Pool Boiling in Binary Mixtures of Ammonia/Water. Effect of Heat of Dilution and Dissolution and Heat Transfer Coefficient.

Abstract

Nucleate boiling heat transfer coefficients have been measured during pool boiling of non-azeotropic mixtures of ammonia/water on a horizontal heated wire. The experiment was carried out at pressures of 0.4 and 0.7 MPa and at heat fluxes below 2.0×106 W/m2 and in overall range of mass fraction. The heat transfer coefficients in the mixtures are smaller than those in single component substances. No existing correlation is found to predict boiling heat transfer data over the range of mass fraction. In the mixtures of ammonia/water, heat of dilution and dissolution is generated near vapor-liquid interface, when vapor of higher concentration of ammonia is condensed and then is diffused into the bulk liquid, while in the most of mixtures, little heat is generated during any dilution and dissolution. In relation to this heat generated, the effect of the heat of dilution and dissolution on pressure and temperature in a system (pressure vessel) is shown.