Hollow Cylinder- Thermal Effects

[wforider]

Say you have an aluminum hollow cylinder with an OD and ID and length L. You uniformly change the temperature of the entire hollow cylinder by DT. I want to calculate the change in the OD of the hollow cylinder. Is it simply the original OD * alpha * DT?

Or is there an influence of the ID?

Does a hollow cylinder's OD behave the same as a solid cylinder's OD under thermal effects alone?

 

[flash3780]

The OD will change by dOD = OD*alpha*dT and the ID will change by dID = ID*alpha*dT. As long as the temperature is uniform, the scaling is uniform (alpha*dT).

 

[wforider]

Thanks for that.

So, the change is OD is the same for a hollow cylinder or a solid cylinder?

 

[flash3780]

Yes. Unless it's otherwise restrained.

 

[davefitz]

in order to change the temperature, then heat must be transferred in some manner. To understand the change in temperature distribution thru the cylinder wall, you need to define how the heat is transferred to the cylinder. Is it heated only at teh ID? or only at the OD? or at both? or is there some sort of internal heat generation rate ? Inquiring minds need to know.

 

[wforider]

The situation I originally posted is a shrink fit application. I'm placing the tube in liquid nitrogen to reduce its OD, placing the tube in the corresponding bore to have an interference fit when ambient temperature resumes. I wanted to know if the parts could be hand assembled. From my calcs, the tubes will drop right in after the Dewar dip.

 

[racookpe1978]

So, how are you (the people assembling the gadgets) going to hold on to a dangerously-cold wet-and-slippery-but-smoothed-and-highly machined surface while they are "slipping" into position?

How will you (those people) accurately get the cylinder accurately and consistently positioned axially inside the outer wall every time?