Heat transfer and mass flow correlations for ventilated facades

Natural convection heat transfer and mass flow phenomena in ventilated facades are numerically investigated in this work. The study focuses on the determination of accurate results in terms of correlations for the average Nusselt number at each of the two walls of the ventilated facade and for the mass flow induced in the cavity, as functions of the descriptive geometrical and thermal parameters, covering the laminar region with modified Rayleigh numbers Ra_b* ranging from 10⁰ to 10⁵. Comparison with available experimental data and numerical results is first presented to validate the validity of the numerical procedure. Then correlations are proposed for the heat and the mass flow in symmetrically and asymmetrically heated channels. These correlations are developed as a contribution for the thermal models of ventilated facades, in which the accurate determination of heat transfer coefficients and induced mass flow rates are of great importance to establish the energetic performances of the element.