Effect of Dimple Intrusions and Curvature Radius of Rounded Corner Triangular Duct on Fluid Flow and Heat Transfer

The sharp corner significantly affects the flow through triangular duct. In the corners, flow gets stagnant, which results in poor heat transfer. Therefore, in the present study, one corner of the duct is kept rounded with variable curvature radius values (Rc). The curvature radius is selected in such a way that it varied from the minimum value (i.e., Rc = 0.33 times duct height; h) to a maximum value (i.e., Rc = 0.67h,which named as conventional duct in the work). In addition to this, the combined effect of both rounded corner and dimple-shaped intrusion has also been studied on flow of air and heat transfer and for this purpose; the relative streamwise distance (z/e) is varied from 6 to 14 with constant relative transverse distance (x/e) that is10. Steady-state, turbulent flow heat transfer under thermal boundary conditions is analyzed for Reynolds number from 5600 to 17,700. ANSYS (Fluent) 12.1 software is used to perform numerical simulations and good match has been observed between the simulated and experimental results. Due to rounded corner and dimple intrusions, velocity near the corner region has higher value in comparison to the conventional duct. The uniform temperature distribution is seen in the case of dimple intruded duct as compared to conventional and rounded corner duct (with Rc value of 0.33h). In comparison to conventional duct, the heat transfer increased about 21–25%, 13–20%, and 5–8%, for the Rc value of 0.33h, 0.49h, and 0.57h, respectively, but the combination of rounded corner and dimple-shaped intrusion augments heat transfer by 46–94%, 75–127%, 60–110%, for the z/e value of 6, 10, and 14, respectively, with the Reynolds number increase from 5600 to 17,700.

The Effect of Reynolds and Prandtl Number on Flow inside of Plan Channel of Waved Bottom Wall under Mixed Convection

2D simulations of incompressible fluid in plan channel of waved bottom wall is carried out in this paper to understand and to determine correctly the effects of the Reynolds, Prandtl and Richardson numbers on the fluid flow and heat transfer of waved channel wall. The governing equations involving continuity, momentum and energy are solved numerically based on commercial code which called ANSYS-CFX. The results are presented and discussed for the range of following conditions as:Re= 60 to 250,Pr= 0.7 to 30,Ri= 0 to 1 at fixed value of blockage ratio. The numerical results showed that increase in Richardson number and/ or Prantl number For Reynolds number limited between 60 and 200 increases tightly the heat transfer rate. For the value 250 of Reynolds number increase in the buoyancy strength reduces the value of heat transfer rate.

Numerical Investigation of Turbulent Magnetic Nanofluid Flow inside Straight Channels

A numerical study using computational fluid dynamics method with an approach of single phase has been presented in order to determine the effects of the concentration of the nanoparticles and flow rate on the convective heat transfer and friction factor in turbulent regime flowing through three different straight channels (straight, circular and triangular) with different Reynolds number (5000 ≤ Re ≤ 20000) using constant applied heat flux. The nanofluid was used consist of Fe3O4 magnetic nanoparticles with average diameter of (13nm) dispersed in water with four volume fraction (0, 0.2, 0.4, 0.6%). The results revealed that as volume fraction and Reynolds number increase Nusselt number increase and the heat transfer rate in circular cross section tube is better than that in square and triangular cross section channels.

Effectiveness of Jet Impingement Cooling System on Convex Surface

Jet impingement is one of cooling method used in order to achieve high heat transfer coefficient and widely used in industry applications such as drying of textile and film, glass and plastic sheets, cooling of electronic equipment, and heat treatment of metals. In this research, it focused on the effectiveness of the jet impingement cooling system on the convex surface based on mass blowing rate and nozzle exit to surface parameters. The scope of experiment research encompasses are convex surface made of aluminum alloy and diameter 12.5cm. For mass blowing rate parameters, it use ʋjet = 1.98m/s, 3.03m/s, 4.97m/s and 6.00m/s which has Reynolds number range from 643 until 1946. Nozzle exit to surface distance,s/d = 4.0, 8.0 and 12.0. In this experiment model, a major components that involved are a compressor, nozzle, convex surface model, K thermocouple and heater. For the result of the experiment, it is based on the data obtain through a heat transfer coefficient and Nusselt number which the plotted graph focus on the space spacing and Reynolds number parameters. For the graph Nusselt number versus s/d at stagnation point c/d=0, it shown that when the Reynolds number increase, the Nusselt number also increase. In term of effectiveness, the s/d=12.0 has a good effectiveness jet impingement cooling system. For the graph of Nusselt number versus Reynolds at stagnation point, c/d=0, as Reynolds number increase, the Nusselt number increase too. From this experiment the better cooling effect is at Reynolds number, Re=1946. Thus, it can conclude that, effectiveness for jet impingement cooling system on the convex surface occurs at the highest Reynolds number.

