Mixed Convection From an Isothermal Rough Plate

TL;DR

This paper develops formulas to predict heat transfer from an isotropic rough plate in mixed convection, validated with extensive experimental data showing high accuracy across various orientations and flow conditions.

Contribution

The study introduces new predictive formulas for mixed convective heat transfer from rough surfaces, validated against a large dataset with low error margins.

Findings

Formulas predict heat transfer with RMSRE between 1.3% and 6.5%.

Experimental validation covers multiple orientations and flow velocities.

High accuracy demonstrated across diverse rough surface configurations.

Abstract

This investigation derives formulas to predict the mixed convective surface conductance of a flat isotropic surface roughness having a convex perimeter in a Newtonian fluid with a steady forced flow in the plane of that roughness. Heat transfer measurements of a 30.5 cm square rough plate with forced air velocities between 0.1 m/s and 2.5 m/s were made by the present apparatus in two inclined and all five orthogonal orientations. The present work's formulas are compared with 104 measurements in twelve data-sets. The twelve data-sets have root-mean-square relative error (RMSRE) values between 1.3% and 4% relative to the present theory. The present work's formulas are also compared with 78 measurements in 28 data-sets on five vertical rough surfaces in horizontal flow from Rowley, Algren, and Blackshaw (1930). The five stucco data-sets have RMSRE values between 2.5% and 6.5%; the other data-sets have RMSRE values between 0.2% and 5%.