Investigation on thermal behavior of common types of roofs in buildings using computational fluid dynamics method

In this study, the influence of type and structure of different roofing systems were investigated using computational fluid dynamic method. The considered roofing systems include beam and block types (clay brick, light weight concrete block, polystyrene) and Uboot slab which were designed for 6m and 8m span. To simulate the fluid flow and heat transfer, the computational fluid dynamic method was employed based on control volume scheme. Heat transfer inside air cavities is carried out via free convection and radiation while heat transfers via conduction within solid walls. The thermal simulation of the roofing systems was analyzed for both summer (downward heat flow) and winter (upward heat flow). Two dimensional natural heat transfer was considered to be transient with laminar and incompressible flow inside cavities. To assess the thermal performance of the flooring systems, equivalent thermal conductivity, decrement factor and time lag were studied. Finally, the best roofing system was introduced in terms of heat transfer and thermal mass efficiency. The results showed that the roof with polystyrene block has the lowest value of equivalent thermal conductivity and Uboot system has the highest heat loss among the studied cases.