Computational Analysis and Experimental Investigation of the Performance of an Evacuated Tube Solar Air Heater Incorporating Therminol-55 as a Thermal Energy Storage Medium

The evacuated tube solar air heaters (ETSAHs) are gaining popularity today because of their reduced heat loss capability. A performance evaluation of the evacuated tube solar collector (ETSC) using a thermal energy storage (TES) facility was carried out during the study. A new heat pipe (HP) system with a TES unit directly integrated into it was used in the study along with ETSAH. The novel HP system directly stores the thermal energy and is capable of heating the air uniformly from all directions. Therminol-55 (T-55) was the sensible heat storage material integrated inside a common condenser HP system. The solar collector's performance was evaluated at air flow rates ranging from 0.003 to 0.02 kg/s. The HP and T-55 exhibited a maximum temperature of 121°C and 127°C. The highest temperature of the air leaving ETSAH-TES was 128°C. ETSAH-TES delivered hot air over 100°C continuously for 7 h. The results depict that even when solar energy was erratic, the HP developed in this research supplied a continuous hot air flow. The average energy and exergy efficiency achieved was 37.87% and 2.8%, respectively. T-55 can store a maximum of 1920 kJ of energy. With a standard deviation ranging from 0.2% to 1.87%, the ETSC-TES numerical analysis is in excellent agreement with experimental results.