MIL-HDBK-1011/2

APPENDIX C (continued)

Wi = ))) ft2 = ))) ft2

(15)

Calculate the inlet window area

for the proposed design, Wi.

RFi = ))))))) = )))))))

(16)

Correct using resistance factor, RFi,

for partially open, windows, window

type, screens, etc., from Table C-5 and Figure C-6.

Calculate the effective open inlet are, Ai. Ai = ))) ft2 = ))) ft2

(17)

Ai = Wi x RFi

Ao = ))) ft2 = ))) ft2

(18)

Calculate required open outlet area, Ao.

Ao = A x Ai / [(Ai2 - A2)]

Wo = ))) ft2 = ))) ft2

(19)

Calculate the outlet window area

for the proposed design, Wo.

RFo = ))))))) = )))))))

(20)

for the outlet openings from Table C-5.

(21)

Calculate the effective outlet opening,

Ae = ))) ft2 = ))) ft2

Ae.

Ae = Wo x RFo.

(22)

Compare the required outlet opening with the

effective outlet opening:

Worst Month: )))))))))))))))

2nd worst month: ))))))))))

Ao = )))))))))))))))))))))

Ao = ))))))))))))))))))))

Ae = )))))))))))))))))))))

Ae = ))))))))))))))))))))

If Ao < Ae, then the required air speed will be obtained and comfort can

be expected. If Ao > Ae, then the required air speed will not be

obtained.

If required air speed is not obtained, possible methods to obtain the

required air speed are to:

a)

Increase the size of the openings.

b)

Increase the effectiveness of the openings by changing window

type, removing screens, or removing interior partitions.

c)

Increase the pressure coefficients by spacing buildings farther

apart, rotating the building, relocating windows, elevating the building, or

adding wingwalls.

1.2

ASHRAE Wind and Thermal Buoyancy (Stack Effect) Formulae. The two

driving forces producing natural ventilation in a building are wind pressure

and thermal buoyancy (the stack effect). The following is a summary of

formulae for calculating interior airflow.

1.2.1 Flow Due to Wind--Single Opening. Factors affecting ventilation

wind forces include average velocity, prevailing direction, seasonal and daily

variation in velocity and direction, and local obstructions such as nearby

buildings, hills, trees, and shrubbery. For a space with only a single

opening, use Equation 8.

113

Integrated Publishing, Inc. |