Cooperative Optimization of System Parameters and Heat Exchanger Structure for Geothermal Organic Rankine Cycle

Organic Rankine cycle (ORC) is a promising geothermal power generation technology. While, the high purchased cost of heat exchangers is a key obstacle for its promotion. To further enhance the thermo-economic performance and competitive advantage of geothermal ORC systems, the cooperative optimization of system parameters and heat exchanger structure is proposed in this work. The common shell-and-tube heat exchanger is focused. The influences of the inner diameter and wall thickness of heat exchange tube on the optimum design and thermo-economic performance of ORC system are analyzed. The performance improvement effects of cooperative optimization way are evaluated. The results show that the inner diameter and wall thickness have non-negligible influences on the optimum design and thermo-economic performance of geothermal ORC system. A larger thermo-economic benefit can be obtained by optimizing the inner diameter and wall thickness at low geothermal temperature and large geothermal flow rate. While, the thermo-economic benefits only differ slightly for various organic fluids. The cooperative optimization is confirmed as an effective way to substantially enhance the thermo-economic performance of geothermal ORC system, and the minimum specific investment cost can decrease by 12.5–15.6% compared with the traditional system-level optimization.