Optical Methods in Heat Transfer

Hauf, Werner; Grigull, Ulrich

doi:10.1016/s0065-2717(08)70151-5

Cited by 259 publications

(132 citation statements)

References 50 publications

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“…These patterns were then captured by a video camcorder which was, in most cases, aimed at the middle section of the cavity. Hauf and Grigull [30] and Naylor [31]. A more detailed description of the interferometer used in the present experiment is offered by Machin et al [32].…”

Section: Smoke Flow Visualizationmentioning

confidence: 99%

Flow visualization of natural convection in a tall, air-filled vertical cavity

Wright

Jin²,

Hollands

et al. 2006

International Journal of Heat and Mass Transfer

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Natural convection of air in a tall vertical cavity was studied using a smoke patterns and interferometry. Experiments covered Rayleigh numbers of 4,850 < Ra < 54,800 and aspect ratio A ≈ 40. Secondary cells were noted at Ra as low as 6,228. The flow was stable at Ra < 10 4 . As Ra exceeded 10 4 the flow became irregular, the core flow became increasingly unsteady and 3-D motion became evident. Interferometry showed that most of the temperature drop exists in boundary layers near the walls. The core is well-mixed and of relatively uniform temperature with little or no vertical stratification.

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Section: Smoke Flow Visualizationmentioning

confidence: 99%

Flow visualization of natural convection in a tall, air-filled vertical cavity

Wright

Jin²,

Hollands

et al. 2006

International Journal of Heat and Mass Transfer

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“…These methods relatively easily allow to obtain a lot of relevant information on the flow field that can be used to analyze the physics of the phenomenon. There are three basic methods of optical visualization: shadowgraph, Schlieren and interference [5,6]. The Schlieren method has a special role because it shows a natural, easy to interpret the image of the field of the refractive index gradient.…”

Section: General Characteristics Of the Schlieren Methodsmentioning

confidence: 99%

“…Devices using above-mentioned phenomenon to the visualization of the inhomogeneity of the medium are called the Schlieren apparatuses. The study of natural convection makes use of the effect of fluid density inhomogeneity caused by varying temperature field on the propagation of light [6]. The changes in light intensity after passing through the test space, as visualized by the Schlieren system, are proportional to the first derivative of the fluid density [7]: (1) where: ΔI/I -the relative change of the light intensity after passing through the apparatus optical system (the light intensity, W/m 2 ); ρ -the density of the test medium, kg/m 3 ; x -the direction of the normal to the surface of the equal density, m.…”

Section: General Characteristics Of the Schlieren Methodsmentioning

confidence: 99%

Use of the Schlieren Method to the Convection Analysis in the Steel Charge of Mixed Porosity / Wykorzystanie Metody Schlierena Do Analizy Zjawiska Konwekcji W Przypadku Wsadu Stalowego O Porowatości Mieszanej

Wyczółkowski

Kolmasiak

Urbaniak

et al. 2015

Archives of Metallurgy and Materials

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The paper presents experimental studies devoted to the convection phenomenon within the steel charge of mixed porosity. Such charges constitute bundles of hollow long elements such as pipes or rectangular sections which are heat treated. A significant portion of the gas phase in the volume of the charge makes that natural convection of the gas occurring within the individual elements may have an effect on the course of heating. To the tests the Schlieren method was used which is one of the optical visualization methods applied to the analysis of the flow phenomena in the transparent and non luminous media such as air or water. The tested samples have the form of porous charge beds made from pipes and rectangular profiles. During the experiments the samples were heating up for the constant heat flux rate. The direction of flux was vertical, from the bottom to the top.

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“…Interferometry is based on the principle of measuring a phase shift of beams while passing through an inhomogeneous transparent object. It is possible to visualise a phase shift by means of interference fringes, namely by the comparison of a light beam which passes through the object and the reference light beam (Hauf and Grigull, 1970;Merzkirch, 1974).…”

Section: Visualisation Of Temperature Fields In the Surroundings Of Smentioning

confidence: 99%

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

Černecký¹,

Koniar²,

Brodnianská³

2013

Chemical and Process Engineering

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The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients α x , recorded in a CFD simulation.

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Optical Methods in Heat Transfer

Cited by 259 publications

References 50 publications

Flow visualization of natural convection in a tall, air-filled vertical cavity

Flow visualization of natural convection in a tall, air-filled vertical cavity

Use of the Schlieren Method to the Convection Analysis in the Steel Charge of Mixed Porosity / Wykorzystanie Metody Schlierena Do Analizy Zjawiska Konwekcji W Przypadku Wsadu Stalowego O Porowatości Mieszanej

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

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