Thermal performance estimation of ammonia-water plate bubble absorbers for compression/absorption hybrid heat pump application

The objectives of this paper are to analyze the heat transfer characteristics during the NH3-H2O absorption process in plate heat exchangers and to develop the experimental correlations of the heat transfer coefficient for the compression/absorption hybrid heat pump application. The parametric analysis on the effects of the absorber internal pressure, ammonia weak solution concentration and absorber geometric dimensions on the absorber capacity and system COP (coefficient of performance) is carried out. From the experimental results, the maximum absorber capacity of 7.3 kW, COP of 2.66 and the maximum hot water outlet temperature of 80.7 °C are obtained. It is concluded that the heat transfer coefficient of solution side increases with increasing the aspect ratio (L/D) while it does not significantly depend upon the aspect ratio (W/D). Finally, an experimental Nusselt number correlation is developed with ±20% error band and compared with the other correlation from the literature.