Differential equations for airflow through FADS
With FADS, air is firstly driven into the cavity of FADS (nonporous
media zone), and compelled through tiny pores in the
porous fiber (porous media zone). The air then exchanges heat and
humidity with indoor air. The following assumptions about airflow
and fiber material are made in the present work: (a) the airflow is
treated to be isothermal, incompressible, and steady with constant
physical properties; (b) the fiber material is assumed to be rigid,
isotropic, and saturated. Based on the above assumptions, the mass
and momentum conservation equations of airflow through FADS
are written in tensor notation as follows [11].