A novel method for assessment of pinch point characteristics of heat exchangers with different combinations of pure fluid and binary mixture as hot and cold streams

Highlights: • A novel numerical method is proposed in order to analyze pinch point characteristics. • The different combinations of the binary mixture and pure fluid are used. • To converge the answers, a method similar to the bisection is used. • Heat exchangers are considered to be counter-flow. • The calculations are performed in EES software by writing an internal procedure. -- Abstract: A novel numerical method is proposed in order to analyze pinch point (PP) characteristics in the heat exchangers such as evaporator, condenser, regenerator, preheater and so on. The different combinations of the binary mixture and pure fluid are used as hot and cold streams. In addition, using the correlation between isobaric specific heat and temperature, an extra algorithm is presented in order to calculate the temperature of fluids like commercial oils with respect to dimensionless enthalpy. In this work after a comprehensive interpretation of the presented method, a parametric study is carried out for the selected commercial oils (e.g. Therminol-66), ammonia and water as pure fluids and ammonia-water mixture as a binary mixture. The effects of parameters like ammonia mass fraction in the solution and PP temperature difference on the PP characteristics such as PP position, mass flow ratio and average temperature difference between hot and cold streams are studied afterwards. This novel method is used for all heat transfer processes in heat exchangers including binary mixtures or pure fluid as one or even both of the hot and cold streams.