Search Results for resistance heater design

Electrical resistance alloys used to control or regulate electrical properties are called resistance alloys, and those used to generate heat are referred to as heating alloys. This article covers both alloy types, describing the construction and use of resistors as well as heating elements. It also discusses soldering and joining methods, sensitivity and stability factors, and various design coefficients. In addition, it provides a detailed account of the properties and applications of thermostat metals and discusses the design of resistance heaters and their operating ranges.

This article provides a rough estimate of the basic parameters, including coil efficiency, power, and frequency in induction heating of billets, rods, and bars. It focuses on the frequency selection for heating solid cylinders made of nonmagnetic metals, frequency selection when heating solid cylinders made from nonmagnetic alloys, and frequency selection when heating solid cylinders made from magnetic alloys. The article describes several design concepts that can be used for induction billet heating, namely, static heating and progressive/continuous heating. It presents the four major factors associated with the location and magnitude of subsurface overheating: frequency, refractory, final temperature, and power distribution along the heating line. The article summarizes the pros and cons of using a single power supply. It also reviews the design features of modular systems, and concludes with information on the temperature profile modeling software.

Porcelain enamel is a fusion bonded glass coating that resists chemical and abrasive attack, provides thermal and electrical insulation, and improves aesthetic qualities. It is used on cast iron as well as steel and aluminum alloys. This article provides a review of the porcelain enameling process, the composition of frits, and the preparation of coating substrates. It also provides information on chemical, mechanical, and electrical properties and sheds light on process consistency and quality control.

Electrical resistance alloys include those types used in instruments, control equipment, heating elements, and devices that convert heat generated to mechanical energy. This article discusses the basic classification of electrical resistance alloys (resistance alloys, heating alloys, and thermostat metals), their subtypes, properties, service life, and operating temperatures. It describes the designing and fabrication of open resistance and sheathed heaters. The article contains a collection of tables and graphs that provide information on the mechanical properties, chemical composition, temperature coefficient of resistance, furnace operating temperatures, length and spacing of loops, ribbon size, and electrical capacity of heating elements.

This article describes the characteristics of tubing of heat exchangers with respect to general corrosion, stress-corrosion cracking, selective leaching, and oxygen-cell attack, with examples. It illustrates the examination of failed parts of heat exchangers by using sample selection, visual examination, microscopic examination, chemical analysis, and mechanical tests. The article explains corrosion fatigue of tubing of heat exchangers caused by aggressive environment and cyclic stress. It also discusses the effects of design, welding practices, and elevated temperatures on the failures of heat exchangers.

Advances in vehicle design and technology require engine coolant technology to minimize the degradation of nonmetals and prevent the corrosion of the metals in the cooling system. This article provides a detailed discussion on the functions, operation, materials, and major components of the cooling system. It discusses various forms of corrosion that occur in cooling systems, including uniform corrosion, galvanic corrosion, crevice corrosion, pitting corrosion, intergranular corrosion, erosion corrosion, and cavitation corrosion. The article presents information on engine coolant base components and inhibitors used for corrosion prevention. It reviews the coolant performance tests recommended by ASTM, SAE, and vehicle manufacturers. The article concludes with a description on the difference between light-duty automotive and heavy-duty diesel engine coolants.

This article addresses the major heat-transfer components of the water-steam loop of a power plant. It describes the various types of condensers, including water-cooled condensers and air-cooled condensers. The article explains the corrosion mechanisms encountered in the condensers, including erosion-corrosion, galvanic corrosion, and pitting corrosion. It discusses the types of deaerators and deals with their corrosion problems. The article provides a discussion on two types of feedwater heaters: channel feedwater heaters and header feedwater heaters. It summarizes the corrosion problems associated with common feedwater heater tube materials.

Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.

This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

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.

Temperature control in heat treating is of paramount importance in maintaining the quality and achieving the desired metallurgical results. This article provides a detailed account of the factors affecting temperature control in heat treating furnaces, with information on temperature control systems, including contact sensors, noncontact sensors, controllers, energy-flow regulators, measurement instruments, and set-point programmers. Common contact sensors include temperature scales, thermocouples, and resistance temperature detectors, whereas optical pyrometers and on-line radiation thermometers fall under the noncontact type. The article describes two types of instrumentation used in heat treating: field test instruments for temperature-uniformity surveys and system-accuracy tests; and controlling, monitoring, and recording instruments for digital instrumentation.

