Prediction and analysis of thermal-hydraulic performance with slit fins in small diameter (3 mm to 4 mm) heat exchangers

Abstract

The simulation model describes the thermal-hydraulic performance and is verified well by comparing with the experimental data. The 122 runs taking 7 geometric parameters and Reynolds number into account are carried out based on the Response Surface Methodology (RSM). The correlations of the heat transfer (j-factor) and flow friction (f-factor and Eu-number) in 3 mm diameter are proposed. The mean deviations of the correlations with j-factor, f-factor and Eu-number are 3.78%, 2.56% and 2.51% respectively. The effects of 7 geometric parameters are investigated using the RSM model in detail at Re = 500, and it can be found that the height of the slit (Sh) has the greatest influence on j-factor. The differences in the change rate of f-factor and Eu-number are emphatically analyzed. And the effects of the transverse tube pitch (Pt) on f-factor and Eu-number are opposite. The f-factor is positively correlated with Pt, while the Eu-number is negatively correlated with Pt. In addition, the coefficients of correction for j-factor, f-factor and Eu-number are obtained to make available for different collar diameters. In the range of 3.19–4.19 mm collar diameter, the mean deviations of the modified correlations including j-factor, f-factor and Eu-number are 6.24%, 5.46%, and 4.26% respectively.