A Numerical Model for Heat and Moisture Transfer in Porous Media of Building Envelopes

Abstract

This study presents a one-dimensional quantitative analysis of unsaturated flow in natural stones using a numerical model (Finite Difference Method) and a mass balance for the heat flow. For that, we considered heat and moisture transfer between the external environment and a porous media (sandstone and limestone) with homogeneous characteristics. For unsaturated water flow, Richards’ equation and the formulation proposed by Gardner for volumetric water content and hydraulic conductivity were considered. The results of the numerical analysis showed that the evaporation of porewater throughout summer days (January 3rd and 4th) considerably reduced the temperature of the roof by about 8°C. The accumulated conductive heat flow and the volumetric water content were also reduced due to the evaporation process. This fact indicates that evaporation can be useful in providing thermal comfort and, consequently, in improving the energy efficiency of buildings with natural stones as envelopes.

Numerical Simulation of 2D Shallow water equation with constant external body force by using Finite difference method

“…In this section we will use finite difference method [3,27] For the solution of (07)-(09) the Crank Nicolson explicit Finite difference method is applied due its advantage of being unconditionally stable. For the discretization of these equations the central difference scheme for the space variables x and y are used but discretization of time derivative function forward difference scheme are used that are defined as Forward difference in time.…”

Statistical Analysis of the Factors influencing the In Situ U-Value of Walls

“…U-value also regulates the energy consumption and thermal comfort inside the building. The conductive heat flow was reduced due to the evaporation process with natural stones as a building material, which increased the thermal comfort inside with a reduction in energy consumption [7]. Natural convection heat transfer rates increase in an open enclosure with an air cavity with an aspect ratio of 2 [8].…”