The Experimental Investigation of Impinging Heat Transfer of Pulsation Jet on the Flat Plate

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Yuan-wei Lyu ◽  
Jing-zhou Zhang ◽  
Yong Shan ◽  
Xiao-ming Tan
Keyword(s):  
Heat Transfer ◽  
Strouhal Number ◽  
Measurement Data ◽  
Jet Impingement ◽  
Transfer Enhancement ◽  
Surface Distance ◽  
Impingement Heat Transfer ◽  
Enhancement Factors ◽  
Pulsating Jet ◽  
The Relationship

A series of tests were performed for the pulsating jet impingement heat transfer by varying the Reynolds number (5000 ≤ Re ≤ 20,000), operation frequency (10 Hz ≤ f ≤ 25 Hz), and dimensionless nozzle-to-surface distance (1≤H/d≤8) while fixing the duty cycle (DC) = 0.5(280 measurement data in total). Specific attention was paid to examine the relationship between the pulsating jet impingement and the steady jet impingement. By using a modified Strouhal number (Sr(H/d)), the test data are analyzed according to three classifications of the enhancement factors a = Nupulsation jet/Nusteady jet (such as a ∈ (Min,0.899), a ∈ (0.95, 1.049) and a ∈ (1.1, Max)). The results show that the identification of pulsating jet impingement in related to the steady jet impingement is suitable by using the modified Strouhal number (Sr(H/d)). Within the scope of this study, the most possibilities for the heat transfer enhancement by using pulsating jet impingement are suggested as the following conditions: Re ≤ 7500 and Sr(H/d) ≥ 0.04, Re ≥ 17500, and 0.01 ≤ Sr(H/d) ≤ 0.03; 10 Hz ≤ f ≤ 20 Hz and Sr(H/d) ≥ 0.04; H/d ≥ 6 and most of current Sr(H/d). While under such conditions, 7500 ≤ Re ≤ 15,000 and Sr(H/d) ≤ 0.02; f ≥ 20 Hz and Sr(H/d) ≤ 0.04; H/d ≤ 2 and Sr(H/d) ≤ 0.02, the pulsating jet impingement makes the heat transfer weaker than the steady jet impingement more obviously.

Pulsating Jet Impingement Heat Transfer Enhancement

2008 ◽  
Vol 26 (4) ◽  
pp. 433-442 ◽  
Author(s):  
W. Liewkongsataporn ◽  
T. Patterson ◽  
F. Ahrens
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Jet Impingement ◽  
Transfer Enhancement ◽  
Impingement Heat Transfer ◽  
Pulsating Jet

Experimental Research on CO2 Pool Boiling Heat Transfer Outside a Single Tube

2016 ◽  
Author(s):  
Shengchun Liu ◽  
Ziteng Dong ◽  
Wenkai Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Research ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Smooth Tube ◽  
Transfer Enhancement ◽  
Pool Boiling Heat Transfer ◽  
Theoretical Support ◽  
Enhancement Factors ◽  
The Relationship

Both theoretical and experimental research on CO2 physical characteristics and pool boiling heat transfer are taken in this paper. It is analyzed that CO2 pool boiling heat transfer outside the screwed and smooth tube based on experimental study. It is resulted with the relationship between heat transfer coefficient, evaporating pressure and the heat flux. It is also indicated the enhancement factors of three screwed tube compared with smooth tube. The results provides a basis for promoting CO2 heat transfer enhancement, and also provides a theoretical support in engineering.

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.

Circulation of a Vortex Ring Generated by Pulsating Jet Flow

2011 ◽  
Author(s):  
Fujio Akagi ◽  
Keisuke Kawabata ◽  
Youichi Ando ◽  
Sumio Yamaguchi ◽  
Masato Furukawa
Keyword(s):  
Strouhal Number ◽  
Measurement Data ◽  
Jet Flow ◽  
Shear Layers ◽  
Convection Velocity ◽  
Formation Time ◽  
Vortex Rings ◽  
Translation Velocity ◽  
Pulsating Jet ◽  
The Relationship

In order to use vortex rings for mass and momentum transport, the relationship between the circulation of vortex rings generated continuously by a pulsating jet flow, which are referred to herein as ‘cyclic vortex rings’, and the conditions of jet flow are investigated experimentally. The results indicate that the formation time at which the cyclic vortex rings reach maximum circulation, i.e., become optimal vortex rings, can be estimated using the concept proposed by Gharib et al. Based on their concept, the optimal vortex rings are formed when the translation velocity of the vortex core becomes equal to the convection velocity of the shear layer of the jet. The translation velocity of vortex rings and the convection velocity of shear layers can be estimated by empirical equations under pulsating jet conditions. Therefore, the formation time of the optimal vortex rings can be estimated from the pulsating jet conditions, when the circulation of vortex rings stop growing and the vortex rings start to become disconnected from the shear layers. The circulation of vortex rings estimated using this method is in good agreement with the measurement data within the measurement error. There exists a specific Strouhal number at which the circulation of the vortex rings reaches the maximum value. This Strouhal number is expected to be the optimal generating condition of cyclic vortex rings for using transportation.

Impingement Heat Transfer Innovations and Enhancements: a Discussion on Selected Geometrical Features

2021 ◽  
Author(s):  
Sandip Dutta ◽  
Prashant Singh
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Jet Impingement ◽  
Target Surface ◽  
High Porosity ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Impingement Heat Transfer ◽  
Geometrical Features ◽  
Target Spacing

Abstract Impingement heat transfer is considered as one of the most effective cooling technologies that yields in high localized convective heat transfer coefficient. This paper studies different configurational parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand what are critical and how these heat transfer enhancement concepts work. These enhancement factors have been explored in detail by many researchers, including standard parameters such as normalized distance between adjacent jets and jet-to-target spacing, and those known benefits are not repeated here. The aim of this paper is to stimulate the current scientific knowledge of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to 3D printing technologies. However, the orifice studies show that it is hard to beat a sharp-edged round orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number. Reduction in crossflow has been attempted with channel modifications. Use of high porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion are provided in conclusion.

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.

Jet Impingement Heat Transfer Enhancement on a rib-roughened Flat Plate

2016 ◽  
Author(s):  
A H. Alenezi ◽  
Joao Amaral Teixeira ◽  
Abdulmajid Addali A. ◽  
Abdelaziz Gamil A. A. ◽  
Hamad M. Alhajeri
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Heat Transfer Enhancement ◽  
Jet Impingement ◽  
Transfer Enhancement ◽  
Impingement Heat Transfer ◽  
Rib Roughened
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