In this study, the natural and forced convection heat transfer in an enclosure with vertical heated block and baffles are experimentally and numerically investigated. The enclosure walls are kept as adiabatic, and the heating block contains extended baffles and receives heat flux. The effect of heat flux, Reynolds number and baffle configuration on the heat transfer characteristics and flow behaviour inside the enclosure is examined. The configuration parameter for natural and forced convection involves three heating block models, namely, block without baffle (plain), block with baffles and block with partially cut baffles. The widths of baffles are 2.5, 5 and 10 cm for the block with baffle case, and the width of partially cut baffle is 5 cm. The heat flux (q) ranges from 240 w/m 2 to 1425 w/m 2 for all the models. The Reynolds number (Re) ranges from 5650 to 15950 for forced convection heat transfer. In the numerical part, a finite volume method (via Ansys Fluent) is used to solve the governing equations. Result shows that the increase in baffle width has no remarkable effect on the heat transfer, and the partially cut baffles provide an enhancement of approximately 30% compared with the plain heating block. The baffle cases have an evident effect in reducing the block surface temperature by approximately 11% compared with the plain case at Re = 0 and q = 240 w/m 2 . Empirical correlations for the block with baffles are obtained for each heat flux to predict the average Nusselt number.
This paper investigates numerically pressure drop and forced convection heat transfer of TiO2-water nanofluids laminar flow through a horizontal curvilinear form or wavy duct with using four baffle height ratio h/H=0.15, 0.25, 0.35 and 0.45. This flow has been investigated assuming constant wall heat flux boundary condition by using ANSYS-Fluent with the finite volume method to discretize the nanofluids. The study has aimed to show the possibility of intensification of heat transfer by adding nanoparticles to the main coolant. The model employed in this study is a single phase (homogenous and dispersion). The effects of various factors, such as Reynolds number (Re) and nanoparticle concentration (φ), on the flow field and thermal distribution of the Nanofluids, have been analysed. The present results show that nanoparticle concentration and Reynolds number play a prevalent role in the horizontal wavy duct. The Nusselt number has increased by 54 % when using high nanoparticle concentration of (0.4 vol. %) at high Reynolds number of (1250), also the skin friction factor increased by (32%) in the same conditions. The results provide good predictions to enhancement the heat transfer. Predictably, as nanoparticle volume fraction and/or the Reynolds number increases, the heat transfer increases. However, the flow is accompanied by high friction factor and consequently, higher pressure drop.
Poppet valve development requires study of the complex flow inside it. This needs an advanced technology, such as particle image velocimetry (PIV) technique and CFD flow simulation. The main keys of this work are experimental investigation of the flow structure through a truncated conical poppet valve by using PIV technique. A numerical model of the valve is validated using experimental results. This validation gives the ability to modify the valve geometry and improve the flow structure, furthermore, and minimize the energy losses. The experiments have been done using the three flow rate values (Q) (25, 35, 45) L/min, each of them with three poppet displacements (Xv) (3.5, 5.5, 7.5) mm. The vortex radius and intensity, which is an indicator of losses magnitude, increased with the increasing of flow rate and decreasing of poppet movement Xv. The experimental results showed a good agreement with the numerical one, beyond some difference for flow out of the metering area. The three-dimensional effects may be the reason of this difference. The results provide good information to design process.
The modeling of the lubrication of human ankle joint has been considered in this present research. Many parameters were carried out such as joint geometry parameters as (minimum film thickness h, radial clearance c, Eccentricity e), lubricant parameters as (synovial fluid viscusity μ, couple stress property η) and cartilage matrix parameters as (Ratio of microstructure size to pore β, Permeability of the cartilage ϕ, Porous layer thickness H). The effects of these parameters on the synovial fluid velocity, pressure in the porous region, load carrying capacity per unit length of the bearing and the coefficient of friction were investigated. The model starts from the theory of boosted lubrication for the human articular joints lubrication and takes into account the fluid transport across the articular cartilage using Reynolds equation and modified Darcy’s equation. The results show that the pressure increased with increasing the couple stress length and the eccentricity ratio parameters. The synovial velocity profile was changing from Newtonian at (l*=0.0) to non-Newtonian profile as increasing the couple stress length. Finally the coefficient of friction increases with decreasing the eccentricity ratio and with increasing the joint radial clearance.
The purpose of this work to estimate oil temperature of hydraulic circuit that leads to affect the efficiency of the system. An expert system is built depending on the available knowledge. This model is generated in a computer program named “Thermal Analysis of Hydraulic System (TAHS)”. The program is used to calculate partial power losses at different components of hydraulic system (pump, motor, valves, cylinder, pipe and fittings). The expert system is capable to estimate oil temperature and power loss with different types of (pumps, oils, circuits and actuator dimension). The chosen experimental conditions are oil flow rate, setting pressure, ambient temperature and duty time. The model is validated experimentally and with other works. The results show an acceptable agreement with average deviation about 2.6% & 6.4% respectively.
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