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°).

scholarly journals Turbulent heat transfer for impinging jet flowing inside a cylindrical hot cavity

2015 ◽  
Vol 19 (1) ◽  
pp. 141-154 ◽  
Author(s):  
Yacine Halouane ◽  
Amina Mataoui ◽  
Farida Iachachene
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Reverse Flow ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Cavity Bottom

Convective heat transfer from an isothermal hot cylindrical cavity due to a turbulent round jet impingement is investigated numerically. Three-dimensional turbulent flow is considered in this work. The Reynolds stress second order turbulence model with wall standard treatment is used for the turbulence predictions the problem parameters are the jet exit Reynolds number, ranging from 2x104 to 105and the normalized impinging distance to the cavity bottom and the jet exit Lf, ranging from 4 to 35. The computed flow patterns and isotherms for various combinations of these parameters are analyzed in order to understand the effect of the cavity confinement on the heat transfer phenomena. The flow in the cavity is divided into three parts, the area of free jet, and the area of the jet interaction with the reverse flow and the semi-quiescent flow in the region of the cavity bottom. The distribution of the local and mean Nusselt numbers along the cavity walls for above combinations of the flow parameters are detailed. Results are compared against to corresponding cases for impinging jet on a plate for the case of the bottom wall. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number. Finally, it was found that the average Nusselt number at the stagnation point could be correlated by a relationship in the form Nu=f(Lf,Re).

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.

Effects of Nanoparticle Shape on Slot-Jet Impingement Cooling of a Corrugated Surface With Nanofluids

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Jet Impingement ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Corrugated Surface ◽  
Nanoparticle Shapes

Numerical study of jet impingement cooling of a corrugated surface with water–SiO2 nanofluid of different nanoparticle shapes was performed. The bottom wall is corrugated and kept at constant surface temperature, while the jet emerges from a rectangular slot with cold uniform temperature. The finite volume method is utilized to solve the governing equations. The effects of Reynolds number (between 100 and 500), corrugation amplitude (between 0 and 0.3), corrugation frequency (between 0 and 20), nanoparticle volume fraction (between 0 and 0.04), and nanoparticle shapes (spherical, blade, brick, and cylindrical) on the fluid flow and heat transfer characteristics were studied. Stagnation point and average Nusselt number enhance with Reynolds number and solid particle volume fraction for both flat and corrugated surface configurations. An optimal value for the corrugation amplitude and frequency was found to maximize the average heat transfer at the highest value of Reynolds number. Among various nanoparticle shapes, cylindrical ones perform the best heat transfer characteristics in terms of stagnation and average Nusselt number values. At the highest solid volume concentration of the nanoparticles, heat transfer values are higher for a corrugated surface when compared to a flat surface case.

Liquid Single-Phase Flow in an Array of Micro-Pin-Fins—Part I: Heat Transfer Characteristics

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Weilin Qu ◽  
Abel Siu-Ho
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Pin Fin ◽  
Pin Fins ◽  
Micro Pin Fins

This is Paper I of a two-part study concerning thermal and hydrodynamic characteristics of liquid single-phase flow in an array of micro-pin-fins. This paper reports the heat transfer results of the study. An array of 1950 staggered square micro-pin-fins with 200×200 μm2 cross-section by 670 μm height were fabricated into a copper test section. De-ionized water was used as the cooling liquid. Two coolant inlet temperatures of 30°C and 60°C and six maximum mass velocities for each inlet temperature ranging from 183 to 420 kg/m2 s were tested. The corresponding inlet Reynolds number ranged from 45.9 to 179.6. General characteristics of average and local heat transfer were described. Six previous conventional long and intermediate pin-fin correlations and two micro-pin-fin correlations were examined and were found to overpredict the average Nusselt number data. Two new heat transfer correlations were proposed for the average heat transfer based on the present data, in which the average Nusselt number is correlated with the average Reynolds number by power law. Values of the exponent m of the Reynolds number for the two new correlations are fairly close to those for the two previous micro-pin-fin correlations but substantially higher than those for the previous conventional pin-fin correlations, indicating a stronger dependence of the Nusselt number on the Reynolds number in micro-pin-fin arrays. The correlations developed for the average Nusselt number can adequately predict the local Nusselt number data.

