Vapor−Liquid Equilibrium of Aqueous Alkaline Nitrate and Nitrite Solutions for Absorption Refrigeration Cycles with High-Temperature Driving Heat

Abstract

Vapor−liquid equilibria of aqueous solutions of lithium nitrate + potassium nitrate + sodium nitrate in the mass ratio (53:28:19) and lithium nitrate + potassium nitrate + sodium nitrite in mass ratio (53:35:12) were obtained using a static method in the temperature range (333.15 to 473.15) K at 20 K intervals. Both mixtures were considered as binary working fluids (water/salts). The salt mass fraction was varied from 0.50 to 0.95. Barker’s method was used to calculate the liquid composition from the initial overall composition of the sample and the measured pressure and temperature. The vapor−liquid equilibrium data obtained were correlated using an analytical polynomial equation. The calculated and measured data showed good agreement. The vapor−liquid equilibrium data of both mixtures showed similar behavior, but the risk of crystallization is lower for the solution of lithium nitrate + potassium nitrate + sodium nitrite in mass ratio (53:35:12), which favors the operation of absorption refrigeration cycles driven by high-temperature heat sources.