Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?

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Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 13:40

To avoid or greatly limit the evaporation of a mass of hot water from a solar thermal buffer (therefore not boiling), it is necessary to block the contact of the water with the air. I think a thin layer (2-3mm) of a liquid that doesn't evaporate and spread over the entire surface might do the trick. Kind of oil?

The goal is to optimize the internal evaporation of my solar thermal pad that I featured here years ago.

Solar-thermal / thermal-solar-buffer-optimization-and-repair-t4517.html
solar-thermal / cop-d-un-solar-thermal-with-drainage-de-20-ans-d-age-t8220.html

A rare photo from the time when the level had dropped a lot when I moved in (2007) ... I had it repaired and isolated Solar-thermal / thermal-solar-buffer-optimization-and-repair-t4517.html

Image

Once I find the right product to add to the surface, I'll open it again ... 15 years later and dozens of MWhs in storage later to see what it is!

Indeed: even if the evaporated water condenses on the top slab of the thermal buffer, this creates a "heat pump" which causes the hot water to lose calories in the buffer ... For a swimming pool evaporation constitutes the main part of the heating losses! In the case of a thermal buffer, the air is quickly saturated the effect is less great BUT the temperature can be much higher suddenly there are necessarily losses all the same (I cut the heating of the buffer at 65 ° C because each ° C gained during the day above 65 ° C, will be lost the following night...)

So 2 questions:

a) what type of oil would be the most suitable over time and for health (in the case of an indoor tampon) Vegetable? Motor ? Hydraulic?
And what rank? The buffer varies from 20 to 70 ° C ...


If you know of other products that float in water and that prevent surface evaporation, this interests me ...

b) What thickness so what quantity needed to be sure that the layer occupies the entire surface homogeneously?

Knowing that once it's put on ... it will be very difficult to remove it! So I don't want to be wrong!

I don't have to worry about putting 30 or 50L of oil in it, but if you need 200 or 300L I'm not sure to do it!

No worries about testing "in glasses"! : Cheesy:

Also read about thermal buffers:
heating-insulation / thermal-concrete-heat-storage-buffer-t6335.html
Solar-thermal / a-house-a-solar-thermal buffer-almost-self-t5233.html
Solar-thermal / solar-installation-the-wood-of-Tigger-with-buffer-thermal t5200.html

Edit: photos from 2021 here science-and-technology / thermal-buffer-to-avoid-surface-evaporation-of-hot-water-with-oil-or-another-blocker-t16964-70. html

Edit addition: start of the experiment here science-and-technology / thermal-buffer-to-prevent-surface-evaporation-of-hot-water-with-oil-or-another-blocker-t16964-100. html # p462217

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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 13:47

Ah yes the surface is about 28 m² ... 28L of product will therefore make an "evapo blocking" layer of 1 mm ... provided that it manages to be distributed over the entire surface ... and there I have a doubt...

ABC? Do you know the surface tension equations?
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 14:05

Another solution: put X thousand ping pong balls on the surface ... but it could cost an arm and a leg!

And less effective than a homogeneous layer of product blocking evaporation ...
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by GuyGadeboisTheBack » 16/08/21, 14:09

If the room does not have a complicated shape, an insulating cover (bubble cover) for swimming pool could do the trick ...
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 14:13

Yes guy, the shape is rectangular but no because it would be impossible to apply it correctly: there are the top attachment points of the exchanger, pumping and filling pipes ... therefore not possible to apply a tarpaulin easily ... and the effectiveness of a tarpaulin is reduced because it never applies uniformly to the surface, especially at 50 ° C or more!

This is why we need a "self-leveling" product ... What remains to be found ... and at what price (5 € per L ok ... 50 € per L it's not worth it!).

For the moment, apart from the oil I can't see.
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 14:14

Otherwise, let's be crazy, I would have collected a few drums of low-level nuclear waste and put a little boron in the water ... does anyone have any leads for this kind of product? : Lol: : Lol: : Lol: : Lol:
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Obamot » 16/08/21, 15:17

There is a solution to your problem, but I will first let “the physicist” answer :)
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by GuyGadeboisTheBack » 16/08/21, 15:40

Evaporation.JPG
Evaporation.JPG (91.41 KiB) Viewed 2090 times

https://www.sciencesetavenir.fr/nature- ... l-eau_4937
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Christophe » 16/08/21, 15:44

Interesting guy but 45% is not 100% ... the technique you quote is for drinking water ... me it's stagnant water ...

A good layer of oil is -100% evaporation ... a priori
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Re: Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?




by Obamot » 16/08/21, 16:33

GuyGadeboisLeRetour wrote:Evaporation.JPG
https://www.sciencesetavenir.fr/nature- ... l-eau_4937
Calcium hydroxide floats?


ABC2019 wrote:on the one hand nothing of this "new physics" contradicts the great principles of physics

So what's up
Last edited by Obamot the 16 / 08 / 21, 16: 48, 1 edited once.
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