Air Jet Impingement Heat Transfer at Low Nozzle-to-Plate Spacings Under a Fixed Pumping Power Condition

2009 ◽  
Author(s):  
Kyo Sung Choo ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flow Rate ◽  
Jet Impingement ◽  
Pumping Power ◽  
Heat Transfer Characteristics ◽  
Nusselt Numbers ◽  
Plate Spacing ◽  
Air Jet ◽  
Impingement Heat Transfer

Heat transfer characteristics of an impinging air jet are experimentally investigated under a fixed pumping power condition. The effects of dimensionless pumping power on the Nusselt number are considered. The focus is on cases where the nozzle-to-plate spacing is equal to or less than one nozzle diameter. The results show that the Nusselt number is independent of the nozzle-to-plate spacing under fixed pumping power conditions, while the Nusselt number increases with decreasing the nozzle-to-plate spacing under fixed flow rate conditions. Based on the experimental results, new correlations for the stagnation and average Nusselt numbers of the impinging jet are developed as a function of the pumping power alone.

Investigation of Circular Water Jet Impingement Heat Transfer

2011 ◽  
Author(s):  
Cuicui Liu ◽  
Zeyi Jiang ◽  
Xinxin Zhang ◽  
Qiang Ma ◽  
Yusheng Sun
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Jet Impingement ◽  
Water Jet ◽  
Nozzle Diameter ◽  
Constant Flow Rate ◽  
Impingement Heat Transfer

Mathematical model combining theoretical analysis approach and differential numerical solving techniques has been set up to predict the free surface water jet impingement heat transfer. Heat transfer properties are obtained and validated by comparison with experiments. The characteristic of Nu-r/d distribution is discussed and the effect of nozzle diameter is analyzed. In addition, nozzle arrangements are studied for water jet equipment designation purpose. The results show that: Reynolds number is the dominate parameter in Nu-r/d distribution and area-averaged Nusselt number increases with increasing nozzle diameter. The best heat transfer effect appears when the aspect ratio of rectangular surface equals to 1. Fewer nozzles and bigger single impinged area could get larger Nusselt number under a given total water flow rate and given total impinged area. At a constant flow rate, larger nozzle diameter and smaller Reynolds number present a larger Nusselt number.

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.

Convective Heat Transfer From a Heated Plate to the Orthogonally Impinging Air Jet

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Abhishek B. Bhagwat ◽  
Arunkumar Sridharan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Jet Impingement ◽  
Secondary Peak ◽  
Plate Spacing ◽  
Air Jet ◽  
Plate Distance

The convective heat transfer process between the orthogonal air jet impingement on a uniformly heated flat plate is studied numerically. In this numerical study, three-dimensional (3D) simulations are carried out in Fluent 14.0 to investigate the effect of Reynolds number, distance between nozzle exit and the plate on the heat transfer characteristics. V2F turbulence model has been used to model turbulence. Standard κ–ε, Realizable κ–ε, κ–ε RNG, SST κ–ω, Standard κ–ω, V2F turbulence models have been studied for orthogonal jet impingement in this work. It is observed that for jet exit to plate distance (Z/d) of 0.5 ≤ Z/d ≤ 6, V2F model is best suited. For Z/d ≤ 0.5 and Z/d ≥ 6, numerical results vary significantly from the experimental results. Reynolds number of 12,000, 20,000, and 28,000 has been studied. In this paper, results for various jet exit to the plate distance (Z/d) from 0.5 to 10 are presented. At low jet plate spacing Z/d < 4, secondary peak in Nusselt number distribution over the plate is visible in experimental results. V2F model correctly predicts the secondary peak in Nusselt number variation over the plate. Other models fail to predict the secondary peak which is of significant importance in air jet impingement at low jet-plate spacing (Z/d < 4).

