Re: [TRNSYS-users] Condensation problem

The freezing of the air will also be a problem. Ice formation will also release energy (latent heat of freezing). The latent gains refered to by the buillding model refers to the part of the total energy that is in water vapour form. In the industry this is refered to as latent heat gain. It is not the heat released into the air by the forming water when condensation occurs, as far as I know. A building this cold with just infiltration must be similar to my deepfreeze section at home. The latent heat of condensation and freezing may be small enough to ignor. See this wiki article http://en.wikipedia.org/wiki/Latent_heat and try out the formula in it

The latent heat of condensation of water in the temperature range from −40 °C to 40 °C is approximated by the following empirical cubic function:

$L_{water}(T)=-0.0000614342 T^3+0.00158927 T^2-2.36418 T+2500.79$ ^[7] [J / g]

with a determination coefficient of $R^2=0.999988$ , where $T$ is in °C

On 24 April 2012 16:32, Alexis Fabre (3E) <Alexis.Fabre@3e.eu> wrote:

Dear all,

I’m working on a fish factory project located in Nigeria.

I need to simulate the building based on the outside temperature (around 30°C) and the required temperature inside the factory (the temperature level depends on the room but will vary between 13°C and -40°C).

I set the internal gains (lightings, fish, workers, water cleaning), insulation thickness…there is no ventilation and I considered an infiltration factor for each room.
I simulated the building and got the energy needs of the building to provide all the cooling demand.

I realized that I considered as main output the sensible cooling demand for the building.

Problem: The relative humidity of the outside air (entering the building when fish load goes in or out) is high in Nigeria (between 60 and 90%). Therefore when fresh air enter the building, the temperature decrease and the relative humidity reach 100% really quickly. There is condensation and thus heat release (latent heat). This amount of heat is high specially when the outside air (around 30°C) has to reach a temperature of -40°C!

I decided to analyse the TRNSYS output: QLATG (latent energy gains including ventilation, infiltration…). Then I’ve compared it with the sensible heat and I noticed the following:

Sensible heat =10000 x Latent heat.
I was expected that the latent heat would have been about the same as the sensible heat (calculation done with a mollier diagram).

I decided to check the relative humidity inside the rooms: the relative humidity is almost always at 100%.

Question: I’m wondering if TRNSYS considers the heat released during condensation. The impact is probably huge on the energy demand of the building.

Does anybody know if TRNSYS can give me the energy which is released when the humidity inside the air is condensated?
I did not fix any humidity level inside the rooms.

Thanks a lot for your help

Best regards

Alexis Fabre

Alexis Fabre

Project engineer

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