Abstract
High-temperature processing has an irreplaceable role in many research and industrial applications. Despite remarkable development spanning over a century, the pursuit of even higher thermal flux density and more rapid thermal transients has not slowed down. As part of the ongoing energy evolution, many industrial applications are transitioning from direct combustion of fossil fuels as primary energy sources to increasing electrification, capable of adapting to renewable power grids. Thus, there is an emerging need for electrical heaters that can replace burners and supply the heat demand, especially at the highest temperatures. In this study, we report on a radiant heater design that can achieve cyclic heating/cooling rates of up to 400 K min–1 and a temperature range in excess of 1,800 K, comparable to those of commercial infrared gold image furnaces, at high surface and volumetric power densities. The heater consists of a modular unit of incandescent tungsten filament and is enclosed in an evacuated ceramic envelope, chemically inert, tolerant of thermal shock, and impervious to gasses. The material and manufacture cost of such heaters, which is estimated at ∼$0.05/W, is less than 0.03% of that for infrared gold image furnaces, which is at >$2/W. Tests of more than 10,000 demanding cycles (high temperature and high heating/cooling rate) over 350 h of total operational time and in different temperature ranges confirm the robust performance of radiant heater prototypes. The design is widely applicable to high-temperature reactor and furnace designs. In thermochemistry research and practice, these radiant heaters could offer multiple benefits compared to solar simulators, lasers, infrared gold furnaces, ceramic heaters, or direct concentration of solar input.
Highlights
High-temperature processing is essential for the functioning of human society, including the production of most of the materials in use today, such as cement and lime manufacture, brick and ceramic manufacture, most metal processing, glass making, etc., These processes generally require combustion of fossil fuels as the primary heat supply (Jenkins and Mullinger, 2008)
With the primary energy supply of the world moving toward renewables, high-temperature electric heating can potentially substitute fossil fuel combustion in industrial processes (Van Geem et al, 2019)
We report of a novel radiant heater design capable of achieving high temperatures, high power densities, and outstanding ramp rates
Summary
High-temperature processing is essential for the functioning of human society, including the production of most of the materials in use today, such as cement and lime manufacture, brick and ceramic manufacture, most metal processing, glass making, etc., These processes generally require combustion of fossil fuels as the primary heat supply (Jenkins and Mullinger, 2008). We report of a novel radiant heater design capable of achieving high temperatures, high power densities, and outstanding ramp rates To describe it briefly, the heater consists of a refractory ceramic envelope and an internal tungsten or similar refractory metal filament as the active heating element. Because of the substantial emissivity difference between K- and S-type thermocouples (εK ∼ 0.6–0.8, εS ∼ 0.1–0.2) (Bradley and Entwistle, 1961; Roberts et al, 2011; Hindasageri et al, 2013) and the radiation-dominated heat transfer, we conducted cross-comparison temperature measurements under identical heater and insulation conditions These showed differences of no more than 1 K, well within our margin of experimental error. The Supplementary Material contains additional results of the heater performance, including temperature profiles of a single heater at 350–400 K min−1 heating/cooling rates for over 2,000 cycles, filament current response with respect to instant power shifts between 15 and 145.5 W, a heater reaching a steady temperature of 1,835 K, and the cavity temperature response with a single heater under steadily increasing (up to 190 W) and cyclic (58.5 and 190 W) power outputs
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