Comparative Thermal Analysis of Serpentine and Spiral Tube Configurations in Concrete Solar Collectors Using Numerical and Experimental Approaches

ABSTRACT Enhancing the concrete solar collectors provided insights into the development of efficient and sustainable solar energy systems for advancing low cost, sustainable energy systems. Two tube configurations, serpentine and spiral (inward and outward), had been analyzed for optimal heat transfer and uniform temperature distribution under varying Reynolds numbers 262, 524, 786, and 1052 with heat flux values 500, 750, and 1000 W/m². Numerical simulations by COMSOL MULTIPHYSICS SOFTWARE validated by experimental tests were conducted to evaluate temperature differences, surface temperature distributions, and thermal efficiency. Results show that the outward spiral flow achieved the best performance, with the lowest temperature differences and the highest efficiency 45.98% at heat flux 500 W/m² and Reynolds number 786 with an average surface temperature of approximately 306 K. The inward spiral flow performed slightly less efficiently and recorded an efficiency of about 45.2% with highest temperature difference 15 K. The serpentine flow exhibited the highest temperature differences and the lowest efficiency, 44.18% at heat flux 500 W/m² and Reynolds number 1052. At heat flux 1000 W/m² and Re = 1052, the temperature difference reached 12 K in the outward spiral, 13 K in the inward spiral, and 13 K in the serpentine flow. At Re = 262, the differences were 22 K, 25 K, and 42 K, respectively. The outward spiral provides the best performance, efficient heat dissipation and uniform surface temperature, particularly at medium to high Reynolds numbers with recommendations for adopting outward spiral flow designs in practical applications.