scholarly journals Numerical Investigation of Heat Transfer and Pressure Force from Multiple Jets Impinging on a Moving Flat Surface

2020 ◽  
Vol 38 (3) ◽  
pp. 601-610
Author(s):  
Ali Chitsazan ◽  
Birgit Glasmacher
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Relative Velocity ◽  
Flat Surface ◽  
Velocity Ratio ◽  
Jet Impingement ◽  
Pressure Force ◽  
Heat Transfer Characteristics ◽  
Single Row ◽  
Surface Distance

In this paper extensive numerical investigation of the heat transfer characteristics and the pressure force of jet impingement from the single row and multiple rows on a fixed and moving flat surface are reported. The computations were carried out over a wide range of parameters: relative nozzle-to-surface distance (H/d) from 0.5 to 6, relative nozzle to nozzle distances (S/d) from 4 to 10, jet angle from 45° to 90°, relative velocity ratio (Vplate/Vj) i.e. ratio of surface velocity to jet velocity from 0 to 1. The jet Reynolds number (Re) of 2,500, 3,400, 10,000, 20,000, and 23,000 and the number of jet rows of 1, 2, 4, and 8 have been used. It was found that the numerical accuracy by SST k-ω model is reasonably high to allow for a discussion of the main flow and heat transfer characteristics. The jet impingement heat transfer performance is generally enhanced with the increase of jet Reynolds number and jet angle and with the decrease of surface distance (H/d), jet distance (S/d) and the relative velocity ratio (Vplate/Vj) within the range examined. The pressure force coefficients on the impingement surface are relatively insensitive to Re number and the velocity ratio within the range examined, while it has highly dependent on H/d, S/d and jet angle. For multiple rows of aligned jet holes, the flow pattern exhibited a different shape due to the different intensity of the interference between adjacent air jets. The effect of multiple rows with regards to the impact on average Nu and pressure force coefficient for different geometry variations such as Re, H/d, S/d, VR and ɵ is negligible compared to the single row by approximately 9 and 13% in average respectively. Based on the computed results, equations of dimensionless parameters are correlated.

Experimental Investigation of Jet Impingement Heat Transfer in Cross-Flow Modified by a V-Shaped Rib

2014 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Heat Transfer ◽  
The Cross

Experimental studies are carried out to investigate the jet impingement heat transfer characteristics in cross-flow with and without the presence of a 45 deg V-shaped rib. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. The ratio of nozzle-to-surface spacing to jet diameter is 3.56, the jet Reynolds number is kept at 17,000, the cross-flow Reynolds number spans from 32,700 to 65,000, the velocity ratio of jet to cross-flow ranges from 1.5 to 3.0. The impingement heat transfer characteristics in cross-flow are changed from the results without the cross-flow, and they are strongly affected by the velocity ratio. The presence of a V-shaped rib significantly modifies the heat transfer patterns of the impinging jet in cross-flow. Compared to the results without ribs, the heat transfer over the ribbed surface is enhanced for a low velocity ratio but retarded for a high velocity ratio, depending on the interaction between the rib induced flow and the impinging jet.

Heat Transfer Characteristics of an Impinging Jet in Crossflow

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Lei Wang ◽  
Bengt Sundén ◽  
Andreas Borg ◽  
Hans Abrahamsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Velocity Ratio ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Jet In Crossflow

The heat transfer characteristics of an impinging jet into a crossflow have been investigated by the liquid crystal thermography technique. The jet nozzle is circular and is inclined at 10 deg with respect to the target wall. In a turbulent flow regime, the effects of the jet Reynolds number, the velocity ratio, and the crossflow Reynolds number on the heat transfer are examined. The results show that the heat transfer patterns are strongly affected by the jet Reynolds number and the velocity ratio. For a given jet Reynolds number, it is found that the crossflow diminishes the peak Nusselt number in the jet impingement region. However, in the wall jet region, the results suggest that the local heat transfer is nearly independent of the crossflow Reynolds number.

Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement Cooling

2011 ◽  
Vol 148-149 ◽  
pp. 680-683
Author(s):  
Run Peng Sun ◽  
Wei Bing Zhu ◽  
Hong Chen ◽  
Chang Jiang Chen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Cross Flow ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Transfer Characteristic ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Three-dimensional numerical study is conducted to investigate the heat transfer characteristics for the flow impingement cooling in the narrow passage based on cooling technology of turbine blade.The effects of the jet Reynolds number, impingement distance and initial cross-flow on heat transfer characteristic are investigated.Results show that when other parameters remain unchanged local heat transfer coefficient increases with increase of jet Reynolds number；overall heat transfer effect is reduced by initial cross-flow；there is an optimal distance to the best effect of heat transfer.

