作者：KAZUO OHTA;YUKIFUMI SAKAI;KUNIO HAYAMIZU;
作者單位：Research & Development Center, Toshiba Ceramics Co., Ltd. 30 Soya, Hadano-shi, Kanagawa-ken 257-8566
刊名：Taikabutsu Overseas
ISSN：0285-0028
出版年：2002-01-05
卷：22
期：2
起頁：136
止頁：140
分類號：TQ175
語種：英文
關鍵詞：
內容簡介1) Static stress analysis was carried out for the outer tube of a radiant tube unit, assuming that it was placed horizontally and fastened in place by pressing its flange against a furnace wall. The analysis revealed stress concentration localized in the upper part of the circumferential joint between the flange and the tube. The maximum stress in the model tube was only 3.54 MPa, an extremely small value compared to the fracture stress of 450 MPa of the material. The model tube weighed about 29 kg. The analysis showed that radiant tubes made of sintered silicon carbide, which is characterized by low weight and high strength, could be held horizontally with a support at one end by a proper fastening of the flange onto the furnace wall.2) Stress analysis repeated for a variety of values of the chamfering radius Rs and the flange thickness L_1 gave 10 mm and 20 mm as the optimum values of Rs and L_1 respectively. This meant that the numerical analysis could be used to optimize the shape and dimensions of a radiant tube. It also confirmed the efficacy of product evaluation by numerical analysis before a product is used by clients.3) Thermal stress induced by the difference between the temperatures inside and outside the radiant tube in use was analyzed. Our analysis showed that the temperature difference along the tube thickness was much smaller than that between the atmospheres inside and outside the tube. It also showed that the thermal stress induced by that small temperature difference along the tube thickness was also very small and way below the tolerance level that corresponds to the strength of the material. The small temperature difference along the tube thickness is attributed to the high thermal conductivity of sintered silicon carbide. The resultant small thermal stress and the large fracture strength of the material contribute to a large safety factor.FEM analysis is an effective tool to evaluate a product before it is used. The excellent resistance against heat and corrosion of sintered silicon carbide make it an attractive material for the heat transfer tube of gasification melting furnaces. Although the direction of heat flow of the heat transfer tube is different from that of the radiant tube, both tubes can be analyzed in the same way in the FEM analysis.When in use, radiant tubes may experience large temperature differences in their longitudinal direction. Since those differences depend on how radiant tubes are installed and heated, and what is happening in the furnace, it is difficult to set up an analytical model under simplified conditions. FEM analysis may be usable even in those cases, if the actual temperature distribution can be estimated from temperature measurements or by other methods.
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