Heat transfer and evaporation of salt solution on a horizontal heating wall

Abstract

An experimental study of non-isothermal heat transfer and evaporation of thin layers of aqueous solutions of salts has been carried out. Evaporation was realized on a horizontal heated wall in the air atmosphere at a pressure of 1 bar. In the evaporation of water and salt solution, the heat transfer coefficient is constant for a long time period and increases in the final stage due to the multiple reduction of the layer thickness. Evaporation curves for different types of salt solutions have a different character. Due to the increase in salt concentration, the evaporation rate of LiBr-water, CaCl2-water, LiCl-water, and MgCl2-water decreases over time. Salt solutions decreases with time. Evaporation rates for solutions of NaCl-water, CsCl-water, and BaCl2-water slightly change over time. To analyze the effect of free convection on heat transfer, experimental curves for the ratio of Nusselt numbers (A = Nu(salt)/Nu(water)) for the salt and water solution have been built. Parameter A is greater than one and increases with time. The effect of convection on heat transfer varies with time and depends on the current salt concentration and solution layer height, which should be considered in the simulation.