Space-Age Refractory Fibers Improve Gas-Fired Infrared Generators for Heat Processing Textile Webs

Abstract

Gas-fired infrared neaters have been in use in industrial processing for a number of years. Recent material technology advances have made significant heating efficiency improvements. This technology pertains to the infrared generators that utilize a refractory fiber matrix material originally developed for use in rocket nose cones. The matrix contains thousands of specially treated, high emissive power, alumina silica fibers, which upon heating become incandescent and release their energy outwardly, at the speed of light, in the form of infrared radiation. The heating zone is contained in the upper 1/16" of the face of the matrix while the rest of the matrix acts as an insulator to prevent heat energy from being conducted backwards where it will be lost as heat available to do work. This narrow heating zone has several dramatic advantages. The generators are operating within 95% of full output within 5 seconds, can cool down enough to touch within about 3 seconds, and can be modulated to change the heat intensity rapidly because of the low mass of fibers that are actually heated. This is an important consideration in textile web processing because burning and fires can be prevented and no time or money is wasted waiting for heaters to cool down or warm up. The conversion of gross fuel gas energy to emitted radiant energy is highly efficient because the flame front produced by the combusting fuel is maintained in the presence of thousands of fibers per square inch. This very large surface area, per unit area, provides an excellent means for the hot gas molecules to conduct their heat energy to the fiber molecules. In most cases, textile manufacturers have reported fuel savings of 40-60% in their heating operations using this new technology. This paper will briefly review the three types of heat transfer, discuss the physics involved in radiation heat transfer, specifically in vestigate infrared heating, present the various types of infrared heaters available, detail how the special refractory fibers have improved heating efficiency and control, and finally delve into the various ap plications for this new type of heater.