Thermal Load

[Anonymous]

I am trying to apply an 80 degree thermal load to the upper surface of an RC Shell but it won't let me specify a temperature in the "surface > thermal loads" window. I can assign a gradient and apply it to the shell but no temperature.

[Rafal.Gaweda]

Example: http://screencast.com/t/c08lYme4Ku

Example: http://screencast.com/t/AyyDhU54OJW

[Anonymous]

Sorry for the late reply, I've tried these already... I'm designing a flat RC slab and the option to input a temperature is not available.

I do "load definition", trying both "live" and "temperature" but within both of these the program does not allow me to input a temperature, only a gradient as seen in the image attached.

I wish to apply a temperature of 80 degrees C to the top surface of the slab, I'm designing it within "Plate Design".

[Rafal.Gaweda]

 temperature gradient along an element's thickness , along local Z.

Convention:

gradient value -> on top = +half of gradient value , on bottom  = -half of gradient value.

[Anonymous]

So for a slab thickness 650mm where it is desired to have 80 degrees at the upper surface and 20 at the base.... I would specify a gradient of -60/0.65 = -92.31 oC/m and this will simulate the desired affect?

[Rafal.Gaweda · Accepted solution]

No, 

In such case you have to change structure type on Shell then:

if you consider assembling temperature as 0 deg then:

if you consider assembling temperature as 20 deg then (elements have already temp 20 deg):

[Rafal.Gaweda]

Important : message 6 updated \ corrected!

[Anonymous]

Thanks a lot for the help!

My slab is 650mm deep does this affect the gradient in any way?

[Rafal.Gaweda]

My slab is 650mm deep does this affect the gradient in any way?

No ;  gradient between top and bottom layers whatever slab thicness is.

[Refaat]

Dear Rafal

What is the meaning of  "assembling temperature" and what is the difference between assembling temperature and  the value of  "dT1" in the "thermal load 3p window" ?

Thanks

Refaat

[Rafal.Gaweda]

 

What is the meaning of  "assembling temperature" and what is the difference between assembling temperature and  the value of  "dT1" in the "thermal load 3p window" ?

This is written just above second screen shot in message 6:

"if you consider assembling temperature as 20 deg then (elements have already temp 20 deg):" - it means starting temp is already 20 so you need to "heat it' +30 and gradient 60.

[Refaat]

Dear Rafal

What about  this situation , how can I calculate the  " temperature and gradient values" in the thermal  load window definition ?

Initial  temp. = 20 c

(Maximum temperature )Summer temp. = + 45 c

(Minimum temperature )Winter temp. = - 5 c

Minimum thermal gradient ,ΔT= (-5-20) = -25 c

Maximum thermal gradient ,ΔT=(45-20) = + 25 c

Thanks in advance

Refaat

[Rafal.Gaweda]

 

Initial  temp. = 20 c

(Maximum temperature )Summer temp. = + 45 c

(Minimum temperature )Winter temp. = - 5 c

Minimum thermal gradient ,ΔT= (-5-20) = -25 c

Maximum thermal gradient ,ΔT=(45-20) = + 25 c

The meaning of "gradient" in robot temp panel load is the temp difference between top and bottom layers of panel (difference along panel thickness)

so in your case(s) (I understood the whole panel has the temp +45 or -5 along thickness)

1. Summer : load window setings : Temperature = +25, Gradient = 0.

1. Winter :  load window setings : Temperature = -25, Gradient = 0.

[Refaat]

Dear Rafal

Thanks a lot for your advise

Refaat

[Anonymous]

how should i apply a thermal load with gradiient 

external temperature in winter = -15 c

in summer = 40c

internal tempreature = 20 C

i have concrete wall of 20 cm thickness with internal insolation

kindly show me how to calculate the DT and the gradient to use in a Robot model

[Rafal.Gaweda]

considering initial temp = 0:
summer: Temperature = 30, Gradient = 20
winter: Temperature = 2,5, Gradient = -35

[Anonymous]

can u plz send how u calculated the temperature ?

[Rafal.Gaweda]

http://forums.autodesk.com/t5/robot-structural-analysis/thermal-load/m-p/3817573#M12030 -> top screen shot

[Anonymous]

If i undserstand your post :
I have only one case of temperature (dT1) for summer and winter : 50 if assembling temperature is 0° C and 30 if assembling temperature is 20° C.
Can you explain how you have 50° C ??
 
And there is a mistake in your post if i consedering 20° C assembling temperature
:
30 + 30  = 60 (not 80° C)
30-30 = 0 (not 20° C)
 
So we have gradient = 60 - 0 = 60.
 

[Rafal.Gaweda]

I assume you are refering to second screen shot in post 6

Assembling temperature is the temparature which "already has the panel" so to reach 80 deg on outer fibers you need to add uniform temp of 30 + gradient 60 (which will give 30 on top fibers) so finally on top:  20(assembling ; see text above 80 on screen shot) + 30 uniform + 30 (coming from gradient) gives 80 

similar way on bottom