Forced Convection Nanofluid Heat Transfer as a Function of Distance in Microchannels

Abstract

As electronic devices become smaller and more powerful, the demand for micro-scale thermal management becomes necessary in achieving a more compact design. One way to do that is enhancing the forced convection heat transfer by adding nanoparticles into the base liquid. In this study, the nanofluid forced convection heat transfer coefficient was measured inside stainless-steel microchannels (ID = 210 μm) and heat transfer coefficient as a function of distance was measured to explore the effects of base liquid, crystal phase, nanoparticle material, and size on heat transfer coefficient. It was found that crystal phase, characteristics of nanoparticles, the thermal conductivity and viscosity of nanofluid can play a significant role on heat transfer coefficient. In addition, the effects of man-made and commercial TiO2 on heat transfer coefficient were investigated and it was found that man-made anatase TiO2 nanoparticles were more effective to enhance the heat transfer coefficient, for given conditions. This study also conducted a brief literature review on nanofluid forced convection heat transfer to investigate how nanofluid heat transfer coefficient as a function of distance would be affected by effective parameters such as base liquid, flow regime, concentration, and the characteristics of nanoparticles (material and size).

Heat Transfer Enhancement in the Microscale: Optimization of Fluid Flow

“…The standard deviations for each point were found to be very small in comparison to the value of the heat transfer coefficient, so the average value was taken without use of error bars. Similar results were found by Rea et al [ 51 ] and Vafaei et al [ 29 ].…”

“…Looking at literature examined [ 50 ] and our previous experiences [ 29 ], it was found that Fe 3 O 4 -water nanofluid would work best in the present experiment. The experiment was conducted using 99.5% pure Fe 3 O 4 nanoparticles purchased from US Research Nanomaterials, Inc, Houston, TX, USA.…”

“…The characteristics and concentration of nanoparticles have significant effects on the heat transfer properties of the resulting nanofluid, including the thermal conductivity, viscosity, and heat transfer coefficient [ 29 ]. As shown in Figure 1 , nanoparticle inclusion tends to increase the thermal conductivity relative to the base fluid.…”

“…This trend was found to hold for nanofluids of varying base fluid and nanoparticle materials with varying effectiveness, but it was observed that the thermal conductivity may decrease at high enough concentrations. This may be due to particle agglomeration at high concentrations [ 29 ]. It was found that that base fluids with higher thermal conductivities caused nanofluids with higher thermal conductivities.…”

“…However, Kwek et al [ 28 ] also investigated the effect of changing nanoparticle size on Al 2 O 3 nanoparticles in water and found that the thermal conductivity can sometimes increase with increasing nanoparticle size, which may be caused by an increase in diffusive heat transfer. The effects of nanoparticles size were explained in reference [ 29 ] in detail.…”