We were calculating vessel skirt expansion from a chart in older days.
Later, people started using the same in equation form:

avg skirt temp (deg C) = (t-tamb)* 83.6/(k* h/ sqrt(thk) + 15.5) + t amb
where t, tamb are in degc, k = 1 for firebrick insul & 1.6 for no insul & h & thk are skirt height & thickness (k*h/sqrt(thk) > 120 to have this expression as valid). I wish my mentors here to help with the units of h & thk - are both of these in mm?

regards,

sam

I can't tell you about the equation form, but I have an old chart that I use, a 1960 ver. from Kellogg. It got a curve and you go to (K*h/sqrt t) on the bottom and read the factor "F" on the side to multiply by (t-amb) for average delta t.

h is in feet, and
t is in inches

On mine, the K factors are,

1.0 for Skirt Fully Insulated
1.7 for Skirt Firebrick Insulated
2.7 for Skirt with no Insulation

Is this the one you needed? For lack of anything better, I still use this.

One would surmise, in the absence of concrete evidence, that h and thk would be defined as in Appendix D of the Codes. For temperatures in C, that would be SI units.

Dear Nozzle Twister,

You are right. Please check the curve results with some typical value the expression I shown with h & thk in inch; do they match ?

regards,

sam

Sam,

For your equation to work, h and t are millimetres.

Cheers.

Thanks, Moverz,

I checked the graph & yes h and t are millimetres.
regards,

sam

For folks who are interested more in Skirt expansion,Refer ""Theory And Design Of Pressure Vessels: John F. Harvey"" pg 437, Non linear thermal gradient in vessel skirts.

Ram