Alexander S. Lobasov

Measurement of the heat transfer coefficient of a nanofluid based on water and copper oxide particles in a cylindrical channel

The heat transfer coefficient of a nanofluid in a cylindrical channel under constant heat flux density at the walls is measured experimentally. The studied fluid was prepared based on distilled water and CuO nanoparticles with an average size of 55 nm. To stabilize the nanofluid, a biopolymer was used. The volume concentration of nanoparticles was in the range from 0.25 to 2%. It is shown that the nanofluid is Newtonian at the lowest concentration of nanoparticles, and in all other cases, its rheology is described well by the model of a power-law fluid. A correlation of the dependence of the parameters of this model on the concentration of nanoparticles is obtained. It is found that the presence of nanoparticles greatly intensifies the heat transfer.

Experiment-Calculated Investigation of the Forced Convection of Nanofluids Using Single Fluid Approach

An experiment-calculated investigation of forced convection of nanofluids based on Al2O3 nanoparticles was carried out. The hydrodynamic description and a model of homogeneous nanofluids were used. The homogeneous nanofluids model assumes that the hydrodynamics and heat transfer can be described by conventional Navier-Stokes and heat transfer equations with the physical parameters corresponding to nanofluids. The results showed that this model very well described the experimental data in some cases. However, in some other cases, there are discrepancies between experiment and theory that can be explained by the real heterogeneity of nanofluids and the errors in the experimental determination of thermal conductivity and viscosity of nanofluids.

Flow Modes of Non-Newtonian Fluids with Power-Law Rheology in a T-Shaped Micromixer

The flow and mixing modes of non-Newtonian fluids in a T-shaped micromixer were studied by numerical simulation in the range of Reynolds numbers 1–250. The non-Newtonian fluid was described using the power-law model. The exponent n was varied: 0.3, 0.5, and 0.8. The mixing efficiency and pressure drop in the channel were correlated with the exponent n and Reynolds number. The exponent n was shown to significantly affect the flow structure before and especially after the transition from symmetric to asymmetric flow modes.

INVESTIGATION OF MIXING EFFICIENCY AND PRESSURE DROP IN T-SHAPED MICROMIXERS

Abstract The numerical investigation of the flow regimes in the T-shaped microchannels with different width-to-height aspect ratios of mixing channel was carried out. In the first case, the mixing channel width was varied from 200 μm to 1000 μm while its height was constant; in the second case, the mixing channel height was varied from 100 μm to 2000 μm, while its width was constant. The Reynolds number was varied from 5 to 700. The dependences of fluids mixing efficiency and the pressure drop on the Reynolds number at different width-to-height aspect ratios of mixing channel were numerically established. The correlations to determine the critical Reynolds number, as well as the friction factor at different widths and heights of the mixing channel, were proposed. The mixing efficiency, reduced to the pressure drop and the volume unit was analyzed for the first time. The optimal range of parameters in terms of the working efficiency of the micromixer was determined.