# Using the TL-2P heat exchanger in simscape to simulate an external threaded tube heat exchanger

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Commented: 忠宇 on 3 Jun 2024 at 15:00
Using the TL-2P heat exchanger in simscape to simulate an external threaded tube heat exchanger, water and refrigerant are in a countercurrent process, water flows in the tube, and refrigerant r134a flows in a ring outside the tube. Then I use the experimental data to set in simscape, but the heat transfer cannot achieve the desired effect. What is the reason? I analyzed that it is caused by multiple encircling, is there any way to solve this problem
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Thank you very much for your reply. Actually, I refer to a heat exchanger with a big tube covered with a small tube for serpentine coil. The use of a system-level heat exchanger can indeed reach the working point I need, but I still want to obtain an accurate model by setting the size. It may be caused by the circulation of the fins of the threaded tube and the serpentine tube, but I don't know how to set the fin area

I'm not sure how to estimate the parameters

Yifeng Tang on 3 Jun 2024 at 14:45
The way you set up the heat exchanger looks promising to me.
I would use the Parameter Estimator App (Documentation) to estimate the coefficients for the Colburn equations. Go through the examples in the documentation so you understand how it works and how to set up the test harness. You may see an example of test harness for heat exchangers here.
What parameters in the Colburn equation to tune, I think, should depend on what reference data you have. If you have reference data at different flow rates, that allows you to tune the factor b's for the Reynolds number dependency. Different thermodynamic states can help with Prandtl number dependence. And whether your two-phase fluids covers all the phases in your test data also affect whether you can tune all three zones.
Regarding the fin area, if the thread is outside the tubes, it should count towards the fin for the two-phase fluid. If it's inside the tubes, it's for the TL-side. I suggest that you get an estimate of the total surface area vs the smooth pipe surface area, and use the difference to set up the fin area. You can also use fin area and fin efficiency as tunable parameters, but I would suggest you use caution or at least set some tight limit in the estimation process. In general, you want to use true information from physical system as much as possible, and leave the ones that's hard to measure to the estimation workflow.
Hope this helps.

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