Effect of Vertical Baffle Installation on Forced Convective Heat Transfer in Channel Having a Backward Facing Step

2013 ◽  
Vol 388 ◽  
pp. 169-175 ◽  
Author(s):  
Amirhossein Heshmati ◽  
Hussein A. Mohammed ◽  
Mohammad Parsazadeh ◽  
Farshid Fathinia ◽  
Mazlan A. Wahid ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Convective Heat Transfer ◽  
Skin Friction ◽  
Convective Heat ◽  
Average Nusselt Number ◽  
Skin Friction Coefficient ◽  
Expansion Ratio ◽  
Forced Convective Heat Transfer

In this study, forced convective heat transfer is considered in channel over a backward facing step having a baffle on the top wall. Four different geometries with different expansion ratios and different type of baffles are numerically investigated. The study clearly shows that the geometry with expansion ratio 2 and solid baffle has the highest Nusselt number compared to other geometries. Considering both Nusselt number and skin friction coefficient for all four geometries clearly illustrated an increase in average Nusselt number by increasing the expansion ratio. This study clearly shows that mounting a slotted baffle at the top wall instead of a solid baffle caused a decline in average Nusselt number. It is also found that for geometry with expansion ratio of 3 and a slotted baffle on the top of the channel, skin friction coefficient in both bottom wall and step wall has its minimal compared to other geometries.

An Experimental Study of Chilton–Colburn Analogy Between Turbulent Flow and Convective Heat Transfer of Supercritical Kerosene

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Yongjiang Zhang ◽  
Fengquan Zhong ◽  
Yunfei Xing ◽  
Xinyu Zhang
Keyword(s):  
Heat Transfer ◽  
Friction Coefficient ◽  
Turbulent Flow ◽  
Convective Heat Transfer ◽  
Skin Friction ◽  
Convective Heat ◽  
Control Volume ◽  
Skin Friction Coefficient ◽  
Fuel Temperature ◽  
Number Range

In this paper, characteristics of turbulent flow and convective heat transfer of supercritical China RP-3 kerosene in a horizontal straight circular tube are studied experimentally, and the validity of Chilton–Colburn analogy is examined. Using a three-stage heating system, experiments are conducted at a fuel temperature range of 650–800 K, a pressure range of 3–4 MPa, and a Reynolds number range of 1 × 105–3.5 × 105. The Nusselt number and skin friction coefficient are calculated through control volume analysis proposed in this paper. Heat transfer enhancement and deterioration were observed in the experiments as well as the similar change of skin friction coefficient. The present results show that Chilton–Colburn analogy is also valid for turbulent flow and heat transfer of supercritical kerosene in horizontal straight circular tubes.

Hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching/shrinking surface

2019 ◽  
Vol 29 (9) ◽  
pp. 3110-3127 ◽  
Author(s):  
Iskandar Waini ◽  
Anuar Ishak ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Local Nusselt Number ◽  
Skin Friction Coefficient ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Shrinking Surface

PurposeThis paper aims to investigate the steady flow and heat transfer of a Cu-Al2O3/water hybrid nanofluid over a nonlinear permeable stretching/shrinking surface with radiation effects. The surface velocity condition is assumed to be of the power-law form with an exponent of 1/3. The governing equations of the problem are converted into a system of similarity equations by using a similarity transformation.Design/methodology/approachThe problem is solved numerically using the boundary value problem solver (bvp4c) in Matlab software. The results of the skin friction coefficient and the local Nusselt number as well as the velocity and temperature profiles are presented through graphs and tables for several values of the parameters. The effects of these parameters on the flow and heat transfer characteristics are examined and discussed.FindingsResults found that dual solutions exist for a certain range of the stretching/shrinking and suction parameters. The increment of the skin friction coefficient and reduction of the local Nusselt number on the shrinking sheet is observed with the increasing of copper (Cu) nanoparticle volume fractions for the upper branch. The skin friction coefficient and the local Nusselt number increase when suction parameter is increased for the upper branch. Meanwhile, the temperature increases in the presence of the radiation parameter for both branches.Originality/valueThe problem of Cu-Al2O3/water hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching/shrinking surface with radiation effects is the important originality of the present study where the dual solutions for the flow reversals are obtained.

