Process design methodology for rankine cycle based on heat matching

The Rankine cycle serves as a crucial technical tool for waste-heat recovery. Matching heat sources and working fluids presents a challenging problem among the extensive research on the process design and selection of working fluids for the Rankine cycle. This study introduces a process design methodology for the Rankine cycle based on heat matching. It can optimize the performance between heat sources and working fluids without the need to preset the configuration for the cycle. The objective is to ultimately derive the most efficient configuration and operating conditions for the Rankine cycle. This method relies on establishing a matching relationship between temperature and heat diagram curves of both heat sources and working fluids. The relationship can be described by a simple linear programming problem, serving as the fundamental model for the proposed method. Demonstration of the feasibility and accuracy of this method involved computing the performance of a subcritical Rankine cycle for waste heat recovery in an ammonia-diesel dual-fuel engine. Three different working fluids were considered: ammonia, R123, and R245fa. Ammonia exhibited superior performance with an overall system efficiency improvement of 5.18 %, surpassing R123 (5.01 %) and R245fa (5.00 %). The competitiveness of the ammonia Rankine cycle has been established, resulting in a nearly zero-carbon-emission power system potentially achieving an overall efficiency of 53.23 %. The process design method based on heat matching notably reduces the modeling efforts required for the Rankine cycle. This reduction provides substantial support for engineering design and facilitates wider applications of the Rankine cycle.