Search

A computational study of cooling in-line array of heated obstacles simulating electronic components by jet impingement in cross-flow (JICF) has been investigated using RNG k - ε turbulence model. The jet position has been changed to impinge each obstacle consecutively at different jet-to-channel Reynolds number ratios, Re j / Re c = 1, 2, and 4. The main flow structure, the static pressure, local and average Nusselt numbers as well as the thermal enhancement factor have been investigated. The results show that there is a significant variation between the flow structures around an obstacle when subjected to JICF or CF. The friction factor for JICF is greater than that for cross-flow only (CF) by 88% at the first jet position and Re j / Re c = 4. The irregular distribution of local Nusselt number ( Nu ) on the impinged obstacle is moderated by increasing the Reynolds number ratios. Increasing Reynolds number ratio increases the average Nusselt number ( Nu ‾ ) of the downstream obstacles and decreases it for the upstream obstacles. The increment of Nu ‾ for whole array for JICF than CF is about 26% at JP3 and Re j / Re c = 4. Moreover, the highest value of thermal enhancement factor is attained at JP3 and it equals 12% for Re j / Re c = 4. [ABSTRACT FROM AUTHOR]

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 ( E f ), heat transfer enhancement factor ( E hn ), 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 ( E f ), while decreasing the friction factor ( f ) and the heat transfer enhancement factor ( E hn ) which, has a great effect on the universal evaluation parameter (PEC) rather than the pressure drop penalty factor ( E f ). Moreover, a correlation of the relative surface roughness ( ε ) and the universal evaluation parameter (PEC) was obtained. [ABSTRACT FROM AUTHOR]