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Dear TessLib experts,
I am simulating a solar thermal collector coupled with a horizontal tank. Within the horizontal tank, an immersed horizontal coiled HX carries the working fluid along the length of the cyclinder (from side to side). The attached image may help you picture the assembly.
I have been using Type 1533-coiled-v2a from Tess Libs 18. Type 1533 offers 4 options of HX geometry : Horizontal tube bank, Vertical tube bank, Coiled and Serpentine.
In the Mathematical References manual, while the axis of the noding of the first 2 geometries is explicitly mentionned ( horizontal and vertical), for the latter 2, it is only says" divided into N hx nodes along the flow direction". Assuming that it means the flow inside the HX tube, the direction remains unclear.
On the other hand, given that the tank is divided along the vertical axis, and that I can assign mutliple HX nodes to 1 horizontal tank node, but not the opposite : this should indicate that the coiled Hx is positionned vertically.
While I may have already answered myself, I still want to verify :
- Are the coiled and serpentine HX within Type 1533 assumed vertical ?
and followingly, I would like to ask :
- Is there a possible tweak of parameters ( perhaps in the datafile version? ) that would allow me to change the HX orientation ( or maybe change the noding axis for the tank itself ? )
I hope my question was clear.
Regards,
Mehdi_S
Greetings to all,
Well, it seems my post went unnoticed for a month now .. or maybe I said things in a complicated way...
So with all due diligence, allow me to reformulate things in a much simpler way:
I am simulating a solar thermal collector ( thermosiphon) that has a horizontal coiled HX inside a horizontal tank.
I am using TESS Library Type 1533.
After reading the docs, it seems to me that Type 1533 only supports vertical oiled HX inside the horizontale tank , is that so ?
and is there a way to configure the Type 1533 ( via Dat file or Type studio) to make the HX horizontal ?
I would be grateful if somebody could provide some guidance, as this is fundemental for my work.
Thank you in advance !
@mehdi_s you are correct that I didn't see your previous post! Sorry about that.
The configuration for a coiled tube heat exchanger in a horizontally cylindrical tank as modeled by Type1533 is as shown in the attached png file. In your case, do the coils follow the circumference of the tank such that the long axis of the cylinder formed by the heat exchanger is in the same direction as the long axis of the horizontal tank? If so, that surprises me; the reason the coiled tube is oriented so that its vertical axis is in the same direction as the diameter of the tank is to preserve thermal stratification. If the coil is oriented the other way then stratification would be diminished in the tank.
david
Mehdi_S Topic starter
25/10/2024 8:14 am
Hello @davidbradley,
Thank you so much for your reply.
Indeed, I did look into the Type 1533 description, saw the same illustration. But I still wanted to be sure, as it was not explicitly explained in the text.
I do understand the reasoning about having a vertical coil to sustain a vertical thermal gradient. But in my case, I am working on collectors that have a horizontal HX, as you described ( see the picture attached) within installations that are already operational and experimentally monitored... intrestingly enough, the sensors show a vertical gradient ranging between 2 to 5 °C during operating , depending on weather and load.
I will try to figureout if I can change the coil orientation using Typestudio . Any tips or guidance would be welcome ! 🙂
@mehdi_s It will be very difficult to modify the Type to change the orientation of the coiled heat exchanger. The heat exchanger would need to enter and exit multiple nodes at multiple points along its length, which is both geometrically and thermally a difficult problem to solve.
One thing you could do is just model the entire tank as a single-node, isothermal tank. In that case, the entire coil will be within a single node (the only node), and the orientation of the coiled heat exchanger will not matter. As @davidbradley said, the orientation of the coil will mitigate thermal stratification anyway, so theoretically this should be an acceptable modeling solution. I know you said the sensors showed thermal stratification even with the horizontal coil. The other thing you could try is placing the entire coil within the middle node and using a handle like additional thermal conductivity or a forced flow between the nodes to tune the thermal stratification to what's measured by your sensors.
Please keep in mind that this user forum is intended for community discussion, and that we volunteer to reply to threads as our time and resources allow. There is no guarantee or expectation of technical support through the forum. Your TRNSYS distributor is your first point of contact for technical support. If you do not know who your TRNSYS distributor is, you may copy and paste the contents of the user18.id file in your main TRNSYS directory into an email to techsupport@tess-inc.com, and we can look up your distributor. I am rather disinclined to provide ongoing support for users who have not acknowledged the time or lengths I have gone to to help them in the past.
Mehdi_S Topic starter
28/10/2024 3:17 pm
@a_weiss I am really grateful for the attention and the time you dedicated to answer my question. Thank you for the tip regarding tank discretization.
I do understand your reserves on answering my post, and I do apologize if I may have behaved in an unconsiderate manner in any of my previous posts. My work on this storage topic was very intermittent, as I had surely missed following up on previous posts due to that.
Again, sincere apologies. I was not expecting any garanteed answer. I only tagged you as I was awere of your direct affiliation with TESS.
On a side note, my organization are open to requesting ( and paying for) a custom Type from TESS if this is possible. If so, we will contact you through the email you indicated above.
Thank you again for your collaboration,
Mehdi.
