[TRNSYS-users] too high relative humidity

[Adriana Angelotti]

Dear trnsys group,

I'm simulating a simple room in free floating in summer in Italy, 
with 0.5 vol/h ventilation of outside air and internal gains from 2 
occupants for 9h a day.
Each occupant contributes with 75W sensible input and 75W latent 
input (see activity level 4 in the ISO 7730 table available in type 56).
The humidity model is the Effective Capacitance model with a moisture 
capacitance ratio=1.

Then the output of the simulation is that the relative humidity in 
the room is generally very high, over 90% and easily reaching 100%.
This doesn't sound realistic to me. It doesn't correspond to our 
everyday experience.

It might be:
1) that the natural ventilation rate is too low;
2) that the moisture capacitance ratio is too low.

By increasing the ventilation rate I could lower the rel hum. By 
increasing the ratio I could dampen the rel hum oscillations, thus 
lowering the peaks.

Did anybody face any similar situation?
May anybody suggest realistic values for natural ventilation rates 
and/or moisture capacitance ratio?

Many thanks

Adriana Agelotti





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Adriana Angelotti, PhD
Politecnico di Milano
Dipartimento di Scienza e Tecnologie dell'Ambiente Costruito (Best)
v. Bonardi 3
20133 Milano, Italy
Ph    +39 02.2399.5183
Fax  +39 02.2399.5118
e-mail adriana.angelotti at polimi.it