2020 年 106 巻 8 号 p. 556-563
Cold heat generation system using chemical reaction from unused thermal energy is investigated. In this study, water/urea system is particularly studied. While dissolution of urea in water is endothermic process, deposition of urea from water solution is exothermic process. Therefore, endothermic dissolution of urea in water is utilized for generation of cold heat. On the other hand, thermal energy can be released by the exothermic deposition of urea from water solution. This is the advantage of the system because total thermal energy required to evaporate the water can be reduced by the exothermic deposition of urea. The cyclic operation of dissolution and deposition of urea is experimentally studied. As a result, cold heat generated by the dissolution can be estimated from the energy balance and enthalpy of dissolution. Based on the experimental results, a numerical model to estimate temperature of water/urea solution and performance of the system is developed. From the numerical results, heat exchange rate of the deposition (concentration) process is essential especially for the improvement of the performance of the system.