Experimental study of convective heat transfer coefficient of MgO nanofluid in a cylindrical microchannel heat sink

Convective heat transfer of MgO-water nanofluid in a microchannel heat sink is experimentally investigated in various concentrations of ۰.۰۱, ۰.۰۵, ۰.۱, and ۰.۶ wt%. The microchannel consisted of ۴۸ parallel rectangular cross section channels with the height of ۸۰۰ µm, width of ۵۲۴ µm and length of ۵۲ mm. A well stability duration (ca. ۱ month) was resulted by a ۱۸۰ min ultra-sonication of the MgO suspension. The experiments in the microchannel were then performed in a flow rate range of ۰.۵ to ۲.۲ l/min while the inlet temperature and heat flux were constant. The results indicated that using the MgO nanofluid in low flow rates and concentration has less effect in improving the heat transfer coefficient, while it becomes highly efficient by the simultaneous increase of flow rate and concentration. An enhancement of ۱۶۲.۳% in convective heat transfer coefficient at the channel inlet was achieved at the concentration of ۰.۶ wt% and the flow rate of ۲.۲ l/min. The average Nusselt number also increased at the mentioned condition up to ۵۲.۸%. However, the nanofluid at ۰.۱ wt% was more efficient compared to the other concentrations in increasing Nu at higher Re.

Keywords:

Convective heat transfer coefficient , Microchannel heat sink , MgO nanofluid , stability