this paper presents a three-dimensional numerical investigation carried out in turbulent forced convection in a tube with helical ribs. enhancement of heat transfer using helically corrugated tubes has beenstudied experimentally by many researchers but there exist a few published numerical analyses results. the paper also introduces the results of heat transfer and friction factor data for inco...

A three-dimensional numerical simulation of flow through serpentine microchannels with designed roughness in form of obstructions placed along the channels walls is conducted here. CFD-ACE+ is used for the numerical simulations. The effect of the roughness height (surface roughness), geometry, Reynolds number on the friction factor is investigated. It is found that the friction factor increases...

In order to increase the efficiency of the conveyance of the granular solids, a new experimental set-up is designed. The test rig has longitudinal trapezoidal slots in its conveying pipes. Through experimentation, a correlation for friction factor in terms of solid mass flow rate, fluid flow rate and Froude number is presented. It is shown that the mixture friction factor for pipes with inn...

Deformation of the material during cyclic expansion extrusion (CEE) is investigated using upper-bound theorem. The analytical approximation of forming loads agrees very well with the FEM results for different amounts of chamber diameter, friction factor and also for lower die angles. However, the difference between analytical and numerical solution increases at higher die angles which are expla...

Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In these cases, adopting a constant friction factor for the lubricant-surface pair may not be a valid ass...

This paper develops a model to assess the quantitative effect of entry cost and financial friction on cross-country income and total factor productivity (TFP) differences. The main focus is on the interaction between entry cost and financial friction. The model is calibrated to match establishment-level statistics for the U.S. economy assuming a perfect financial market. The quantitative analys...

The major losses of fluid flow in plastic pipes due to friction are usually few or negligible some cases, and this is the assumption that value factor small (small roughness). This work aimed estimate vs Reynolds number compared against previous data, was estimated using an experimental model consisting a polypropylene pipe with nominal outside diameter 16mm length 8.5 meter eighteen elbows con...

in this paper, the rolling force and reduction ratio have been investigated in multilayer strip rolling. for this purpose, two different set of multilayers have been selected which are al/st/al and cu/al/cu layouts. at first, the validation of the numerical analysis was performed by using an experimental test. after validation of the numerical results, two set of multilayer layouts were simulat...

The friction of surfaces moving relative to each other must derive from the atomic interaction at interfaces. However, recent experiments bring into question the fundamental understanding of this phenomenon. The analytic theories predict that most perfect clean incommensurate interfaces would produce no static friction, whereas commensurate aligned surfaces would have very high friction. In con...

We have studied friction and dissipation in single and bilayer graphene films grown epitaxially on SiC. The friction on SiC is greatly reduced by a single layer of graphene and reduced by another factor of 2 on bilayer graphene. The friction contrast between single and bilayer graphene arises from a dramatic difference in electron-phonon coupling, which we discovered by means of angle-resolved ...