Comparison of Energy Performance of Organic Rankine and Kalina Cycles Considering Combined Heat Sources at Different Temperature

Abstract

Abstract An organic Rankine cycle (ORC) and Kalina cycle are both promising ways for low-temperature waste heat utilization, and these two technologies have their own applicable occasions. It is significant to choose a proper cycle considering waste heat features for efficient utilization of energy. For combined heat source, the ratio of latent heat to sensible heat, R, is a very important parameter to choose a suitable cycle. When R is small, it is proper to choose a Kalina cycle; while when R is large, it is better to choose an ORC. There is a turning point of R, which is related to the heat source temperature, working fluids and cycle parameters. In this paper, based on the simulation models developed for ORC and Kalina cycles in Aspen HYSYS, the optimum working fluids of ORC are selected, and cycle parameters of both cycles are optimized. Then the turning point of R is found at different waste heat temperatures. Results show that the turning point of R fluctuates with increase of waste heat temperature at range of 150-200°C, and it peaks at 150°C and 180°C. When waste heat temperature is higher than 190°C, ORC is better than Kalina cycle whatever R is. The paper can provide a reference to choose a suitable power generation system for combined heat source at different waste heat temperatures.