Felipe1976
Mechanical
- Feb 20, 2007
- 1
Hello there!
I'm currently trying to validate a model I'm using to analyze heat from friction in a huge slide bearing.
My input is power and it's applied in time steps of 5 seconds.
The model is axisymmetric (meshed with element PLANE55) with a layer for convection with SURF151 elements. There's also a node with environmental temperature to connect the model with the environment.
Softwawe is ANSYS release 14
At first it seems that the calculations are ok, it's giving nice plots of temperatures with coherent values.
Now I'm trying to validate using the heat equation Q = m.c.dT to compare with the inputted energy, there is where I'm having problems:
1 - The inputted energy is power being applied during 50 seconds: Qi = P . t = 500000 . 50 = 25000000J
2 - With the average increase in temperature (temperatures in all nodes) I apply the heat equation to check the energy in the model after the load case is run: Qo = m . c .dT = 29348000J
Qi and Qo differs in 15%. I was expecting the energy values to be pretty closed. But It's like the model is adding energy to the inputted value. I've been trying a lot to figure out what is going on but no success so far. The power is being applied in 13 nodes, I've also noticed that if I apply in one or two nodes the difference drops to 10.5%, but it's till too hight to validate.
Could anyone help me with a hint of tell me what I am doing wrong?
Thanks in advance,
Felipe
I'm currently trying to validate a model I'm using to analyze heat from friction in a huge slide bearing.
My input is power and it's applied in time steps of 5 seconds.
The model is axisymmetric (meshed with element PLANE55) with a layer for convection with SURF151 elements. There's also a node with environmental temperature to connect the model with the environment.
Softwawe is ANSYS release 14
At first it seems that the calculations are ok, it's giving nice plots of temperatures with coherent values.
Now I'm trying to validate using the heat equation Q = m.c.dT to compare with the inputted energy, there is where I'm having problems:
1 - The inputted energy is power being applied during 50 seconds: Qi = P . t = 500000 . 50 = 25000000J
2 - With the average increase in temperature (temperatures in all nodes) I apply the heat equation to check the energy in the model after the load case is run: Qo = m . c .dT = 29348000J
Qi and Qo differs in 15%. I was expecting the energy values to be pretty closed. But It's like the model is adding energy to the inputted value. I've been trying a lot to figure out what is going on but no success so far. The power is being applied in 13 nodes, I've also noticed that if I apply in one or two nodes the difference drops to 10.5%, but it's till too hight to validate.
Could anyone help me with a hint of tell me what I am doing wrong?
Thanks in advance,
Felipe