Surface Curvature Effect on Slot-Air-Jet Impingement Cooling Flow and Heat Transfer Process

1991 ◽  
Vol 113 (4) ◽  
pp. 858-864 ◽  
Author(s):  
C. Gau ◽  
C. M. Chung
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Transfer Process ◽  
Convex Surface ◽  
Heat Transfer Process ◽  
Surface Curvature ◽  
Curvature Effect ◽  
Impingement Cooling ◽  
Cooling Flow ◽  
Air Jet

Experiments are performed to study surface curvature effects on the impingement cooling flow and the heat transfer processes over a concave and a convex surface. A single air jet issuing from different size slots continuously impinges normally on the concave side or the convexside of a heated semicylindrical surface. An electrical resistance wire is used to generate smoke, which allows us to visualize the impinging flow structure. The local heat transfer Nusselt number along the surfaces is measured. For impingement on a convex surface, three-dimensional counterrotating vortices on the stagnation point are initiated, which result in the enhancement of the heat transfer process. For impingement on a concave surface, the heat transfer Nusselt number increases with increasing surface curvature, which suggests the initiation of Taylor–Go¨rtler vortices along the surface. In the experiment, the Reynolds number ranges from 6000 to 350,000, the slot-to-plate spacing from 2 to 16, and the diameter-to-slot-width ratio D/b from 8 to 45.7. Correlations of both the stagnation point and the average Nusselt number over the curved surface, which account for the surface curvature effect, are presented.

Effectiveness of Jet Impingement Cooling System on Convex Surface

2016 ◽  
Vol 819 ◽  
pp. 74-77
Author(s):  
Mohamad Nor Musa ◽  
Mohamad Faizal Fauzi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Convex Surface ◽  
Cooling System ◽  
Jet Impingement ◽  
Impingement Cooling ◽  
Reynolds Number Increase ◽  
Number Increase

Jet impingement is one of cooling method used in order to achieve high heat transfer coefficient and widely used in industry applications such as drying of textile and film, glass and plastic sheets, cooling of electronic equipment, and heat treatment of metals. In this research, it focused on the effectiveness of the jet impingement cooling system on the convex surface based on mass blowing rate and nozzle exit to surface parameters. The scope of experiment research encompasses are convex surface made of aluminum alloy and diameter 12.5cm. For mass blowing rate parameters, it use ʋjet = 1.98m/s, 3.03m/s, 4.97m/s and 6.00m/s which has Reynolds number range from 643 until 1946. Nozzle exit to surface distance,s/d = 4.0, 8.0 and 12.0. In this experiment model, a major components that involved are a compressor, nozzle, convex surface model, K thermocouple and heater. For the result of the experiment, it is based on the data obtain through a heat transfer coefficient and Nusselt number which the plotted graph focus on the space spacing and Reynolds number parameters. For the graph Nusselt number versus s/d at stagnation point c/d=0, it shown that when the Reynolds number increase, the Nusselt number also increase. In term of effectiveness, the s/d=12.0 has a good effectiveness jet impingement cooling system. For the graph of Nusselt number versus Reynolds at stagnation point, c/d=0, as Reynolds number increase, the Nusselt number increase too. From this experiment the better cooling effect is at Reynolds number, Re=1946. Thus, it can conclude that, effectiveness for jet impingement cooling system on the convex surface occurs at the highest Reynolds number.

Thermal Characteristics of a Free Radial Liquid Jet Impinging on a Hot Surface

2001 ◽  
Author(s):  
Ahmed Hassaneen ◽  
Muhammad M. Rahman
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Transfer Process ◽  
Average Nusselt Number ◽  
Incidence Angle ◽  
Thermal Characteristics ◽  
Heat Transfer Process ◽  
Liquid Jet ◽  
Geometrical Parameters

Abstract This paper presents results of CFD computation of the heat transfer process in a radial impinging free liquid jet. The jet is impinging on a flat circular disk and the flow downstream of the impinging area spreads outward and inward on the disk. The solution is made under steady state and laminar flow conditions. The solution is obtained for the axisymmetric radial jet with two free surfaces. Different incidence angle of the jet and different flow Reynolds number (Re) were considered in the analysis. The effect of jet elevation from the disk is discussed in addition to different thickness of the hot plate. Due to lack of experimental data on this typical flow problem, the results were qualitatively compared with the available experimental data of the closest flow condition in the literature. The jet incidence angle and jet elevation were found to have strong effects on the velocity field and the free surface position of the spreading flow on the disk and consequently affected the heat transfer process. The disc thickness is also found to have a strong effect on the local and average Nusselt number. Results are documented by plotting the distribution of local and average Nusselt number versus the geometrical parameters.

scholarly journals Enhanced heat transfer under the influence of coherent structure induced by arc vortex generator in square pipe flows

