Search Results for heat radiation

Temperature is a typical parameter characterizing the heating level of any particle belonging to a heated body. The basic problem of heat transfer computation is associated with appropriate determination of heat transfer coefficients. This article provides a discussion on the basic equations, initial and boundary conditions, and multiple reflection phenomena of mathematical modeling. These boundary conditions include the Dirichlet, Neumann, and Henkel conditions.

This article is a comprehensive collection of formulas, tables, and analytical solutions, addressing hundreds of heat-transfer scenarios encountered in science and engineering. With detailed explanations and dimensioned drawings, the article demonstrates how to set up and solve real-world problems, accounting for material properties, environmental variables, boundary and state conditions, and the primary modes of heat transfer: conduction, convection, and radiation. The article also includes reference data and provides closed-form solutions for common heat-transfer applications such as insulated pipes, cooling fins, radiation shields, and composite structures and configurations.

This article is a comprehensive collection of formulas, tables, and analytical solutions, addressing hundreds of heat-transfer scenarios encountered in science and engineering. It also demonstrates how to set up and solve real-world problems, while accounting for material properties, environmental variables, boundary and state conditions, and the primary modes of heat transfer: conduction, convection, and radiation.

The hazards associated with thermal spray deposition processes include ultraviolet and infrared radiation; acoustical noise; and by-product production in the forms of nitrous oxides, ozone, fumes, and dust. The most important consideration in health and safety is to use the engineered controls of hazards. This article provides a brief description of the spray booth, the most commonly used engineering tool to separate the operator from the thermal spray process and confine the associated hazards. It also presents guidelines on the proper and safe handling of industrial gases and ventilation and heat exhaust. The article provides information on the personal protective equipment for eyes and skin from radiation, and ears from noise. It also discusses other potential safety hazards associated with thermal spraying, namely, magnetic fields and infrasound.

Paints and protective coatings are the most common means of protecting materials from deterioration. This article focuses on coating degradation that results from the environmental interaction with the coatings. The major environmental influences of the degradation include energy (solar radiation, heat and temperature variation, and nuclear radiation), permeation (moisture, solvent retention, chemical, and oxygen), stress (drying and curing, vibration, and impact and abrasion), and biological influences (microbiological and macrobiological).

This article presents an overview of the material properties of carbon-carbon composites. It provides information on the applications of carbon-carbon composites in electronic thermal planes, spacecraft thermal doublers, spacecraft thermal shields, spacecraft radiators, and aircraft heat exchangers.

Thermal inspection comprises all methods in which heat-sensing devices or substances are used to detect irregular temperatures. Inspection of workpieces can be used to detect flaws and undesirable distribution of heat during service. Though there are several methods of thermal inspection and many types of temperature-measuring devices and substances, this article focuses only on thermography, which is the mapping of isotherms, or contours of equal temperature, over a test surface, and on thermometry, which is the measurement of temperature. Thermography techniques can be classified as contact thermographic methods using cholesteric liquid crystals, thermally quenched phosphors, and heat-sensitive paints, and noncontact techniques using hand-held infrared scanners, high-resolution infrared imaging systems, and thermal wave interferometer systems. Contact thermometric inspection devices include bolometers, thermocouples, thermopiles, and meltable substances, whereas radiometers and pyrometers come under the noncontact category.

The most popular metal hot working processes for which induction heating is applied are forging, forming, extrusion, and rolling. This article focuses on estimation techniques to determine basic induction heating process parameters, including coil power, length of heating line, and frequency selection. It discusses three modes of heat transfer: conduction, convection, and radiation, in induction heating. The article describes the factors affected by a distortion of the magnetic field at the coil end through a schematic illustration of distribution of three magnetic force components experienced by the turns of the coil. It concludes with information on some case studies of numerical simulation.

Welding as an assembly process has become increasingly more attractive to designers of space structures because of its sufficient strength, endurance, reliability during their service lives, and ease of repair. This article reviews a variety of applications for welding in space and low-gravity environments and describes the unique aspects of the space environment. It compares the applicable welding processes, namely, electron-beam welding, laser-beam welding, and gas-tungsten arc welding and examines the metallurgy of low-gravity welds. Steps taken to ensure the continued development of welding technology in space are also discussed.

Thermal nondestructive evaluation (TNDE) is an indirect process, so that regardless of the form of energy used to excite the sample, interaction with the internal structure of a part occurs through the process of heat conduction. This article discusses the steady-state configuration and selective excitation configuration of the signal-generation mechanisms in thermal nondestructive evaluation methods. The three widely used approaches to TNDE are surface-excited thermography, vibrothermography, and thermoelastic stress analysis. The article provides information on the common features, characteristics, and limitations of these approaches.

Induction heating computations deal with a multiphysics problem containing analysis of several coupled physical fields such as electromagnetic, temperature, mechanical, and metallurgical. In order to solve coupled electromagnetic-temperature field problems, it is necessary to develop suitable algorithms and numerical procedures, which make it possible to deal with these nonlinear coupled problems. This article focuses on the most common approaches to coupled electromagnetic and heat transfer problems, namely, weak-, quasi-, and hard-coupled formulations.

This article provides information on the heat-source model, conduction heat-transfer model of parts and fixtures, and the radiation heat-transfer and convection heat-transfer models in a furnace. It describes the two types of furnaces used for heat treating: batch furnaces and continuous furnaces. The heating methods, such as direct-fired heating, radiant-tube heating, and electrical heating, are also discussed. Furnace temperature control is essential to ensure quality heat treatment. The article explains the operating procedure of the automatic temperature controllers used in most furnace operations. Heating simulations can be validated by comparison with measured results in full-scale furnaces. The article also presents several case studies to illustrate the use of the simulations.

Induction heating is a combination of several interrelated physical phenomena, including heat transfer, electromagnetics, and metallurgy. This article presents a brief review of different heat transfer modes, namely, heat conduction, thermal radiation, and convection. It focuses on the specifics of induction heating and heat treating applications. The article discusses the nonlinear and interrelated nature of a particular heat transfer phenomenon, physical property, and skin effect. It also presents simple case studies and general physical laws governing different heat transfer modes. The article also discusses the basic concepts of direct current and alternating current circuits, and reviews the theory of electromagnetic fields.