Influence of moving plate velocity on conjugate heat transfer due to the impingement of an inclined slot jet

2019 ◽  
Vol 30 (12) ◽  
pp. 2050006 ◽  
Author(s):  
Shashikant Pawar ◽  
Devendra Kumar Patel
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Numerical Study ◽  
Finite Thickness ◽  
Skin Friction Coefficient ◽  
Moving Plate ◽  
Potential Core ◽  
Plate Velocity

In this paper, a dimensionless numerical study of the flow-field and heat transfer characteristics of an incompressible turbulent slot jet impinging obliquely over a moving surface of finite thickness is presented. Simulations were performed using [Formula: see text] eddy viscosity turbulence model. The temperature field was solved simultaneously in the solid and the fluid domain. For a fixed impingement distance and a fixed Reynolds number, the impingement angle ([Formula: see text]) and plate velocity ([Formula: see text]) were varied in the range of 30–75∘ and 0–0.3, respectively. In the results, the length of the potential core depends on the jet inclination, which increases with increase in jet angle. The jet angle and plate velocity have more influence on the uphill side compared to the downhill side. The location of stagnation displaces toward the uphill side as the inclination angle decreases, and the drifting of stagnation point is noted with the variation in plate velocity. The average skin-friction coefficient increases with increase in [Formula: see text] and [Formula: see text], and the influence of [Formula: see text] on the skin-friction coefficient is reduced as [Formula: see text] increases. The maximum Nusselt number ([Formula: see text]) increases with increase in [Formula: see text], and the drifting of [Formula: see text] is observed with increase in plate velocity. It is found that the average Nusselt number increases quickly with increase in plate velocity for lower angles of impingement. The distribution of local heat flux follows the same trend as the local Nusselt number.

scholarly journals Magnetohydrodynamic Flow and Heat Transfer Over an Exponentially Stretching/Shrinking Sheet in Ferrofluids

2021 ◽  
Vol 29 (3) ◽  
Author(s):  
Nurfazila Rasli ◽  
Norshafira Ramli
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Differential Equations ◽  
Skin Friction ◽  
Skin Friction Coefficient ◽  
Magnetohydrodynamic Flow ◽  
Shrinking Sheet ◽  
Flow And Heat Transfer ◽  
Exponentially Stretching

In this research, the problem of magnetohydrodynamic flow and heat transfer over an exponentially stretching/shrinking sheet in ferrofluids is presented. The governing partial differential equations are transformed into nonlinear ordinary differential equations by applying suitable similarity transformations. These equations are then solved numerically using the shooting method for some pertinent parameters. For this research, the water-based ferrofluid is considered with three types of ferroparticles: magnetite, cobalt ferrite, and manganese-zinc ferrite. The numerical solutions on the skin friction coefficient, Nusselt number, velocity and temperature profiles influenced by the magnetic parameter, wall mass transfer parameter, stretching/shrinking parameter, and volume fraction of solid ferroparticle are graphically displayed and discussed in more details. The existences of dual solutions are noticeable for the stretching/shrinking case in a specific range of limit. For the first solution, an increasing number in magnetic and suction will also give an increment of skin friction coefficient and Nusselt number over stretching/shrinking sheet. For the skin friction coefficient only, it is showed a decreasing pattern after the intersection. Besides, the presence of ferroparticles in the fluids causes a high number of the fluid’s thermal conductivity and heat transfer rate.

