EFFECT OF VENTED ATTIC POSITIONS ON HEAT TRANSFER AND AIR FLOW OF NATURALLY VENTILATED ATTICS FOR PASSIVE COOLING SYSTEM

The effect of vent size and position on heat transfer and air flow for naturally ventilated attics used for passive cooling system is studied in this paper using a steady state two dimensional finite volume methods (FVM). The v2f turbulent model is employed to investigate the effect of turbulence in low Reynolds number buoyancy driven air flow and natural convection heat transfer. Thermal conditions and air flow performance are compared between the ceiling vented attic and the roof vented (ridge vent) attic, and also comparison is made on varying the size of the soffit vent. The predicted temperature field revealed the occurrence of thermal stratification for all the configurations and symmetric air flow patterns. Furthermore, the air flow and heat transfer rate for the roof vented attic is greater than that of the ceiling vented attic for all cases of soffit vent size. The result showed that increasing vent size leads to higher attic cooling load but barely affects the ventilation air flow while vent positions have higher effect on air flow ventilation and attic cooling load. Thus for effective passive cooling system in dry season, a ridge vent in combination of small soffit vent is recommended.