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1379-1386
Author(s):  
Wei Wang ◽  
Xiao-Jiao Sun ◽  
Yang Gao ◽  
Xin-Lei Guan ◽  
Chu-Wen Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbulent Flows ◽  
Transfer Process ◽  
Coherent Structures ◽  
Vortex Generator ◽  
Heat Transfer Process ◽  
Turbulent Fluctuation ◽  
Hairpin Vortices ◽  
Eddy Simulation

Experiments and numerical simulations were both performed to investigate coherent structures and heat transfer process in a square pipe turbulent flows induced by arc vortex generator. The velocity fields of induced turbulent flow was obtained by planar particle image velocimetry. The analysis of velocity profiles revealed the co-existence of various coherent structures. Turbulent fluctuation quantities, such as turbulent intensities, Reynolds stress, etc. exhibited the different behaviors of fluid motions introduced by arc vortex generator. Probability density function of swirling strength showed the complication of the vortex-rotating. Heat transfer process was simulated using large eddy simulation. The results of Nusselt number achieved the maximal improvement 57% with the use of arc vortex generator. The distribution of Nusselt number was in good agreement with the distribution of coherent structures, especially hairpin vortices and subsequent secondary coherent structures, which highlighted the influence of coherent structures by arc vortex generator on heat transfer enhancement.

The Consequence of Target Surface Curvature in the Jet Impingement Cooling

2015 ◽  
Vol 766-767 ◽  
pp. 1148-1152
Author(s):  
M. Karthigairajan ◽  
S. Mohanamurugan ◽  
K. Umanath
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convex Surface ◽  
Heated Surface ◽  
Jet Impingement ◽  
Target Surface ◽  
Uniform Heat Flux ◽  
Impingement Cooling ◽  
Air Jet ◽  
Increase With Increase

An experiment sturdy has been carried out for jet impingement cooling on the spherically convex surface is the development of mechanism. The effect of curvature, Space between jet exit and target surface, and Reynolds number on heat transfer is investigated for around air jet on hemispherical surface. The flow at the jet exit has fully developed velocity profile. A uniform heat flux boundary is created on the heated surface. The experiments are performed for 5000<Re<25000, 2<L/d<10, and jet diameters ranging from 1.3, 2.1, 3.4, 4.0 and 5.2 cm. In the mean time effect of curvature on local heat transfer is negligible at the wall jet region corresponding to r/d>0.5. From the experimental results the variation of the D/d ratio with local Nusselt number (Nust) for various Reynolds numbers and various L/d ratios are plotted. The results show that Nust increase with increase in curvature and the effect of the curvature will high at high Reynolds number. i.e. Nust at Re=25000 is 25% higher than at Re= 5000 This may be attributed to an increase in curvature increases acceleration, & size of three dimensional counter rotating vortices at stagnation point and the increment of Reynolds number increases the jet momentum, and also enhances the vortices creation. Nust is peaking in the L/d ratio of 6 because of high turbulence intensity as this distance.

Mixed Convection in Cooling of a Surface by Two-Dimensional Confined Slot Jet Impingement

2003 ◽  
Author(s):  
Dipankar Sahoo ◽  
M. A. R. Sharif
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Transfer Process ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Heat Transfer Process ◽  
Two Dimensional ◽  
Hot Surface

The flow and heat transfer characteristics in the cooling of a heated surface by impinging confined jets have been investigated numerically through the steady state solution of laminar two-dimensional Navier-Stokes and energy equations. The principal objective of this study is to investigate the effect of buoyancy on the associated heat transfer process. Numerical computations are done for vertically downward directed two-dimensional confined slot jets impinging on a hot isothermal surface at the bottom. The computed flow patterns and isotherms for various domain aspect ratios and for a range of jet exit Reynolds numbers (100–500) and Richardson numbers (0–10) are analyzed to understand the heat transfer phenomena. The local and average Nusselt numbers at the hot surface for various conditions are compared. It is observed that for a given domain aspect ratio and Richardson number, the average Nusselt number at the hot surface increases with increasing jet exit Reynolds number. On the other hand, for a given aspect ratio and Reynolds number the average Nusselt number does not change significantly with Richardson number indicating that the buoyancy effects are not very significant on the overall heat transfer process for the range of jet Reynolds number considered in this study.

Design of the Blast Furnace Wall Structure Made of Efficient Materials. Part 4. Calculation Examples

2020 ◽  
Vol 786 (11) ◽  
pp. 30-34
Author(s):  
A.M. IBRAGIMOV ◽  
◽  
L.Yu. GNEDINA ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Blast Furnace ◽  
Boundary Value Problems ◽  
Transfer Process ◽  
Rational Design ◽  
Boundary Value ◽  
Heat Transfer Process ◽  
Furnace Wall ◽  
Time Interval

