Natural air circulation

[Sandro Baptista]

Hi Guys,

A cold store sandwich panels manufacturer purpose on its manual the prevention of the freezing ground done by natural air circulation as it is show in the file.

I don't agree with this. Despite the the H value I don't see how it can achieve a less density value than at the inlet. I accept that if the tube at the outlet is heated around it (with electric heater bands for example).

If the air outlet tube is get colder inside than the inlet I even think that the air circulation should be at opposite sense.

What are your opinion about that? What your experience reveals?


Regards

[mbc]

If holes are big and you use air force by fan that is ok. Or if the high of hole is more than 30 cm in dry area it is ok in wet area it should be more than 50 cm with air force <O:p</O:p

[US Iceman]

I have seen these used in large storage facilities, but typically only in warmer climates.

[Tesla]

HI Sadros
The method shown relies on the "Thermosysphon Effect" where a fluid in a tube is warmed in the upper region, this inturn expands and becomes lighter, with the differance of density flow occures. And you would be correct in assuming if the outlet were cooler than the inlet the air could flow in the opposite direction. But the differance in the head of pressure of the fluid incourages flow towards the outlet. The thermosyphon is used extensively on solar hot water systems.

[Sandro Baptista]

If holes are big and you use air force by fan that is ok. Or if the high of hole is more than 30 cm in dry area it is ok in wet area it should be more than 50 cm with air force <O:p</O:p

Yes forced ventilation (fans) it's okay.

What do you meant with dry and wet areas?

Thanks.

[Sandro Baptista]

HI Sadros
The method shown relies on the "Thermosysphon Effect" where a fluid in a tube is warmed in the upper region, this inturn expands and becomes lighter, with the differance of density flow occures. And you would be correct in assuming if the outlet were cooler than the inlet the air could flow in the opposite direction. But the differance in the head of pressure of the fluid incourages flow towards the outlet. The thermosyphon is used extensively on solar hot water systems.


How the tube is warmed in the upper region? It would need to be more hot than at inlet so it could flow » (thermosyphon in solar hot water systems).
How the inlet can be more cold?!?

Now forgetting the effect of the tube heating, the hidrostatic force caused by the air column weight at the inlet and at outlet are the same, regardless the existing of tube or not. Don't you think?

Regards

[mbc]

The area you are going to put your cool rooms . ((Floor)) or the area has more moisture.<O:p</O:p
In my experience I use concrete block ( shape = H ) wide 25 cm/ High 30 cm/ length 40 cm <O:p</O:p
1-I lay those on floor
2- put 10 cm concrete on top of that
3- put 2 layer thick plastic sheet <O:p</O:p
4- put insulation (20 cm plastofom with P= 25kg )
5- put Min 10 cm concrete with metal bars
6 - I use forced air for crulation (air ventilation system)<O:p</O:p