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.

Experimental Study on Heat Transfer Characteristics of Water and Ethanol Flow Boiling in Micro-Channel

2013 ◽  
Vol 330 ◽  
pp. 788-791
Author(s):  
Xia Weng ◽  
Dong Yao Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Bond Number ◽  
Micro Channel ◽  
Vapor Quality ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

The Heat transfer characteristics of water and ethanol flow boiling in micro-channel are studied. Flow boiling of different mass and heat flux is carried out in 61 parallel microchannel with hydro diameter of 0.293mm, and the local heat transfer coefficient (HTC) of is calculated. The results indicate that the HTC decreases with the increasing of vapor quality, and depends on heat flux. Two latest correlations are used to predict the experiment, and the results indicate that the Bond number plays an important role in the correlation.

Effect of Swirl Intensity on Heat Transfer Characteristics of Swirling Flame Impinging on a Flat Surface

2013 ◽  
Author(s):  
Gurpreet Singh ◽  
Subhash Chander
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stagnation Point ◽  
Flat Surface ◽  
Operating Conditions ◽  
Uniform Heat Flux ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Swirl Intensity ◽  
Swirling Flame

An experimental investigation has been carried out to determine the effect of swirl intensity on heat transfer characteristics of swirling flame impinging on a flat surface. The swirl intensity was varied by using helical vane swirlers having angles of 15°, 30° and 60° (low, medium and high swirl). Qualitative flame structures were studied by taking direct photographs of impinging flames. Experiments were conducted for different helical vane swirlers at different dimensionless separation distances (H/d = 1–6) for fixed value of Reynolds number (Re = 5000) and equivalence ratio (ϕ = 1.0). A dip in heat flux was observed at stagnation point for all levels of swirl. Peak heat flux was observed slightly away from the stagnation point due to centrifugal effect. A comparison of stagnation point heat flux has been done for different swirl intensities and for fixed operating conditions. Most uniform heat flux distribution was obtained corresponds to 30° helical vane swirler (medium swirl) at all separation distances.

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.

A Combined Experimental and Numerical Study of Heat Transfer Characteristics for Methane/Air Flame Impinging Normally on a Flat Surface

2008 ◽  
Author(s):  
Subhash Chander ◽  
Anjan Ray
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flat Surface ◽  
Numerical Study ◽  
Combustion Process ◽  
Sharp Peak ◽  
Numerical Code ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Simulation Results

An experimental and numerical study has been conducted to determine the heat transfer characteristics for laminar methane/air flame impinging on a flat surface. A commercial numerical code (FLUENT) was used to simulate the laminar premixed flame. Simulation results were compared with the experimental results and there was good agreement between the results. The purpose of simulation is to understand the impinging flame structure and the chemical physical combustion process. Further, simulation results are presented to define the reasons for a sharp peak in radial heat flux distribution when the inner reaction zone was intercepted by the plate. Here, it has been observed that the resultant effect of peak in radial velocity, axial velocity and velocity magnitude along with peak in the temperature and temperature gradient caused that sharp peak in heat flux value in the radial direction.

Heat Transfer Characteristics of Downward Facing Hot Horizontal Surfaces Using Mist Jet Impingement

2017 ◽  
Author(s):  
Ashutosh Kumar Yadav ◽  
Parantak Sharma ◽  
Avadhesh Kumar Sharma ◽  
Mayank Modak ◽  
Vishal Nirgude ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Cooling System ◽  
Water Pressure ◽  
Jet Impingement ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Impinging jet cooling technique has been widely used extensively in various industrial processes, namely, cooling and drying of films and papers, processing of metals and glasses, cooling of gas turbine blades and most recently cooling of various components of electronic devices. Due to high heat removal rate the jet impingement cooling of the hot surfaces is being used in nuclear industries. During the loss of coolant accidents (LOCA) in nuclear power plant, an emergency core cooling system (ECCS) cool the cluster of clad tubes using consisting of fuel rods. Controlled cooling, as an important procedure of thermal-mechanical control processing technology, is helpful to improve the microstructure and mechanical properties of steel. In industries for heat transfer efficiency and homogeneous cooling performance which usually requires a jet impingement with improved heat transfer capacity and controllability. It provides better cooling in comparison to air. Rapid quenching by water jet, sometimes, may lead to formation of cracks and poor ductility to the quenched surface. Spray and mist jet impingement offers an alternative method to uncontrolled rapid cooling, particularly in steel and electronics industries. Mist jet impingement cooling of downward facing hot surface has not been extensively studied in the literature. The present experimental study analyzes the heat transfer characteristics a 0.15mm thick hot horizontal stainless steel (SS-304) foil using Internal mixing full cone (spray angle 20 deg) mist nozzle from the bottom side. Experiments have been performed for the varied range of water pressure (0.7–4.0 bar) and air pressure (0.4–5.8 bar). The effect of water and air inlet pressures, on the surface heat flux has been examined in this study. The maximum surface heat flux is achieved at stagnation point and is not affected by the change in nozzle to plate distance, Air and Water flow rates.

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