Comparison of Heat Transfer Characteristics of Radial Jet Reattachment Nozzle to In-Line Impinging Jet Nozzle

1998 ◽  
Vol 120 (2) ◽  
pp. 335-341 ◽  
Author(s):  
J. Seyed-Yagoobi ◽  
V. Narayanan ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Peak Pressure ◽  
Exit Angle ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Zero Degree ◽  
Jet Nozzle ◽  
Flow Power ◽  
Impingement Surface

The heat transfer characteristics of three submerged radial jet reattachment (RJR) nozzles with exit angles of +45, 0, and −10 deg are compared to the heat transfer characteristics of a conventional submerged in-line jet (ILJ) nozzle. The nozzles are compared at their favorable spacing from the impingement surface. The comparisons are based on two criteria: (1) identical fluid flow power, and (2) identical peak pressure exerted on the impingement surface. The local and area-averaged Nusselt numbers are presented. Experiments were conducted for two different flow power conditions. Comparison under identical flow power indicates that significant enhancements in local and comparable enhancements in area-averaged Nusselt numbers can be achieved with the RJR nozzles over the conventional ILJ nozzle while being able to control the net force exerted on the impingement surface. The comparison between the ILJ and RJR nozzles on the basis of the same peak pressure exerted on the impingement surface indicates that the zero degree exit angle RJR nozzle heat transfer characteristics are superior to the ILJ nozzle.

Heat Transfer Characteristics of a Radial Jet Reattachment Flame

1997 ◽  
Vol 119 (2) ◽  
pp. 258-264 ◽  
Author(s):  
J. W. Mohr ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Combustion Process ◽  
Local Heat ◽  
Operating Conditions ◽  
Recirculation Region ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.

Flow and Heat Transfer Enhancement Characteristics of Impinging Jets in Transitional Time Periodic Flow Regimes

2010 ◽  
Author(s):  
Julian P. Gutierrez ◽  
Alfonso Ortega ◽  
Amador M. Guzman
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temporal Evolution ◽  
Flow Regimes ◽  
Periodic Flow ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Time Average

The flow and heat transfer characteristics of an impinging jet on a perpendicular flat surface are obtained by two dimensional numerical simulations of laminar and transitional flow regimes for the Reynolds number of Re = 300, 350, and 400 for a Prandtl number of Pr = 0.7. A fixed jet to plate spacing of H/W = 5 and a given heat flux on the plate surface are considered. Temporal evolution of velocity and temperature fields, Fourier spectra of the velocity temporal evolution and time average local and global Nusselt numbers are obtained for increasing Reynolds numbers for determining the time depending behavior and its effect on the heat transfer characteristics. Numerical simulation results demonstrate that self-sustained transitional periodic flow regimes arise from a laminar regime, when the Reynolds number is further increased to Re = 400 and that these regimes spread out to the whole domain with similar time dependent characteristics due to the flow incompressibility. Evaluations of time average local and global Nusselt numbers demonstrate the asymmetric Gaussian-type spatial distribution and the increase of both parameters when the flow evolves through the transitional periodic regime, with reasonable increases on the pumping power requirements.

Modal Effects on the Local Heat Transfer Characteristics of a Vibrating Body

1999 ◽  
Vol 122 (2) ◽  
pp. 233-239 ◽  
Author(s):  
K. D. Murphy ◽  
T. A. Lambert,
Keyword(s):  
Heat Transfer ◽  
Structural Response ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vibration Modes ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Transverse Vibrations ◽  
Resonance Frequencies

This is an experimental investigation of the effects of forced transverse vibrations on the local heat transfer characteristics of a heated, pinned-pinned beam. In particular, the response of a cylindrical beam near its first two natural frequencies, corresponding to the first two vibration modes, is considered. The results show that there is a strong spatial variation in the local Nusselt number and that these variations are closely related to the mode shape of the response. Because the heat transfer measurements were taken at the resonance frequencies, where the structural response was greatest, the measured Nusselt numbers provide an upper bound for the increased convection due to flexible body vibrations, i.e., in the absence of any rigid-body mode. The possibility of large-amplitude nonlinear vibrations are discussed (though they were not witnessed experimentally) in a theoretical framework. [S0022-1481(00)01702-3]

Heat Transfer Characteristics for Inline and Staggered Arrays of Circular Jets with Crossflow of Spent Air

