Advanced thermodynamic cycles for finite heat sources: Proposals for closed and open heat sources applications

Abstract

This paper analyses two non-conventional thermodynamic cycles designed to work with finite heat sources, which are suitable for maximum temperatures of about 400 °C. The Hybrid Rankine-Brayton (HRB) cycle fits well to closed heat sources and, in the paper, it is analysed considering its exergy efficiency and some requirements for the maximum and minimum temperature of the heat transfer fluid that feeds the cycle, obtaining promising results. The other one is a new proposal called Recuperated and Double Expanded (RDE) cycle, aimed to translate the good features of HRB from closed heat sources to open ones, where the performance of HRB is limited.Both cycles are compared to some reference ones. Results show that the HRB cycle is a good candidate for finite closed heat sources, particularly with maximum temperature around 400 °C and with temperature changes of the heat transfer fluid from 100 °C to 150 °C. The RDE cycle exhibits good performance for finite open heat sources with maximum temperatures between 200 °C and 400 °C, and it behaves similarly to tri-lateral cycles.