Radiant electric heaters

Double-Bubble Method. In the double-bubble method (Fig. 11), the resin is extruded as a tube that is quenched and gauged in cold water. The tube is then reheated and oriented by blowing it into a bubble. Simultaneously, the speed of the takeoff roll is increased for MD orientation radiant electrical heaters control temperature. The bubble is collapsed, passed through nip rolls, reinflated, annealed in a controlled-temperature chamber, and collapsed again. After trimming the edges, it is separated into two webs, which are then treated by electric discharge for printability and wound onto rolls. 

Applications. Defroster tubes (refrigerators), radiant electric heater substrates, lab ware, high-temperature fumace/stove windows, UV-transmitting windows, UV lamps. These are examples only many specialized applications exist... 

In the figure shown an electric heater is installed in surface l such that a constant heat flux of 100 kW/m2 is generated at the surface. The four surrounding surfaces are in radiant balance with surface 1 and the large room at 20°C. The surface properties are C = 0.8 and e2 = e3 = e4 = e, = 0.4. Determine the temperatures of all surfaces. The back side of surface 1 is insulated. Repeat the calculation assuming surfaces 2, 3, 4, and 5 are just one surface uniform in temperature. 

Two parallel disks 30 cm in diameter are separated by a distance of 5 cm in a large room at 20°C. One disk contains an electric heater that produces a constant heat flux of 100 kW/m2 and t = 0.9 on the surface facing the other disk. Us back surface is insulated. The other disk has e = 0.5 on both sides and is in radiant balance with the other disk and room. Calculate the temperatures of both disks. 

Infrared waves have less energy than visible light. Infrared radiation is given off by the human body and most other warm objects. We experience infrared rays as the radiant heat you feel near a fire or an electric heater. 

In this equation, q",.dA is the net radiative heat flux at the moving material surface imposed by external sources such as radiant burners/heaters or electric resistance heaters. Both parabolic, boundary layer [80], and full, elliptic [61,81] problem solutions have been reported. Because of the nature of the problem, the heat transfer results can t be given in terms of correlations. The interested reader is referred to Refs. 62 and 79 for citation of relevant references. 

For the purpose of this article, fire tests are associated with the second strategy and defined as experimental methods to characterize the behavior of polymers under more severe thermal exposure conditions that are representative of the growth phase of a compartment fire. These conditions are simulated with a gas-fired or electrical heater or a large gas burner turbulent diffusion flame (flame length of the order of a meter or several feet). The incident heat flux to the specimen is primarily radiative when heaters are used, and mainly convective for flame exposure. Total incident heat flux varies from approximately 1 kW/m to more than 100 kW/m. Note that the maximum radiant heat flux from the sim on earth is approximately 1 kW/m. Polymers that are not treated with fire retardant chemicals typically ignite when exposed to heat fluxes of 10-20 kW/m in the presence of a small pilot flame or hot spark. 

A square sample of 100 x 100 mm is exposed to the radiant flux of an electric heater. The heater has the shape of a truncated cone (hence the name of the instrument) and is capable of providing heat fluxes to the specimen up to 100 kW/m. An electric spark plug is used for piloted ignition. Heater temperature is measured as an average of the readings of three thermoconples in contact with the coil. It is set and maintained at a certain level by a three-term controller. Calibration of heat flnx as a function of heater temperatnre is performed with a total heat flux meter of the Schmidt-Boelter type. Prior to testing, the heater temperatnre is set at the appropriate value resulting in the desired heat flux. 

Catalytic gas combustion radiant heaters have generated substantial interest. The combustible air-gas mixture is introduced to the heater directly below a porous bed of catalyst that is similar to the catalyst used in automotive exhaust systems or camper heaters. Combustion and radiation occur at the catalyst surface. Catalytic gas systems are desired for their uniform surface temperature and low operating cost. Lack of temperature modulation is the major problem with gas combustion heaters. The catalytic gas system needs many gas lines and controls, as well as, an electric heater that must preheat the catalyst bed prior to initiating combustion. As a result, the initial installation cost is very high compared to the allelectric heating systems. 

Space-heating appliances should be both safe and effective. Hot-water radiators or ducted hot-air systems are best for workrooms because they do not attain sufficient temperatures to ignite flammable vapours. Whatever system is used must be capable of maintaining an adequate temperature, since otherwise there is a tendency towards uncontrolled introduction of portable items, such as radiant electric fires, oil-filled radiators and gas heaters. 

XI.4 The results firom the above experiment demonstrate the effect the extraneous radiant heat firom the electric heater had on the dry point, and also suggest a means whereby this effect could be greatly reduced. 

Deglor [Detoxification and glassification of residues] A process for vitrifying wastes, such as fly ash, by heating to 1,400°C in an electric furnace. Some of the heat is provided by radiant heaters, some by passage of electricity through the melt. Developed and piloted by ABB in Switzerland from the 1980s, commercialized in Japan in 1996. 

In industrial processes heat energy is transferred by a variety of methods, including conduction in electric-resistance heaters conduction-convection in exchangers, boilers, and condensers radiation in furnaces and radiant-heat dryers and by special methods such as dielectric heating. Often the equipment operates under steady-state conditions, but in many processes it operates cyclically, as in regenerative furnaces and agitated process vessels. 

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