Effect Of Artificial Roughness Research Articles

Effect of Artificial Roughness on the Heat Transfer and Friction Characteristics of Solar Air Heater-A Review

Effect of Artificial Roughness on the Heat Transfer and Friction Characteristics of Solar Air Heater-A Review

Effect of artificial roughness on flow and heat transfer of transcritical methane

This study performed 3D steady-state simulations of the flow and heat transfer of transcritical methane in a rectangular channel with and without artificial roughness under asymmetric heating conditions. The effect of artificial roughness with different rib height and pitch on the results was analyzed. The simulation results demonstrate that the artificial roughness disturbs the flow field near the ribs severely. With the increase of the rib height, the temperature of the coolant near the bottom increases gradually due to enhanced heat transfer, which results in the core region of the flow moving towards the upper surface of the channel. In addition, the presence of artificial roughness smoothens the transcritical process, and deteriorates the hindrance of heat transfer between fluids due to the extreme value of specific heat near the pseudo-critical temperature. This suppresses the deterioration of heat transfer, reduces the peak wall temperature, and moves it downstream. However, the addition of artificial roughness can significantly increase the pressure loss, which can be further enhanced by increasing the rib height or reducing the rib pitch. The overall performance of artificial roughness is evaluated by the thermal performance factor, which takes both the heat transfer enhancement and pressure loss into consideration. Based on this parameter, the best comprehensive performance can be obtained for a rib height of 0.3 mm and a rib pitch of 5 mm under the cases adopted in this paper.

Mass transfer phenomenon in photocatalytic cascade disc reactor: Effects of artificial roughness and flow rate

Photocatalytic process is a green technology that has been widely used in textile wastewater treatment. Mass transfer phenomenon plays an important role in photoreactor with photocatalyst immobilized on surface. In this study, a novel photocatalytic cascade disc reactor coated with ZnO nanoparticles was first applied to investigate the effect of two influential parameters, i.e. artificial roughness and flow rate on photocatalysis degradation of Reactive Yellow 81 (RY81). Mass transfer coefficients were then determined to describe the effect of those parameters on photocatalytic process based on benzoic acid dissolution method. Fluid flow and concentration fields were simulated to explore the characteristics of mass transfer process with OpenFOAM software. Based on the experimental and simulation results, it was found that as artificial roughness and flow rate value increase, Reynolds number and consequently the first order reaction rate constant of RY81 and mass transfer coefficients significantly increase.

Effect of artificial roughness on heat transfer and friction characteristics having multiple arc shaped roughness element on the absorber plate

In this present experimental investigation the effect of geometrical parameters of multiple arc shaped roughness element on heat transfer and friction characteristics of rectangular duct solar air heater having roughness on the underside of the absorber plate have been studied. The parameters were selected on the basis of practical considerations and operating conditions of solar air heaters. The experiments carried out encompasses Reynolds number (Re) in the range of 2200–22,000, relative roughness height (e/D) range of 0.018–0.045, relative roughness width (W/w) ranges from 1 to 7, relative roughness pitch (p/e) range of 4–16 andarc angle (α) ranges from 30 to 75°. The thermo-hydraulic performance parameter was found to be best for relative roughness width (W/w) of 5.

人工粗度の配置が水面模様に与える影響

人工粗度の配置が水面模様に与える影響

Effect of artificial roughness on heat transfer and friction factor in a solar air heater

Convective heat transfer coefficient between absorber plate and air in a flat-plate solar air heater can be enhanced by providing the absorber plate with artificial roughness. An investigation of fully developed turbulent flow in a solar air heater duct with small diameter protrusion wires on the absorber plate has been carried out and expressions for prediction of average Stanton number and average friction factor have been developed. The results of these expressions have been compared with available data. The results have been found to compare with a mean deviation of 6.3% for friction factor and −10.7% for the Nusselt number. The effect of height and pitch of the roughness elements on the heat transfer rate and friction has also been investigated.