# Heat-exchanger in PreCICE **URL:** \ **Category:** Official adapters and tutorials\ **Tags:** openfoam, data-mapping, calculix\ **Created:** [April 12, 2022, 3:56am UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019 "2022-04-12T03:56:41Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![tianhk](https://avatars.discourse-cdn.com/v4/letter/t/49beb7/32.png) [@tianhk](https://precice.discourse.group/u/tianhk)\ **Post date:** [April 12, 2022, 3:56am UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019/1 "2022-04-12T03:56:41Z")
Hi everyone, I recently had a problem using the heat-exchanger example in PreCICE. Why are temperature and heat-transfer-coefficient exchanged in this example? I think it should exchange temperature and heat-flux. That is, fluid gives Temperature to solid and solid gives heat-flux to fluid. If the coefficient of heat transfer-coefficient is exchanged, why do we give a fixed value in Calculix? I think the coefficient of heat transfer-coefficient is calculated by the formula, so I am confused here. Can someone please help me to explain? Thank you very much! ![1](https://global.discourse-cdn.com/free1/uploads/precice/original/2X/9/9e2a6ddce891364e3bbdbf056c6af81ac60eab2e.png) ![2](https://global.discourse-cdn.com/free1/uploads/precice/original/2X/e/e37240a15412159e074d08f292c2300493b5eb40.png) ---
**Author:** ![ajaust](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/ajaust/32/160_2.png) [@ajaust](https://precice.discourse.group/u/ajaust)\ **Post date:** [April 12, 2022, 8:43am UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019/2 "2022-04-12T08:43:47Z")
I would guess it depends on the kind of coupling conditions being used. If you check out the [test case’s documentation](https://precice.org/tutorials-heat-exchanger.html) it links to the [master’s thesis](https://www5.in.tum.de/pub/Cheung2016_Thesis.pdf) of [Lucia Cheung Yau](https://github.com/ludcila). The master’s thesis discusses different coupling conditions, see e.g., chapter 2.4 and 4.1 in the thesis. I the use of Robin-type coupling conditions is the reason for the heat transfer coefficient and temperature to be exchanged. Maybe someone from the preCICE team can comment on that and verify my guess. ---
**Author:** ![Makis](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/makis/32/25_2.png) [@Makis](https://precice.discourse.group/u/Makis)\ **Post date:** [April 12, 2022, 9:17pm UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019/3 "2022-04-12T21:17:48Z")
Exactly! In the [flow-over-heated-plate tutorial](https://precice.org/tutorials-flow-over-heated-plate.html), we are using a Dirichlet-Neumann coupling. In this case, we are using a Robin-Robin coupling. In her thesis, Lucia found the Robin-Robin coupling to be a better/more stable option for this case. For us, this tutorial remains an important test case for this type of coupling. ---
**Author:** ![tianhk](https://avatars.discourse-cdn.com/v4/letter/t/49beb7/32.png) [@tianhk](https://precice.discourse.group/u/tianhk)\ **Post date:** [April 13, 2022, 1:38pm UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019/4 "2022-04-13T13:38:01Z")
Thank you for your reply. I have read the relevant chapters of this literature and found the answers I needed. ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/precice/original/1X/67d2a5fa6f80e597e2267ff17fa8c1673cd11caa.svg) [@system](https://precice.discourse.group/u/system)\ **Post date:** [April 16, 2022, 1:38pm UTC](https://precice.discourse.group/t/heat-exchanger-in-precice/1019/5 "2022-04-16T13:38:41Z")
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