Analysis of flow boiling resistance characteristics in confined microchannels under oscillatory vibration conditions

Microchannel heat exchangers find extensive applications across diverse sectors, including electronics cooling, aerospace engineering, and automotive industries, owing to their exceptional thermal efficiency, space-saving design, and lightweight construction. However, mechanical vibrations common in practical engineering expose them to a coupled thermal-vibration environment, significantly degrading internal fluid flow and heat transfer performance. Thus, studying flow boiling resistance in confined channels is critical for their safe operation. Experiments used a visualization system to study flow patterns and pressure drop in 2 × 3 mm multi-parallel channels under sinusoidal vibration. The experiment utilized R141b as the working fluid under vibrational conditions spanning frequencies of 0 to 21 Hz and amplitudes of 0 to 12 mm. Findings reveal that oscillating pressure variations generate alternating countercurrent and co-current flows in the gas-liquid mixture. Oscillatory vibrations amplify these fluctuations and increase such cycles. The vibrational frictional pressure drop rises with heat flux, amplitude, and frequency and rises sharply under high heat flux and large amplitude, while stable annular flow at medium frequency slows its growth. A pressure drop model for oscillatory vibration was built via the vibration effect ratio. This work offers key insights for microchannel heat exchanger stability under non-static conditions and provides a model for their design in vibration-prone environments.