Local Heat Transfer in a Rotating Square Channel With Jet Impingement

1999 ◽  
Vol 121 (4) ◽  
pp. 811-818 ◽  
Author(s):  
S.-S. Hsieh ◽  
J.-T. Huang ◽  
C.-F. Liu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient

The influence of rotation and jet mass flow rate on the local heat transfer coefficient for a single confined impinging round jet with a fixed jet-to-wall spacing of H/d = 5 was studied for the jet Reynolds number from 6500 to 26,000 and the rotational Reynolds number from 0 to 112,000. The local heat transfer coefficient along the surface is measured and the effect of the rotation on the stagnation (peak) point, local and average Nusselt number, is presented and discussed. Furthermore, a correlation was developed for the average Nusselt number in terms of the parameters of Rej and ReΩ. In general, the combined jet impingement and rotation effect are shown to affect the heat transfer response. Rotation decreases the average Nusselt number values from 15 to 25 percent in outward and inward radial flow, respectively. Finally, comparisons of the present data with existing results for multijets with rotation were also made.

Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement

2011 ◽  
Author(s):  
Xinjun Wang ◽  
Rui Liu ◽  
Xiaowei Bai ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

A mathematical model used for studying jet impingement cooling characteristics is established, and the rationality of the calculation model and method is confirmed by the experimental data. The CFX software is used to numerically simulate the jet impingement cooling characteristics on a gas turbine blade. The effects of various parameters, such as the arrays of impinging nozzles, the jet Reynolds number, the jet-to-jet distance, the ratio of nozzle-to-surface spacing to jet diameter H/d, and the radius of curvature of the target surface, on the flow and heat transfer characteristics of a impingement cooling process are studied. The results indicate that the impingement jets can make complex vortex in the cooling channel, the flow boundary layer is extremely thin and highly turbulent. Underneath each impingement nozzle, there will appear a low temperature area and a peak of Nusselt number on the impingement target surface, the distribution of temperature and Nusselt number on the target surface are associated with arrangement of impingement nozzles. The average Nusselt number of the in-line arrangement nozzles is higher than that of the staggered arrangement ones. With the increasing of jet Reynolds number, the velocity impinging on the target surface and Nusselt number increase. However, heat transfer of impingement cooling on target surface is not sensitive to the jet nozzles distance; the velocity impinging on the target surface and Nusselt number decrease with the increasing of the H/d value. For the curved target surface cases, the average Nusselt number of the target surface and the effect of heat transfer decreased with the increasing of curvature radius R.

scholarly journals A detailed analysis of flow and heat transfer characteristics under a turbulent intermittent jet impingement on a concave surface

2021 ◽  
pp. 334-334
Author(s):  
Ali Hajimohammadi ◽  
Mehran Zargarabadi ◽  
Javad Mohammadpour
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Computational Study ◽  
Control Volume ◽  
Simple Algorithm ◽  
Jet Impingement ◽  
Concave Surface ◽  
Flow And Heat Transfer

A computational study is carried out of the three-dimensional flow field and heat transfer under a turbulent intermittent circular jet impingement on a concave surface. The control-volume procedure with the SIMPLE algorithm is employed to solve the unsteady RANS (use full form) equations. The RNG k-? model is implemented to simulate turbulence due to its success in predicting similar flows. The numerical results are validated by comparing them with the experimental data. The effects of jet Reynolds number and oscillation frequency on the flow and heat transfer are evaluated. The profiles of instantaneous and time-averaged Nusselt numbers exhibit different trends in axial (x) and circumferential (s) directions. It is found that increasing frequency from 50 to 200 Hz results in considerable time-averaged Nusselt number enhancement in both axial and curvature directions. The intermittent jet at a frequency of 200 Hz enhances the total average Nusselt number by 51.4%, 40%, and 33.7% compared to the steady jet values at jet Reynolds numbers of 10000, 23000, and 40000, respectively. In addition, a correlation for the average Nusselt number is proposed depending on the Reynolds number and the Strouhal number.

