An Experimental Investigation of Forced Convection Heat Transfer From an Isothermal V-Shaped Plate

2010 ◽  
Author(s):  
Tooraj Yousefi ◽  
Saeed Ebrahimi ◽  
Masood Bigharaz ◽  
Sajjad Mahmoodi Nezhad
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Plate Spacing ◽  
Internal Surfaces

An experimental study has been carried out to investigate heat transfer characteristics on internal surfaces of a V-shaped plate exposed to a slot jet impingement of air. A square-edged nozzle is mounted parallel with V-shaped plate axis and jet flow impinges on the bottom of the V-shaped plate. The study is focused on Rayleigh number 159000, angle of V-shaped plate ranging from 22.5 to 45 degree, low Reynolds numbers ranging from 29.05 to 60.41, and slot-to-(V-shaped plate) spacing from 17 to 21 of the slot width. A Mach-Zehnder interferometer is used for measurement of local Nusselt number on the V-shaped plate. It is observed that the local Nusselt number and average Nusselt number decrease with increasing the jet spacing and increase with increasing the Reynolds number. Also the local Nusselt number and average nusselt number increase with rising the angle of V-shaped plate.

Investigating the effect of nanoparticles diameter on turbulent flow and heat transfer properties of non-Newtonian carboxymethyl cellulose/CuO fluid in a microtube

2019 ◽  
Vol 29 (5) ◽  
pp. 1699-1723 ◽  
Author(s):  
Ali Rahimi Gheynani ◽  
Omid Ali Akbari ◽  
Majid Zarringhalam ◽  
Gholamreza Ahmadi Sheikh Shabani ◽  
Abdulwahab A. Alnaqi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Electronic Devices ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Vlsi Circuits ◽  
Convection Heat Transfer Coefficient ◽  
Content Type ◽  
Competing Interests

Purpose Although many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Design/methodology/approach Present numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10−6 is considered for saving computer memory usage and the time for the numerical solving procedure. Findings In constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent. Research limitations/implications The numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it. Practical implications The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Originality/value This manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.

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.

Forced convection heat transfer study of a blunt-headed cylinder in non-Newtonian power-law fluids

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jaspinder Kaur ◽  
Roderick Melnik ◽  
Anurag Kumar Tiwari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Total Drag ◽  
Shear Thinning Fluids ◽  
Power Law Fluids

Abstract In this present work, forced convection heat transfer from a heated blunt-headed cylinder in power-law fluids has been investigated numerically over the range of parameters, namely, Reynolds number (Re): 1–40, Prandtl number (Pr): 10–100 and power-law index (n): 0.3–1.8. The results are expressed in terms of local parameters, like streamline, isotherm, pressure coefficient, and local Nusselt number and global parameters, like wake length, drag coefficient, and average Nusselt number. The length of the recirculation zone on the rear side of the cylinder increases with the increasing value of Re and n. The effect of the total drag coefficient acting on the cylinder is seen to be higher at the low value of Re and its effect significant in shear-thinning fluids (n < 1). On the heat transfer aspect, the rate of heat transfer in fluids is increased by increasing the value of Re and Pr. The effect of heat transfer is enhanced in shear-thinning fluids up to ∼ 40% and it impedes it’s to ∼20% shear-thickening fluids. In the end, the numerical results of the total drag coefficient and average Nusselt number (in terms of J H −factor) have been correlated by simple expression to estimate the intermediate value for the new application.

scholarly journals Natural convection in a differentially heated enclosure with triangular roof

1970 ◽  
Vol 39 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sumon Saha ◽  
Noman Hasan ◽  
Chowdhury Md Feroz
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Natural Convection ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Element Analysis ◽  
Left Wall ◽  
Square Enclosure

