Experimental investigation of a zeotropic organic Rankine cycle system with liquid-separation condensation for composition adjustment

Abstract

Organic Rankine cycle (ORC) systems often experience a decline in operating performance when subjected to off-design conditions. To address this issue, an emerging method for improving the ORC performance under variable operating conditions is the use of composition adjustment through liquid-separation condensation. In the present study, an experimental facility of a 1 kW zeotropic ORC system that allows for composition adjustment based on liquid-separation condensation is developed. A composition adjustment strategy based on the proposed composition adjustment system is developed, and the stability and effectiveness of the composition adjustment system are experimentally investigated. An experimental comparison is conducted to demonstrate the superiority of the composition-adjustable ORC over the conventional composition-fixed ORC under variable operating conditions. The results indicate that the proposed composition adjustment system can effectively separate mixtures at different compositions within a short period of time. Under variable operating conditions, the composition of R134a/R245fa in the ORC is effectively adjusted from 0.300/0.700 to 0.172/0.828 using the proposed composition adjustment system. As a result, the net power output of the composition-adjustable ORC is found to be 4.79–9.71% higher than that of the composition-fixed ORC.