Experimental analysis of a new thermal energy storage system for air conditioning

Abstract

Maintaining a stable air temperature over prolonged periods in space heating and drying ap plications using solar air heaters remains a significant challenge, particularly under variable solar irradiance conditions. This thesis presents a comprehensive experimental investigation of a hybrid double-pass solar air heater integrated with a latent heat thermal storage unit, with the aim of developing a reliable and efficient system capable of all-weather operation for space heating and drying applications. To ensure a holistic evaluation of the proposed system, a multi criteria assessment methodology that included energy, exergy, economic, and envi ronmental analyses was used. The experimental study was systematically conducted in three consecutive phases. In the first phase, parametric and dimensional analyses were performed on a baseline double-pass solar air heater to investigate the influence of air gap variation on thermal and exergetic performance, showing that increasing the upper air channel height con siderably improved system performance, with a maximum thermal efficiency of 66.4% achieved at a 12 cm air gap configuration, while smaller gaps led in higher irreversibility and increased exergy destruction. The second phase focused on the integration of an auxiliary electric heater and a latent heat thermal storage unit using paraffin wax to improve thermal stability and extend operating hours. This configuration enabled a stable outlet temperature of 54±1.25 °C, prolonged system operation after sunset, and reduced electrical energy consump tion. At an air mass flow rate of 0.024 kg/s, the system achieved average thermal and exerget ic efficiencies of 72.3% and 3.5%, respectively. The third phase addressed further perfor mance optimization through the integration of wavy fins and the evaluation of auxiliary heater positioning. A fin inclination angle of 45° enhanced thermal efficiency by 13.8% compared to a flat absorber, while positioning the auxiliary heater at the outlet section improved tempera ture regulation, minimized fluctuations, and reduced electrical energy consumption by 4.23%. Overall, the findings demonstrate that using both latent heat thermal storage and heat transfer enhancement techniques significantly improves energy efficiency, thermal stability, sustaina bility, and practical applicability of hybrid solar air heaters, making the proposed system a promising and sustainable solution for agricultural drying and space heating applications.