Non-isothermal evaporation and heat transfer of the salt solution layer on a structured wall in the presence of corrosion

Abstract

The layer evaporation with and without corrosion on an iron micro-structured wall with ceramic coating is investigated experimentally. SiO2 coating is obtained. A structured wall is used to intensify heat transfer. Hydrophobic ceramic coating is used to reduce the aggressive effect of salts on the metal wall. Rapid wall corrosion at high temperatures is a significant problem for desalination technologies, high-temperature generators of adsorption heat pumps, and chemical technologies using salts. The evaporation rate of the salt solution (CaCl2/H2O and NaCl/H2O) on the structured heated wall with SiO2 is 25–30% higher than on the smooth surface. Often, to simplify the simulation of heat transfer, free convection in the layer is neglected due to the low layer height and high viscosity of the solution. The novelty of this work lies in the fact that it is free convection that plays a key role. The combined effect of microstructured roughness and anticorrosion coating on heat transfer and convection is considered for the first time. The role of convection depends on whether the salt belongs to the first or second group, characterized by a certain character of evaporation. To date, there are no models that take into account structured surface, corrosion and natural convection on non-isothermal evaporation and heat transfer in a thin solution layer.