Tangential direction conductivity

In the literamre, AC impedance spectroscopy has been widely used for ex situ measurements of the tangential direction conductivity (TDC) [48-50], normal... 

Figure 9.21 shows the diffusion coefficients of H3O+ from MD simulations (a) variation of temperature, (b) variation of water content, (c) variation of temperature and water content, (d) proton conductivity of experimental data, ° (e) MSD average of H3O+ in 5% wt of Krytox-Silica in Nation system, and (f) MSD average of in pure Naflon system. The H3O+ diffusion coefficients as a function of temperature at 100% water molecules (Figure 9.21a) showed that the hydronium ions mobility increases at high temperature, which is consistent with the tangential direction conductivities of Nation, with 91 and 102 mS cm at 25°C and 30°C, respectively. ... 

Heat transfer inside the wood solid depend on its thermal conductivity. This property is anisotropic and increases with the density, the moisture content and the temperature [10-13], The thermal conductivity is higher in the longitudinal direction than in the radial and tangential directions from 1.8 [12] to 2.5 [14, 15]. 

Beginning right at the sphere surface, heat is transferred radially outward by conduction. However, because Pe is large, very small convection velocities can overwhelm thermal conduction, and the heat transfer process becomes convection dominated at a very short distance from the sphere surface. Thus, before the heat released from the sphere can propagate very far outward in the radial direction, it is swept around the sphere and downstream into a wake. Very near the sphere surface where convection comes into play, the dominant velocity component is in the tangential direction. As a result, the region of heated fluid... 

The specific gravity and moisture content dependence of the solid wood thermal conductivity in the transverse (radial and tangential) direction is given by Siau [45] as ... 

The thermal conductivity of wood is affected by a number of basic factors density, moisture content, extractive content, grain direction, structural irregularities such as checks and knots, fibril angle, and temperature. Thermal conductivity increases as density, moisture content, temperature, or extractive content of the wood increases. Thermal conductivity is nearly the same in the radial and tangential directions with respect to the growth rings. 

Boron nitride in the hot-pressed state is easily machinable and may be formed into various shapes. The properties are highly anisotropic and vary considerably in the normal and tangential directions of the pressing force. The thermal conductivity in the normal direction is very high and the TCE is very low, making BN an attractive possibility for a substrate material. However, it has not yet been proved possible to metallize BN, and the range of applications is therefore limited. It can be used in contact with various metals, including, copper, tin, and aluminum, and may be used as a thermally conductive electrical insulator. Applications of BN include microwave tubes and crucibles. 

In this case study we assiune a constant even flow and concentration at the inlet and only consider steady state. However, the concentration will have a radial variation downstream due to the reaction and the radial difference in residence time. Assuming an even inflow and a minor effect of gravity in the radial and tangential directions, the convective radial transport terms can be removed. Axial viscous transport, diffusion, and conduction can also be neglected because the convective axial transport is much larger. After a sufficiently long period of time, the transient terms become very small, and we obtain a model with steady axial convection, radial diffusion, and conduction with a reaction soiuce term. 

In these equations x and y denote independent spatial coordinates T, the temperature Tib, the mass fraction of the species p, the pressure u and v the tangential and the transverse components of the velocity, respectively p, the mass density Wk, the molecular weight of the species W, the mean molecular weight of the mixture R, the universal gas constant A, the thermal conductivity of the mixture Cp, the constant pressure heat capacity of the mixture Cp, the constant pressure heat capacity of the species Wk, the molar rate of production of the k species per unit volume hk, the speciflc enthalpy of the species p the viscosity of the mixture and the diffusion velocity of the A species in the y direction. The free stream tangential and transverse velocities at the edge of the boundaiy layer are given by = ax and Vg = —ay, respectively, where a is the strain rate. The strain rate is a measure of the stretch in the flame due to the imposed flow. The form of the chemical production rates and the diffusion velocities can be found in (7-8). 

Membrane operations are conducted either in a direct flow filtration (also called dead end) mode or in a tangential flow filtration (TFF) mode. Direct flow filtration is simple and easy to implement but has limited capacity for applications with high-solid mass. TFF is capable of processing large-solid masses but is more complex and capital intensive. 

With the walls, the potential at M is a superposition of the direct term from 0 and of image terms, from the points A,A, B,B, etc. These image sources ensure that the correct boundary conditions (no tangential component of electric field) are obeyed on the two conducting walls. 

Another hot research topic about the PFSA proton conductivity is about the direction of the conductivity. There are two kinds of proton conductivity tangential/ in-plane conductivity and normal/through-plane conductivity. Commonly, proton conductivity is measured along the plane of the membrane, since the measurement of the conductivity in the in-plane direction is much easier to carry out with higher stability, reproducibility, and accuracy. However, in practice, the membrane requires proton conduction perpendicular to the manbrane. So, through-plane conductivity of the membrane may have significant effect on the performance of fuel cells. 

---