Hey I am designing a furnace for a creep testing machine capable of max Temp of up to 800degC (for testing tough metals such as titanium). I have a good idea of the the dimensions and shape ie: chamber volume and the outer body volume, a good idea of the heating element that'll be used, an adequate range of possible insulation materials. Now my real question is, How do I work out the thickness of insulation needed to maintain T= 800degC in the chamber for a lengthy period of time - days, using a 1.6kW (or so) heating element, and T= 20degC (~ ambient room temp) on the outer surface of the furnace body? - by how, I am preferably looking for a suitable energy equation that'll get there directly. The furnace chamber should be completely sealed (with ceramic fibre insulation) and there shouldn't be a significant pressure build up during operation due to the nature of the heating process (will be relatively slow,~ +10degC/min). Therefore, the air in the chamber should remain at atmospheric pressure during the course of the test. -I have tried equations such as: electrical Work in = [mCp(T2-T1)]air +[mCp(T2-T1)]ins. and from that tried to find the mass of insulation needed and from that and the dimensions, tried to find the thickness. -I have also tried using the resistance equations Q = (T1-T2)/Rt In both cases i'm getting absurd final values for thickness. I am only in the first stages of design development and I appreciate any help you can give me. Thanks a lot for your time. Noah
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