i am trying to simulate heat transfer of a chip on a PCB within a steady fluid. but i would like to get the variation of temperature with repect of time. i have the chip enclosed in the box (air part included) and the chip, the box, the air part and the board are enclosed in a bigger enclosure with another air part included also.
i would like to get a plot result of themperature with respect of time.
Is Transient Coupled fluid flow and thermal analysis is the right one to use, i am trying now and the Analysis progress continuous to run for more than 20 hours, is there a problem converging?
i have no problem with Steady coupled analysis for this model.
Transient coupled is required to get temperature versus time.
Steady coupled usually has a more difficult time of converging than transient because some (most?) situations do not have a steady state solution. Whether the transient analysis is having difficulty converging is a question that only you can answer: does the log file (the text that scrolls in the analysis window) show the percent completion increasing after a few iterations or after many iterations? (The online Help describes the text given in the log file: search for "coupled log".) Does the time step increase in the results environment?
The logs for the coupled analyses are tricky because there are three log files:
- one for the coupling between fluid and thermal. This is the log file shown in the analysis window as the simulation is running.
- one for the heat transfer analysis. This usually does not have anything of importance regarding convergence unless your simulation includes radiation, temperature dependent materials, or temperature dependent load. This log file is viewable from the "Report" environment.
- one for the fluid analysis. This log file is viewable from the "Report" environment.
15 years experience with Simulation Mechanical
If I remember correctly, the last time I tried transient coupled fluid flow and thermal analysis, the graphic window does not update the results as the analysis was running. This made me a little bit confused and thought that my analysis setup was wrong. But when it was finished, the results for the all timesteps were accessible. Regardless, it was hard to determine whether the analysis is progressing or not.