The mathematical model of kitchen smoke exhaust system in high-rise residential buildings considering the Influence of Stack effect

In high-rise buildings with large indoor and outdoor temperature difference,neglecting the effect of stack effect in smoke exhaust shafts may cause calculation error of the fluid network model.In this paper,the mathematical model of kitchen smoke exhaust system considering the influence of stack effect was put forward and it can be inserted different range hood sub-models.Compared with the results of six working conditions of the model without considering the stack effect,the error of the proposed model were reduced by 7.6%,4.3%,4.1%,2.8%,2.4%,and 2.1%.While the indoor and outdoor temperature difference varies from−5℃ to 49℃,the effect of stack effect on the pressure in the flue and the flow rate for each user was studied for six operating rates s.The results show that under the combined effect of stack effect and flue resistance,the static pressure of the kitchen smoke exhaust system showed a low-high-low distribution,and the maximum static pressure in the flue moved toward the bottom with the increase of temperature difference.User flow rates exhibit a low-high-low-high distribution,with an increased flow rate in the bottom users and the largest flow rate in the top users.

Optimization of smoke exhaust efficiency under a lateral central exhaust ventilation mode in an extra-wide immersed tunnel

This study focused on increasing the efficiency of the smoke exhaust system of an extra-wide(eight-lane,dual-directional)immersed tunnel with a specific quantity of exhaust.The Shenzhen-Zhongshan immersed tunnel was selected as the application example.A numerical simulation based on fire dynamics simulator was conducted.In the model,the concrete structure of the main body of the immersed tubes was not altered.The adoption of supplementary exhaust ducts increased the efficiency from 73%to 98%under the condition of no longitudinal wind.When a 50-MW fire occurred between two adjacent ducts,with a longitudinal wind velocity of 2 m/s,the efficiency reached 88%or more when the two ducts were opened.Furthermore,a safety evacuation path was developed.The results suggest that the addition of supplementary exhaust ducts combined with a rational longitudinal wind velocity is necessary for an extra-wide immersed tunnel.

Pressure and flowrate distribution in central exhaust shaft with multiple randomly operating range hoods

Central flues are now commonly adopted in high-rise residential buildings in China for cooking oil fumes(COF)exhaust.Range hoods of all floors are connected to the central shaft,where oil fumes were gathered and exhausted through the outlet at the building roof.As households may cook and use their range hood at random periods,there is great uncertainty of the amount of COF being exhausted.In addition,users can often adjust the exhaust rate of the range hood according to their needs.As a result,thousands of possible operating conditions consisting of distinct combinations of on/off conditions and fan speed occur randomly in the central COF exhaust system,causing the exhaust performance to vary considerably from condition to condition.This work developed a mathematical model for characterizing the operation of the central COF exhaust system in a high-rise residential building as well as its iterative solving method.Full-scale tests coupled with CFD simulation referring to a real 30-floor building were conducted to validate the proposed model.The results show that the model agreed well with the CFD and experimental data under various system operating conditions.Moreover,the Monte-Carlo method was introduced to simulate the random operating characteristics of the system,and a hundred thousand cases corresponding to distinct system operating conditions were sampled and statistically analyzed.