externalWallHeatFluxTemperature BC with h as a function of Twall
Hi foamers,
I'm trying to simulating a heat transfer case with chtMultiRegionFoam where one of the boundaries transfers heat with the environment by convection. This is a simple problem where the boundary is defined as "externalWallHeatFluxTemperature" defining both values of "Ta" and "h". So far it is a basic case. However, I would like to define the heat transfer in the boundary wall using a variable value of "h" where its value depends on the value of T at the boundary. The first thing I thought about was to use swak4foam but I'm not sure how to tackle it. ----------------------1st Question---------------------- Would it be possible to use the same boundary type (externalWallHeatFluxTemperature), but adding some lines with the expressions needed to calculate h? I don't think so but I ask for it just in case... ------------------------------------------------------------- I haven't much experince using swak4foam, actually I only used it like one year ago to create a BC for convective heat transfer before I found out that externalWallHeatFluxTemperature existed. This was the definition I used: Code:
sup_convection ----------------------2nd Question---------------------- a)How can I access the value of T at the boundary to use it in the calculations? b)Imagine I have a set of expressions to be used in the calculations depending on the value of T at the boundary that need to satisfy a condition such as: Code:
if T<a ---> expr.1 ------------------------------------------------------------- I have been reading the documentation of swak4foam and trying some tutorials and, although I think this is what I need, I still don't know how to do it. If you can give me any hint about the most proper aproach to solve my problem, don't hesitate to do it! I will appreaciate any word you can give me! Remember, you can give me a really nice (and free) Christmas present! :D Many thanks in advance! Alex Note: I am using OF 2.3.x and I noticed that some swak's tutorial cases are outdated since I couldn't solve the chtMultiRegion case because of a wrong boundary definition for the pressure. |
Hi Alex,
Sorry for reviving your old thread, but this seems like one of the only relevant ones to what I'm trying to find out. I'm new to using groovyBC, and trying to find out whether the heat flux is calculated on a patch (presumably as an average or similar) or on each individual cell? I have a case with heat loss through several patches, and am wondering how it is calculated. Thanks, Mick. |
Hi Mick,
Good question! I always just assumed groovyBC was calculating it for each individual cell, but perhaps you could use the wallHeatFlux post-processing utility to visualise the heat flux on the patches as a test? (If you have an incomprssible case you can use wallHeatFluxIncompressible which can be downloaded here: http://www.cfd-online.com/Forums/ope...ance-flow.html) |
Hi Alex and Nicole,
Thanks for the responses, I have since worked it out, and it does in fact calculate the heat loss on a cell-by-cell basis, when applied properly. The issue that I was having was that the way I was specifiying the temperature applied, Code:
Toutlet{backwall}=oldTime(T) To my understanding, groovyBC is able to compute a variable heat flux, although because it does not perform an energy balance, it instead must apply a temperature gradient. To do this, input the usual heat loss equation for the boundary, but divide it by the thermal conductivity of the material losing heat. I learned this here: http://www.cfd-online.com/Forums/ope...hase-flow.html Thanks for the link to the wallHeatFlux utility, I'll use it down the track to validate that my heat loss is correct. |
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