Temperature Distribution In Layers Research Articles

Fire Model Analysis and Experimental Validation on Smoke Compartments

Referring to fire accidental data, more than half the deaths from accidental fires are due to smoke rather than fire. In addition to using smoke curtain to accumulate smoke, it is necessary to consider appropriate smoke compartmentation effects for practical smoke control design. Otherwise evacuation and extinguishing systems would not be operated adequately. However, under the existing fire code of Taiwan, there are many constraints applied to construct smoke compartments inside buildings. Sometimes, it cannot work out for practical design purposes, such as the area of smoke compartments were limited without exception of performance consideration. Therefore, the purpose of this paper is to investigate the phenomena related to fire, heat, and smoke during some postulated fire scenarios occurring in a multicompartment enclosure and the distribution of smoke flow field. Two different fundamental fire models, CFAST and SMARTFIRE, are used for analyzing and predicting the experimental results from a full-scale test. The comparison results show quite reasonable variations between numerical simulation and experimental data. Although the temperature data are higher than experimental data, the predicted smoke layer heights are lower than experimental data. However, the fire models present correct trend of accumulated smoke layer height and temperature distributions in a multi-compartment structure.

Film cooling from two rows of holes with opposite orientation angles: injectant behavior and adiabatic film cooling effectiveness

The present paper is aiming at describing the injectant behaviors from two rows of film cooling holes with opposite orientation angles. Boundary layer temperature distributions were measured in the streamwise normal plane to illustrate the interaction between the injectant from the holes in the upstream row and from the downstream row. Detailed adiabatic film cooling effectiveness distributions were also measured using thermochromic liquid crystal to investigate how well the injectant covers the film cooled surface. Four film cooling hole arrangements were considered including inline and staggered ones. And three blowing ratios of 0.5, 1.0 and 2.0 were studied. At the blowing ratio of 0.5, the injectant is centered near film cooled surface irrespective of hole configurations to show high film cooling effectiveness. When the blowing ratio exceeds unity the injectant tends to lift off from the wall due to the increase of the wall normal momentum. With the inline configuration, not like other configurations, the injectant is still well attached to the wall with the help of the downwash flow formed at the hole exit.

Effect of bulk flow pulsations on film cooling with compound angle holes

Experiments are conducted to investigate the effects of bulk flow pulsations on film cooling with compound angle holes. A row of five film cooling holes is considered with orientation angles of 0°, 30°, 60°, and 90° at a fixed inclination angle of 35°. Static pressure pulsations are produced by an array of six rotating shutter blades, which extend across the span of the exit of the wind tunnel test section. The pulsation frequency is fixed at 36 Hz, but changes in the time-averaged blowing ratios of 0.5, 1.0 and 2.0 produce three different coolant Strouhal numbers, 3.6, 1.8 and 0.9, respectively. Detailed film cooled boundary layer temperature distributions are measured by a cold wire and the adiabatic film cooling effectiveness by thermochromic liquid crystal (TLC). The boundary layer temperature surveys show that pulsations induce large disruptions to the boundary layer temperature distribution and the film coverage. As the orientation angle increases, the injectant concentration spreads further into the spanwise direction because of pulsations than the steady case. With pulsations the adiabatic film cooling effectiveness value decreases regardless of the orientation angle. The amount of reduction, however, depends on the orientation angle in such a way that the larger the orientation angle is, the smaller the reduction is.

Modeling of the thermal field of a workpiece in milling of austenitic steel by a finger-type cutter

The authors report results of modeling thermal fields by the method of finite elements under conditions of milling of 00H17N14M2A austenitic steel by a finger‐type cutter. A solution of the problem of unsteady nonlinear heat conduction has made it possible to find the temperature distribution in the surface layers of a workpiece as a function of the cutting rate and the position of the tip of the cutter edge.

