Análise numérica do coeficiente de transferência de calor convectivo forçado interno em edificações

Abstract

A prime factor for improving building energy efficiency is the correct understanding of heat transfer phenomena within the enclosures for accurate assessment of conduction loads through the building envelope. The magnitude and the interaction between convective and radiative heat transfer modes may have a significant impact on heating or cooling loads and, therefore, on the building energy performance. The conductive and radiative heat transfer modes are modelled with a reasonable accuracy by using models traditionally employed by building energy simulation codes. However, significant uncertainties may appear related to internal convective heat transfer coefficients (CHTC) due to complex geometries, buoyant effects and thermal asymmetries, besides effects associated to natural ventilation and the presence of furniture. Concerning forced or mixed convection, the validity of CHTC found in the literature is often a matter of doubt due to internal airflow patterns caused by different air inlet/outlet configurations. Therefore, to better understand the airflow patterns created by split type air conditioners, two-dimensional (2D) Computational Fluid Dynamics (CFD) simulations are performed, providing data for the assessment of CHTC for vertical walls, ceiling and floor. Different airflow rates and surface temperatures are used to analyse the influence of air recirculation through the evaporator, which has been barely explored in the literature. Comparisons with existing correlations and the important impact of internal CHTC on energy consumption of a split type air conditioner are presented and discussed.