The present work considered the modeling of a refrigeration absorption machine with either air or water cooling at 25 and 35°C, respectively to test binary hydrocarbon mixtures as working fluids, namely n-propane and n-butane as refrigerants and n-heptane, n-octane, n-decane as absorbents.
The calculations consisted of mass and heatbalancesover the main machine partsand also on the vapor-liquid phase equilibria using thermodynamics models like the NRTL and the UNIFAC for the activity coefficients predictions in the liquid phase and the viriel and Peng-Robinson equations of state for the fugacity coefficients in the vapor phase.
Coefficients of performance (COP) values of of 0.632 and 0.6 were obtained for the mixtures n-C3H8/n- C10H24 and n-C4H10/n- C10H24, respectively.
The results showed the great reliability of the NRTL model compared to the UNIFAC which was characterized by some limitations due to the approximations induced by the group contribution concept.
Through this study one can measure how difficult is to choose the most appropriate model to calculate the enthalpies for the different involved streams.
The systems achieving the best performances i.e. n-C3H8/n- C10H24 and n-C4H10/n- C10H24 are non toxic and can be regarded as competitors of Ammonia.