Theoretical Analyses and Experimental Simulations on Smoke Movement in Enclosures with Underfloor Heating

The smoke movement in enclosures with underfloor heating has some distinctive characteristics which are much different from those with the routine heating or no heating. It is very important to study these characteristics to guide smoke control design in this kind of enclosures. In the paper, the characteristics of smoke movement in enclosures with underfloor heating are analyzed and a model of smoke movement in such enclosures is established according to the classic double-plume theory. Based on the theoretical analyses, a small-scale facility including the main test box with external dimension of 0.65 m × 0.65 m × 1.5 m (high) has been designed to carry out experiments to investigate the smoke movement pattern in such enclosures, and the so-obtained results have been used to verify the validity of the theoretical model. The experimental fire source with two sizes of 5 × 5 cm and 10 × 10 cm was produced by diesel burning, and the diameters of smoke exit were taken as 15 mm, 30 mm and 50 mm. The findings show that the underfloor heating could speed up the smoke movement in enclosures for both the ascending and descending velocities of smoke increase, the ascending and descending times are separately about 80% and 50% of those with no heating under the same size of fire source and diameter of smoke exit; the theoretical model could well predict the smoke movement in such enclosures, for example, the maximum error between the theoretically calculated and experimentally tested temperatures of smoke was lower than 10%, and the relative error between tested and calculated times needed for the smoke to reach the ceiling ranges from 2.74% to 22.45% (the mean value is about 12.76%). The relevant results in the present study can be used to guide the further researches on the topic in large-scale enclosures and the smoke control design for the enclosures with underfloor heating.