![]() ![]() The real/effective source temperature is then lower than the natural or undisturbed source temperature, thus penalizing efficiency. Right side: in the case of coupled heat sources, heat extraction may substantially alter source temperatures. Left side: in the case of uncoupled heat sources, usually ambient air, heat extraction does not affect the source temperature. The mechanical work to allow this heat flow to occur ( W) depends strongly on the temperature difference to be overcome. A heat pump extracts heat from the ambient at temperature T 2 and supplies heat to the demand at a (higher) temperature T 1. Reflective backings can be used to focus IR radiation for heating long and narrow regions in one plane or to disperse radiation for uniform heating of large areas.įigure 5.1. Ni–Cr heaters are available in different shapes, such as tubular, and can reach a temperature of 850☌ (1562☏) in minutes, radiating at 2–5 μm wavelengths. Tungsten filaments produce intense radiation however, they are only available in linear and spot shapes and are sensitive to pigmentation and formulation of the materials being welded. Quartz and halogen radiators are used for higher temperatures, 1000–3000☌ (1832–5432☏) and maximum emission occurs at wavelengths of 0.9–1.0 μm. Ceramic-coated heating elements are used for lower temperatures and can produce joint surface temperatures of 320–530☌ (608–986☏) at a heating distance of 1.5–2.0 mm (0.06–0.08 inches). Radiant heaters or lamps used in IR welding include quartz-halogen, tungsten, nickel-chromium (Ni-Cr), or ceramic-coated heating elements. In Handbook of Plastics Joining (Second Edition), 2009 9.5 Equipment ![]()
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