A study was made of the coking of a commercial fresh sulfide Ni-Mo/Al2O3 catalyst in a fixed-bed reactor. The catalyst was coked using different coke precursors in the gas oil under accelerated conditions at temperatures of 400 to 450°C to yield different deactivated catalysts containing 2-20 wt% C. Two cases were studied; crushed catalyst without diffusional ...

This paper presents a comprehensive and exclusive thermodynamic analysis of counter flow heat exchanger under various operating and geometrical conditions. Analysis system (ANSYS) workbench 14.0 has been used for computational analysis and comparison with previous literature has been carried out in view of variable temperature and mass flow rate of hot and cold fluids. An analytical and statist...

The induced transient viscous flow due to a suddenly stretched surface is studied. After a similarity transform, the unsteady Navier–Stokes equation is solved by several methods, including perturbation for small times, numerical integration, and asymptotic analysis for large times. It is found that the validity of the small-time series can be greatly extended and the approach to steady state is...

Correlated velocity models (CVMs) have proven themselves to be effective tools for describing a wide range of solute transport behaviors in heterogeneous porous media. In particular, spatial Markov (SMMs) are class CVMs where subsequent Lagrangian velocities along trajectories depend only on the current velocity, and not past history. Such provide powerful tool modeling terms limited number flo...

Darcy’s law is the basic of flow, and it produces a partial differential equation similar to heat transfer when coupled with an continuity that explains conservation fluid mass during flow through porous media. This article, titled groundwater equation, covers derivation equations in both steady transient states. We look at some most common approaches methods for developing analytical or numeri...

Measurements of the time-varying flow in a centrifugal blood pump operating as a left ventricular assist device (LVAD) are presented. This includes changes in both the pump flow rate as a function of the left ventricle contraction and the interaction of the rotating impeller and fixed exit volute. When operating with a pulsing ventricle, the flow rate through the LVAD varies from 0-11 L/min dur...

Application of nonlinearity continuation method to numerical solution steady-state groundwater flow in variably saturated conditions is presented. In order solve the system nonlinear equations obtained by finite volume discretization Richards equation, a series problems with increasing are solved using Newton method. This approach compared pseudo-transient on several test cases, including real ...

An analysis of the effect of flow on 2D fully balanced steady state free precession (SSFP) imaging is presented. Transient and steady-state SSFP signal intensities in the presence of steady and pulsatile flow were simulated using a matrix formalism based on the Bloch equations. Various through-plane flow waveforms and rates were modeled numerically considering factors such as the excitation sli...

hydraulic simulation of water flow in irrigation canals may reveal management shortcomings and help managers find solutions to them. hydraulic simulation models can be appropriate tools for understanding hydraulic behavior of irrigation systems. in the present study, the steady state hec-ras model was tested and compared with the mike 11 unsteady state model. a secondary irrigation canal in the...

An asymptotic treatment of thin accretion disks, introduced by Kluźniak & Kita (2000) for a steady-state disk flow, is extended to a time-dependent problem. Transient growth of axisymmetric disturbances is analytically shown to occur on the global disk scale. The implications of this result on the theory of hydrodynamical thin accretion disks, as well as future prospects, are discussed.