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Experimental study on flame spread and heat transfer characteristics of discrete polymethyl methacrylate (PMMA) plate array with different spacings (L) was conducted in this work. For larger L, flame height in the middle of PMMA plate is larger than those on the sides. Flame merging phenomenon is observed when 6 mm ≤ L ≤ 10 mm. A heat transfer model for upward flame spread over PMMA plate array is established. The model predicts that flame spread rate drops as the spacing rises, consistent with experimental results. And through the flame spread rate prediction equation, it is found that the predicted value is very consistent with the experimental value, and the error does not exceed 10%. The experimental results also indicate that influence of spacing on flame spread rate is slight for 8 mm ≤ L ≤ 10 mm, while the influence is significant for other ranges of L. The experimental results indicate that average flame height first rises and then drops with the increase in the spacing. A mathematical model is built to predict the average flame height. The changing trend of predicted results versus spacing agrees with the experimental results. It is found from the temperature field that smaller spacing corresponds to larger high-temperature zone and pyrolysis area. By observing the surface temperature of PMMA and calculating the theoretical value of radiative heat flux on the surface of preheating zone, it is found that the view factor decreases and radiative heat flux decreases with the increase in spacing, which is consistent with the variation trend of flame spread rate.

In the global effort to reduce CO2 emissions and mitigate climate change, there is significant interest in replacing internal combustion engine vehicles with electric vehicles. Furthermore, the use of radiant heaters rather than conventional air conditioning systems may reduce the energy consumption in electric vehicles. In this work, a thermal physiology model that includes the effect of local radiant heaters was developed to predict the temperature change in a human body in a cold or warm environment. The developed model indicated an increase in the mean skin temperature when radiant heaters were used in a cold environment. Local and overall thermal sensation and thermal comfort predicted from simulation showed an escalation in the sensation and comfort, thereby suggesting an improvement in passenger comfort with the addition of local radiant heaters. This study might contribute to effective energy saving strategies and passenger comfort in electric vehicles.

Painted surfaces are useful for thermal control in spacecrafts. Knowledge of emissivity of such painted surfaces over the range of working temperatures is critical in eventually deciding the adequacy of any thermal control strategy. In view of the very low temperatures involved and also because of the variation of temperature in the spacecraft, the emissivity is invariably a function of temperature, which makes its determination formidable and challenging. A “straight forward” technique to measure or estimate emissivity at cryogenic temperatures is to use a steady state calorimetric technique coupled with energy balance. This involves heat transfer by radiation under steady state conditions between an evacuated cryogenic shroud and a heated test sample, centrally suspended inside the shroud. Apart from the heat supplied, knowledge of temperatures, the internal surface area and emissivity of the shroud is required to estimate the emissivity of the unknown test sample. The view factor can be taken care of, if the test sample is much smaller compared to the shroud, resulting in a view factor of 1 between the sample and the shroud. The key difficulty associated with the seemingly simple procedure is the shroud emissivity, which is often unknown at very low cryogenic temperatures. This paper presents a novel experimental approach for the in-situ estimation of cryogenic shroud (coated with ECP2200 paint) emissivity using measured data from experiments on a plane surface substrate and a cavity surface substrate (a surface with an array of hexagonal cavities) coated with an unknown test sample (Aeroglaze Z307 paint). For an average cryogenic shroud temperature of 32.53 K, the shroud emissivity has been estimated to be 0.355. Following this, the emissivities of the plane surface substrate and the cavity surface substrate coated with Aeroglaze Z307 are estimated. The associated measurement uncertainties are systematically quantified and presented.

A view factor is an important morphological parameter used in parameterizing in-canyon radiative energy exchange process as well as in characterizing local climate over urban environments. For realistic representation of the in-canyon radiative processes, a complete set of view factors at the horizontal and vertical surfaces of urban facets is required. Various analytical and numerical methods have been suggested to determine the view factors for urban environments, but most of the methods provide only sky-view factor at the ground level of a specific location or assume simplified morphology of complex urban environments. In this study, a numerical method that can determine the sky-view factors (ψ ga and ψ wa ) and wall-view factors (ψ gw and ψ ww ) at the horizontal and vertical surfaces is presented for application to real urban morphology, which are derived from an analytical formulation of the view factor between two blackbody surfaces of arbitrary geometry. The established numerical method is validated against the analytical sky-view factor estimation for ideal street canyon geometries, showing a consolidate confidence in accuracy with errors of less than 0.2 %. Using a three-dimensional building database, the numerical method is also demonstrated to be applicable in determining the sky-view factors at the horizontal (roofs and roads) and vertical (walls) surfaces in real urban environments. The results suggest that the analytically based numerical method can be used for the radiative process parameterization of urban numerical models as well as for the characterization of local urban climate.

