Efficient heat recovery for temperature swing processes: Experimental analysis of the thermal wave method

Industrial processes release large amounts of ultralow-grade heat, mostly unused due to inefficient recovery technologies. This study explores the thermal wave method as a heat recovery (HR) strategy for temperature swing adsorption (TSA) heat conversion (e.g. adsorption cooling) and gas separation (e.g. direct air capture) processes, where the rejection of large fraction of the heat input to the environment limits their scalability. A dedicated experimental setup was developed to quantify recovery with robust performance metrics, addressing inconsistencies in prior studies. Experiments in the range of temperatures between 30 °C and 80 °C achieved 55 % of heat input recovered, further improved to 61.5 % with a regenerative heat exchanger, surpassing conventional TSA thermal management strategies. Efficiency proved highly sensitive to flowrates, with an optimum in the range between 0.12 and 0.15 L min−1 of the internal energy recovery loop. A predictive model, parameterised using the number of transfer units and effective heat capacity, captured dynamic behaviour with ∼3.3 % variance. This work provides the first systematic validation of the thermal wave method, demonstrating >60 % efficiency and establishing a pathway to more commercially viable TSA and related thermal systems.