OCR Text |
Show 6 by use of a conventional burner, and it is concentrated near the burner combustion tube, at each bend, and at the tube end of the burner set side, with strong stresses in the cross sectional direction. Calculated Condition (1) Constra i nt Condi t i on • No.1 Tube ~ Supported • No.4 Tube Edge ~ Fi xed • No.3 Bend ~ Supported (2) Load Cond i t i on • R/T. We i ght (SUS304) • Temp. D i st r i but i on (3) Output Cond i t ion ci. E CD ~ 900 /(a) /(b) OL.-...L..-____ -'--- o 4 100 Time (Hr) ~\ V ~ d ~ ~~ I r= I-F '?Ii ~ \ --:::tir ....w- - \ I L! -+- 1£ tHo ~ -- -+- ;.. - -~ (a) (b) .;1'f: "t< -+- -r- -'I- -+- --t- ~ Fig.3 Distribution of stress in the radiant tube calculated by finite element method -+- ~ X ..,. ~~ ~~ ~ --+-- >.V! 1:A -- -I: y ,y'. ~ v.\, ~ --"- 'f/ The phenomenon of stress concentration near the end of the burner combustion tube can be explained as follow: The temperature gradient between near the end of the burner combustion tube and the end of No.1 straight tube is large at 0.5 °C/mm, whereas the temperature gradient between No.1 bend and near the end of the combustion tube is small at 0.1 °C/mm, and therefore a stress resulting from the difference in expansion in the cross sectional direction is present near the end of the burner combustion tube where the temperature gradient varies. |