This work is part of a series of articles under the general title The structural design of the blast furnace wall from efficient materials [1–3]. In part 1, Problem statement and calculation prerequisites, typical multilayer enclosing structures of a blast furnace are considered. The layers that make up these structures are described. The main attention is paid to the lining layer. The process of iron smelting and temperature conditions in the characteristic layers of the internal environment of the furnace is briefly described. Based on the theory of A.V. Lykov, the initial equations describing the interrelated transfer of heat and mass in a solid are analyzed in relation to the task – an adequate description of the processes for the purpose of further rational design of the multilayer enclosing structure of the blast furnace. A priori the enclosing structure is considered from a mathematical point of view as the unlimited plate. In part 2, Solving boundary value problems of heat transfer, boundary value problems of heat transfer in individual layers of a structure with different boundary conditions are considered, their solutions, which are basic when developing a mathematical model of a non-stationary heat transfer process in a multi-layer enclosing structure, are given. Part 3 presents a mathematical model of the heat transfer process in the enclosing structure and an algorithm for its implementation. The proposed mathematical model makes it possible to solve a large number of problems. Part 4 presents a number of examples of calculating the heat transfer process in a multilayer blast furnace enclosing structure. The results obtained correlate with the results obtained by other authors, this makes it possible to conclude that the new mathematical model is suitable for solving the problem of rational design of the enclosing structure, as well as to simulate situations that occur at any time interval of operation of the blast furnace enclosure.

Numerical Simulation for Microconvection Around Nano-Particle With Brownian Motion in Liquid

2003 ◽  
Author(s):  
B. X. Wang ◽  
H. Li ◽  
X. F. Peng ◽  
L. X. Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Brownian Motion ◽  
Numerical Model ◽  
Temperature Gradient ◽  
Transfer Process ◽  
Heat Transfer Process ◽  
Nano Particles ◽  
Analytic Method ◽  
Nano Particle

The development of a numerical model for analyzing the effect of the nano-particles’ Brownian motion on the heat transfer is described. By using the Maxwell velocity distribution relations to calculate the most possible velocity of fluid molecules at certain temperature gradient location around the nano-particle, the interaction between fluid molecules and one single nano-particle is analyzed and calculated. Based on this, a syntonic system is proposed and the coupled effect that Brownian motion of nano-particles has on fluid molecules is simulated. This is used to formulate a reasonable analytic method, facilitating laboratory study. The results provide the essential features of the heat transfer process, contributed by micro-convection to be considered.

The 3-D Numerical Simulation of Heat Transfer Process of Finned Copper Tube

2011 ◽  
Vol 393-395 ◽  
pp. 412-415
Author(s):  
Jian Hua Zhong ◽  
Li Ming Jiang ◽  
Kai Feng
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Theoretical Calculations ◽  
Structural Parameters ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Finned Tube ◽  
Copper Tube ◽  
Central Air Conditioning ◽  
Fin Thickness

In this article, finned copper tube used in the central air conditioning was acted as the discussed object. According to the combination with actual processing and theoretical calculations, Five finned tube was selected with typical structural parameters, and established their entity model using Pro/E, then the heat transfer process of finned tube was simulated through the ANSYS, the effect of the fin height, fin thickness and other structure parameters to the heat transfer enhancement of finned tube was researched. Meantime the efficiency of the heat transfer under different convection heat transfer coefficient was also studied.

Impingement Cooling Flow and Heat Transfer Under Acoustic Excitations

1997 ◽  
Vol 119 (4) ◽  
pp. 810-817 ◽  
Author(s):  
C. Gau ◽  
W. Y. Sheu ◽  
C. H. Shen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Shear Layer ◽  
Turbulence Intensity ◽  
Pressure Level ◽  
Unstable Wave ◽  
Impingement Cooling ◽  
Cooling Flow ◽  
Acoustic Excitations ◽  
Excitation Pressure

Experiments are performed to study (a) slot air jet impingement cooling flow and (b) the heat transfer under acoustic excitations. Both flow visualization and spectral energy evolution measurements along the shear layer are made. The acoustic excitation at either inherent or noninherent frequencies can make the upstream shift for both the most unstable waves and the resulting vortex formation and its subsequent pairing processes. At inherent frequencies the most unstable wave can be amplified, which increases the turbulence intensity in both the shear layer and the core and enhances the heat transfer. Both the turbulence intensity and the heat transfer increase with increasing excitation pressure levels Spl until partial breakdown of the vortex occurs. At noninherent frequencies, however, the most unstable wave can be suppressed, which reduces the turbulence intensity and decreases the heat transfer. Both the turbulence intensity and the heat transfer decreases with increasing Spl, but increases with increasing Spl when the excitation frequency becomes dominant. For excitation at high Reynolds number with either inherent or noninherent frequency, a greater excitation pressure level is needed to cause the enhancement or the reduction in heat transfer. During the experiments, the inherent frequencies selected for excitation are Fo/2 and Fo/4, the noninherent frequencies are 0.71 Fo, 0.75 Fo, and 0.8 Fo, the acoustic pressure level varies from 70 dB to 100 dB, and the Reynolds number varies from 5500 to 22,000.

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