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.

The use of boiling nanofluids for cooling high-temperature perorating surfaces allows intensifying considerably the process of cooling by increasing the heat transfer coefficient nanofluid compared to the pure base fluid. A significant influence on the intensity of heat transfer during the boiling of nanofluid will turn out properties of nanoparticles and their concentration in the base fluid, under heating of base fluid to saturation temperature. In this study, the mathematical model of the numerical solution and the results of the simulation calculation of characteristics of film boiling of Al2O3, CuO, ZnO, TiO2, ZrO2 and SiO2 water nanofluid for various nanoparticles concentration φ∞ of (0.1, 0.2, 0.3, 0.4, and 0.5) Water nanofluid on the vertical heated wall were presented. The theoretical results obtained allow us to estimate the influence of physical properties of nanofluids on heat and mass transfer during cooling low-temperature surfaces. It is shown that the greatest impact on the processes heat and mass transfer during film boiling nanofluids overheating of the wall depended upon the ratio of temperatures, Brownian diffusion, and concentration of nanoparticles in a base fluid. Also, the results showed that the use of nanofluids as coolants for heat exchange equipment in the mode of supercritical heat exchange increases the heat transfer and accelerate the process of cooling high-temperature surfaces. Increasing the concentration of nanoparticles in the nanofluids will contribute to a greater increase in heat transfer in the supercritical heat transfer due to the low thermal capacity of steam compared to that fluid conductivity. While increasing the nanoparticle concentration will lead to an increase in the effective viscosity of the nanofluids.

The current experimental study is made to investigate the heat transfer characteristics and pressure losses for both impingement and impingement/effusion cooling systems. The experiments are carried out on a metal test plate. The numerical work is made to analyze the flow behavior in the test section. The benefit of introducing the present experimental method is the capability of investigating and analyzing the performance of both impingement and impingement/effusion cooling systems by the same test rig. The impinging jet device configurations are designed as inline round multihole arrays with jet to jet spacing of 4 jet hole diameter. The effusion holes configurations are inline round multi-hole arrays. Staggered arrangement between jet and effusion holes is maintained. The Jet Reynolds numbers (Re j ) of 5000 to 15000 and jet height to diameter ratio ( H D ⁄ ) of 1.5, 2.0, and 3.0 are maintained. For impingement/effusion case, the best wall cooling effectiveness is obtained at (H D ⁄ = 2), and maximum increment in the wall cooling effectiveness over that of impingement case is 23% at (Re j = 5000), 16 % at (Re j = 7500), and 14% at (Re j = 15000). Jet spacing in impingement case and blowing ratio in impingement/effusion case show an evident effect on the discharge coefficients.

The current experimental study focuses on the heat transfer characteristics and pressure losses for impingement system which is used in cooling the liner of gas turbine combustor. Recent experiment method of conductive heat transfer technique with resistive film in the back side target plate is introduced. The present experimental model measured both the heat transfer coefficient for inner target surface and the wall cooling effectiveness for outer target surface. To physically explain the phenomena associated with interaction flow area, a computational fluid dynamic code (Fluent 14) is employed. The continuity, momentum and energy equations are computationally solved to analyze the flow field in the jet impingement area. The tests models of the impingement plate are made from round jet holes of inline and staggered arrays arrangement with jet to jet spacing of four-hole diameter. Jet Reynolds numbers of 4200 to 15000 and jet height to diameter ratio of 1.5, 2.0, and 3.0 are maintained. The inline array, as expected enhanced the wall cooling effectiveness over that of the staggered array by 10.3% and both jet spacing and Reynolds number have an evident effect on the discharge coefficient. Empirical correlations are obtained for both arrays arrangement to predict the area-averaged Nusselt number as a function of jet governing parameters.