Thermal Shock Analysis

[strainstress]

I am trying to figure thermal shock stresses imposed by sudden inflow of pressurized steam at 650F in the tube at ambient conditions.

How do I go about calculating the thermal shock stresses generated ? Any pointer/references will be greatly appreciated.

Thanks

StressStrain

 

[BigInch]

Calculate the stresses at temperature intervals along the way from ambient to 650F.

I hate Windowz 8!!!!

 

[strainstress]

After having performed thermal analysis the stress calculated per equation comes out to be much greater than yield strength. In such a case, how do one typically reduce the imposed stress ?

Sigma = alpha*E*Delta_T/(2*(1-Poisson))

 

[IRstuff]

Reduce the temperature change rate?

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[BigInch]

Stress will remain high until some movement is allowed. If your stress is above allowable, you must allow enough movement to reduce the stress below the allowable value. Put in an expansion loop such that relative movement between the elbows takes the place of allowing that movement at the anchor points.

I hate Windowz 8!!!!

 

[strainstress]

This thermal shock on the tube is due to internal constraint wherein inner surface has high temperature and outer surface is at ambient, the inner surface watns to expand and outer does not, hence creates an internal stress. This, I believe, has independent of any external constraints.

 

[3DDave]

If possible, insulate the inside of the pipe to slow the rate of heat transfer or preheat the pipe.

You can also shot peen the outside of the pipe to pre-stress it with a compressive load to offset the tensile load due to thermal shock.

Also, see this thread

http://www.eng-tips.com/viewthread.cfm?qid=320112

 

[TGS4]

That your stresses are in excess of yield is not necessarily a problem. In this particular case, your stresses would be classified as F (peak stresses due to thermal loads). These types of stresses are not considered for protection against plastic collapse, nor are they considered for ratcheting (although you may want to consider if they could cause ratcheting) - they are only considered for fatigue.

So, what failure mode are you concerned about.

(BTW - don't double post. Or if you think it absolutely necessary, please link back to the original post)

 

[BigInch]

OK, now I understand what you want. 3DDave already mentioned that you should insulate the pipe to reduce the temperature difference between inside and outside of the pipe wall.

I hate Windowz 8!!!!