Numerical computation of economic cooling water rate for multi-stage azeotropic refrigerating systems

With a view to conserve high grade electrical energy the use of azerotropes in a multi-stage refrigerating system is quite attractive. Economic cooling water rates that minimize the total operating cost and yield maximum coefficient of performance are searched out numerically for two-stage refrigerating systems that operate azeotropes R-500 and R-502. Main design quantities of interest such as inter-stage and condensing temperatures, coefficient of performance etc. are obtained at various optimal points pertaining to numerous feasible operating conditions. The results are presented graphically as well as in tabular forms for ready reference to design and refrigerating engineers. The effects of various controlling parameters/variables on the optimum design quantities are also analysed.