A study on fluid flow and heat transfer in rectangular microchannels with various longitudinal vortex generators

Based on our previous study, experiments were conducted to explore frictional pressure drop and heat transfer performance of de-ionized water flowing through rectangular microchannels having longitudinal vortex generators (LVGs). The experimental investigation was conducted under three-sided constant wall temperature boundary condition for the Reynolds numbers ranging from 350 to 1500 for LVGs with different number of pairs and dimensions. The aspect ratios of rectangular microchannels were 0.25 and 0.0667, and the corresponding hydraulic diameters were 160 μm and 187.5 μm, respectively. The heights of associated LVGs were 1/4H, 3/4H and H, respectively, where H was the height of microchannel. It was found that heat transfer performance was enhanced by 12.3–73.8% and 3.4–45.4% for microchannels with aspect ratios of 0.0667 and 0.25, respectively, while the pressure losses were increased by 40.3–158.6% and 6.5–47.7%, respectively; and the overall heat transfer performances of some specific microchannels were more than 1 in our study. With the help of LVGs, the critical Reynolds numbers were lower than 1000, which were smaller than the generally accepted value of 2300 for regular channel flow.