Heat transfer coefficients for helical components inside an Absorption Heat Transformer

Abstract

The evaporator and absorber are relevant components inside an Absorption Heat Transformer, because the refrigerant reaches a high latent heat, which is absorbed by the strong binary mixture at high pressure for obtaining the useful heat. Their heat transfer coefficients influence on the design and performance of an AHT. This paper shows the local and overall heat transfer coefficients for evaporator and absorber, by using experimental tests in a compact AHT of 2 kW, which was designed, built and characterized using only two shells (low and high pressure). Every component was made with nested helical coils and water-lithium bromide solution was used as working solution. The variables considered for this analysis were the heating temperature, the mass flux rate, pressure and concentrations. For the evaporator, an overall heat transfer coefficient of 1227.6 W/m2 K was reached with a heating temperature of 358.2 K. In the absorber, the strong binary mixture influences notoriously for the heat transfer coefficients, where the best result was of 157.2 W/m2 K with a concentrations delta of 6%.