Effects of Orientation Angles on Film Cooling Over a Flat Plate: Boundary Layer Temperature Distributions and Adiabatic Film Cooling Effectiveness

Presented are experimental results describing the effects of orientation angle of film cooling holes on boundary layer temperature distributions and film cooling effectiveness. Film flow data were obtained from a row of five film cooling holes on a flat test plate. The inclination angle of the hole was fixed at 35 deg and four orientation angles of 0, 30, 60, and 90 deg were investigated. The velocity ratios surveyed were 0.5, 1.0, and 2.0. The boundary layer temperature distributions were measured at three downstream locations using 1μm platinum wire. Detailed adiabatic film cooling effectiveness distributions were measured using thermochromic liquid crystal. Results show that the increased lateral momentum in the case of large orientation angle injection strongly affects boundary layer temperature distributions. Temperature distribution characteristics are, in general, explained in the context of the interactions between injectant and free-stream fluid and between injectants issuing from adjacent holes. The adiabatic film cooling effectiveness distributions are discussed in connection with the boundary layer temperature distributions. Spanwise-averaged effectiveness distributions and space-averaged effectiveness distributions are also presented with respect to the velocity ratios and the orientation angles. [S0889-504X(00)01701-3]

A laser interferometric measurement of the temperature distribution in convective thermal transfer boundary layers

By means of a double mirror interferometry a two-dimensional temperature distribution measurement in convective thermal boundary layers is presented. When the cold air flows along a hot plate model, the interferometric fringe inside the boundary layer will bend. According to the displacement of the fringe and the relation between temperature and index of refraction, a two-dimensional temperature profile is obtained. All is accomplished by optical device with the help of micro-computer without any contact with the flow field.

Behavior of thermal radiation properties of oxide ceramics under subsecond laser heating

It is shown that the data on spectral emissivity and reflectivity obtained in subsecond laser heating experiments differ from values which are obtained by the conventional methods. Owing to the semitransparency of oxides, these thermal radiation properties depend on the temperature distribution in near-surface layers and cannot be related to a definite temperature value. The condensation of the products of oxide evaporation at high temperatures, which takes place in air surrounding a sample, may affect the measurement of temperature, reflectivity, and emissivity.

Machanism of Iron Oxide Reduction and Heat Transfer in the Smelting Reduction Process with a Thick Layer of Slag.

It is possible to stably operate the smelting reduction process of iron oxide with a thick layer of slag by controlling slag foaming with carbonaceous materials. In the present paper, the iron oxide reduction and the heat transfer in this process is investigated.(1) The overall rate constant of reduction, post combustion, heat efficiency and the state of the slag layer (temperature gradient and distribution of metal droplets) were measured by 5 t and 100 t scale experiments.(2) The amounts of reduction occurring at slag-metal bath, slag-metal droplets and slag-carbonaceous materials interfaces were estimated for the process under various conditions. Though the reduction at slag-metal bath inferface is predominant in a small furnace, the amounts of reduction at each site are almost equal in a 100 t experiment.(3) Heat transfer by radiation and gas convection was calculated by using a mathematical model and was compared with actual data. This model was constructed by dividing the furnace into three regions depending on the modes of reaction and heat transfer and by taking the mass and heat balances throughout each region. When the gas temperature is as high as 2170°C, the actual heat transfer can be explained mainly by radiation. But, under practical conditions (gas temperature ≤ 1765°C), the contribution of radiation and gas convection on heat transfer is only 20-30%. Therefore, heat transfer by circulation of super-heated carbonaceous material was assumed. The assumption coincides with the dependence of apparent activation energy of reduction on an experimental scale.(4) The appropriate condition for operating the smelting reduction process with a thick layer of slag is the combination of a sufficient amount of carbonaceous material and moderate intensity of stirring.

