Experimental investigation on RORC system performance for recovering LNG cold energy under heating and cooling capacities variations

Abstract

A large amount of available cold energy exists in Liquid Natural Gas (LNG). While it is not efficiently utilized and is released into the ocean. To efficiently utilize LNG cold energy, a power generation test bench based on the organic Rankine cycle has been established with R290 as the working fluid, a scroll expander as the thermal conversion device, and a multi-stream heat exchanger as the high-efficiency heat exchange device. The low-grade heat source and LNG are simulated by electrically heated hot water and −198 °C liquid nitrogen. The following are the main conclusions: (1) Heating and cooling capacities have different degrees of influence on system performance, and there is a matching relationship between the two capacities; (2) system maximum thermal efficiency and cold energy utilization rate are 6.13% and 12.04%, respectively. The comprehensive performance reaches the highest when the ratio of heating-to-cooling capacity is 1.96; (3) among the main components in the system, the increasing proportion of expander exergy destruction plays a positive role in improving the total system exergy efficiency. While the increasing proportion of heat exchangers exergy destruction has a negative influence in system exergy efficiency.