Experimental investigation on a novel solid-gas thermochemical sorption heat transformer for energy upgrade with a large temperature lift

Abstract

Heat transformer is an effective technology for the recovery and reutilization of low-grade waste heat by upgrading its temperature to meet the energy demand. Low temperature-lift capacity is the common drawback for conventional heat transformers based on sorption process or heat pumps. A novel solid-gas thermochemical sorption heat transformer was developed for the energy upgrade of low-grade waste heat with a large temperature lift based on the pressure-reducing desorption and temperature-lifting adsorption techniques. The working performance and feasibility of the large-temperature-lift thermochemical sorption heat transformer was investigated and analyzed using a group of sorption working pairs of MnCl2-SrCl2-NH3. Expanded graphite was employed as the porous additive to enhance the heat and mass transfer of reactive salts. The experimental results showed that the proposed solid-gas thermochemical sorption heat transformer is feasible to achieve energy upgrade with a large temperature lift. It has the potential to upgrade the low-grade heat from 96°C to 161°C using MnCl2-SrCl2-NH3 sorption working pairs, and the exergy efficiency and energy efficiency are as high as 0.75 and 0.43, respectively. The temperature-lift range is relevant to the global conversion of reactive salt and sensible heat consumption of reactor. It is desirable to improve the temperature-lift range and energy efficiency by increasing the global conversion and decreasing the mass ratio of metallic part of reactor to reactive salt.