In closed incubators, radiative heat loss (R) which is assessed from the mean radiant temperature \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ (\overline{T}_{r} ) $$\end{document} accounts for 40–60% of the neonate’s total heat loss. In the absence of a benchmark method to calculate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document}—often considered to be the same as the air incubator temperature—errors could have a considerable impact on the thermal management of neonates. We compared \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} using two conventional methods (measurement with a black-globe thermometer and a radiative “view factor” approach) and two methods based on nude thermal manikins (a simple, schematic design from Wheldon and a multisegment, anthropometric device developed in our laboratory). By taking the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} estimations for each method, we calculated metabolic heat production values by partitional calorimetry and then compared them with the values calculated from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{{{\text{O}}_{ 2} }} $$\end{document} and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{{{\text{CO}}_{ 2} }} $$\end{document} measured in 13 preterm neonates. Comparisons between the calculated and measured metabolic heat production values showed that the two conventional methods and Wheldon’s manikin underestimated R, whereas when using the anthropomorphic thermal manikin, the simulated versus clinical difference was not statistically significant. In conclusion, there is a need for a safety standard for measuring \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} in a closed incubator. This standard should also make available estimating equations for all avenues of the neonate’s heat exchange considering the metabolic heat production and the modifying influence of the thermal insulation provided by the diaper and by the mattress. Although thermal manikins appear to be particularly appropriate for measuring \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document}, the current lack of standardized procedures limits their widespread use.

The sky view factor (SVF) describes the surface geometry and is a commonly used and important measure in urban climate investigations whose aim is the exploration of effects of a complex urban surface on climatological processes in built-up areas. A selection of methods and models for calculating the SVF was compared. For this purpose, fish eye images were taken at several locations in the city of Szeged, southern Hungary. The fish eye images equidistantly follow linear transects to cover a range of SVF values and to analyze the reaction of the methods to a continuously changing environment. The fish eye pictures were evaluated by three methods: the method according to Steyn (Atmos-Ocean 18(3):245–258, 1980) implemented in a GIS-Script, the “Edit free sky view factor” tool of the RayMan model and BMSkyView. The SVF values at the coordinates of the fish eye pictures were calculated with three numerical models (SkyHelios, ArcView SVF extension, and SOLWEIG) with a 3D building data base as input. After comparing the results of the first run, a deviation occurs. The deviation disappears after implementing an option to include a weighting factor in some of the models.

The current development of global warming and CO2 emission problems cannot be overlooked. Thus, global scale measures of efforts are becoming crucial. Thermal properties of insulation materials need to be considered as high performance thermal insulation systems are crucial for efficient energy saving. The most important parameter as indicator of a thermal insulation material is the effective thermal conductivity, but elements that affect the thermal insulation performance are rather complicated. Generally, conduction and radiation heat transfer are needed to be separately considered in precisely evaluating the thermal insulation performance as they coexist in the heat transfer process inside a multilayer insulation system. In this paper, numerical analysis of a complete diffusive enclosure model as a thermal insulation is observed to investigate the radiation effects by its dispersive heat transfer mechanisms. View factor of each relatively large dispersed material is derived in the enclosure model, where it is applicable to various shapes and any particular arrangements of dispersed materials. As this paper is the first part of a three-part working research paper, numerical analysis in this paper is carried out by assuming that the medium within the space inside the insulation system is taken to be nonparticipating, therefore conduction and convection effects during the heat exchange are negligible. This paper will be continued with application of the numerical analysis in observing radiation heating effects by wall-ceiling integration towards indoor environment and radiation–conduction heat transfer mechanisms in one-dimensional multilayer insulation system.

