Flow mal-distribution study in cryogenic counter-flow plate fin heat exchangers

Abstract

Plate Fin Heat Exchangers are one of the main components in modern large capacity helium liquefiers/refrigerators. These heat exchangers should have more than 95% effectiveness in order to liquefy helium gas. Design of these heat exchangers are complex one and govern by many parameters such as flow mal-distribution, variable fluid properties, heat-in-leak from ambient and longitudinal heat conduction through wall. Among these design parameters, flow mal-distribution within heat exchanger layers is one of the important design parameters for achieving higher effectiveness. Flow mal-distribution reduces the effectiveness significantly and may bring down it to a much lower value than design value. In the present study, a numerical model has been developed which is capable to evaluate layer by layer temperature distribution in presence of flow mal-distribution. Two major mal-distribution conditions, linear weighted and center weighted, might occurs when flow leads from nozzle to different layers in plate fin heat exchangers. Present work studied the effect of these two conditions on performance of plate fin heat exchanger in the temperature range of 300-90 K as a case study.