Experimental study of a graphite disk generator into an absorption heat transformer

Abstract

Absorption heat pumps main consist of four heat exchangers: Generator, Absorber, Evaporator and Condenser. The heat transfer carried out in every process has a direct impact on the performance of the whole system. A weakness of heat pumps by absorption at low pressure is the leaks in the Generator because the lithium bromide-water working solution attacks the material and the thermodynamic cycle is broken. For this reason, an experimental study about a novel Generator with 18 disk of graphite is analyzed as a component for an Absorption Heat Transformer (AHT). Graphite is used because of its high resistance to corrosion, support thermal shocks and its similar thermal conductivity with respect to stainless steel. For this study, the thermodynamic analysis is carried out under the following scenario: the heat for the generator was supplied by heating water with volumetric flows of 1.6, 2.1, 2.6 and 3.6 LPM and temperatures of 70, 73, 76 and 79° C. This study consists of knowing the thermal capacity, heat transfer coefficients and experimental behavior of the generator to compare it with generators made of stainless steel, also know the complete performance of the AHT. As results, the overall heat transfer coefficient obtained was of 50–240 W/m2 °C, similar values with generators made of stainless steel, while the coefficient of performance (COP), regarding external heats was from 0.253 to 0.483. The results about corrosion are notable due to the component has been working for 8 years without leaks problems.