Effect of Operating Conditions on Modified Kalina Cycle Performance

Abstract

Simple Kalina cycle system (SKCS) is used for low temperature, intermediate temperature and high temperature heat recoveries. However, its efficiency is rather low. Therefore, a modification is suggested to improve its efficiency. In this work a computer program is developed to predict the energy-exergy performance of a modified Kalina Cycle System (MKCS) using aqua ammonia solution. It consists of heat recovery vapor generator (HRVG), condenser, heat exchanger, separator, turbine, throttling valve, absorber and pump. The modification is implemented by introducing a heat exchanger (HE) between the separator and expansion valve. This HE is used to reheat the work solution which comes from the pump by the high temperature hot weak solution which comes from the separator. The effect of many operating conditions such as dryness fraction (DF) at separator inlet, low pressure and ammonia (NH3) mass fraction with constant high pressure on cycle performance is studied. The results show that the modified cycle efficiency is higher than the simple cycle efficiency by about 33.6% while the net power by about 27.8%. The highest efficiency and highest net output power are 14.7% and 0.5641 kW respectively. The exergy efficiencies for modified Kalina and simple Kalina are 24.8% and 11.7% respectively.