A numerical study has been carried out for laminar natural convection heat transfer within a two-dimensional modified square enclosure having a triangular roof. The vertical sidewalls are differentially heated considering a constant flux heat source strip is flush mounted with the left wall. The opposite wall is considered isothermal having a temperature of the surrounding fluid. The rest of the walls are adiabatic. Air is considered as the fluid inside the enclosure. The solution has been carried out on the basis of finite element analysis by a non-linear parametric solver to examine the heat transfer and fluid flow characteristics. Different heights of the triangular roof have been considered for the present analysis. Fluid flow fields and isotherm patterns and the average Nusselt number are presented for the Rayleigh numbers ranging from 103 to 106 in order to show the effects of these governing parameters. The average Nusselt number computed for the case of isoflux heating is also compared with the case of isothermal heating as available in the literature. The outcome of the present investigation shows that the convective phenomenon is greatly influenced by the inclined roof height. Keywords: Natural convection, triangular roof, Rayleigh number, isoflux heating. Doi:10.3329/jme.v39i1.1826 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 1-7

Effect of Variation of Pin-fin Height on Jet Impingement Heat Transfer on a Rotating Surface

2021 ◽  
Author(s):  
Pratik S. Bhansali ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Rotating Disc ◽  
Disc Surface ◽  
Pin Fins

Abstract Heat transfer over rotating surfaces is of particular interest in rotating machinery such as gas turbine engines. The rotation of the gas turbine disc creates a radially outward flow on the disc surface, which may lead to ingress of hot gases into the narrow cavity between the disc and the stator. Impingement of cooling jet is an effective way of cooling the disc and countering the ingress of the hot gases. Present study focusses on investigating the effect of introducing pin-fins over the rotating disc on the heat transfer. The jet Reynolds number has been varied from 5000 to 18000, and the rotating Reynolds number has been varied from 5487 to 12803 for an aluminum disc of thickness 6.35mm and diameter 10.16 cm, over which square pins have been arranged in an inline fashion. Steady state temperature measurements have been taken using thermocouples embedded in the disc close to the target surface, and area average Nusselt number has been calculated. The effects of varying the height of the pin-fins, distance between nozzle and the disc surface and the inclination of the impinging jet with the axis of rotation have also been studied. The results have been compared with those for a smooth aluminum disc of equal dimensions and without any pin-fins. The average Nusselt number is significantly enhanced by the presence of pin fins. In the impingement dominant regime, where the effect of disc rotation is minimal for a smooth disc, the heat transfer increases with rotational speed in case of pin fins. The effect of inclination angle of the impinging jet is insignificant in the range explored in this paper (0° to 20°).

Enhancement of Heat Transfer to an Air Jet Impinging on a Flat Plate

Volume 1 ◽  
2004 ◽  
Author(s):  
D. P. Mishra ◽  
D. Mishra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flat Plate ◽  
Average Nusselt Number ◽  
Cooling System ◽  
Reynolds Numbers ◽  
Heated Plate ◽  
Maximum Heat ◽  
Air Jet ◽  
Maximum Heat Transfer

An experimental investigation of the impinging jet cooling from a heated flat plate has been carried out for several Reynolds numbers (Re) and nozzle to plate distances. The present results indicate that the maximum heat transfer occurs from the heated plate at stagnation point and decreases with radial distances for all cases. The maximum value of the stagnation as well as average Nusselt number is found to occur at separation distance, H/D = 6.0 for Re = 55000. An attempt is also made to study effects of nozzle exit configuration on the heat transfer using a sharp edged orifice for same set of Reynolds numbers and nozzle to plate distance. The stagnation Nusselt numbers of sharp orifice jets are found to be enhanced by around 16–21.4% in comparison to that of square edged orifice. However, the enhancement in the average Nusselt number of sharp orifice is found to be in the range of 7–18.9% as compared to the square edged orifice. The maximum enhancement of 18.9% in average Nu is achieved for Re = 55 000 at H/D = 6. Two separate correlations in terms of Nuo, Re, H/D for both square and sharp edged orifice are obtained which will be useful for designing impinging cooling system.

