Experimental analysis of the heat transfer coefficient enhancement for a heated cylinder in cross-flow downstream of a grid flow perturbation

2012 ◽  
Vol 35 ◽  
pp. 55-59 ◽  
Author(s):  
Alessandro Quintino
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Experimental Analysis ◽  
Cross Flow ◽  
Flow Perturbation ◽  
Heated Cylinder ◽  
The Heat Transfer Coefficient

Experimental Investigation of Air–Water Mist Jet Impingement Cooling Over a Heated Cylinder

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Chunkyraj Khangembam ◽  
Dushyant Singh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stagnation Point ◽  
Jet Impingement ◽  
Water Mist ◽  
Heated Cylinder ◽  
Air Jet ◽  
The Heat Transfer Coefficient

Experimental investigation on heat transfer mechanism of air–water mist jet impingement cooling on a heated cylinder is presented. The target cylinder was electrically heated and was maintained under the boiling temperature of water. Parametric studies were carried out for four different values of mist loading fractions, Reynolds numbers, and nozzle-to-surface spacings. Reynolds number, Rehyd, defined based on the hydraulic diameter, was varied from 8820 to 17,106; mist loading fraction, f ranges from 0.25% to 1.0%; and nozzle-to-surface spacing, H/d was varied from 30 to 60. The increment in the heat transfer coefficient with respect to air-jet impingement is presented along with variation in the heat transfer coefficient along the axial and circumferential direction. It is observed that the increase in mist loading greatly increases the heat transfer rate. Increment in the heat transfer coefficient at the stagnation point is found to be 185%, 234%, 272%, and 312% for mist loading fraction 0.25%, 0.50%, 0.75%, and 1.0%, respectively. Experimental study shows identical increment in stagnation point heat transfer coefficient with increasing Reynolds number, with lowest Reynolds number yielding highest increment. Stagnation point heat transfer coefficient increased 263%, 259%, 241%, and 241% as compared to air-jet impingement for Reynolds number 8820, 11,493, 14,166, and 17,106, respectively. The increment in the heat transfer coefficient is observed with a decrease in nozzle-to-surface spacing. Stagnation point heat transfer coefficient increased 282%, 248%, 239%, and 232% as compared to air-jet impingement for nozzle-to-surface spacing of 30, 40, 50, and 60, respectively, is obtained from the experimental analysis. Based on the experimental results, a correlation for stagnation point heat transfer coefficient increment is also proposed.

Experimental Analysis of Fluid Flow and Surface Heat Transfer in a Three-Pass Trapezoidal Serpentine Smooth Passage

1998 ◽  
Author(s):  
C. Cravero ◽  
C. Giusto ◽  
A. F. Massardo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Experimental Analysis ◽  
Fluid Dynamic ◽  
Flow Analysis ◽  
Strong Impact ◽  
Wide Range ◽  
Rectangular Configuration ◽  
The Heat Transfer Coefficient

The fluid-dynamic and heat transfer experimental analysis of a gas turbine internal three-pass blade cooling channel is presented. The passage is composed of three rectilinear channels joined by two sharp 180 degree turns; moreover the channel section is trapezoidal instead of the rectangular configuration already analysed in depth in literature. The trapezoidal section is more representative of the actual geometrical configuration of the blade and, in comparison with the rectangular section, it shows significant aspect ratio and hydraulic diameter variations along the channel. These variations have a strong impact on the flow field and the heat transfer coefficient distributions. The flow analysis experimental results — wall pressure distributions, flow visualisations — are presented and discussed. The heat transfer coefficient distributions, Nusselt enhancement factor, obtained using Thermocromic Liquid Crystals (TLC), have been studied as well. In order to understand the influence of the cooling mass flow rate, a wide range of flow regimes-Reynolds numbers- has been considered.

Combined Effect of Slot Injection, Effusion Array and Dilution Hole on the Heat Transfer Coefficient of a Real Combustor Liner: Part 1—Experimental Analysis

2010 ◽  
Author(s):  
Bruno Facchini ◽  
Francesco Maiuolo ◽  
Lorenzo Tarchi ◽  
Daniele Coutandin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Experimental Analysis ◽  
Rectangular Cross Section ◽  
Cross Flow ◽  
Blowing Ratio ◽  
Engine Cooling ◽  
Flow Parameters ◽  
Element Approach

