in dry-out phenomena, superior liquid-vapor patterns and heat transfer performance were observed as filling ratio was 60%. Following that, theoretical modeling results confirmed that, within the critical pipe diameter, larger saturated vapor pressure and lower surface tension were significantly beneficial for the application of PHPs-solar collector. Considering dimensionless parameters and experimental data, Genetic Algorithm-Back Propagation Neural Network (GA-BPNN) was further built to predict the heat transfer performance of PHPs, which was in great agreement with the experimental data. Optimal filling ratios were further confirmed depending on the best Ku performance, within average deviation being no more than 10%. Present theoretical and experimental researches could facilitate the optimization and application of PHP- solar collectors, greatly exploiting solar energy for buildings.