Experimental and numerical study on the thermal and hydraulic characteristics of an improved PCHE with high-viscosity fluid

The increasing heat load in the lubricating oil system imposes higher requirements on the heat dissipation capacity of the fuel–oil heat exchanger. A Printed Circuit Heat Exchanger (PCHE) has emerged as a promising candidate to substitute for the traditional shell-tube heat exchanger due to its exceptional thermal efficiency and compact design. In this study, a new PCHE configuration is designed which staggered discontinuous fins with modified airfoil fins and cylindrical spoiler columns located at the inlet and outlet to avoid the high-velocity and negative pressure gradient areas while improving strength and flow field uniformity. Experimental results show that the thermal–hydraulic performance on the oil side is significantly influenced by the inlet temperature because the viscosity varies more sharply with temperature at the same Reynolds number, unlike the fuel side. Further numerical investigations reveal larger regions of high heat flux, high temperature, and high velocity on the oil side at lower inlet temperatures, which lead to increased heat conduction and more effective heat transfer in laminar flow. Additionally, the correlations for the Nusselt number (Nu) and the friction coefficient of fuel and oil in modified airfoil fins PCHE have been developed. Under the laminar flow, the modified airfoil fins PCHE exhibits superior heat transfer, with the Nu being 1.70 times higher than that of airfoil fins (S₁ = 6.0 mm), 2.10 times higher than that of zigzag channels, 2.83 times higher than that of airfoil fins (S₁ = 2.4 mm), and 4.70 times higher than that of straight channels at Re = 396.