Heat, air and moisture transfer through hollow porous blocks

Abstract The combined heat, air and moisture transfer in building hollow elements is of paramount importance in the construction area for accurate energy consumption prediction, thermal comfort evaluation, moisture growth risk assessment and material deterioration analysis. In this way, a mathematical model considering the combined two-dimensional heat, air and moisture transport through unsaturated building hollow bricks is presented. In the brick porous domain, the differential governing equations are based on driving potentials of temperature, moist air pressure and water vapor pressure gradients, while, in the air domain, a lumped approach is considered for modeling the heat and mass transfer through the brick cavity. The discretized algebraic equations are solved using the MTDMA (MultiTriDiagonal-Matrix Algorithm) for the three driving potentials. Comparisons in terms of heat and vapor fluxes at the internal boundary are presented for hollow, massive and insulating brick blocks. Despite most of building energy simulation codes disregard the moisture effect and the transport multidimensional nature, results show those hypotheses may cause great discrepancy on the prediction of hygrothermal building performance.

[2]  Kuan-chao Chen,et al.  Natural convection in an air layer enclosed within rectangular cavities , 1978 .

[3]  A. E. Gill.  The boundary-layer regime for convection in a rectangular cavity , 1966, Journal of Fluid Mechanics.

[4]  Majed M. Alhazmy.  Analysis of coupled natural convection–conduction effects on the heat transport through hollow building blocks , 2006 .

[5]  Carsten Rode Pedersen,et al.  Prediction of moisture transfer in building constructions , 1992 .

[6]  Natural convection with unsaturated humid air in vertical cavities , 1997 .

[7]  Nathan Mendes,et al.  Analysis of numerical methods and simulation time step effects on the prediction of building thermal performance , 2004 .

[8]  Rachel Becker,et al.  Model for Moisture-Content Evolution in Porous Building Elements with Hygro-Thermal Bridges and Air-Voids , 2000 .

[9]  D. Poulikakos,et al.  On the effective thermal conductivity of a three-dimensionally structured fluid-saturated metal foam , 2001 .

[10]  Yi Li,et al.  NUMERICAL SIMULATION OF COUPLED HEAT AND MASS TRANSFER IN HYGROSCOPIC POROUS MATERIALS CONSIDERING THE INFLUENCE OF ATMOSPHERIC PRESSURE , 2004 .

[11]  L. A. Richards.  Capillary conduction of liquids through porous mediums , 1931 .

[12]  C. Hoogendoorn,et al.  The Stratification in Natural Convection in Vertical Enclosures , 1983 .

[13]  Nathan Mendes,et al.  A method for predicting heat and moisture transfer through multilayered walls based on temperature and moisture content gradients , 2005 .

[15]  Carey J. Simonson,et al.  Measuring and modeling vapor boundary layer growth during transient diffusion heat and moisture transfer in cellulose insulation , 2005 .

[16]  J. R. Philip,et al.  Moisture movement in porous materials under temperature gradients , 1957 .

[17]  M. G. Van Geem.  Thermal Transmittance of Concrete Block Walls with Core Insulation , 1985 .

[18]  Nathan Mendes,et al.  A new mathematical method to solve highly coupled equations of heat and mass transfer in porous media , 2002 .

[19]  Hartwig M. Künzel,et al.  Calculation of heat and moisture transfer in exposed building components , 1996 .

[20]  S. Patankar.  Numerical Heat Transfer and Fluid Flow , 2018, Lecture Notes in Mechanical Engineering.

[21]  W. Tao,et al.  Natural convections in conjugated single and double enclosures , 1995 .

[22]  G. de Vahl Davis,et al.  Laminar natural convection in an enclosed rectangular cavity , 1968 .

[23]  Sylvie Lorente,et al.  The effects of temperature conditions on the thermal resistance of walls made with different shapes vertical hollow bricks , 1998 .

[24]  Sylvie Lorente,et al.  Simplified analytical model for thermal transfer in vertical hollow brick , 1996 .

[25]  P. J. García Nieto,et al.  Nonlinear thermal optimization of external light concrete multi-holed brick walls by the finite element method , 2008 .

[26]  Sylvie Lorente,et al.  Study of convective phenomena inside cavities coupled with heat and mass transfers through porous media—application to vertical hollow bricks—a first approach , 1998 .

[27]  Nathan Mendes,et al.  Multitridiagonal-Matrix Algorithm for Coupled Heat Transfer in Porous Media: Stability Analysis and Computational Performance , 2004 .