Heat Transfer and Pressure Loss Characteristics of Pin-Fins With Different Shapes in a Wide Channel

2017 ◽  
Author(s):  
Jin Xu ◽  
Jiaxu Yao ◽  
Pengfei Su ◽  
Jiang Lei ◽  
Junmei Wu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Bottom Surface ◽  
Number Range ◽  
Pin Fin ◽  
Nominal Diameter ◽  
Pin Fins

Convective heat transfer enhancement and pressure loss characteristics in a wide rectangular channel (AR = 4) with staggered pin fin arrays are investigated experimentally. Six sets of pin fins with the same nominal diameter (Dn = 8mm) are tested, including: Circular, Elliptic, Oblong, Dropform, NACA and Lancet. The relative spanwise pitch (S/Dn = 2) and streamwise pitch (X/Dn = 4.5) are kept the same for all six sets. Same nominal diameter and arrangement guarantee the same blockage area in the channel for each set. Reynolds number based on channel hydraulic diameter is from 10000 to 70000 with an increment of 10000. Using thermochromic liquid crystal (R40C20W), heat transfer coefficients on bottom surface of the channel are achieved. The obtained friction factor, Nusselt number and overall thermal performance are compared with the previously published data from other groups. The averaged Nusselt number of Circular pin fins is the largest in these six pin fins under different Re. Though Elliptic has a moderate level of Nusselt number, its pressure loss is next to the lowest. Elliptic pin fins have pretty good overall thermal performance in the tested Reynolds number range. When Re>40000, Lancet has a same level of performance as Circular, but its pressure loss is much lower than Circular. These two types are both promising alternative configuration to Circular pin fin used in gas turbine blade.

Convective Heat Transfer From Heated Extended Surfaces With a Confined Slot Jet Impingement

2004 ◽  
Author(s):  
L. K. Liu ◽  
M. C. Wu ◽  
C. J. Fang ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Separation Distance ◽  
Nusselt Numbers ◽  
Transfer Behavior ◽  
Extended Surfaces

A series of experimental investigations with stringent measurement methods on the studies related to mixed convection from the horizontally confined extended surfaces with a slot jet impingement have been successfully conducted. The relevant parameters influencing mixed convection performance due to jet impingement and buoyancy include the Grashof number, ratio of jet separation distance to nozzle width, ratio of extended surfaces height to nozzle width and jet Reynolds number. The range of these parameters studied are Grs = 3.77 × 105 – 1.84 × 106, H/W = 1–10, Hs/W = 0.74–3.40 and Re = 63–1383. In the study, the heat transfer behavior on the extended surfaces with confined slot jet impingement such as the temperature distribution, local and average Nusselt numbers on the extended surfaces has been systematically explored. The results manifest that the effect of steady-state Grashof number on heat transfer behavior such as stagnation, local and average Nusselt number is not significant; while the heat transfer performance increases with decreasing jet separation distance or with increasing extended surface height and jet Reynolds number. Besides, two new correlations of local and average Nusselt numbers in terms of H/W, Hs/W and Re are proposed for the cases of extended surfaces. A satisfactory agreement is achieved between the results predicted by these correlations and the experimental data. Finally, a complete composite correlation of steady-state average Nusselt number for mixed convection due to jet impingement and buoyancy is proposed. The comparison of the predictions evaluated by this correlation with all the present experimental data is made. The maximum and average deviations of the predictions from the experimental data are 7.46% and 2.87%, respectively.

Study of a Cooling Feed Pipe With a Covering Plate on a Ribbed Turbine Case

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Fangyuan Liu ◽  
Junkui Mao ◽  
Chao Han ◽  
Yuanjian Liu ◽  
Xingsi Han ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Experimental Tests ◽  
Impinging Jet ◽  
Nusselt Numbers ◽  
Spacing Ratio ◽  
Wall Flow ◽  
Complicated Geometry ◽  
Clearance Control

Considering the complicated geometry in an active clearance control (ACC) system, the design of an improved cooling feed pipe with a covering plate for a high pressure ribbed turbine case was investigated. Numerical calculations were analyzed to obtain the interactions between the impinging jet arrays fed by the pipe. Experimental tests were performed to explore the effect of the Reynolds number (2000–20,000) and the jet-to-surface spacing ratio (6–10) on the streamwise-averaged Nusselt numbers. Additionally, the effect of the crossflow produced by the configuration was investigated. Results showed a confined curved channel was formed by the pipe and ribbed case, which resulted in crossflow. The crossflow evolved into vortices and the streamwise-averaged Nusselt number on the high ribs was subsequently increased. Furthermore, the distribution of the heat transfer on the entire surface became more uniform compared with that of traditional impinging jet arrays. A higher Nusselt number was achieved by decreasing the jet-to-surface spacing and increasing the Reynolds number. This investigation has revealed a cooling configuration for controlling the wall flow and evening the heat transfer on the case surface, especially for the ribs.

Sign in / Sign up

Export Citation Format

Share Document