An experimental and numerical simulation of mixed convection in large baffled rectangular chambers

The effects of mixed convection within large baffled chambers for both ‘aided’ and ‘opposed’ buoyant forces are investigated. Experimental and numerical results are compared for the momentum boundary layer thickness and temperature distribution within the chamber. Two- and three-dimensional transient laminar numerical models are formulated using a fully implicit finite-difference scheme. The inlet and wall temperatures are held constant while maintaining a uniform inlet velocity. Two tiers of four (two per tier) horizontal baffles are located axisymmetrically about the vertical axis with the inlet at the top and exhaust at the base of the chamber. The difference between the inlet and wall temperatures ranges between −1.0 and 3.3°C with a Prandtl number, Pr = 0.7, inlet Reynolds number. Re = 32 and 235, and inlet Rayleigh number, Ra = 0–6.8 × 10 7. It is concluded that the flow is predominantly buoyant and asymmetric in nature. The development of the flow is sensitive to small variations in the temperature difference between the inlet and wall.

Package thermal resistance: geometrical effects in conventional and hybrid packages

The effect of package geometry on thermal resistance for a set of six package configurations is studied. With thermal resistance network models it is possible to determine the junction-to-ambient thermal resistance for each package type under a variety of external cooling conditions. It is found that as the external package cooling technology improves, the thermal resistances for different package configurations separate into distinct ranges. In general, packages which have the lowest thermal resistance under free convection will have the largest thermal resistance under conditions of advanced forced liquid cooling, and vice versa. It is found that the surface area and internal thermal resistance serve as good indicators of thermal performance throughout the range from natural convection to microchannel cooling. On the basis of simple models, nonuniform chip active layer temperature distribution, spatially localized hot spot formation, and the effect of lower chip-to-ambient thermal resistance on the chip temperature profile are discussed. >

Radiative cooling of a layer with nonuniform velocity - A separable solution

Analyzed here is the cooling of a flowing plane layer filled with hot particles or liquid droplets that emit, absorb, and scatter radiation. The velocity distribution is nonuniform across the layer and the specified shape of this distribution affects the layer temperature distribution and emittance. The velocity distribution determined is one that will cause the layer to cool at a uniform temperature. Thus, if the layer initially has a uniform temperature, it will retain the same emittance throughout its length. A separable solution is found that applies in a 'fully developed' region following an initial cooling length. In this developed region, the solution shows that there is a constant emittance based on the local heat loss and local bulk mean layer temperature. This emittance is a function of the velocity distribution, optical thickness, and scattering albedo.

Measurement of flame temperature distribution by IR emission computed tomography

Noncontact and nondestructive measurements for determining flame temperature distribution are under investigation. This paper proposes a new method we have called infrared emission computed tomography to measure the temperature distribution in arbitrary transaxial layers of the flame by calculating the infrared radiation intensity emitted from a flame as the projection data. We developed an experimental system using an infrared sensor as the detector and applied our method to a laminar flame. We obtained good images of the temperature distribution in a flame. In addition, temperature profiles obtained by this method were in good agreement with the results of the thermocouple probe measurement.

A differential model for salt-stratified, double-diffusive systems heated from below

A differential model is developed and used to predict the transient response of a salt-stratified, double-diffusive system heated from below. Predicted mixed layer heights and temperature distributions are in good agreement with data and in reasonable agreement with predictions based on simpler one- and two-layer models. Key features of the system, such as the substantial density difference across the interfacial boundary layer, negligible variation of the salinity profile in the stable region, and locations of highly anisotropic fluid motion are well described by the model. Predicted turbulence characteristics are plausible, and predicted mixed layer growth rates are consistent with accepted correlations involving a convective velocity and a mixed layer Richardson number.

Heterodyne holographic interferometry: concentration and temperature measurements in gas mixtures

Heterodyne holographic interferometry is employed to measure refractive-index distributions in transparent media. A system using a He-Ne laser and relatively modest electronic instrumentation is described. The system was used to measure temperature and specie-concentration distribution in natural convection boundary layers in air adjacent to heated surfaces through which a second gas is emitted or injected.

