Investigation On Enhanced Heat Transfer Of Nanofluids And Mathematical Model

Nanofluids is a multiphase system that nanoparticles is dispersed in base liquid stably. Due to the nanofluids in viscosity, specific heat, thermal conductivity, heat capacity and other characteristics of nanofluids are quite different from traditional liquids,It can be used as a more efficient heat transfer and cooling system.To improve the engine more efficiency, exhaust gas and reduce fuel consumption, to accelerate the compact cooling system, light-weighted cooling system and raise engine heat efficient.The purpose of this paper is to nano-Mg O powders experiment, the preparation of nanofluids and the choice of the dispersants experiment, nano-Mg O in propylene glycol scattered on the stability of the research, the research of nanometer fluid transportation parameters, heat transfer performance of nanofluids and the mathematical model of nanofluids studies several aspects, study Mg O/propylene glycol nanofluids suspension stability of the fluid strengthen heat transfer mechanism and performance are discussed.The main works are as follows:1 Experiment of preparation of nano-Mg O powdersIn different liquid phase chemical preparation of nano-Mg O powders, familiar with the process of preparation, preparation technology.2 Experiment of preparation of nanofluids and dispersant selectionThrough the nano-Mg O powders directly mixed with propylene glycol directly "two-step" preparation of nano-Mg O /propanediol fluid;By adopting the method of ultrasonic vibration, mechanical mixing and sedimentation test optimization selecting make Mg O /propanediol nanofluids stable suspension of dispersant.3 Dispersion and stability of Nano-Mg O powders in propylene glycolBy the method of ball mill modification with coupling agent modification nanoMg O powders, thus increasing suspension dispersion stability;And experimental analysis of the ultrasonic vibration, mechanical mixing, dispersing agent and other factors on the nanofluids, the influence of nano-Mg O powders best dispersion process in propylene glycol.From the Angle of the particle sedimentation and diffusion mechanism through theoretical analysis on the stability of nanofluids, came to the conclusion that in order to make the nanoparticles in liquid medium and long-term stability, we must can make the surface of the nanoparticles with smaller and larger diffusion rate and potential energy of the high and low between nanoparticles have important influence on the stability of the nanofluids, the lower the total potential energy, the greater the stability of the nanofluids.4 Transport properties of nanofluidsPower flow method is developed fluid heat capacity of the unit, under different temperature was measured by different concentrations of Mg O/propylene glycol, the specific heat of the nanofluids found fluid heat capacity gain characteristic with temperature changes.Measured by NDJ-8 digital viscosimeter the Mg O/propylene glycol nano fluid viscosity, the experimental results show that the particles of the share, base fluid properties, temperature, and the stability of the suspension has important influence on the viscosity of nanofluids.5 Heat transfer characteristics of nanofluidsDetermination of propylene glycol base is the natural convection heat transfer coefficient of nanofluids, design and assembling nanofluids can be used to measure the thermal conductivity of the transient hot wire method for measuring device, the measurement of different coefficient of thermal conductivity of nanofluids, combined with the experimental results the specificity and the principles of heat transfer enhancement nanofluids.6 Mathematical model of nanofluidsIntroduction of the fractal dimension in descripting the cluster of nanoparticles, and analyze the microcosmic structure of nanoparticles, to modify the traditional H-C model, deduce a predicted low concentration model of thermal conductivity of nanofluids coefficient of thermal conductivity.By studying the influence of temperature and concentration on the viscosity, deduced the viscosity calculation model about the temperature and the concentration factors.