International audience; Stretch blow molding or thermoforming processes includes an infrared heating stage of the thermoplastic preform by infrared heaters. The knowledge of the temperature distribution on the surface and through the thickness of the preform is important to make good prediction of thickness and properties of the manufactured parts. Currently in industry, the fitting of the process parameters is given by experience and is expensive. Our objective is to provide tools that are able to simulate the heat transfers between infrared heaters and preforms in order to reduce the fitting cost and to control the qualities of the end products. The optical method called ``ray tracing'' is used to simulate the radiative transfer. First, we compare the ray tracing method with the view factor method on a simple example: the heating of a square sheet by one infrared lamp. Then, we perform 3D heating stage simulations and compare with experiments. The ray tracing method allows to compute a source term in the transient heat balance equation. Then commercial finite element method softwares can be used to solve the heat balance equation.

Experimental and numerical studies were performed by considering convective and radiative heat transfer to predict the transient thermal behavior of a plate in an indirectly fired continuous heat treatment furnace. The temperature profiles in the plate were determined by solving the transient one-dimensional heat conduction equation in conjunction with appropriate boundary conditions by using a time marching scheme. The results obtained from the transient analysis were substantiated by comparing with experimental results. Additionally, parametric investigations were performed to examine how the thermal behavior of the plate is affected by plate and refractory emissivities, charging temperature and residence time of the plate, gas temperature of the work and drive sides of the heat treatment furnace, and plate thickness.

Photoionised plasmas are common in astrophysical environments and new high resolution spectra from such sources have been recorded in recent years by the Chandra and XMM-Newton satellites. These provide a wealth of spectroscopic information and have motivated recent efforts aimed at obtaining a detailed understanding of the atomic-kinetic and radiative characteristics of photoionised plasmas. The Z-pinch facility at the Sandia National Laboratories is the most powerful terrestrial source of X-rays and provides an opportunity to produce photoionised plasmas in a well characterised radiation environment. We present modelling work and experimental design considerations for a forthcoming experiment at Sandia in which X-rays from a collapsing Z-pinch will be used to photoionise low density neon contained in a gas cell. View factor calculations were used to evaluate the radiation environment at the gas cell; the hydrodynamic characteristics of the gas cell were examined using the Helios-CR code, in particular looking at the heating, temperature and ionisation of the neon and the absorption of radiation. Emission and absorption spectra were also computed, giving estimates of spectra likely to be observed experimentally.

In areas where irrigation facilities are not available or in mountainous areas, reservoirs are used for paddy rice culture in Japan. Water temperature must be adequately maintained because it affects water quality and has a significant impact on the growth and yield of the rice crop. Stratification of water in a reservoir occurs due to heat storage on the water surface by solar radiation, and destratification results from vertical mixing by wind-induced flow and heat convection. This study used a simple topography model to estimate numerically the spatial distribution of longwave radiation on the water surface of an agriculture reservoir surrounded by mountains. A radiation thermometer was used to estimate global longwave radiation. The spatial and temporal variations of longwave radiation on the water surface were calculated using view factors of objects surrounding the reservoir. The simulation showed that longwave radiation absorbed by the water surface increased with distance from the center of the reservoir. The proposed procedure can be used to estimate the longwave radiation environment and heat balance on a water body such as a reservoir and a stream.

An analysis has been carried out to investigate the effect of the reflectivity on the temperature distribution of a glass panel by infrared radiant heating. Halogen lamps are used to heat the panel, located near the top and bottom of the rectangular chamber. The thermal energy is transferred from the lamps to the panel only by radiation and it is considered by using view factor. The conductive transfer is limited inside the panel. The results show that the uniformity of the temperature distribution of the panel is improved and, at the same time, the time for heating increases as the wall reflectivity increases. The temperature difference between the center and the corner reaches a maximum in the early stage of the heating process and then decreases until it reaches a uniform steady-state value.

Accurate delineation of sky view and determination of view-factors in urban canyons is crucial parameter used to characterize radiation properties on urban areas and to express the relationship between the visible area of the sky and the portion of the sky covered by buildings viewed from a specific point of observation. However, to date, most sky view and view-factor calculation endeavors have been done manually and by high cost-equipment methods. As a mean to resolve this problem, this paper presents the use of 3-dimensional Geographic Information System (GIS) for simulating a spatial representation of urban canyons obstructions to sky vault automatically in real-time, in place of many other high cost-equipment methods for delineating sky view and determining view factor, while allowing an automatic delineation of urban canyon geometry. Furthermore, this tool can simulate the current constellation status of positioning-satellite like Global Positioning System (GPS), and evaluate the satellite-based positioning environment concern to signal-shading problem.

