I have designed a helical coil heat exchanger however it is unconventional so I am having a hard time on the computation. I have designed a twin coil and my HE doesn't have an annulus. Also, I have put a partition plate between the coils. I could not find sources on how to compute for the overall heat transfer coefficient (sources i found requires an annulus in the computations)
I have attached the picture of my design for reference. Note that the flow is countercurrent (my diagram indicates otherwise).
Any tips on how to calculate the heat transfer? I will be neglecting the heat transfer due to the baffles. Should I also neglect the one from the partition plate?
Hi Leila,
I would separate it in into a couple of part exchangers, which you can calculate with simplifications. The number should not be too high. Starting with 12 or 16 would be a good idea.
In each cell, you have a flow of outer medium with capacity, wall capacity and a flow of inner medium with capacity. Also consider the heat transfer coefficient is depending on flow velocity.
Choose your time constant not to small, to be sure the transferred heat does not exceed the delta temperature between medium and cell, otherwise you will get numerical oscillations.
If you simulate with Matlab, you can see when it get stable.
For the unconventional shape , I think it is difficult to compute directly using equations or well known formula.
My suggestion is to use finite element/volume method and CFD analysis. There are commercial software and open source software. You can use open foam for free one.
Sir Fache Axel
I have tried this method. Thank you very much! I think it worked because I have computed not so questionable values :)However I was unable to account the heat exchange for the baffle plates.
Fache Axel
my design does not have an annulus. Cooling water will be in direct contact to the coils.
Sir Andreas Gotter thank you for your suggestion! I have adapted sectioning the equipment in my calculations.
May I ask if it's safe to assume that the heat transfer in baffle plates would be negligible in comparison to the heat exchange due to the coils?
The heat transfer in baffle plates would be negligible, if they are very thin or have no welded connection to the coils.
Tri Ayodha Ajiwiguna Thank you for you suggestion sir! I will try it out for accurate computations.
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Heat Transfer