Experimental Investigation on Convective Heat Transfer Enhancement of Laminar Slot Jet Impingement in the Presence of Porous Medium

2016 ◽  
Author(s):  
Sampath Kumar Chinige ◽  
Arvind Pattamatta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Porous Medium ◽  
Porous Media ◽  
Nusselt Number ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Transfer Enhancement ◽  
Porous Obstacle

An experimental study using Liquid crystal thermography technique is conducted to study the convective heat transfer enhancement in jet impingement cooling in the presence of porous media. Aluminium porous sample of 10 PPI with permeability 2.48e−7 and porosity 0.95 is used in the present study. Results are presented for two different Reynolds number 400 and 700 with four different configurations of jet impingement (1) without porous foams (2) over porous heat sink (3) with porous obstacle case (4) through porous passage. Jet impingement with porous heat sink showed a deterioration in average Nusselt number by 10.5% and 18.1% for Reynolds number of 400 and 700 respectively when compared with jet impingement without porous heat sink configuration. The results show that for Reynolds number 400, jet impingement through porous passage augments average Nusselt number by 30.73% whereas obstacle configuration enhances the heat transfer by 25.6% over jet impingement without porous medium. Similarly for Reynolds number 700, the porous passage configuration shows average Nusselt number enhancement by 71.09% and porous obstacle by 33.4 % over jet impingement in the absence of porous media respectively.

Local Heat Transfer Coefficients Under an Axisymmetric, Single-Phase Liquid Jet

1991 ◽  
Vol 113 (1) ◽  
pp. 71-78 ◽  
Author(s):  
J. Stevens ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Single Phase ◽  
Radial Distance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Plate Spacing

The purpose of this investigation was to characterize local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface. The problem parameters investigated were jet Reynolds number Re, nozzle-to-plate spacing z, and jet diameter d. A region of near-constant Nusselt number was observed for the region bounded by 0≤r/d≤0.75, where r is the radial distance from the impingement point. The local Nusselt number profiles exhibited a sharp drop for r/d > 0.75, followed by an inflection and a slower decrease there-after. Increasing the nozzle-to-plate spacing generally decreased the heat transfer slightly. The local Nusselt number characteristics were found to be dependent on nozzle diameter. This was explained by the influence of the free-stream velocity gradient on local heat transfer, as predicted in the classical analysis of infinite jet stagnation flow and heat transfer. Correlations for local and average Nusselt numbers reveal an approximate Nusselt number dependence on Re1/3.

Localized Heat Transfer in Buoyancy Driven Convection in Open Cavities

2006 ◽  
Vol 129 (2) ◽  
pp. 167-178 ◽  
Author(s):  
Wilson Terrell ◽  
Ty A. Newell
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Ambient Air ◽  
Nusselt Numbers ◽  
Transient Nature ◽  
Inclination Angles ◽  
Buoyancy Driven Convection ◽  
The Heat Transfer Coefficient

Background. An experimental study of buoyancy driven convection heat transfer in an open cavity was conducted. Method of Approach. Test cavities were constructed with calorimeter plates bonded to Styrofoam insulation. The inside of the cavities was heated and then exposed to ambient air for approximately thirty minutes. Different size cavities were examined at inclination angles of 0, 45, and 90deg. The heat transfer coefficient was determined from an energy balance on each calorimeter plate. The cavity’s plate temperatures varied spatially due to the transient nature of the tests. A parameter describing the nonisothermal cavity wall temperature variation was defined in order to compare with isothermal cavity heat transfer results. Results. Results showed that the cavity Nusselt number, based on a cavity averaged temperature, was insensitive to the transient development of nonisothermal conditions within the cavity. Comparison of cavity-average Nusselt number for the current study, where the Rayleigh number ranged from 5×106 to 2×108, to data from the literature showed good agreement. Cavity-average Nusselt number relations for inclination angles of 0, 45, and 90deg in the form of NuH,cav=CRa1∕3 resulted in coefficients of 0.091, 0.105, 0.093, respectively. The 45deg inclination angle orientation yielded the largest Nusselt numbers, which was similar to previous literature results. Trends in the local plate Nusselt numbers were examined and found similar to data from the literature.

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