Experimental Investigation of the Influence of Different Flooring Emissivity on Night-Time Cooling using Displacement Ventilation

Night-time ventilation is a promising approach to reduce the energy needed for cooling buildings without reducing thermal comfort. The objective of the present paper is to determine how different emissivity of flooring influence the heat transfer in a room and the efficiency of night-time ventilation using displacement ventilation. Experimental work was conducted on the basis of the work performed by Artmann et al. (2009) in a similar previous study. An aluminum-foil floor cover was installed in a full scale test room. Experimental results obtained with aluminum flooring were compared to results obtained by Artmann et al. with a flooring consisting of expanded polystyrene (EPS). Results showed that the surface temperature of the floor decreased with decreasing emissivity. Mean convective heat fluxes were similar for experiments conducted with both EPS and aluminum-foil floor cover, but it was seen that the emissivity of the flooring affected the heat transfer ratio at the internal surfaces. The convective heat flux increased at the ceiling and decreased at the floor for experiments with aluminum flooring compared to the experiments with EPS floor. Temperature efficiency was slightly higher for experiments with aluminum flooring than for EPS floor. As the efficiency was only a bit higher with an extremely low emissivity of the floor cover, it was concluded that the influence of different emissivity of floor covers can be neglected concerning efficiency of displacement night-time ventilation.