Easy and ecological freezing protection of a room or greenhouse

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
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Easy and ecological freezing protection of a room or greenhouse




by Christophe » 15/07/07, 12:28

Following : https://www.econologie.com/de-l-eau-liqu ... -3501.html

There is a solution (from our big mothers) effective enough to keep a room or a greenhouse out of frost without spending a gram of fossil energy.

Just put a large basin filled with water in the center of the room.

Indeed, as long as the pan is not completely frozen, the temperature CANNOT drop below 0 ° C thus protecting what is in the room.

Obviously, the longer the gel duration, the greater the quantity of liquid water. If the subject interests you, we will do the calculations.

In addition, this quantity of water makes it possible to smooth the temperature variations (thermal amplitude) during the same day. I'm going to do some tests on this next time ...
Last edited by Christophe the 10 / 10 / 07, 15: 26, 3 edited once.
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by Christophe » 08/10/07, 13:27

With winter approaching, here is an estimate of the "thermal power" provided by this method.

- Latent heat of fusion of water: 330 kJ / kg ( http://fr.wikipedia.org/wiki/Chaleur_latente )

- Example, a 50L basin at 0 ° C (therefore just before it freezes, ie at the stage of solidification) "contains" therefore 330 * 50 = 16 kJ or the equivalent of 500 L of domestic fuel!
Indeed, the fuel oil PCI = 34 900 kj / L see https://www.econologie.com/pouvoirs-calo ... s-534.html

- Suppose that it freezes for 48 hours in a row (ie not a solar Joules brought to the greenhouse) and that the bowl is completely frozen after these 48 hours. The average power provided by this basin would therefore be 16 / 500 * 48 = 3600 W and the greenhouse would never have dropped below 96 ° C!

Strictly, a calculation of "loss" of the greenhouse (or the room) would, conversely, determine the number of liters of water required to keep it out of freezing.

However, the uncertainties are too great to be able to make a general calculation since many parameters come into play:
- Initial greenhouse temperature
- Outside temperature
- Duration of frost without thaw
- Surface and materials of the greenhouse -> losses (rare are double glazed greenhouses so they are very important)
- Content of the greenhouse or the room (personal wood is dried there, so it increases the inertia).

In any case, I will try it out this winter (if it freezes) and keep you posted.

Here it gives me idea: this "method" allows to know with precision the losses of a room, it is enough to have the exact duration of freezing of the entirety of the water :) ... and a fairly long frost period ...
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by Christophe » 22/12/07, 19:30

As it is finally very cold, I filled a 70L bucket of water in our greenhouse (glued to the house) this afternoon in order to test the method "in real life".

So tonight it's -5 ° C outside and in the greenhouse ...- 2.5 ° C.

I placed the probe on a board placed on the bucket (so logically where it has the most "calories").

In addition I do not know if this temperature difference would not come from inertia: from the greenhouse but also from the walls of the house.

In short it may not be such a good method ... more readings later ...
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by bolt » 22/12/07, 22:28

good evening Christophe

Image
calculates the contact surface of the greenhouse with the outside

calculate the total exterior surface of your 70 liter container of water


you get, from your container, a "heating" surface of 0 ° C as long as the water is not completely frozen

antagonist at the greenhouse contact surface with the atmosphere which is (example) -5 ° C

if the surface ratio is 20, the average T ° of the interior of your greenhouse will be -4,75 ° C
(between 0 ° C and -5 ° C)

note that your greenhouse may be built with insulation that limits the power of the cold
and that the soil probably provides a little bit of earth's heat

bolt
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by Christophe » 22/12/07, 22:51

Interesting this area ratio method I had never heard of ... : Idea: The surface ratio must be greater than 20 ...

As for the insulation, it must be close to 0: aluminum profile and simple "glazing" in corrugated plastic sheet ...
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by Gregconstruct » 23/12/07, 09:20

Interesting this method of keeping frost-free!

And logical moreover since we know that the oceans allow the thermal inertia of the planet and that if they did not exist, we would know unbearable thermal amplitudes between day and night!
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by Christophe » 23/12/07, 10:31

Well the problem is that it is far from maintaining FREEZE as I thought, it just allows to smooth the fall in T ° ... Cf the calculation of Bolt ... or so it would take a volume and a surface of the very important water reserve.

This morning, at 10am, the greenhouse was at -3.2 while the outside was at -3.5.

As soon as the jump is completely frozen I make some measurements without liquid water so ...
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by Gregconstruct » 23/12/07, 10:34

You would need almost 300 liters and maybe even more, to keep it frost-free ... :?
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by Christophe » 23/12/07, 10:49

Well if the bolt method is correct, with water at 0 ° C you can never keep frost free since it will be a barycenter of the surfaces between the T ° of the water (0 ° C therefore) and the T ° outside.

With water at 10 ° C for example you can keep it frost-free but in this case the energy of water from 10 ° C to 0 ° C is much less important than that of fusion from 0 ° C to -0.1 ° C ...
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by Gregconstruct » 23/12/07, 11:17

You had to tell us that you wanted an indoor pool !!! : Mrgreen: : Mrgreen: : Mrgreen:

In fact, if I understood correctly, the important thing is the exchange surface that matters and not just the volume of water :?: :?: :?:
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