Dynamic characteristics of a mechanically coupled organic Rankine-vapor compression system for heat-driven cooling

Abstract

There are large quantities of compression heat wasted and cooling capacity required in cryogenic air separation units (ASUs). Mechanically coupled organic Rankine-vapor compression (ORVC) system is an attractive technology to realize heat-driven refrigeration for compression heat recovery and compression power saving in cryogenic ASUs. As the states of the compression heat inevitably change with the ambient environment, off-design operation of the ORVC system is worth investigating. A mechanically coupled ORVC test bench is designed and built in this paper. Off-design experiments are carried out to figure out the dynamic response characteristics and system performance variations. Results show that, the ORC working fluid flowrate and the opening of the throttle valve are the key operation parameters affecting the system dynamic response. The experimental system responds quickly with delay time less than 10 s and response time less than 1 min. The opening of the throttle valve has the greatest impact on the cooling capacity and system COP which reaches up to 0.61. This research may provide reference for control scheme design and actual operation for the compression heat recovery system in cryogenic ASUs.