Accumulation and distribution of higher hydrocarbons in the pores of a cobalt catalyst during low-temperature Fischer-Tropsch fixed-bed synthesis

During low-temperature Fischer-Tropsch synthesis (FTS), the catalyst pores are filled with liquid hydrocarbons. In a fixed-bed reactor, axial concentration gradients are present in the gas phase (CO, H2, evaporated hydrocarbons...

Modeling the Device Behavior of Biological and Synthetic Nanopores with Reduced Models

Biological ion channels and synthetic nanopores are responsible for passive transport of ions through a membrane between two compartments. Modeling these ionic currents is especially amenable to reduced models because the device functions of these pores, the relation of input parameters (e.g., applied voltage, bath concentrations) and output parameters (e.g., current, rectification, selectivity), are well defined. Reduced models focus on the physics that produces the device functions (i.e., the physics of how inputs become outputs) rather than the atomic/molecular-scale physics inside the pore. Here, we propose four rules of thumb for constructing good reduced models of ion channels and nanopores. They are about (1) the importance of the axial concentration profiles, (2) the importance of the pore charges, (3) choosing the right explicit degrees of freedom, and (4) creating the proper response functions. We provide examples for how each rule of thumb helps in creating a reduced model of device behavior.

Numerical simulations of blood cell flow in non-Newtonian fluid

We investigated how non-Newtonian viscosity behavior affects the flow characteristics of blood cells. Our findings offer insight about how shear thinning affects the dispersion of liposome-encapsulated hemoglobin and red blood cells in blood. The lattice Boltzmann method was used for fluid calculations, and the rheological properties of the non-Newtonian fluid were modeled with power-law relationships. The deformable three-dimensional red blood cell model was applied. First, we investigated the effects of shear thinning on the flow behavior of single blood cell. Simulation results indicate that shear thinning promotes the axial concentration of red blood cells. Next, varied the hematocrit to see how mutual interference between blood cells affects flow. At low hematocrit, shear thinning clearly promotes the axial concentration of red blood cells. As the hematocrit increases, in contrast, mutual interference has a greater effect, which counteracts shear thinning so the red blood cell distribution resembles the distribution within a Newtonian fluid.

Effect of Prandtl Number in Turbulent Buoyant Jet Simulation

Turbulent Prandtl number used in numerical simulation has effect on exact prediction of velocity and heat transferring with two dimensional buoyant mathematical models. Various Prandtl number values advised by experiments are used to study its effect on numerical results approaching to real ones with model under axisymmetric coordinate. It shows that axial velocities can’t be affected by using various values of of Prandtl number in numerical simulations and can be predicted well. However, it affects the exact prediction of axial concentration to extent, and a smaller value of Prandtl number tends to forecast a smaller axial concentration than real one, and vice versa. A reasonable range of turbulent Prandtl number for various Reynold numbers was suggested.

Performance of Canola Methyl Ester Biofuel in a Partial Swirl Spray Flame Combustor

The performance of canola methyl ester (CME) biofuel in a partial swirl spray flame combustor is compared to that of No. 2 diesel fuel in this paper. The spray flame was enclosed in an optically accessible combustor and operated at atmospheric pressure with a co-flow of heated air. Fuel was delivered through a swirl-type air-blast atomizer with an injector diameter of 300 microns. A two-component phase Doppler particle analyzer was used to measure the spray droplet size, axial and radial velocity distributions. Radial and axial concentration measurements of NO, CO, CO2 and O2 were made in the flame environment. Axial and radial flame temperature measurements were made using a Type R thermocouple. The volumetric flow rates of fuel, atomization air and co-flow air were kept constant for both fuels. The droplet SMD at the nozzle exit for CME biofuel are smaller than the No. 2 diesel fuel implying faster vaporization rates for the CME biofuel. Flame temperature decreases more rapidly for the CME biofuel than for the No. 2 diesel fuel in both axial and radial directions. CME biofuel produced lower in-flame NO and CO peak concentrations than No. 2 diesel fuel.