Influences of fluid corrosivity and heat exchanger materials on design and thermo-economic performance of organic Rankine cycle systems

Abstract

Various heat sources and cooling fluids bring different requirements on the anti-corrosion performance of heat exchangers in organic Rankine cycle (ORC) systems. Using different materials may change optimal parameters and thermo-economic performance of ORC systems due to substantially different thermal conductivities and cost coefficients. This paper studied the influences of heat exchanger materials on optimal design and thermo-economic performance of ORC systems for various heat source conditions. The widely-used shell-and-tube heat exchanger was selected, and carbon steel, copper, and stainless steel were focused. The utilization costs of different types of heat sources were compared. Results indicate that the corrosivity of heat source and cooling fluid is a key factor deciding the utilization cost. The difference of specific investment cost (SIC) caused by different heat exchanger materials is up to 25.5%, which substantially exceeds that caused by different working fluids (2.3%). Even the corrosivity restriction is not considered, the maximum difference in SIC is still 11.0%, and the low-cost material is preferred. The lower the temperature and flow rate of heat source, the more significant the influences of heat exchanger materials. The improper selection of heat exchanger materials will underestimate the economic benefits of ORC technology.