When it was ?1Pa, the maximum axial velocity occurred at the approximately same position and Y-27632 molecular weight the airflows were inhaled into the exhaust hood in disorder. The maximum axial velocity occurred not only at the middle of the annulus and the exhaust hood inlet but also around the exhaust hood inlet when it was changed to ?3Pa. However, the maximum axial velocity occurred around the exhaust hood inlet when it reached ?5Pa. The velocity field characteristics of annular buoyant jets were pretty similar when the negative pressure at the exhaust hood was smaller than ?5Pa. In a word, the airflow could be effectively controlled without great passive pressure at the exhaust hood inlet.4.

ConclusionsThe aim of this study was to numerically investigate the flow characteristics of high-temperature annular buoyant jets and the air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system. Based on the analysis of the simulation results and comparisons with previous studies, the following remarkable conclusions were drawn.(1) Two peak velocities occurred in the process of high-temperature annular buoyant jets development with the ratio of outer diameter to inner diameter of the annulus smaller than 5/2. The middle peak velocity was mainly caused by the vortex with buoyant jets at the sides expanding to the center. In contrast, peak velocities at the sides occurred when acceleration action due to buoyancy and velocity decay due to entrainment were in equilibrium.

The middle peak velocity gradually decreased and disappeared eventually with the increase of width of high-temperature annular buoyant jets.(2) Radial velocity developments of high-temperature annular buoyant jets with different annular jet widths revealed that the annular flow merged towards the axis of the annulus forming a velocity profile further downstream similar to that for a circular jet.(3) When the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics of high-temperature annular buoyant jets had significant difference compared to circular buoyant jets with the same Carfilzomib outer diameter. In this case, the high-temperature annular buoyant jets could not be simplified as circular buoyant jets.(4) The reattachment points for ratio of outer diameter to inner diameter of 5/4, 5/3, 5/2, and 5/1 correspondingly occurred at Z/D0 = 2.60, 2.40, 1.90, and 1.80. For similar diameter ratios, reattachments in this paper occurred further downstream in contrast to previous study. This phenomenon might be due to the strong buoyancy force effects on the hot air jets.(5) The volumetric flow rate was increasing continuously along with the height due to entrainment on ambient air.