Experimental investigation of flow boiling heat transfer in a minichannel heat exchanger with countercurrent hot and cold fluid circuits

Abstract

This study presents a novel experimental investigation of flow boiling heat transfer in a minichannel module with simultaneous hot and cold fluid circuits. The novelty of the work lies in the analysis of a multilayer minichannel configuration with interacting hot and cold working fluids, enabling detailed evaluation of interfacial heat transfer mechanisms. Experiments were conducted in two groups of six parallel minichannels with rectangular cross-sections (1.5 mm depth, 20 mm width, and 140 mm length, hydraulic diameter 2.77 mm), heated by a 1000 W halogen lamp. The system was tested under steady laminar countercurrent flow conditions at a heat flux of 6000 W/m2, with FC-72 fluid and distilled water mass flow rates of 0.006 kg/s and 0.0087 kg/s, respectively, and an inclination angle of 165°. The temperature of the outer copper plate surface was measured using an infrared camera. Local heat transfer coefficients were calculated using a one-dimensional computational approach at the heated plate – FC-72, FC-72 – central plate, central plate – water and water – closing plate interfaces. The results show the distributions of temperature and heat transfer coefficients along the channel length. An increase in the heat transfer coefficient was observed at the heated plate – FC-72 interface, whereas decreasing values were found at the remaining interfaces. The one-dimensional approach was validated using computational fluid dynamics simulations, showing a maximum discrepancy of 26.6% at the heated plate – FC-72 interface across all minichannels. These results offer insight into interfacial heat transfer in multilayer minichannel systems and support the design of compact, high-performance devices.