Flow Characteristics And Numerical Simulation Of Centralized Exhaust Flue With Multi-power Sources In Residential Kitchens

The excessive concentration of population and the scarcity of urban land resources make high-rise buildings the main architectural form of urban dwellings,and people are increasingly demanding indoor air quality.The kitchen is an important part of the house and one of the main sources of indoor pollutants.At present,the high-rise residential kitchen exhaust fumes mainly adopt a vertical concentrated exhaust fume system,and the exhaust fume method has problems such as uneven smoke exhaust between the floors,odor of string smoke,and insufficient amount of smoke at the bottom layer.Based on the related research at home and abroad,this paper analyzes the cross-section centralized fume system in residential kitchens by theoretical analysis,CFD numerical simulation calculation and experimental comparison and verification,and explores many problems in the exhaust system.Firstly,the hydraulic calculation of the 6-layer smoke exhaust system recommended by the Atlas shows that there is a serious imbalance of the system.Using the fluid mechanics knowledge such as Bernoulli equation and continuity equation to theoretically calculate the equivalent section exhaust system,and provide theoretical basis for the subsequent numerical simulation calculation.Secondly,the flow characteristics of the 6-,20-,and 30-layer flue systems were analyzed by CFD numerical simulation.The distribution of the pressure in the main flue and the amount of flue gas in each branch were studied.The effects of the operating rate of the range hood,the uneven distribution of the hood,and the cross-section size of the flue on the effect of the system exhaust fumes are analyzed.The results show that there are various problems such as unbalanced exhaust and insufficient exhaust smoke.Then,in view of the problems existing in the exhaust system,this paper applies the roof fan to replace the unpowered hood of the existing system,explores the application of the roof fan in the exhaust fan system of the residential kitchen,and analyzes the influence of various types of roof fans on the smoke exhausting effect of the system.The results show that the roof fan can reduce the static pressure in the main flue and increase the exhaust volume of the branch pipe,but at the same time,the uniformity of the system exhaust smoke is obviously deteriorated,and the exhaust volume of the high-level users is too large.The roof fan exhaust system with a flat performance curve is relatively uniform.At the same time,in order to make the exhaust volume of each branch pipe meet the minimum standard requirements,the air volume parameters of the roof fan at different operating rates of different heights are determined.Finally,the concept of double-row flue system is proposed to demonstrate the feasibility of the double-row flue system from the theoretical and economic perspective.Through the numerical simulation,the effects of three types of double-row flue systems were compared.It is concluded that the double-row flue system can significantly improve the problem of insufficient bottom smoke and uneven smoke in the single-row flue.The cross-sectional dimensions were optimized for economical purposes,and the most economical cross-sectional dimension of the 20-story double-row flue system was 400×250 mm.