An experimental investigation on fluid flow and heat transfer of rough mini-channel with rectangular cross section

•Heat transfer and fluid flow characteristics were experimentally tested through rough mini-channels.•The rough mini-channel has more influences on the friction factor for the laminar flow.•Heat transfer enhancement with increase of roughness surface.•New correlation of the universal evaluation parameter, PEC, was obtained.

In this study, experimental investigation has been conducted on fluid flow and heat transfer of rough mini-channels with rectangular cross sections. The mini-channel considered consists of twelve identical rectangular channels with 4 mm width, 8 mm height, and 80 mm length. Air is employed as the working fluid with Reynolds number varied from 1500 to 5000. Four mini-channels were examined with different values of relative surface roughness (ɛ) 1.6 ∗ 10−4, 3.45 ∗ 10−4, 6.15 ∗ 10−4, and 10.5 ∗ 10−4. The friction factor (f), average Nusselt number (Nu), pressure drop penalty factor (Ef), heat transfer enhancement factor (Ehn), and universal evaluation parameter (PEC) were evaluated to study fluid flow and heat transfer of rough mini-channels with rectangular cross sections.The results showed that increasing the Reynolds number (Re) of air passing through the rectangular rough mini-channel, increases the average Nusselt number (Nu) and the pressure drop penalty factor (Ef), while decreasing the friction factor (f) and the heat transfer enhancement factor (Ehn) which, has a great effect on the universal evaluation parameter (PEC) rather than the pressure drop penalty factor (Ef). Moreover, a correlation of the relative surface roughness (ε) and the universal evaluation parameter (PEC) was obtained.