An innovative design of a high strength and low weight sudden micro expansion by considering a nanofluid: Electronic cooling application

The present study has been numerically surveyed the effect of different expansion angles on the heat transfer and pressure drop characteristics of a sudden expansion in a microtube. For this purpose, Cu/water nanofluids flowing with Reynolds numbers (Re) of 10, 25, 50, and 100 through expansion angles of 30 degrees, 45 degrees, 60 degrees, and 90 degrees were modeled. Governing equations were solved by the finite volume method (FVM). The findings indicated that the heat transfer coefficient (HTC) could enhance by nanoparticles concentration and Re augmentation. Also, It was revealed that HTC of a sudden expansion with an angle of 45 degrees has optimum hydrodynamic performance; then, sudden expansions of 30 degrees, 90 degrees, and 60 degrees are followed. The highest HTC was achieved for a microtube containing 4 vol% nanofluids at Re = 100 with a 45 degrees expansion angle, 43.63% higher than conventional expansion angle (90 degrees) working with distilled water at Re = 10 degrees By comparing HTC at various angles, it can be found that there is a 14.57% further HTC by changing the expansion angle from alpha = 90 degrees with alpha = 45 degrees. Furthermore, the pressure drop investigation showed that the expansion angle with alpha = 30 degrees has the lowest pressure drop. In contrast, alpha = 45 degrees produced the highest pressure drop because of giant vortices created along the tube wall. The velocity streamlines and contours explained the reason for a lower pressure drop of alpha = 30 degrees, 45 degrees, and 60 degrees which was regular streamlines along the tube wall due to the Coanda effect.

Automated summary

This study numerically investigated the effects of different expansion angles on heat transfer and pressure drop characteristics in a microtube sudden expansion. The findings showed that a sudden expansion with a 45-degree angle had the optimum hydrodynamic performance while a 30-degree angle resulted in the lowest pressure drop.