An advanced analytical model of the Diffusion Absorption Refrigerator cycle

The results about the performance of a new DAR’s thermodynamic model are compared with the predictions of Zohar et al. (2009). The main difference is due to an accurate modeling of the refrigerant composition, assumed there as pure ammonia. A sensitivity analysis shows that, as the generator temperature increases, the rich solution mass flowrate reduces more than that of the refrigerant one, and COP decreases. This happens as the absorption temperature increases as well, due to the lower absorption of ammonia in the weak solution. COP was found to increase when the ammonia concentration decreases. In addition, for lower heat fluxes supplied to the generator, the heat dissipation toward ambient dominates and COP becomes small; when the heat flux overtakes a threshold, the evaporator reaches its maximum heat transfer, that remains constant for any further increase of heat supplied. COP presents its highest values over a limited range of the generator’s operating conditions.

► The most updated model of a DAR cycle was improved with new assumptions.
► The main difference is the refrigerant composition, not assumed as pure ammonia.
► COP increases as the ammonia concentration decreases in the refrigerant.
► COP presents its highest values over a range of operating conditions.