An experimental analysis of a real engine cooling scheme was performed on a test article replicating a slot injection and an effusion array with a central large dilution hole. Test section consists of a rectangular cross-section duct with a flat plate comprised of 270 holes arranged in 29 staggered rows (D = 1.65mm, Sx/D = 7.6, Sy/D = 6, L/D = 5.5, α = 30deg) and a dilution hole (D = 18.75mm) located at the 14th row. Both effusion and dilution holes are fed by a channel replicating combustor annulus, that allows to control cold gas side cross-flow parameters, especially in terms of Reynolds number of both annulus and effusion holes. Upstream the first row, a 6mm high slot, ensure the protection of the very first region of the liner. Final aim was the measurement of both heat transfer coefficient and Net Heat Flux Reduction of the cooling scheme, by means of a steady-state Thermochromic Liquid Crystals (TLC) technique with a thin Inconel heating foil. A data reduction procedure based on a Finite Element approach has been developed to take into account the non uniform heat generation and conduction due to the large amount of holes. Experiments were carried out considering the combined effects of slot, effusion and dilution holes. Three different effusion blowing ratios (BR = 3–5–7) are investigated, keeping constant the slot flow parameters (BR = 1.3). Results highlight a large influence of effusion blowing ratio on heat transfer coefficient. A steep increase was found in the first rows, while the large dilution hole does not influences significantly the heat transfer behaviour in the downstream area.

Experimental Investigation on the Effects of a Large Recirculating Area on the Performance of an Effusion Cooled Combustor Liner

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Lorenzo Tarchi ◽  
Bruno Facchini ◽  
Francesco Maiuolo ◽  
Daniele Coutandin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rectangular Cross Section ◽  
Cross Flow ◽  
Engine Cooling ◽  
Flow Parameters ◽  
Element Approach ◽  
Combustor Liner ◽  
The Heat Transfer Coefficient

An experimental analysis of a realistic engine cooling scheme was performed on a test article replicating a slot injection and an effusion array with a central large dilution hole. A test section consists of a rectangular cross-section duct with a flat plate comprised of 270 effusion holes arranged in 29 staggered rows (D = 1.65 mm, Sx/D = 7.6, Sy/D = 6, L/D = 5.5, α = 30 deg) and a dilution hole (D = 18.75 mm) located at the 14th row. Both effusion and dilution holes are fed by a channel replicating a combustor annulus, which allows to control of cold gas side cross-flow parameters, especially in terms of Reynolds number of both annulus and effusion holes. Upstream the first row, a 6 mm high slot ensures the protection of the very first region of the liner. In order to simulate the combustor flowpath, a backward facing step was installed upstream the slot to generate a large recirculating area. Adiabatic effectiveness, heat transfer coefficient and net heat flux reduction were evaluated and compared with non- recirculating experiments. Measurements were performed by means of a steady-state Thermochromic liquid crystals (TLC) technique with a thin Inconel heating foil for the heat transfer measurements. A data reduction procedure based on a finite element approach has been developed to take into account the non uniform heat generation and conduction due to the large amount of holes. Experiments were carried out considering the combined effects of slot, effusion and dilution holes. Three different effusion blowing ratios (BR = 3-5-7) are investigated, keeping constant the slot flow parameters (BR = 1.3). Results highlight that the presence of the step leads to a general reduction of effectiveness while does not have effects on the heat transfer coefficient.

Experimental and Numerical Investigations on the Heat Transfer of Film Cooling With Cylindrical Holes Fed With Internal Coolant Cross Flows

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Lin Ye ◽  
Cun-Liang Liu ◽  
Dao-En Zhou ◽  
Hui-Ren Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Cross Flow ◽  
Skewed Distribution ◽  
Transfer Enhancement ◽  
High Heat Transfer ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

Abstract The heat transfer coefficient of cylindrical holes fed by varying internal cross-flow channels with different cross-flow Reynolds numbers Rec is experimentally studied on a low-speed flat-plate facility. Three coolant cross flow cases, including a smooth case and two ribbed cases with 45/135-deg ribs, are studied at Rec = 50,000, and 100,000 with varying blowing ratios M of 0.5, 1.0, and 2.0. A transient liquid-crystal (LC) measurement technique is used to determine the heat transfer coefficient. At lower M, the heat transfer enhancement regions are asymmetrical for the smooth and 45-deg cases. The asymmetrical vortex is more pronounced with increasing cross-flow direction velocity, resulting in a more skewed distribution at Rec = 100,000. Conversely, the contours are laterally symmetric in the 135-deg case at varying Rec. A fork-shaped trend with a relatively high heat transfer coefficient appears upstream, and the increases in the heat transfer in the 135-deg cases are lower than those in the 45-deg cases. As M increases to 2.0, the vortex intensity increases, resulting in a stronger scouring effect upstream, especially at large Rec. The range and degree are affected by Rec at M = 2.0. The core of the heat transfer enhancement is skewed to the −Y side for both cases.

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