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Vekke 09-28-2021 10:25 AM

DIY solar air heater

Here is a puzzle for all you CFD experts. I yesterday released my solar heater design, but it still needs little bit design before making first real world tests and I was wondering if you could help.

I ended at the moment making that kind of holes for the aluminum tin paper. Target is to get even flow speeds under the aluminum tin and on top of it on the visible side. On the visible side flow speeds can be little bit slower. At the moment I have left there little bit more room 30mm vs 20mm under the AL foil. I would like to have little bit slower flow speed on that side as the PC sheet will be "cold"compared to the inside of the collector.

Would like to make quick and dirty CFD run, but sadly I don`t have any software currently in use that could do such a simulation.

What you think would this design work well or would you think any other cutting patterns?

Main targets
1. Maximal surface area under the PC sheet which has AL tin foil.
2. pretty even flow in liters in each channel and little bit less near the PC
3. Idea is to have even laminar flow inside heater to minimize losses and get even temperatures inside the collector, which will lead to greater overall efficiency, because hot spots will be minimal.

Link to yesterdays video in comments.

#aerodynamics #cfd #puzzle #airheater #flowoptimization #laminar #flow #engineering #fluidflow #simulation

freebeard 09-28-2021 10:30 PM

Thanks. I've often envisioned a similar box 3x16 feet on my flat roof.

I'd be concerned about airflow through those outer channels. Suppose you offset the holes to the 1/4 and 3/4 points. Essentially, split the difference on the outer fences instead of the central one.

I'm not sure how to equalize the flow (If it's really needed) otherwise.

rmay635703 09-28-2021 11:18 PM

My father built a solar heater in the 70’s it was an insulated wooden triangle with a flat black aluminum sheet, a small Airgap with a translucent plastic lense

He used a simple in out air duct with a thermocouple and a small fan that would suck air from the top into the ceiling of our house.

It would make heat year round and he would simply cover it with white foam in the summer

freebeard 09-29-2021 03:44 AM

The house my parents built had a slanted box ('triangular') with a 60-80 gallon black painted water tank in it, in the top of a greenhouse addition roof gable. But the so-called 'solar contractor' put it two feet from the exterior glazing and that cut down the already marginal light capture, due to internal shading.

Vekke 10-11-2021 10:43 AM

First CFD simulation is ready.

Thanks to Gaurav Kamde and Anand Kulkarni making this simulation possible. In this video you will see CFD simulation results of the 1st design version of the flat plate solar heat air collector. I will go through the simulation results and the modification done to make the flow pattern better to get best efficiency for the collector.

This is a opensource project so final version design details and drawings will be released to everyone so you can make it easily yourself and help to save our climate and save yourself little bit money on heating costs.

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