1979 ◽  
Vol 101 (3) ◽  
pp. 526-531 ◽  
Author(s):  
D. E. Metzger ◽  
L. W. Florschuetz ◽  
D. I. Takeuchi ◽  
R. D. Behee ◽  
R. A. Berry
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Surface ◽  
Geometric Parameters ◽  
Channel Height ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Circular Jets ◽  
Impinging Flow

Heat transfer characteristics were measured for two-dimensional arrays of jets impinging on a surface parallel to the jet orifice plate. The impinging flow was constrained to exit in a single direction along the channel formed by the jet plate and the heat transfer surface. Both mean Nusselt numbers and streamwise Nusselt number profiles are presented as a function of Reynolds number and geometric parameters. The results show that significant periodic variations occur in the streamwise Nusselt number profiles, persisting downstream for at least ten rows of jet holes. Both channel height and hole spacing can have a significant effect on the streamwise profiles, smoothed across the periodic variations. Where significant differences exist, inline hole patterns provide better heat transfer than staggered ones, particularly downstream. These and other effects of the geometric parameters are presented and discussed.

Heat Transfer Characteristics Within the Matrix Cooling Channels

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Andallib Tariq ◽  
Anjana N. Prajapati
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbine Blades ◽  
Percentage Increase ◽  
Heat Transfer Characteristics ◽  
Cooling Channels ◽  
Liquid Crystal Thermography ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
The Matrix

Abstract Matrix or latticework cooling has become a new area of research due to its advantage of providing a structural rigidity to the fragile structures like gas turbine blades, electronic components or circuitries, and compact heat exchangers. In this article, the heat transfer characteristics in matrix cooling channels with different rib angles have been studied using liquid crystal thermography. A total of three matrix models with rib angles 35 deg, 45 deg, and 55 deg having a common subchannel aspect ratio 0.8 have been studied. The results are evaluated in terms of local and average augmentation Nusselt numbers for different regions of the matrix. The augmentation Nusselt number has been found to increase in each region as the angle increases from 35 deg to 45 deg and the same has been found to decrease slightly upon the further increase in angle from 45 deg to 55 deg. The highest percentage increase in augmentation Nusselt number up to 50% has been observed in entry region, whereas the same remained nearly 26–30% in middle and exit regions in streamwise directions, i.e., the effect of the matrix rib angle is more prominent in the entry region. The higher resistance offered by the greater number of ribs for angle 55 deg is believed to be responsible for the decrease in augmentation Nusselt number for Re ≤ 9000.

Numerical Investigation of an Integrated Impingement and Pin-Fin Cooling Configuration in a Wedge Duct

2014 ◽  
Author(s):  
Xiaoxing Feng ◽  
Shuqing Tian ◽  
Jiangtao Bai ◽  
Hong Zhang ◽  
Kefei Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Heat Transfer Characteristics ◽  
Convergence Angle ◽  
Turbine Blade Cooling ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Pin Fins ◽  
Cooling Design

In the gas turbine blade cooling design, impingement insert and pin-fins arranged as an array in the trailing region are usually used to enhance the heat transfer. To investigate the heat transfer characteristics of the integrated impingement and the pin-fin cooling configuration in wedge channels, the numerical simulations with k-ε turbulence model and scalable wall function algorithm are carried out using a commercial CFD code. To reveal the factors that enhance the heat transfer in the blade internal trailing channel, heat transfer characteristics of pin-fins with impingement slot are compared with that without impingement slot. The effect of the ratio of jet impingement distance to pin-fin diameter on the heat transfer is analyzed. The convergence angle of the channel is studied. The heat transfer characteristics of the integrated impingement and pin-fin cooling configuration in the wedge channels are evaluated. The results reveal that the impinging jet enhances largely the heat transfer in the first two rows. In the studied range of L/D = 0.5∼2.0, the heat transfer of the pin-fins with impingement is about 20%∼25% higher than that without impingement. The averaged Nusselt numbers on the endwall surface, the pin surface, and the overall surfaces respectively in the wedge duct increase linearly with the increase of Reynolds number, decrease gradually with the increase of the impingement distance and increase with the increase of the convergence angle.

scholarly journals Effect of Rotation Number on Heat Transfer Characteristics of a Row of Impinging Jets in Confined Channel