Molten salt baths are anhydrous, fused chemical baths used at elevated temperatures for a variety of industrial cleaning applications. This article discusses their applications in paint stripping, polymer removal, casting cleaning, glass removal, and plasma/flame spray removal. It provides an overview of the basic design and safety considerations of the salt bath equipment and describes the environmental impact of molten salt bath cleaning.

Unexpected and frequently costly failures occur due to the lack of sound and reliable engineering design. Therefore, designing against corrosion is essential for reducing such failures. This article provides a discussion on design considerations and general corrosion awareness. It details the functional requirements, such as design and materials selection, which assist in controlling corrosion in different environments. The article also illustrates the design factors that accelerate corrosion.

Porcelain enamels are glass coatings applied primarily to products or parts made of sheet steel, cast iron, and aluminum to improve appearance and to protect the metal surface. This article describes the types of porcelain enamels, and details enamel frits for these materials. It provides a list of steels suitable for porcelain enameling and discusses the most important factors considered in the selection of steel for porcelain enameling. The article briefly presents the preparation methods of these materials for porcelain enameling and covers the methods, and furnaces of porcelain enameling. It examines the role of coating thickness, firing time and temperature, metal substrate, and color on the performance of enameled surfaces. The article concludes with a discussion on the properties of enameled surfaces, factors considered in process control, and test procedures for evaluating the quality of enameled surfaces.

This article discusses the fundamentals of thermal vaporization and condensation and provides information on the various vaporization sources and methods of vacuum deposition. It offers an overview of reactive evaporation and its deposition techniques. The article also explains the advantages, limitations, and applications of vacuum deposition processes. Finally, it provides information on the gas evaporation process, its processing chamber, and related systems.

Dew-point corrosion occurs when gas is cooled below the saturation temperature pertinent to the concentration of condensable species contained by a gas. This article discusses dew-point corrosion problems in the susceptible areas of dry flue gas handling systems. The corrosion problems associated with the nitrate stress-corrosion cracking in heat-recovery steam generators are also discussed. The article presents general comments on the materials selection; plant operation; use of neutralizing additives; and maintenance, good housekeeping, and lagging (insulation). It concludes with information on guidance for maintaining specific sections of the plant.

Plasma melting is a material-processing technique in which the heat of thermal plasma is used to melt a material. This article discusses two typical design principles of plasma torches in the transferred mode: the tungsten tip design and the hollow copper electrode design. It describes the sources of atmospheric contamination in plasma melting furnaces and their control measures. The equipment used in plasma melting furnaces are also discussed. The article provides a detailed discussion on various plasma melting processes, such as plasma consolidation, plasma arc remelting, plasma cold hearth melting, and plasma casting.

This article describes the extrusion process, which converts soft, plastic material into a particular form using an extruder, or screw conveyer. It discusses the two main types of plastic extruders, twin-screw and single-screw, estimation of extruder capacity, and design and operations (heating, cooling, downstream sizing, corrugating, and crossheading) of the screw, the most important component of any extruder. It discusses the shapes produced by screw extrusion and the types of extrusion products produced by extrusion processes, including blown-film extrusion, flat-film or sheet extrusion, chill-roll film extrusion, pipe or tube extrusion, wire and cable coverings, extrusion coating, and profile extrusion, and provides some discussion on multiple-screw extruders. The article describes the dimensional accuracy of extrusion products, and lists common defects that occur frequently in the extrusion process.

Porcelain enamels are glass coatings applied primarily to products or parts made of sheet steel, cast iron, or aluminum to improve appearance and to protect the metal surface. This article provides information on the types and properties of the porcelain enamels and frits for porcelain enameling. It describes the corrosion resistance of the porcelain enamels in a variety of environments. Evaluation of properties of the porcelain-enameled products to control specifications and quality of porcelain-enamel coatings is also reviewed. The article contains a table that lists the specific test methods for evaluating various properties of porcelain enamels.