Dimensioning CTA

[Ulkina]

I realized the losses of a BBC building and for a surface of approximately 100m² (amphitheater) I found 3400W. Does this seem reasonable to you?
In addition I have to dimension a CTA (which consists of a hot battery and a cross-flow recuperator of efficiency 0.6). This room has underfloor heating (emission power: 5550w) with backup provided by the CTA. This double flow ventilation ensuring the functions of:

• Hygienic ventilation according to occupation and rate of fresh air introduced
• Filtration
• Heat recovery from the extracted air
• Additional heating to basic underfloor heating

Cooling is obtained by night ventilation with air inlet from the north facade and air outlet through the external openings controlled by the south facade.
The underfloor heating is reversible.

I have to size this CTA I do not see how. Could you help?
Kind regards.

[elephant]

Well, if you already remembered what a CTA is!

[dedeleco]

We can't help it if we don't know what it is !!!!!

Air handling unit !!

for large rooms or buildings and have breathable air, with good humidity and a good temperature.

So water evaporator in a quantity controlled by the desired humidity level, more or less associated with a double-flow exchanger and eco-friendly heating, avoiding legionellosis and toxic or allergenic products to kill these bacteria .

Otherwise it becomes a toxic building !!!

See the doc:
http://www.france-air.com/Portals/0/ima ... igivap.pdf

We determine the necessary air flow, proportional to the number of people breathing, of the order of a liter per second and per person and this fixes the water flow to evaporate, according to the humidity of incoming air ( so cold at the start, it's almost zero in winter) and the desired humidity, 50 to 70% often, thanks to the formula and charts given in this pdf, or in wikipedia for humidity, air, dew point, etc. ..
.

[Ulkina]

Thank you for your answers.


Yes I have defined an air renewal of the order of 1440m² / h but where I block it is about the additional heating (underfloor heating).

Since my underfloor heating provides enough power to "eliminate" the losses due to the wall. What is the point of fixing a hot coil in the air handling unit and if it is useful, how will we be able to size it? In spite of the rate of air renewal?

[dedeleco]

losses from a BBC building and for an area of ​​around 100m² (amphitheater) I found 3400W

seems consistent BBC with less than 50KWh / m2 to watch with more care according to the region of France (Paca, Alsace, Brittany ???? which have very different mini T, which are likely to make the underfloor heating insufficient)

Nevertheless, the inputs and outputs of people through the doors risk making losses greater than 3,4KW.

On the other hand, each person releases about 100W (2000Kcal / day) at rest and 10 times more in full gymnastic effort (pedaling Tour de France for example) and therefore if the amphitheater of 100m2 contains 100 people at most, they will release 100x100 = 10KW, 3 times the necessary heating !!!
It will be much more, if it is an intensive gym?

In this case you have to think about it, especially if people stay there very long.

I defined an air renewal of the order of 1440m² / h

According to which method ???

Finally, as a benchmark, the air flow breathed by each person is approximately, 1 liter per second very roughly, ( rejected full of moisture ) and if you want to renew it as polluted, you need for 100 people, a flow rate of 100litres / s or 360m3 / h.
This must be adapted to the number of people and the level of pollution and humidity, automatically.

Also, 1440m3 / h seems a bit high, to analyze with care, because it increases heat losses, even with double flow exchanger, essential in BBC, (losses 10% even at 90% efficiency) otherwise 1440m3 / h makes good thermal losses in winter:
at 1,3Kjoule / ° Cm3 air from 0 ° C to 20 ° C, gives 26W per m3 / h and 1440m3 / h requires:
1,3x20x1440 = 37,440KJ / h / 3600s = 10,400KW , 3 times the heat losses without ventilation, great destruction of the BBC and the 5,55KW underfloor heating will not be enough !!!!
(Figures in specific heat column multiplied by density for air in:
http://fr.wikipedia.org/wiki/Diffusivit%C3%A9_thermique
)

Even with double flow at 90% recovery (max possible rarely reached), it remains 1,04KW, which lowers the BBC and in very cold conditions the underfloor heating will be insufficient !!!

So we have to limit automated ventilation to the minimum necessary for good quality air, and stop it when it is useless, when the amphitheater is empty, or adapt it to very few people and its clean air.

The heating economy will be significant, worthy of BBC.

What is the point of fixing a hot battery in the air handling unit and if it is useful, how will we be able to size it? Finally, the air renewal rate?

Without added heat, the incoming air will be outside T, ie 0 ° C or even -18 ° C sometimes in winter, which is unbearable for someone, poorly placed, receiving this ventilation directly in the figure.
So we need a double flow ventilation unit with 90% efficiency with regulated humidity, for all these reasons, BBC, almost hot air sent to people, etc ...
The underfloor heating will then heat without difficulty.