ANALYSIS OF THE THERMOPHYSICAL PARAMETERS OF MOIST WOOD PARTICLE MATERIAL IN A COUPLED HEAT AND MASS TRANSFER PROCESS OF FREEZING BY USING FINITE ELEMENT METHOD

The coupled heat and moisture transfer in a freezing process of wood particle material was mathematically modeled in the paper. The models were interactively solved by using the numerical method(the finite element method and the finite difference method). By matching the theoretical calculation to an experiment, the nonlinear problem was analyzed and the variable thermophysical parameters concerned was evaluated. The analysis procedure and the evaluation of the parameters were presented in detail. The result of the study showed that by using the method as described in the paper, it was possible to determine the variable (with respect to temperature, moisture content and freezing state) thermophysical parameters which were unknown or difficult to measure as long as the governing equations for a considered process were available. The method can significantly reduces the experiment efforts for determining thermophysical parameters which arc very complicated to measure. The determined variable of the effective heat conductivity of wood particle material was given in the paper. The error of the numerical calculation was also estimated by the comparison with a matched experiment.

Multiphysics of multifunctional nanofluids based on different oxides nanoparticles and glycerol fluid

Nanofluid(NF)materials consisting of glycerol(Gly)and different inorganic nano oxides(TiO_(2),ZnO,Al_(2)O_(3),and SiO_(2) for the oxides concentration of 0.01 wt%to the weight of Gly base fluid)were prepared by a two-step method through ultrasonic cavitation process.These nanofluids were investigated by employing an X-ray diffractometer(XRD),ultraviolet-visible(UV-Vis)spectrophotometer,20 Hz to 1 MHz frequency range dielectric relaxation spectroscopy(DRS),ultrasonic interferometer,and rotational viscometer.The multiphysics of these nanofluids includes structural and optical properties,dielectric permittivity,electrical conductivity,conductivity relaxation,ultrasound velocity,adiabatic compress-ibility,acoustic impedance,viscosity,density,thermal conductivity,and viscoacoustic relaxation were characterized.The XRD patterns identified monodispersed and stable suspensions of these different characteristic nanoparticles in the hydrogen-bonded 3D supramolecular structure of ultra-high viscous glycerol fluid which were supported by their UV-Vis absorbance analyses.The energy band gap values of the TiO_(2)and ZnO containing nanofluids were found primarily ruled by the characteristic optical prop-erties of these oxides nanomaterials.The complex dielectric and various electrical functions studied at 25℃revealed that the suspension of different oxide nanoparticles in the glycerol fluid increased the static permittivity whereas reduced the direct current electrical conductivity which showed strong conductivity relaxation process dependence.The rheological measurements of the formulated nanofluids were performed over a shear rate range of 0.4-40 s^(-1)at temperatures of 25-55℃.The linear rela-tionship between shear rate and shear stress and also the shear rate-independent viscosity revealed the Newtonian behaviour of these nanofluids.The shear viscosity non-linearly decreased with the increase of temperature and exhibited the Arrhenius behaviour for all different oxides containing Gly-based nanofluids.The acoustic parameters of the nanofluids were altered unevenly with types of nano ox-ides and inferred some structure-property correlations.The promising technologically useable properties of these nanofluids were expected to impact their potential applications in optoelectronics,UV-blocking,sensing,nanodielectrics,energy storing and electric insulation,heat transfer systems,and also in ma-terials processing for the development of innovative soft condensed devices.

Factors Affecting Temperature Distribution Along Thickness of Plate During Cooling Process and Their Control Strategies

On the basis of the finite difference method, the factors affecting the temperature distribution along the thickness of plate during cooling process were analyzed, which include transformation heat, coefficient of heat conduction, specific heat, carbon content, cooling time, plate thickness, and unit of water flow volume. To ensure the homogenous temperature distribution along the thickness of plate, some cooling strategies, such as interval cooling, stepped cooling, and unsymmetrical cooling of upper and lower surfaces, were applied online. The online results showed that the cooling strategies can improve the temperature homogeneity greatly and the finite difference method can correctly simulate the cooling process.