2020 ◽  
Vol 77 (1) ◽  
pp. 161-171
Author(s):  
Thantup Nontula ◽  
Natthaporn Kaewchoothong ◽  
Wacharin Kaew-apichai ◽  
Chayut Nuntadusit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rotation Number ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Internal Cooling ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

Jet impingement has been applied for internal cooling in gas turbine blades. In this study, heat transfer characteristics of impinging jets from a row of circular orifices were investigated inside a flow channel with rotations. The Reynolds number (Re) based on the jet mean velocity was fixed at 6,700. Whereas, the rotation number (Ro) of a channel was varied from 0 to 0.0099. The jet-to-impingement distance ratio (L/Dj) and jet pitch ratio (P/Dj) were respective 2 and 4, Dj is a jet diameter of 5 mm. The thermochromic liquid crystals (TLCs) technique was used to measure the heat transfer coefficient distributions on an impingement surface. The results show that heat transfer enhancement on a jet impingement surface depended on the effects of crossflow and Coriolis force. The local Nusselt number at X/Dj?20 on the leading side (LS) was higher than on the trailing side (TS) while heat transfer on the LS at 20?X/Dj?40 gained the lowest, compared to on the TS. The average Nusselt number ratios ( ) on the TS at Ro = 0.0049 gave higher than on the LS of around 2.17%. On the other hand, the on the TS at Ro = 0.0099 was less than the LS of about 0.08%.

Study on Flow and Heat Transfer Characteristics of Tetra-n-Butyl Ammonium Bromide Hydrate Slurry

2011 ◽  
Author(s):  
Hiroyuki Kumano ◽  
Tetsuo Hirata ◽  
Yuki Kobayashi ◽  
Tomoya Kudoh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Solid Fraction ◽  
Flow Condition ◽  
The Other ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
The Difference

Flow and heat transfer characteristics of TBAB hydrate slurry were investigated experimentally. The Reynolds number, diameter of the tubes and solid fraction were varied as experimental parameters. For laminar flow condition, it was found that the ratio of the coefficients of pipe friction and Nusselt numbers increases with solid fraction, and the rate of increase is high in the case of a low Reynolds number. For turbulent flow condition, the ratio of the coefficients of pipe friction and Nusselt numbers was 1 for each condition in the case of a low solid fraction. On the other hand, the ratio of the Nusselt numbers increased with the solid fraction in the high-solid fraction region. Moreover, it was found that the effects of the difference of the size and shape of hydrate particles on the coefficients of pipe friction are large. On the other hand, the effects of the difference of the hydrate particles on the Nusselt number are small.

scholarly journals Effect of Pulsating Flame Jet on Flow and Heat Transfer Characteristics

2020 ◽  
Vol 77 (1) ◽  
pp. 11-23
Author(s):  
Wongsathon Boonyopas ◽  
Nuttamas Uppatam ◽  
Chattawat Aroonrujiphan ◽  
Natthaporn Kaewchoothong ◽  
Somchai Sae-ung ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flame Structure ◽  
Cooling Water ◽  
Digital Camera ◽  
Heat Transfer Characteristics ◽  
Distance Ratio ◽  
Average Heat ◽  
Transfer Characteristics ◽  
Impingement Surface

This research aims to study the effect of pulsating frequency on flame structure and heat transfer characteristics of premixed flame from a pipe nozzle. The LPG and air were used as gas fuel and oxidizer. The equivalence ratios ( ) were evaluated at 0.8, 1.0, and 1.2 under a constant Reynolds number Re = 500. The effect of nozzle-to-impingement surface distance ratio was investigated at H = 2D to 10D, here D is the nozzle diameter at 12 mm. The frequency of pulsating (f) was varied from f = 0 to 10 Hz using a solenoid valve. The flame structures of free flame jet and the impinging flame jet were recorded with a digital camera. The average heat flux on impingement surface was measured with water cooling plate and evaluated from the heat balance of the cooling water. The results show that the pulsating of flame jet become having gap on flame and the mushroom appear at the end of flame. The size of mushroom structure becomes larger when increasing the frequency. While the non-pulsating jet did not appear in this structure. Pulsating flame jet can increase the overall average heat flux on the impingement surface up to about 12% for case of = 1.2 and H = 2D and f = 10 Hz. when compared to case of f = 0 Hz.

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