New correlation of the subcooled flow boiling heat transfer coefficient for hybrid micro/nanostructured surfaces with high heat flux incidence

Abstract

Surfaces manipulated with micro/nanostructures have great potential for imparting high heat removal capacity to heat transfer equipment under high heat flux incidence. However, few correlations of heat transfer coefficients have been developed based on high-heat flux experiments of subcooled flow boiling with nano- and microstructured surfaces, which may limit the further application of this technique in industrial engineering. Aiming at recently developed hybrid micro/nanostructured surfaces for subcooled flow boiling performance enhancement, a series of experiments with different surface structure scale specifications, flow conditions, and heat flux incidence ranges were conducted. In total, 530 experimental data points were obtained with heat fluxes ranging from 3.4 to 13.1 MW/m2, pressures from 0.5 to 1.5 MPa, liquid velocities from 1 to 5 m/s, inlet temperatures from 303.15 to 323.15 K, and structured surfaces with wire apertures of 250, 125, and 58 μm. The 28 existing correlations based on smooth surfaces and structured surfaces failed to predict these experimental data. A new enhancement factor-type correlation model, which included four dimensionless numbers that specialized in the effects of the span dimension and depth dimension of the target hybrid micro/nanostructured surfaces, was developed and shown to have good prediction accuracy and a considerable degree of application adaptability, with a mean absolute deviation of 5.7%.