Effects of shell-and-tube heat exchanger arranged forms on the thermo-economic performance of organic Rankine cycle systems using hydrocarbons

Shell-and-tube heat exchangers are crucial and widely used components in organic Rankine cycle (ORC) systems. Heat exchanger arranged forms, namely, the organic fluid flows either inside or outside the tubes, substantially affect the purchased cost and exergy loss of heat exchangers; and thereby considerably influencing the system thermo-economic performance. Based on various heat exchanger arranged forms, the thermo-economic performance of ORC systems may differ remarkably and even result in opposite conclusions, such as in selecting optimal working fluids and ratios of component purchased cost. However, no published studies have focused on this specific issue. Influence degree exerted by the heat exchanger arranged form on the thermo-economic performance of ORC system remains unclear. Selection guidelines for the optimal arranged forms also need to be developed. This study analyzed the effects of heat exchanger arranged forms on the thermo-economic performance of subcritical ORC systems with shell-and-tube heat exchangers. Three common heat exchanger arranged forms were studied. Heat source temperatures are 100–200 °C, and five hydrocarbons are working fluids. Results show that the heat exchanger arranged forms substantially affect the specific investment cost (SIC) of ORC system, and the largest difference in SIC reaches 14.7% among various arranged forms. The optimal working fluid and system parameters, and ratios of component purchased costs also differ remarkably. Optimal heat exchanger arranged form depends on the working fluid and heat source temperature. This study provides the optimal heat exchanger arranged forms for five hydrocarbons at heat source temperatures of 100–200 °C.