Boundary Layer Resistance and Temperature Distribution on Still and Flapping Leaves

The forced convection of heat from reed (Phragmites communis) leaves was observed in their natural environment. The leaves were painted with liquid crystals, which displayed or indicated their temperature without any interference with natural air flow. Temperature differences as large as 15 C were observed between the leading and trailing edges of the nontranspiring, painted leaves. The turbulence of the natural wind decreased the boundary layer resistance around the leaf to about 40% of the resistance in a laminar steady wind.

Boundary Layer Resistance and Temperature Distribution on Still and Flapping Leaves

If the evaporation is uniform on a flat exposed leaf, forced convection will also be nearly uniform, and the leaf temperature will vary with the square root of the distance from the leading edge. Then the resistance expressed in terms of the proper, i.e., average, temperature has the same value as the resistance of a leaf at uniform temperature. Compared to a steady laminar flow, the turbulence of a realistic wind decreases the resistance by a constant factor of about 2.5. The same constant factor was observed whether the leaf was flapping or not, when the wind velocity was not too low.

Thermal response of human legs during cooling.

ARTICLESThermal response of human legs during coolingJ. W. Mitchell, T. L. Galvez, J. Hengle, G. E. Myers, and K. L. SiebeckerJ. W. Mitchell, T. L. Galvez, J. Hengle, G. E. Myers, and K. L. SiebeckerPublished Online:01 Dec 1970https://doi.org/10.1152/jappl.1970.29.6.859MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByVerified non-linear DPL model with experimental data for analyzing heat transfer in tissue during thermal therapyInternational Journal of Thermal Sciences, Vol. 133INTER-SPECIES EXTRAPOLATION OF SKIN HEATING RESULTING FROM MILLIMETER WAVE IRRADIATION: MODELING AND EXPERIMENTAL RESULTSHealth Physics, Vol. 84, No. 5A study of thermal effect of epithelial tumor on temperature distribution in annular tissue layers of a human body More from this issue > Volume 29Issue 6December 1970Pages 859-865 Copyright & PermissionsCopyright © 1970 the American Physiological Societyhttps://doi.org/10.1152/jappl.1970.29.6.859PubMed5485357History Published online 1 December 1970 Published in print 1 December 1970 Metrics

Thermoregulation through Skin at Low Atmospheric Temperatures

The metabolic heat generation decreases exponentially if the persistence of cooling in human body is sustained. This phenomena is under consideration in dermis and subcutaneous tissue to study the exact solution of temperature distribution in dermal layers at low atmospheric temperatures. Other suitable variable physiological conditions are taken and the solution has been obtained using laplace tranform in one dimensional case. Key words: Thermoregulation; Human dermal part; Laplace transform. 2000 Mathematics Subject Classification: 92 C 35. DOI: 10.3126/kuset.v5i1.2843 Kathmandu University Journal of Science, Engineering and Technology Vol.5, No.1, January 2009, pp 14-22

Recent Developments in Calculation Methods for Turbulent Boundary Layers With Pressure Gradients and Heat Transfer

A review is given of the recent development in turbulent boundary layers. At first, for the case of incompressible flow, the variation of the shape of velocity profile with the pressure gradient is discussed; also the temperature distribution and heat transfer in incompressible boundary layers are treated. Finally, problems of the turbulent boundary layer in compressible flow are considered.

Experimental Formula of Free-Convection Heat-Transfer from a Vertical Cylinder or a Vertical Plate

It was made clear that vortex streets layer was a necessary cource for the transition from laminar flow to turbulent flow, integrating the observation on motions of boundary layers and the measurements on variations of local heat transfer coefficient, temperature distribution in boundary layers, etc. Then, through examinations on various experiments carried out before, the following experimental formulas for nondimentional equations of free-convection heat-transfer coefficients in a range of GrPr 107 to 1011 were obtained : laminar flow : [numerical formula] turbulent flow : [numerical formula] where, Grc1is the transition point from vortex streets flow to turbulent flow and fl may be taken from an Ostrach's theoretical solution of laminar flow.