# Boundary condition for a heater with thermal inertia

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 May 5, 2015, 13:04 Boundary condition for a heater with thermal inertia #1 Senior Member     Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 733 Rep Power: 21 Hello everyone, I'm trying to do a heat transfer simulation where a constant heat flux boundary is cooled by a cold gas jet. I saw that the turbulentHeatFluxTemperature boundary condition provides a nice constant heat flux, but when I cool it down it reaches the gas jet temperature almost instantaneously. I'm thinking of reimplementing this BC as a mixedBC, where there is some contribution from the current wall temperature and some parameters to model the heat transfer from the solid boundary (this is so I don't have to do conjugate heat transfer if I don't have to). Has anyone done a boundary like this, or know of a boundary that already does this so I dont have to? Thanks!

 May 9, 2017, 06:31 #2 New Member   zhou qiyan Join Date: Sep 2016 Posts: 13 Rep Power: 2 hi Marco since this thread is about temperature BC and you are skilled at engine simulation， i want to seek some advices about diesel engine temperature BC here 1. what temperature bc do you use in diesel engine tutorials? 2. how do you treat the heat transfer on BCs? as i know, the most common way to simulate the heat transfer is using temperature wall function, do you have any idea about implement a new temperature function? i have change the turbulentheatfluxtemperature bc into a new one, but i dont know whether it is correct. 3. so, the third question is, what a good bc like when doing diesel engine simulation? thanks

 May 11, 2017, 17:36 #3 Senior Member     Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 733 Rep Power: 21 In most work I've done, we've used very simple constant temperature boundary conditions. Somewhere between the coolant temperature and the in-cylinder temperature pre-ignition. Better results could definitely be obtained with something to model heat transfer through the boundaries to the coolant, but I haven't really had time to delve too deeply. As you mentioned, the turbulentHeatFluxTemperature BC is a good base. They key would be to finding the right model of heat exchange to use. In the end, for my purposes constant temperature has been good enough, provided I can the that temperature close to the steady state average.

 May 14, 2017, 10:46 #4 New Member   zhou qiyan Join Date: Sep 2016 Posts: 13 Rep Power: 2 OK，thanks any way . I have just implemented a wall function for heat transfer, refer to the converge user manual. And thanks again Sent from my iPhone using CFD Online Forum mobile app

 May 15, 2017, 11:17 #5 Senior Member     Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 733 Rep Power: 21 Very cool. If you run any comparions between your new BC and a constant temperature one, let me know the general results. As this may be work related I understand if you can't release details, but even your general opinion regarding how much of a difference the heat tranafwr BC makes and whether the development and computational cost (as well as calibration) is worth the result.

 May 15, 2017, 22:29 #6 New Member   zhou qiyan Join Date: Sep 2016 Posts: 13 Rep Power: 2 I only finished a simple case with single step reactions ,which shows that the new BC can result in a lower pressure and temperature in cylinder. I am trying to verify a case with experiments,however,it will crash when use some chemistry solvers,like ode and sequential,and it also crashes when uses high injection pressure,specifically,120bar. By the way, I am willing to release the details,I also need someone to give me some suggestions or point out some mistakes... However,i am visiting a guest university for a few days...maybe you know,study something related to flamelet...I will post the details as soon as I am back.. Sent from my iPhone using CFD Online Forum mobile app

May 19, 2017, 08:51
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zhou qiyan
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Quote:
 Originally Posted by mturcios777 Very cool. If you run any comparions between your new BC and a constant temperature one, let me know the general results. As this may be work related I understand if you can't release details, but even your general opinion regarding how much of a difference the heat tranafwr BC makes and whether the development and computational cost (as well as calibration) is worth the result.

hi
Since I am not familiar with the forum, I don't know how to post my files...can you email me? I will send the files to you

Sent from my iPhone using CFD Online Forum mobile app

 May 19, 2017, 12:54 #8 Senior Member     Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 733 Rep Power: 21 Sure, I'll send you a PM

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