Heat Transfer Analysis

[triadxyz]

Hello all,
I am required to analyse the heat transferred from a Hot Steel coil (25 Ton, 750*C)to an hydraulic cylinder which is used to raise it (ambient Temp. 21*C). The operation takes around 30secs so the analysis needs to be time dependent. Ive tried using floworks but this seems very complex. Im considering using Ansys Workbench, any advice would be appreciated on best software and procedures. Thanks

 

[desertfox]

Hi triadxyz

What assumptions are you using in your model?
what sort of area of contact does the coil have with the
cylinder?

regards

desertfox

 

[triadxyz]

Hi Desertfox

The coil is raised by two tandem cylinders, i am considering one because they are symmetrical in orientation so Im assuming the values will be equal. The cylinders are frame mounted with support slides and use a steel pad in contact with the coil. The contact area is relatively small so ive modeled it in solid works hoping the mesh would calculate the area. There is no forced convection, just natural, conduction and radiation. Ive taken thermal images which show a max cylinder temp of 41*C and I wish to prove this by modeling (Even my hand calculations cant seem to beat this !). Ive entered all required values for mild steel and air as the medium, but after hours of calculations floworks produces nothing like id expect (or even nothing at all). I have all required data and models if you can help with this. Thanks Again

 

[desertfox]

Hi triadxyz

This is a complicated analysis and a trainsient one, are you trying to do this based on steady state if so maybe thats were your going wrong, post your hand calc's and lets see.

regards

desertfox

 

[omarbakr]

Well first of all altough you may be doing the heat transfer part right you may be forgetting that there is a heat rise due to working fluid pressure lines losses and friction.

 

[MintJulep]

If you have measurement, why do you need to model it?

Anyway, I think you could get reasonable accuracy using a steady state model for the heat transfer and a quick hand calc for temperature.

Assuming that the mass of the coil >> mass of cylinder, and that the coil won't cool off all that much in 30 sec, just assign a constant temp to the cylinder and coil and go for the steady state heat transfer.

That rate X 30 seconds X m X Cp of the cylinder gets you a quick and conservative approximation of the cylinder temp.

 

[dvd]

I am with M. Julep on this. It seems like a waste of time calculating the solution when the objects already know exactly how hot they are. You could mount a couple of thermocouples (or other measurement devices) to your cylinder and hook it up to a data logger to get a very nice temperature curve. Why waste time calculating a solution?

 

[triadxyz]

I will try steady state model and reply back, thanks chaps and Happy New Year !

 

[trashcanman]

Mega Dittos to DVD! Why calculate something you already know. Sometimes, we (including me) get carried away with our math abilities, and forget that math is just a tool. We should calculate only when there is no other practical way to get the answer.