# RE: [EnergyPlus_Support] infiltration

```It may be noted that when outdoor fresh air ventilation is supplied by fans
to the space, as required by codes, then the space is at positive pressure
relative to the outdoors and the infiltration into the space is zero.

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-----Original Message-----
From: HSIEH Chun-Ming [mailto:chunming@xxxxxxxxxxxxxxxxxxx]
Sent: Tuesday, December 10, 2002 8:09 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] infiltration

Here we discussed the A, B, C and D values of infiltration/ventilation
equation.

1. But, do you have any idea about how to set the Design Volume.
It might depend on the how much area of window is opened and the wind
speed outside, right?
I am not sure. Do we have any simple way to calculate the value of
Design Volume?
It's hard for me to imagine that how much the value should be?

2. The design volume of Ventilation with windows opened should be much
higher than that of infilation , right?
by the way, except the Delta T, the calculation in infiltration and
ventilation are the same, right?

Thank you very much.

Chunming

Michael J. Witte wrote:

> The question of typical values for these coefficients is subject to
> debate.  Ideally, one should do a detailed analysis of the
> infiltration situation and then determine a custom set of
> coefficients using methods such as those laid out in Chapter 26 of
> the ASHRAE Handbook of Fundamentals.  The EnergyPlus defaults are
> 1,0,0,0 which gives a constant volume flow of infiltration under all
> conditions.
>
> BLAST used the following values as defaults:  0.606, 0.0202,
> 0.000598, 0.  These coefficients produce a value of 1.0 at 0C deltaT
> and 3.35 m/s (7.5 mph) windspeed, which corresponds to a typical
> summer condition.  At a winter condition of 40C deltaT and 6 m/s
> (13.4 mph) windspeed, these coefficients would increase the
> infiltration rate by a factor of 2.75.
>
> In DOE-2, the air change method defaults are (adjusted to SI units)
> 0, 0, 0.224 (windspeed), 0.  With these coefficients, the summer
> conditions above would give a factor of 0.75, and the winter
> conditions would give 1.34.  A windspeed of 4.47 m/s (10 mph) gives a
> factor of 1.0.
>
> The source of the BLAST defaults is noted in the BLAST documentation
> as:
>
> "Empirical equation and the coefficient default were determined from
> ASHRAE journal articles and other data on the effects of outdoor
> weather conditions."
>
> The source of the DOE-2 defaults is based on examining the
> infiltration relationships decsribed in the ASHRAE Handbook of
> Fundamentals.
>
> Mike
>
>
> On 19 Nov 2002, at 16:48, nuno lourenço wrote:
>
> >
> >
> >
> >
> > In the input-output reference manual (pag 161) you give some values
> > for the parameter A-Constant term coefficient, B-Temperature Term
> > coefficient, C-Velocity Term Coefficient, D-Velocity Squared Term
> > Coefficient. How do you obtained this values? I found my error in the
> > cooling and heating loads. My values for this Parameter were "quite"
> > different and I obtained very high loads.But if I put "our" values the
> > loads are quite similar to those I am expecting.
> >
> > Best regards,
> >
> > Nuno Lourenço
> >
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