SOFTWARE DEVELOPMENT FOR OPTIMIZING A REFRIGERATION SYSTEM

Abstract

Considerable interest in vapour absorption system, first developed in 19th century, has received growing attention in the past two decades with increasing cost of electricity and the potential damaging effects of traditional refrigerants used in vapour compression system. Present "Energy Crisis" has motivated refrigeration scientists to replace compressor (so as to reduce the operating costs of electricity) and traditional refrigerants (like chlorofluro carbons). Thus vapour absorption system is receiving an increasing attention because it uses low grade thermal energy and working fluids have almost no damaging effects on the environment although its COP is low as compared to that of a vapour compression system. In the present dissertation , a simple aqua-ammonia vapour absorption system consisting of condenser, absorber, generator, evaporator, rectifier, liquid heat exchanger (or preheater), subcooler, aqua-pump, expansion valve is considered. The temperature of absorber, condenser and the concentration of refrigerant are chosen as the decision variables to be optimized so that coefficient of performance is maximum for a fixed generator and evaporator temperature. For this, first the thermodynamic property data were explicitly expressed in the form of polynomials of pressure, temperature and concentration so as to carry out the system simulation. Hemstitching method for searching along the constraints has been used to carry out the optimization. The optimum result is obtained by varying the above three variables one at a time. After determining the optimum results, the heat transfer areas for various components are calculated. Also the best fit curves have been plotted so as help the user to choose the operating input parameters. Graphs have also been plotted between operating. variables and input parameters so that optimum values can be obtained directly fromAgraphs.