Improvement of low-grade heat utilization: Sensitivity mechanism of saturated vapor pressure–temperature in dehumidified materials

Abstract

Low-grade heat exists widely in industrial processes and nature, but it is difficult to harvest and utilize due to the limitation of existing technology. In this paper, a new concept for improving low-grade heat utilization efficiency is proposed, which relies on absorption refrigeration or solution dehumidification air conditioning system to achieve heat-driven regeneration at a lower temperature by using a multi-component liquid desiccant solution with stronger saturated vapor pressure–temperature sensitivity. It is proved that the regeneration temperature can be reduced by increasing the P-T sensitivity of the dehumidified materials. Further, the paper quantifies the description of the P-T sensitivity and reveals the mechanism of the sensitivity as follows: the higher the charge concentration of ions, the stronger the ion-water molecule dipole interaction, resulting in the lower the concentration of dehumidification solution is required, and thus the stronger the P-T sensitivity. Finally, experimental verification shows that compared with typical LiBr solution as a liquid desiccant, the regeneration temperature of the solution dehumidification system can be reduced by 7.9 ℃ by using a multicomponent solution with higher P-T sensitivity as a liquid desiccant, which also proves that low-grade heat at a lower temperature can be recovered by using the method recommended in this paper.