Search Results for radiant heat transfer

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.

This article reviews high-temperature corrosion of furnace parts used in heat-treating furnaces. It provides a comparison of cast and wrought materials in the context of their general considerations, advantages, and applications. The article provides information on the heat-resistant alloys used for parts that go through the furnaces, including trays, fixtures, conveyor chains and belts, and quenching fixtures and parts, and the parts that remain in the furnace such as combustion tubes, radiant tubes, burners, thermowells, roller and skid rails, baskets, pots, retorts, muffles, and drive and idler drums. The article also reviews the material characteristics of silicon/silicon carbide composite and reaction-bonded silicon carbide as used in radiant tubes.

This article illustrates the basic components of dry and wet hearth reverberatory furnaces. It discusses stack melters that are used for aluminum metal casting, as they are efficient in sealing the furnace and using the flue gases to preheat the charge materials. The article describes the various factors for improving and maintaining furnace efficiencies. It explains the benefits of circulating molten metal in reverberatory furnaces and circulation methods.

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.

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.

The historical use of induction heating relating to glass melting gives some insight into its use in today's glass manufacturing industry. A patent search on induction heating provides historical information about how induction heating was used in the glass melting industry, from both a direct fired or a susceptor/container approach. This article provides review of historical patents, following an introduction to conductivity in glass and electrical heating. The purpose is to show that induction heating has been and is being used in the glass melting industry.

Hot gas soldering is a process that is commonly used in applications where the workpiece thermal mass is small and the melting temperature of the solder is relatively low. This article describes the characteristics of hot gas heating that are critical to its effectiveness in soldering. These characteristics include the focus of gas flow, gas flow rates (velocity and volume), gas temperature, and typical gas media. The article explains the thermal profile of a component being soldered and the temperature across adjacent components, which helps to understand time-temperature relationship. It concludes with a discussion on reliability concerns and processing concerns when using hot gas soldering in electronics assembly.

Furnace soldering (FS) encompasses a group of reflow soldering techniques in which the parts to be joined and preplaced filler metal are put in a furnace and then heated to the soldering temperature. This article describes three reflow soldering techniques in surface-mount technology, namely, vapor-phase reflow, area conduction, and infrared heating. These three techniques are considered as mass reflow techniques, because all of the solderable interconnections on the surface of a printed wiring board (PWB) assembly are brought through the reflow heating cycle simultaneously. The article explains four regions of reflow profile, namely, preheat (prebake), preflow (soak), reflow, and cooldown. It concludes with a description on the bare copper assembly process, which is carried out in the inert atmosphere.

Furnaces are one of the most versatile types of industrial appliances that span many different areas of use. This article discusses the classification of various furnaces used in heat treating based on the mode of operation (batch-type furnaces and continuous-type furnaces), application, heating method, mode of heat transfer, type of materials handling system, and mode of waste heat recovery (recuperation and regeneration). It provides information on uniform temperature distribution, the general requirements and selection criteria for insulation materials, as well as the basic safety requirements of these furnaces.

Structural applications for advanced ceramics include mineral processing equipment, machine tools, wear components, heat exchangers, automotive products, aerospace components, and medical products. This article begins with an overview of the wear-resistant applications and the parameters affecting wear of ceramics, namely, hardness, thermal conductivity, fracture toughness, and corrosion resistance. The next part of the article addresses temperature-resistant applications of advanced ceramics. Specific applications of ceramic materials addressed include cutting tools, pump and valve components, rolling elements and bearings, paper and wire manufacturing, biomedical implants, heat exchangers, adiabatic diesel engines, advanced gas turbines, and aerospace applications.

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.

A material is flammable if it is subject to easy ignition and rapidly flaming combustion. The plastics that are most widely used are the least expensive and tend to be the most flammable. This article describes the two basic approaches to improving the fire resistance of a polymeric material: modifying or substituting the basic polymer so that exposure to heat and oxygen will not produce rapid combustion, and using flame-retardant additives. It also provides an overview of the burning process and presents two flammability test methods.

This article discusses various molten-metal treatments, namely fluxing, degassing, and molten-metal filtration. It focuses on various molten-metal handling systems for transporting, holding, or delivering molten metal to the mold/die system. These include launders, tundishes, holding furnaces or transport crucibles, molten-metal transfer pumps, teeming ladles, and dosing and pouring furnaces.

Flammability is the ability of a material to undergo easy ignition and rapid flaming combustion. This article provides information on flammability tests of polymers and codes and regulations that cite these tests. Many organizations are involved in the characterization and specification of flammability properties, resulting in several categorization strategies for flammability tests, including tests for specific fire response characteristics, research tests versus acceptance tests, tests for different levels of severity, and tests for basis of origin. The article presents an overview on the basic approaches in improving the fire resistance of polymers and the burning process (heating, decomposition, ignition, combustion, and propagation). It provides a brief description on the test methods which are classified into two types, one based on fire response characteristics and the other on particular applications of polymeric materials.

This article provides an overview of heat treatment processes, namely, solution heat treatment, quenching, natural aging, and artificial aging. It contains a table that lists the various heat treatment tempers commonly practiced for nonferrous castings. The article describes microstructural changes that occur due to the heat treatment of cast alloys.

Forming processes can be divided into three major categories: bulk forming, sheet-metal forming, and semisolid forming and polymer extrusion. This article introduces each process category with a description of the constitutive models. It outlines the required properties for process modeling and describes the test methods for determining these properties. The article discusses several compression tests used to determine stress-strain curves for bulk forming and tensile tests used to obtain stress-strain curves for sheet-metal forming. The article concludes with information on the measurement of viscosity of semisolid alloy materials by using three types of viscometers: the coaxial cylinder viscometer, the cone-and-plate viscometer, and the capillary viscometer.

This article reviews the topic of computational thermodynamics and introduces the calculation of solidification paths for casting alloys. It discusses the calculation of thermophysical properties and the fundamentals of the modeling of solidification processes. The article describes several commonly used microstructure simulation methods and presents ductile iron casting as an example to demonstrate the ability of microstructure simulation. The predictions for the major defects of casting, such as porosity, hot tearing, and macrosegregation, are highlighted. Finally, several industry applications are presented.

This article provides readers with a brief review of the applications of thermography in additive manufacturing (AM), which still is largely a research and development (R&D) effort. There is a particular focus on metals-based laser powder-bed fusion (L-PBF), although applications in directed-energy deposition (DED) and electron beam PBF (E-PBF) also are mentioned. The metrological basis of thermography is discussed in the article. Background information on radiation thermometry is provided, including how the various equations are applied. Finally, specific examples and lessons learned from various AM thermographic studies at the National Institute of Standards and Technology (NIST) are provided.

Quenchant agitation can be obtained by circulating quenchant in a quench tank through pumps and impellers. The selection of the agitation method depends on the tank design, type and volume of the quenchant, part design, and the severity of quench required. This article describes flow measurement methods, temperature control, materials handling, and filtration processes during the agitation process. The maintenance of quenching installations is also discussed.