Qualification of the Energy Charge-Discharge of a Concrete Slab in a Naturally Ventilated Building

An experimental study in a naturally ventilated building was conducted in August 2016. It aimed to highlight the energy charge and discharge of a concrete-slab floor submitted to the day-night-cycles heat exchanges in the southwestern part of France and to identify the heat transfer phenomena that take place in both processes (charge and discharge). To highlight the energy charge and discharge processes, heat flux, temperature, and airspeed measurement techniques were implemented. Measurement zones were distributed all over the concrete-floor surface. To identify the heat transfer phenomena that take part in the charge and discharge process, some important dimensionless numbers were used, along with correlation analysis. Experimental data showed that during the charge period, on the floor surface, radiative heat exchanges were significantly higher compared to convection. The contrary was found during the discharge period. After correlation analysis with dimensionless numbers, results showed that forced and natural convection coexist during the discharge period, where more accurate correlations with the Peclet number than with the Rayleigh number were found. This may suggest that forced convection is stronger than natural convection. Yet, airspeed levels encountered suggest that it is natural convection that should take place rather than forced convection.