TABLE OF CONTENTS - The Professional Green Building Council

Theme B: Creating a livable, healthy and environmentally viable citieswhereC : discharge coefficient (dimensionless), ρ : air density (kg/m 3 ), upout :outside air speed (m/s), c(dimensionless): Flow coefficient (dimensionless), n : flow exponentFrom Eqs. (2)-(3), the airflow speed in cavity due to wind pressure ( uca,w) can beexpressed as Eq. (4).uca,w2c ⎛ u ⎞out= ⎜Cρp ⎟ (4)Ac⎝ 2 ⎠nwhere A c : Cavity cross-section area(m 2 )Under the outdoor circulation mode, cavity airflow is affected by the temperaturedifference and the surface wind pressure simultaneously, and the two factors mustbe combined. The cavity airflow Eq. (5) represents the airflow amount ( Q ca ) thatincorporates both factors, and the airflow speed can be expressed as Eq. (6).Q Q Q= + (5)2 2ca ca, b ca,wifCp≥ 0⎧⎪if⎨⎪⎩elseifelseif Cpu ≥ u : u = u −uca,bca,bca,wca,w2 2ca, b ca,wu < u : u =− u −u< 0:cacacau = u + u2 2ca, w ca,b2 2ca, b ca,w(6)where Qca,b: Airflow rate in the cavity due to temperature differenceThe amount of airflow and the cavity air velocity in the diagonal circulation mode(Fig 5 [5]-[8]) can be calculated as Eqs. (7)-(8) using the inside-outside pressuredifference ( Δ p ).Q = c( Δ p) n(7)umQca= = ( Δ p) n(8)AccAc502