Feasibility study on a novel heat exchanger network for cryogenic liquid regasiflcation with cooling capacity recovery: Theoretical and experimental assessments

摘要

There is an increasing research interest in the recovery of cooling capacity stored in cryogenic liquids (CLs) for industrial applications, especially for LNG regasification systems. In this study, a novel heat exchanger network (HEN) has been designed for cryogenic liquid regasification process to recover the released cooling capacity and develop a frozen-free heat transfer system with compact structure and high efficiency. Firstly, the specific design concept is proposed to employ the gasified CL as multiple cyclic streams to vaporize its own liquid in the evaporator, which allows a large temperature difference and a compact structure for the vaporization of the CL. Then, according to the optimization design of the flow arrangement, heat exchanger structure and flow rate control, the temperature of the heat medium can always be kept above its freezing point in the superheater and recuperator. Finally, the heat medium as the coolant extracts and transports the cryogenic cooling capacity from the CL to other refrigerated spaces, which can achieve various discharge temperatures to meet the requirements of different kinds of applications by adjusting the circulation number of the cyclic streams and the flow rates of the fluids. In the process calculation, the specific design parameters and energy balance relation of the HEN are obtained, and the cooling capacity recovery efficiency of the HEN system is analyzed using the pinch technique. A prototype of the heat exchanger network is designed and corresponding experiments are carried out for the regasification process of liquid nitrogen. The results indicate that the recovered cooling capacity and recovery efficiency of the prototype can, respectively, reach up to 17.5 kW and 90% within a 7.5% error range, which proves the feasibility of the novel HEN proposed in this paper. (C) 2019 Elsevier Ltd. All rights reserved.