Heat Transfer Characteristics of Low Reynolds Number Turbulent Swirling LPG/Air Flame Impinging on a Flat Surface

2010 ◽  
Author(s):  
Arun Kaushal ◽  
Gurpreet Singh ◽  
Subhash Chander ◽  
Anjan Ray
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Surface ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Heat Transfer Characteristics ◽  
Swirl Number ◽  
Transfer Characteristics ◽  
Swirling Flames ◽  
Low Reynolds

An experimental study has been conducted to determine the heat transfer characteristics for low Reynolds number turbulent swirling LPG/Air flames impinging on a flat surface. Effect of variation of Reynolds number (3000–7000), dimensionless separation distance (H/d = 1 to 6) and equivalence ratio (φ = 0.8 to 2) on heat transfer characteristics has been determined at constant swirl number of 4. Further, experiments were also conducted to investigate the effect of swirl number on heat transfer characteristics at Re = 7000, φ = 1.0 and H/d = 5. It has been concluded that the major drawback of flame impingement i.e., non-uniformity in the heating can be resolved by using swirling flames in place of non-swirling flames. With increase in Reynolds number the flame becomes longer and broader. Also, at higher Re the flame becomes noisy and violent because of the enhanced turbulences in the flame. A dip in the temperature was observed at the stagnation point at all Re and this dip was more significant at higher Re. At small separation distances (H/d = 1 and 2) and at large Reynolds numbers (Re = 7000) heating is comparatively more non-uniform because of close proximity of the visible reaction zone to the plate resulting in intense heating in the stagnation region. High average heat fluxes were obtained at low separation distances and at larger Reynolds numbers.

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.

Heat Transfer Characteristics of CuO-Water Nanofluids Jet Impingement on a Hot Surface

2016 ◽  
Author(s):  
Sandesh S. Chougule ◽  
Mayank Modak ◽  
Prajakta D. Gharge ◽  
S. K. Sahu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Test Surface ◽  
Initial Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Heat Transfer ◽  
Hot Surface

In present study, an experimental investigation has been carried out to analyze the heat transfer characteristics of CuO-water nanofluids jets on a hot surface. A rectangular stainless steel foil (AISI-304, 0.15 mm thick) is used as a test surface is electrically heated to obtain the required initial temperature. The distribution of heat flux on the target surface is evaluated from the recorded thermal images during transient cooling. The effect of nanoparticle concentration and Reynolds number of the nanofluids jet impingement heat transfer characteristics is studied. Tests were performed for an initial surface temperature of 500°C, Reynolds number (5000≤Re≤13000), CuO-water nanofluids concentration (Φ= 0.15%, 0.6%) and nozzle to plate distance was l/d= 4.

An Experimental Investigation on Heat Transfer Characteristics of Hot Surface by Using CuO–Water Nanofluids in Circular Jet Impingement Cooling

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Mayank Modak ◽  
Sandesh S. Chougule ◽  
Santosh K. Sahu
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Jet Impingement ◽  
Test Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Hot Surface ◽  
Plate Distance

In the present study, an experimental investigation has been carried out to analyze the heat transfer characteristics of CuO–water nanofluids jet on a hot surface. A rectangular stainless steel foil (AISI-304, 0.15 mm thick) used as the test surface is electrically heated to obtain the required initial temperature (500 °C). The distribution of surface heat flux on the target surface is evaluated from the recorded thermal images during transient cooling. The effect of nanoparticle concentration and Reynolds number of the nanofluids on the heat transfer characteristics is studied. Tests are performed for varied range of Reynolds number (5000 ≤ Re ≤ 12,000), two different CuO–water nanofluids concentration (Ф = 0.15%, 0.6%) and two different nozzle to plate distance (l/d = 6, 12). The enhancement in Nusselt number for CuO–water nanofluids was found to be 14% and 90%, for nanofluids concentration of Ф = 0.15% and Ф = 0.60%, respectively, compared to pure water. The test surface characteristics after nanofluids jet impingement are studied using scanning electron microscope (SEM). Based on the investigation, a correlation among various parameters, namely, Reynolds number (Re), Prandtl number (Pr), nozzle to plate distance (l/d), and Nusselt number (Nu), is presented.

Numerical Investigations of Flow and Heat Transfer Characteristics Between Turbulent Double Jet Impingement and a Moving Plate

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
N. Satish ◽  
K. Venkatasubbaiah
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Jet Impingement ◽  
Heat Transfer Characteristics ◽  
Moving Plate ◽  
Enhancement Of Heat Transfer ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Plate Velocity ◽  
Single Jet