Flow and Heat Transfer in a Newtonian Nanoliquid due to a Curved Stretching Sheet

2017 ◽  
Vol 72 (9) ◽  
pp. 833-842 ◽  
Author(s):  
Pradeep Ganapathi Siddheshwar ◽  
Meenakshi Nerolu ◽  
Igor Pažanin
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Differential Equations ◽  
Skin Friction ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Nonlinear Partial Differential Equations ◽  
Skin Friction Coefficient ◽  
Variable Coefficients

AbstractFlow of a Newtonian nanoliquid due to a curved stretching sheet and heat transfer in it is studied. The governing nonlinear partial differential equations are reduced to nonlinear ordinary differential equations with variable coefficients by using a similarity transformation. The flow characteristics are studied using plots of flow velocity components and the skin-friction coefficient as a function of suction-injection parameter, curvature, and volume fraction. Prescribed surface temperature and prescribed surface heat flux are considered for studying the temperature distribution in the flow. The thermophysical properties of 20 nanoliquids are considered in the investigation by modeling them through the use of phenomenological laws and mixture theory. The results of the corresponding problem involving a plane stretching sheet is obtained as a particular case of those obtained in the present paper. Skin friction coefficient and Nusselt number are evaluated and it is observed that skin friction coefficient decreases with concentration of nanoparticles in the absence as well as presence of suction where as Nusselt number increases with increase in concentration of nanoparticles in a dilute range.

Assessment of Heat Transfer Enhancement Using Metallic Porous Foam Configurations in Laminar Slot Jet Impingement: An Experimental Study

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Chinige Sampath Kumar ◽  
Arvind Pattamatta
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Average Nusselt Number ◽  
Heat Transfer Performance ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Transfer Enhancement

An experimental study using the liquid crystal thermography technique is conducted to investigate the convective heat transfer performance in jet impingement cooling using various porous media configurations. Aluminum porous foams are used in the present study. Four impinging jet configurations are considered: jet impingement (1) without porous media, (2) over the porous heat sink, (3) with porous obstacle case, and (4) through porous passage. These configurations are evaluated on the basis of the convective heat transfer enhancement for two different Reynolds numbers of 400 and 700. Jet impingement with porous heat sink showed deterioration in the average Nusselt number by 9.95% and 18.04% compared to jet impingement without porous media configuration for Reynolds numbers of 400 and 700, respectively. Jet impingement with porous obstacles showed a very negligible enhancement in the average Nusselt number by 3.48% and 2.73% for Reynolds numbers of 400 and 700, respectively. However, jet impingement through porous passage configuration showed a maximum enhancement in the average Nusselt number by 52.71% and 74.68% and stagnation Nusselt numbers by 58.08% and 53.80% compared to the jet impingement without porous medium for Reynolds numbers of 400 and 700, respectively. Within the porous properties considered, it is observed that by decreasing the permeability and porosity the convective heat transfer performance tends to increase.

Convective Heat Transfer Coefficients in a Building-Integrated Photovoltaic/Thermal System

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Luis M. Candanedo ◽  
Andreas Athienitis ◽  
Kwang-Wook Park
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Average Nusselt Number ◽  
Heated Surface ◽  
Reynolds Numbers ◽  
Building Integrated Photovoltaic ◽  
T System

This paper presents an experimental study for the development of convective heat transfer correlations for an open loop air-based building-integrated photovoltaic/thermal (BIPV/T) system. The BIPV/T system absorbs solar energy on the top surface, which includes the photovoltaic panels and generates electricity while also heating air drawn by a variable speed fan through a channel formed by the top roof surface with the photovoltaic modules and an insulated attic layer. The BIPV/T system channel has a length/hydraulic diameter ratio of 38, which is representative of a BIPV/T roof system for 30–45 deg tilt angles. Because of the heating asymmetry in the BIPV/T channel, two average Nusselt number correlations are reported as a function of Reynolds number: one for the top heated surface and the other for the bottom surface. For the top heated surface, the Nusselt number is in the range of 6–48 for Reynolds numbers ranging from 250 to 7500. For the bottom insulated surface, the Nusselt number is in the range of 22–68 for Reynolds numbers ranging from 800 to 7060. This paper presents correlations for the average Nusselt number as a function of Reynolds number; this correlation is considered adequate for the design of BIPV/T systems where forced convection dominates. Local Nusselt number distributions are also presented for laminar and turbulent flow conditions.

scholarly journals Turbulent flow and heat transfer characteristics in U-tubes: A numerical study

