Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Activating Equations

Please login with a confirmed email address before reporting spam

How to activate equations (used in heat source) for particular temperature? And how to intepret them into the heat source (Q)

  1. 400[K] 500[K] Q_sei*exp(a_sei/T[K])
  2. 500[K] 530[K] Q_n*exp(a_n/T[K])
  3. 530[K] 600[K] Q_sei*exp(a_sei/T[K])
  4. 600[K] 620[K] Q_n*exp(a_n/T[K])

4 Replies Last Post 26 août 2020, 02:47 UTC−4
Magnus Ringh COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 4 years ago 13 août 2020, 10:21 UTC−4

Hi Naresh,

You can use Boolean expressions using inequalities, such as

Q_sei*exp(a_sei/T[K]*(T>=400[K]&&T<500[K])+Q_n*exp(a_n/T[K])(a_sei/T[K]*(T>=500[K]&&T<530[K])+...

All those terms will be zero where and when the temperature is outside their limits and equal to the desired expression inside the desired temperature ranges. Here I assume that Q_sei, a_sei, etc. are defined as constants or variables. You should probably also add terms for temperatures outside of the range (above and below) 400 K to 620 K; otherwise, the heat source will be zero for those temperatures.

Best regards,

Magnus Ringh, COMSOL

Hi Naresh, You can use Boolean expressions using inequalities, such as `Q_sei*exp(a_sei/T[K]*(T>=400[K]&&T=500[K]&&T

Please login with a confirmed email address before reporting spam

Posted: 4 years ago 20 août 2020, 10:13 UTC−4

Dear Magnus,

Thank you so much,, this has solved the issue stated.

Dear Magnus, Thank you so much,, this has solved the issue stated.

Please login with a confirmed email address before reporting spam

Posted: 4 years ago 25 août 2020, 05:02 UTC−4

Hi Naresh,

You can use Boolean expressions using inequalities, such as

`Q_seiexp(a_sei/T[K](T>=400[K]&&T=500[K]&&T

Dear Magnus Ringh,

Could you please sort this out for me.

Theme: Heat transfer between bodies in a room filled with air

The initial temperature of one cell is 1000[K] and the others' are at room temperature. The temperature of other cells will increase due to heat conduction through air over time. As soon as the other cells reach 363[K], the temperature has to take a sudden jump to 1400[K]. No reactions, no heat sources. Just a simple jump of temperature is needed to check the heat wave propagation. How can I achieve this?

Many thanks.

>Hi Naresh, > >You can use Boolean expressions using inequalities, such as > >`Q_sei*exp(a_sei/T[K]*(T>=400[K]&&T=500[K]&&T Dear Magnus Ringh, Could you please sort this out for me. Theme: Heat transfer between bodies in a room filled with air The initial temperature of one cell is 1000[K] and the others' are at room temperature. The temperature of other cells will increase due to heat conduction through air over time. As soon as the other cells reach 363[K], the temperature has to take a sudden jump to 1400[K]. No reactions, no heat sources. Just a simple jump of temperature is needed to check the heat wave propagation. How can I achieve this? Many thanks.

Magnus Ringh COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 4 years ago 26 août 2020, 02:47 UTC−4
Updated: 4 years ago 26 août 2020, 09:50 UTC−4

Hi Naresh,

For this type of modeling questions, I suggest that you contact COMSOL's technical support. However, I think that a maximum nonlocal coupling operator, defined in domains away from the heater, would be useful for setting up a conditional expression to achieve what you want to simulate.

Best regards, Magnus Ringh, COMSOL

Hi Naresh, For this type of modeling questions, I suggest that you contact COMSOL's technical support. However, I think that a maximum nonlocal coupling operator, defined in domains away from the heater, would be useful for setting up a conditional expression to achieve what you want to simulate. Best regards, Magnus Ringh, COMSOL

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.