Numerical Study and Comparison of Passive Mixing in Helical Micromixers

A passive mixing inside three micromixers has been studied with water as the mixing fluid. Since the mixing at the micro-level is governed by species diffusion hence it is a time-consuming process that requires an extended length of micromixer for the required amount of mixing. The present study tackles this problem by introducing two helical micromixers, a Three-dimensional helical micromixer (TDHM), and TDHM having four inlets (TDHM-FO). These micromixers need a reduced length of mixing channel while still providing greater efficiency than a simple T-micromixer (STM). A detailed
analysis is being presented to analyse the mixing process and performance. Several other parameters have been calculated and presented in this study along with the efficacious Reynolds number. Both the helical micromixers performed better than simple T-micromixer for all values of Reynolds numbers. For low Reynolds numbers (Re≤75), TDHM-FO is better. TDHM provides the best results
for Re=310 and 400 which is even better than TDHM-FO and the mixing efficiency for TDHM and TDHM-FO is much better than STM for all ranges of Reynolds numbers. It is concluded that both the helical micromixers provide much better efficiency that too with less mixing length compared to STM. While examining a fluid flow, pressure drop becomes an important parameter to study because it indicates about the amount of energy required to make the fluid flow. Higher the mixing, higher will be the pressure drop and hence more pumping power is needed to drive the flow. Among all three micromixers, STM showed the least value of pressure drop while TDHM-FO showed the highest.