2009 ◽  
Vol 13 (4) ◽  
pp. 175-181 ◽  
Author(s):  
Khalid Alammar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Turbulent Flow ◽  
Skin Friction ◽  
Skin Friction Coefficient ◽  
Heat Transfer Characteristics ◽  
Local Skin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Using the standard k-e model, 3-dimensional turbulent flow and heat transfer characteristics in U-tubes are investigated. Uncertainty is approximated using experimental correlations and grid independence study. Increasing the Dean number is shown to intensify a secondary flow within the curved section. The overall Nusselt number for the tube is found to decrease substantially relative to straight tubes, while the overall skin friction coefficient remains practically unaffected. Local skin friction coefficient, Nusselt number, and wall temperature along the tube wall are presented.

Convective Heat Transfer in a Rectangular Channel Filled With Sintered Bronze Beads and Periodically Spaced Heated Blocks

2005 ◽  
Vol 128 (5) ◽  
pp. 453-464 ◽  
Author(s):  
Sheng Chung Tzeng
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Average Nusselt Number ◽  
Rectangular Channel ◽  
Block Height ◽  
Nusselt Number Distribution ◽  
Sintered Bronze ◽  
Block Width

This work numerically investigated the steady state fluid flow and heat transfer behaviors associated with a sintered porous channel that contains periodically spaced heated blocks. Some typical cases are experimentally examined in this study. The relevant varied parameters were the average bead diameter (d), the relative block height (h∕H), the relative block width (w∕H), the relative block spacing (s∕H), and the Reynolds number (Re). The numerical results revealed a lack of global recirculation in regions between the blocks, where the forced convective heat transfer was low, but the heat in those regions was transferred to the metallic block by conduction through porous media, before being dissipated into the fluid that passed over the zone above the heated block. Additionally, the relevant parameters considerably affect the local Nusselt number distribution along the periphery of the block surface. The average Nusselt number for each block decreased along the direction of the flow until it reached its fully developed value. The Nusselt number increased with h∕H or Re in the fully developed region. The effect of h∕H on the fully developed Nusselt number became stronger as Re increased and w∕H decreased. The effects of s∕H and d on the fully developed Nusselt number were insignificant over the ranges of parameters considered herein (d=0.7 and 1.16mm, h∕H=0.12-0.59, w∕H=0.24-0.47, s∕H=0.24-0.7, and Re=1019-5059). Finally, this study summarized the average Nusselt number for different configurations of the heated blocks with various d, h∕H, w∕H, s∕H, and Re.

Heat transfer from electrically heated cylinders

1964 ◽  
Vol 280 (1383) ◽  
pp. 486-527 ◽  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Local Heat Transfer ◽  
Skin Friction Coefficient ◽  
Hot Wire ◽  
Resistance Thermometer ◽  
The Wire ◽  
Good Agreement

The heat transfer from small electrically heated cylinders has been studied with particular reference to the performance of hot-wire anemometers. The thermal equilibrium for a cylinder normal to the flow was investigated in detail and the convective transfer to the fluid, conductive flow to the supports and the radiation losses were measured. A simple model of the heat transfer at the surface showed that the Nusselt number was proportional to the product of the skin friction coefficient, C f , and the Reynolds and Prandtl numbers, and was in good agreement with the measurements. At the same time it was argued that the skin friction coefficient was independent of the temperature of the cylinder, provided that the fluid properties are evaluated for the conditions at the surface in the absence of heat transfer. This is in general agreement with published results and the measurements described here. The same model showed that the coefficient of local heat transfer was expressed by h w = C f ρ V c v k w /π k 0 , where k w is the conductivity of air at the temperature of the wire surface. This expression was also in good agreement with the measurements which showed that the temperature dependence of the heat transfer coefficient can be expressed as h w = h 0 (1 + β T ), if it is assumed that k w = k 0 (1 + β T ). The measurements also showed that h 0 was proportional to the product of the mass flux and the skin friction coefficient, C f . The chief source of experimental error in the measurement of Nusselt number was found to be in the estimation of the surface temperature of the wire, the reason being that the hot wire itself was used as a resistance thermometer for this purpose. This difficulty is a major factor in the large scatter among Nusselt number measurements by different observers.

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