The cooling of hot aqueous media: contributions of evaporative and convective mechanisms

Abstract The cooling of hot aqueous media is a very common process in everyday life and in industrial settings. Most often that occurs with an open surface to the air, enabling the evaporation of water. This imparts a strong cooling effect on the liquid, as the phase change is very endothermic. In parallel, heat is lost by convection at the liquid boundaries. This work starts by presenting the energy balances for such transient processes, and then develops a model for the evaporative effect, which can be coupled with Newton´s law for the convective one. Experiments with hot water are presented to test the model. Excellent agreement is arrived for the predictions of energy loss by each of the mechanisms and the experimental data. Furthermore, a set of heuristic rules regarding the cooling process can be formulated. Therefore, this report can be a good support for lecturers to devise pedagogical activities, but also for professionals that deal with equivalent situations.