The analysis of fluid flow and heat transfer characteristics of double turbulent jet flow impinging on a stationary and moving plate has been numerically studied. Unsteady-state two-dimensional incompressible turbulent forced convection flow is considered for present analysis. Turbulence is modelled by the Reynolds-averaged Navier–Stokes (RANS) equation with the k − ε model and enhanced wall treatment. The governing equations are solved using a finite volume based commercial solver. The results for the effect of single jet and double jet, jet Reynolds number, plate velocity, location, and center spacing between the two jets on flow and heat transfer characteristics are reported. The results show that the enhancement of heat transfer is 32.70% for the double jet compared with the single jet impingement on a stationary plate. As significant enhancement of heat transfer is observed with an increase in the second jet Reynolds number and plate velocity. The results show that the size and shape of the recirculation zones between jets are greatly altered with respect to spacing between the jets to the plate and the center distance between the jets. The results show that the enhancement of heat transfer is 37.3% for moving plate velocity due to a decrease in the spacing between the jets and the plate from 6 to 4. Results show that the local peak Nusselt number is influenced by the plate velocity. These results are validated by experimental and numerical results available in the literature.

Experimental Investigation of Impinging Heat Transfer of the Pulsed Chevron Jet on a Semicylindrical Concave Plate

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Yuan-wei Lyu ◽  
Jing-zhou Zhang ◽  
Xi-cheng Liu ◽  
Yong Shan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flat Surface ◽  
Jet Impingement ◽  
Concave Surface ◽  
Wall Jet ◽  
Surface Distance ◽  
Maximum Reduction ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer

Impinging heat transferred by a pulsed jet induced by a six-chevron nozzle on a semicylindrical concave surface is investigated by varying jet Reynolds numbers (5000 ≤ Re ≤ 20,000), operational frequencies (0 Hz ≤ f ≤ 25 Hz), and dimensionless nozzle-to-surface distances (1 ≤ H/d ≤ 8) while fixing the duty cycle as DC = 0.5. The semicylindrical concave surface has a cylinder diameter-to-nozzle diameter ratio (D/d) of 10. The results show that the nozzle-to-surface distance has a significant impact on the impingement heat transfer of the pulsed chevron jet. An optimal nozzle-to-surface distance for achieving the maximum stagnation Nusselt number appears at H/d  =  6. In the wall jet zone, the averaged Nusselt number is the largest at H/d = 2 and the smallest at H/d = 8. In comparison with the chevron steady jet impingement, the effect of nozzle-to-surface distance on the convective heat transfer becomes less notable for the pulsed chevron jet impingement. The stagnation Nusselt number under the pulsed chevron jet impingement is mostly less than that under the chevron steady jet impingement. However, at H/d = 8, the pulsed chevron jet is more effective than the steady jet. This study confirmed that the pulsed chevron jet produced higher azimuthally averaged Nusselt numbers than the steady chevron jet in the wall jet flow zone at large nozzle-to-surface distances. The stagnation Nusselt numbers by the pulsed chevron jet impingement have a maximum reduction of 21.0% (f = 20 Hz, H/d = 4, and Re = 2000) compared with that of the steady chevron jet impingement. Also, the pulsed chevron jet impingement heat transfer on a concave surface is less effective compared to a flat surface. The stagnation Nusselt numbers on the semicylindrical concave surface have a maximum reduction of about 37.7% (f = 20 Hz, H/d = 8, and Re = 5000) compared with that on the flat surface.

Heat Transfer due to the Impingement of an Axisymmetric Synthetic Jet Emanating From a Circular Orifice: A Numerical Investigation of a Canonical Geometry

2013 ◽  
Author(s):  
M. Ebrahim ◽  
L. Silva ◽  
A. Ortega
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Stokes Equations ◽  
Heated Surface ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Synthetic Jet ◽  
Heated Wall ◽  
Driving Frequency ◽  
Surface Distance

Synthetic jets are produced by periodically injecting and ejecting fluid from an orifice. The mass flow rate is conserved in such a jet but net momentum flux is created due to the difference in the fluid dynamics at the orifice between the ejection and suction parts of each cycle. When pointed towards a heated surface, the synthetic jet can be used for cooling using the well-known advantages of jet impingement. In the present work, we have created a “canonical” jet in order to investigate the flow and heat transfer of a purely periodic synthetic jet which is not influenced by the manner in which it is generated. As such the “canonical” jet and the resulting heat transfer, can be considered to be dependent solely on the driving suction/ejection mechanisms at the orifice and thus can be examined independently of the actuator. The unsteady Navier-Stokes equations and the convection-diffusion equation were solved using a fully unsteady, laminar, three-dimensional axisymmetric finite volume approach in order to capture the complex time-dependent flow field created by different frequencies. The influence of jet-to-surface distance, Reynolds number, and driving frequency on heat transfer were investigated. Both stagnation and averaged Nusselt numbers were observed to be less dependent on frequency. Heat transfer was found to be higher at high Re numbers and low jet-to-surface distance. Results were compared with the steady continuous jet, experimental data of previous studies and the canonical slot synthetic jet at the same Reynolds number. A circular jet was found to be less efficient in removing heat over the heated wall than a slot synthetic jet.

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