Nanoliquid jet impingement heat transfer for a phase change material (PCM) embedded radial heating system

2021 ◽  
pp. 1-10
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Jet Impingement ◽  
Target Surface ◽  
Spatial Average ◽  
Average Heat ◽  
Plate Spacing ◽  
Impingement Heat Transfer ◽  
Change Material

Abstract Nanoliquid impingement heat transfer with phase change material (PCM) installed radial system is considered. Study is performed by using finite element method for various values of Reynolds numbers (100 ≤ Re ≤ 300), height of PCM (0.25H ≤ hpcm = 0.7H ≤ 0.75H) and plate spacing (0.15H ≤ hpcm = 0.7H ≤ 0.40H). Different configurations with using water, nanoliquid and nanoliquid+PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM while best performance is achieved with nanoliquid and PCM installed configuration. At Re=100 and Re=300, heat transfer improvements of 26% and 25.5% are achieved with nanoliquid+PCM system as compared to water without PCM. Height of the PCM layer also influences the heat transfer dynamic behavior while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM height while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation.

Heat Transfer Enhancement of Jet Impingement on a Flat Plate Attached by a Porous Medium with a Center Cavity

2010 ◽  
Vol 297-301 ◽  
pp. 427-432 ◽  
Author(s):  
Pey Shey Wu ◽  
Chia Yu Hsieh ◽  
Shen Ta Tsai
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Nusselt Number ◽  
Flat Plate ◽  
Porous Layer ◽  
Jet Impingement ◽  
Stagnation Zone ◽  
Transfer Enhancement ◽  
Maximum Enhancement ◽  
Impingement Heat Transfer

Jet impingement heat transfer on a target plate covered with a thick porous layer with or without a cylindrical center cavity is experimentally investigated using the transient liquid crystal technique. Based on the results of jet impingement on a bare flat plate, heat transfer enhancement due to the attachment of porous medium is assessed. The varying parameters in the experiments include the nozzle-to-plate distance, jet Reynolds number, jet-to-cavity diameter ratio, and the cavity depth. Results of Nusselt number distribution, stagnation-zone Nusselt number, and averaged Nusselt number over a region of 3 times the hole diameter are documented. Experimental results show that the attachment of the porous layer with a center cavity can either hamper, or effectively enhance the jet impingement heat transfer over a flat plate. The maximum enhancement occurs at jet Reynolds number of 12400 when the cavity is a through hole and the cavity has the same diameter as the jet. The stagnation-zone Nusselt number increases 58.3% and the averaged Nusselt number increases 77.5% at the maximum enhancement condition. On the other hand, the addition of the thick porous layer without a center cavity gave rise to severe adverse effect on jet impingement heat transfer.

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.

Transient Convective Heat Transfer of Air Jet Impinging Onto a Confined Ceramic-Based MCM Disk

2001 ◽  
Author(s):  
W. S. Su ◽  
L. K. Liu ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Jet Impingement ◽  
Disk Surface ◽  
Separation Distance ◽  
Transient Time ◽  
Nusselt Numbers ◽  
Air Jet ◽  
Transient Experiments ◽  
Transfer Behavior

Abstract Transient heat transfer behavior from a horizontally confined ceramic-based MCM disk with jet impingement has been systematically explored. The relevant parameters influencing heat transfer performance are the steady-state Grashof number, jet Reynolds number, and ratio of jet separation distance to nozzle diameter. In addition, an effective time, ton, representing a certain transient time when the mixed convection effect due to jet impingement and buoyancy becomes significant relative to heat conduction, is introduced. Both the transient chip and average Nusselt numbers on the MCM disk surface decrease with time in a very beginning period of 0 ≤ t &lt; ton, whereas it gradually increases or keeps constant with time and finally approaches the steady-state value in the period of ton ≤ t &lt; ts. As compared with the steady-state results, if the transient chip and average heat transfer behaviors may be considered as a superposition of a series of quasi-steady states, the transient chip and average Nusselt numbers in all the present transient experiments can be properly predicted by the existing steady-state correlations when t ≥ 4 min in the power-on transient period.

Sign in / Sign up

Export Citation Format

Share Document