Investigation on the thermohydraulic performance and entropy-generation of novel butterfly-wing vortex generator in a rectangular microchannel

Abstract

• A new butterfly-wing vortex generator is introduced on the bottom wall of microchannel. • Thermohydraulic performance and entropy-generation in microchannel are investigated. • The maximum Pf of 1.23 and minimum N s , a of 0.84 are obtained . • The proposed microchannel is advantageous according 1 st & 2 nd law of thermodynamics. In the present study, a 3D numerical analysis is carried out to understand the effect of the butterfly-wing vortex generator on the thermohydraulic performance and entropy-generation in a rectangular microchannel. To validate the numerical model, experiments are carried out in the plain microchannel of width ( W ) = 1 mm, height ( H ) = 0.63 mm, and length ( L ) = 50 mm. Further, the simulation is extended to study the effect of several geometric parameters of the butterfly-wing vortex generator, i.e., height ( h ) = 0.05, 0.1 & 0.2 mm, bigger width ( w ) = 0.24, 0.36 & 0.48 mm, smaller width ( b ) = 0.12, 0.18 & 0.24 mm, length ( l ) = 1, 2 & 3 mm, and number of wings ( n ) = 5, 8 & 11 with varying Reynolds number ( R e ) in the range of 142 to 945. Thus, a total of tweleve different combination of microchannel are formed by varying the geometric parameters of the butterfly-wing to carry out the parametric study. The simulation results reveal that the presence of the butterfly-wing vortex generator enhances the convective heat transfer rate (10-26)% with an increase in pressure drop (3-14)%, and reduces the total entropy-generation (3-16)% when compared to a plain microchannel. It is also found that with an increase in h, n, and w, the friction factor ( f ) increases (7-13)%, (3-8)% and (1-9)%, respectively,while the average Nusselt number ( Nu avg ) increases (4-11)%, (4-9)%, and (5-12)%, respectively, by increasing Re value from 142 to 945. However, the l has no significant effect on f and Nu avg . A decreasing trend of Nu avg is seen for increasing b, whereas f does not vary significantly with b . The total entropy generation ( S G ) decreasing with the increase in h , n , and w and remain invariant for b and l . For the studied geometric parameters and Re values, the maximum increase in performance of 23% and a maximum reduction in total entropy-generation of 16% are obtained for the microchannel with butterfly-wing of w = 0.48 mm, b = 0.24 mm, l = 3 mm, h = 0.1 mm, n = 5 at Re = 945.