Comparative modeling of hull form resistance for three ocean going vessels using methodical series

This paper presents a comparative estimation of the hull form resistance for Cargo ship, Ocean-going Tug and Container ship. The research study evaluates the influences of various ship hull parameters in relations to the vessel speeds and level of turbulence (Reynolds number). The modeling was done using MATLAB software and the model test technique based on the ITTC, ATTC, Granville and Hughes friction line application. The result shows that the hull form resistances follow the same trend in the ITTC, ATTC and Granville models, while the Hughes model gave a different trend with other techniques. It further revealed that as the speed increases by 10knots, the frictional resistance coefficients decrease by 11.86% for the ITTC & Granville models, and 12.03% for the Hughes model. For Ocean-going Tug and Container Ship, the frictional resistance coefficient decrease by 12.31% for the ITTC & Granville models, and 12.14% for the Hughes model. The Reynolds number increase by 62.52% for every 10knots increase in the speed of the Cargo ship and 62.23% for every 10knots increase in the speed of the Ocean going tug and Containership. At various experimental speeds, the results showed that for every 1 knots increase in the speed of the Containership, the effective power developed increases by 9.45%. This provides a technical and analytical guide on hull form resistance trend for engineers and ship operators.

Combined Convection Heat Transfer of Nanofluids Flow over Forward Facing Step in a Channel Having a Blockage

Numerical simulations of two dimensional laminar combined convection flows using nanofluids over forward facing step with a blockage are analyzed. The continuity, momentum and energy equations are solved using finite volume method (FVM) and the SIMPLE algorithm scheme is applied to examine the effect of the blockage on the heat transfer characteristics. In this project, several parameters such as different types of nanofluids (Al2O3, SiO2, CuO and ZnO), different volume fraction in the range of 1% - 4%, different nanoparticles diameter in the range of 25nm-80nm were used. Effects of different shapes of blockage (Circular, Square and Triangular) were studied. The numerical results indicated that SiO2nanofluid has the highest Nusselt number. The Nusselt number increased as the volume fraction and Reynolds number increase, while it decreases as the nanoparticles diameter increases. Circular blockage produced higher results compared to triangular and square one.

Investigation on Intertube Falling-Film Heat Transfer and Mode Transitions of Aqueous-Alumina Nanofluids

Horizontal-tube falling-film heat transfer characteristics of aqueous aluminum oxide nanofluids at concentrations of 0 vol %, 0.05 vol %(0.20 wt %), 0.5 vol %(1.96 wt %), 1 vol %(3.86 wt %) (with and without sodium dodecylbenzene sulfonate), and 2 vol %(7.51 wt %) are investigated and compared with predictions developed for conventional fluids. The thermophysical properties of the nanofluids, including thermal conductivity, kinematic viscosity, and surface tension, are reported, as is the mode transition behavior of the nanofluids. The experimental results for heat transfer are in good agreement with predictions for falling-film flow and no unusual Nu enhancement was observed in the present studies. Additionally, a 20% mode transitional Reynolds number increase was recorded for transitions between sheets and jets and jet-droplet mode to droplet mode. Although the findings with water-alumina nanofluids are not encouraging with respect to heat transfer, the results extend nanofluid data to a new type of flow and may help improve our understanding of nanofluid behavior. Moreover, this work provides a basis for further work on falling-film nanofluids.

On Cavitation Produced by a Vortex Trailing From a Lifting Surface

An experimental and analytical study is made of cavitation produced by the vortex system trailing from elliptic, rectangular, and delta wings. It is found that the inception of this type of cavitation depends upon the boundary-layer thickness of the lower surface of the wing tip. The thickness of the vortex core is apparently not determined by the induced drag of the wing. For a given wing shape, the critical cavitation index was found to: Increase with increasing Reynolds number; increase nearly linearly with angle of attack; be almost independent of aspect ratio; and, depend significantly upon the undissolved air content.