ACH obtained - calculated natural ventilation

rashmi sonal · Posts: 7

Hi,

Is there anyway I can get to know the ACH obtained in a zone when the model option is set to calculated natutral ventilation. It tells me the heat loss/gain due to external air (kW) but there is no place I could find the resultant ACH in the zone. Thanks.

Regards
Sonal

rashmi sonal · Posts: 7

Hi,

When I set the natural ventilation model to calculated, it gives me the heat loss due to external air. So, can I calculate the resultant ACH in the zone by using the formula:

Heat loss/gain due to external air = mass flow rate * specific heat of air * (outdoor DB - indoor DB)

Thanks.

Regards
Sonal

Andy Tindale · Posts: 1205 Location: Stroud

Sorry for the delay in answering this question - I must have overlooked it.

There is no way at the moment to automatically generate the air change rate when using calculated natural ventilation, though you can use the EnergyPlus IDF file generated by DesignBuilder and add your own reports to get this output. We will be adding tools to calculate the air flows soon, but are currently waiting until the new AIRNET solver is included in EnergyPlus because all the reporting will change.

In the meantime you can use the equation you mention to calculate approximate air flow rates.

Regards
Andy

Andy Tindale · Posts: 1205 Location: Stroud

The next version of EnergyPlus (1.3) due for release mid April this year have the ability to output calculated air change rates and we will be providing an interface to this as soon as possible.

Andy

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