AT-96-17-4 -- A Hydroxide Mixture as Working Fluid for Absorption Heat Pumps PDF

Basic experimental investigations were carried out with an aqueous solution of a mixture of KOH and NaOH for use as an absorbent in absorption heat pumps. Due to its thermophysical properties this mixture allows temperature lifts from evaporator to absorber of more than 75K (135degF) in a single-stage absorption chiller. Thermophysical and hydrodynamical properties of the solution were measured. Vapour-liquid-equilibrium data and specific heat capacities were determined for concentrations ranging from 35% up to 75% and temperatures up to 200degC (392degF). From these data the enthalpy of the solution was calculated. Additionally the crystallisation temperatures, the density, and the viscosity of the solution were determined. The experimental equipment is described. The data are presented as polynominals and diagrams including experimental accuracy. An apparatus was constructed to measure heat and mass transfer coefficients of the absorption process with this solution. The apparatus is a model of a horizontal tube falling-film absorber. The experimental setup of the apparatus and results of the first measurements are presented.

KEYWORDS: year 1996, absorption heat pumps, heat pumps, absorbents, mixtures, temperature lift, evaporators, absorbers, specific heat, content, temperature, heat content, calculating, crystallisation, density, viscosity, properties, accuracy, heat transfer coefficient, heat flow, heat transfer fluids