Effects of wavy channel configurations on thermal-hydraulic characteristics of Printed Circuit Heat Exchanger (PCHE)

Abstract

Printed Circuit Heat Exchanger (PCHE) is a widely chosen plate type compact heat exchanger for high pressure applications. The present work mainly focuses on two high pressure applications; firstly, Helium Cooling System (HCS) of Test Blanket Module (TBM) in International Thermonuclear Experimental Reactor (ITER) and secondly, Intermediate Heat exchangers (IHX) in Very High Temperature Reactors (VHTR). In this work, a reduced numerical model for a single banked PCHE core working in He-He counter flow circuit has been numerically modelled and verified against the results available in the literature. The same model is then extended for studying the effect of three wavy-channel configurations viz. triangular, sinusoidal and trapezoidal in a single banked PCHE core made of Alloy-617. The nature of local flow and heat transfer in the periodic channels has been studied by visualizing the vortex core using iso-normalized helicity surfaces. Thereafter, the thermo-hydraulic performances of these models are compared with straight channel PCHEs. Among the various models studied, the trapezoidal PCHE model is found to offer highest heat transfer with the largest pressure drop compared to sinusoidal, triangular and straight channel based PCHE models. A maximum of 41% increase in the heat transfer rate is predicted for the trapezoidal wavy channel compared to the straight channel PCHEs, for the tested operating conditions. For the sinusoidal and triangular wavy-channel PCHE configurations, the corresponding heat transfer advantages are predicted to be 33% and 28% respectively. The optimal thermo-hydraulic performance is also assessed, considering the thermal performance factor (TPF) obtained for all the three channels. The highest values of TPF are predicted for trapezoidal wavy channels (3.5) which is followed by sinusoidal (2.5) and triangular (1.5) wavy channels.