Diagrams of entropy for ammonia–water mixtures: Applications to absorption refrigeration systems

•We improved mathematical modelling of absorption refrigeration systems, highlighting values of enthalpy and entropy of ammonia–water mixtures.•We did a survey of aspects of entropy associated with the absorption process.•We considered the amount of entropy associated with reaction mixture arising between ammonia and water system.•We determined the entropy of ammonia–water mixture as a function of temperature, pressure, and concentration associated to absorption processes.