We propose a calculation method for shortwave radiation flux and longwave radiation flux within the urban canopy and investigate the influence of urban canopy configuration on net radiation flux. In the assumed urban configuration, buildings of equal size are arranged in a regular lattice within the urban canopy. The net shortwave radiation flux and longwave radiation flux within the urban canopy were calculated by the photon tracking method based on the Monte Carlo method. The albedo value obtained by this method shows close agreement with experimental data, and the average sky view factor shows almost perfect agreement with the theoretical value. Moreover, we calculated the urban albedo for the urban canopy configuration including roads and building height distribution.%Moreover, we calculated net radiation within the urban canopy in %consideration of roads and building height distribution.We found that the sky view factor of the ground surface is high when building coverage is low, building height is low, open space by roads exists, and building height is non-uniform. Moreover, we found that the albedo value is high when building height is small, open space by roads is wide, and building height is uniform. The albedo value was found to vary in a complicated manner with change in building coverage.

The sky view factor (SVF) is used in forest, road and urban climatology to characterise radiative properties. We now propose a method suitable for forest canopies using the raster based and commercially available software IDRISI. It uses quadratic pixels in rows and columns in a scanned equiangular fish-eye image. A threshold value is chosen to divide the image into sky and non-sky areas. The resulting image is then multiplied with a sky view weight image, where the weights of the pixels depend on the angular distance from zenith. The sum of pixel products gives the SVF. Quality analysis of the method is also performed. The choice of threshold value gives some uncertainties due to leaves reflecting sunlight. This error will be reduced by observing details (branches etc.) in the image and by choosing an overcast day for capturing the image. The precision range for SVF calculations will be better than 0.1.

The formula for the duration of possible sunshine has been modified. Two geometrical factors, the circumsolar view factor and the isotropic view factor for calculating solar radiation, have been proposed. The ray-tracing method in computer cartography has been applied to simulating the obstruction of terrain over solar radiation. In addition, the shape factor has been introduced to calculate the reflected radiation from surrounding terrain.

A new absorber configuration has been proposed for parabolic trough solar collector. It consists of a tube through which the working fluid flows. The tube is attached externally to two longitudinal fins which are directed normally to the collector aperture. The absorber aggregate, tube and fins, is encased by a transparent envelope. The heat balance equations for such absorber have been derived and solved. Based on these analyses a study has been carried out on an absorber located in Alexandria (31o N latitude) in Egypt to show the effect of its geometrical parameters on the thermal performance. The results of the study show that a wide range of concentration ratios, higher than the smallest ideal ones, can be chosen. For each concentration ratio, there is a corresponding fin height to absorber tube diameter ratio which maximizes the collector efficiency. The greatest collector efficiency is achieved when the concentration ratio is 1.7 of the smallest ideal one and the ratio of fin height to tube diameter in 0.7. In this case the collector efficiency increases in average ca. 3% over that when using a conventional absorber.

The algebraic methods of Hottel and Sarofim, Gebhart and one recently published by the authors for the calculation of radiant interchange in an enclosure are examined. Each of these formulations, while written in a different form, is shown to be mathematically equivalent to the others. This equivalence is established by deriving the formulations of Hottel and Sarofim and Gebhart from that of the authors. Because of the analytical complexity of these forms their mathematical equivalence cannot be demonstrated by explicit methods. For this reason proof of equivalence is established by numerical programming using a digital computer. Three different numerical examples are used for this purpose.-In addition, the mathematical structure underlying the absorption factor Bij of Gebhart and the total exchange factor $$\overline {S_i S_j }$$ and total view factor ℱij of Hottel and Sarofim is developed.

Radiative heat transfer with account taken for shading in an infinite cylinder whose contour is made up of arbitrary straight-line segments and which has variable temperature and emissivity on its two sides is examined.

A simple surface energy budget model is developed and validated for an aboriginal rock art site in Western Australia. The thermal regime of the rock face is strongly dependent on the sky view factor for a vertical surface element and the sensible and latent heat fluxes are shown to be relatively unimportant. Using climatological data, the model is extended to form the basis for appropriate environmental management and conservation of the rock art.

In the first of this two-part series, the authors discussed the effects of wind on flame bending and trailing. This paper describes investigations of liquid fuel burning rates, flame lengths, wake gas temperatures, and flame radiation. Data are taken from the liquid pool fires described in the earlier article.