| Extract air flow rate is a key control parameter in the design of commercial kitchen ventilation system.However,there are many calculation methods for extract air flow rate in domestic and foreign standards.The calculation parameters are intricate and the calculation results of different methods are also very different.The calculation of extract air flow rate in actual design was often not reasonable,which often resulted in unsatisfactory performance of the ventilation system.Therefore,it is necessary to develop a method for calculating the extract air flow rate suitable for the characteristics of Chinese commercial kitchens.This article summarized 18 methods in domestic and foreign standards for calculating the extract air flow rate of commercial kitchens.Based on the survey data of 48 kitchens in Tianjin,on the one hand,using SPSS analysis method to establish the multiple regression model of extract air flow rate,various influencing factors were weighted in the methods,and the intrinsic connection between different methods was analyzed;on the other hand,in order to explore the appropriate calculation methods of extract air flow rate under different design scenarios or operating conditions,the general rules of commercial kitchens internal layout was researched.Then,a typical commercial kitchen model was established for ventilation simulation.Besides,some problems existing in the relevant standards of our country were discussed.On this basis,a case study was carried out.The ventilation plan and system operation control strategy of the case kitchen was formulated.The main conclusions of this study are summarized as follows:(1)Weight analysis of factors affecting extract air flow rate——Kitchen area,heating power of stove and length of extract hood are the main influencing factors of extract air flow rate.The calculation methods of extract air flow rate were classified into 5 indicators:extract volume per kilowatt of stove heating,velocity across the face of extract hood,capture velocity,air change rate,and extract volume per stove.Besides,a conditional index——calorific value per unit area of kitchen was put forward.The extract air flow rate obtained by the air change rate method is less than that obtained by most methods,when the conditional index is greater than 4.18 k W/m~2.(2)The internal layout of commercial kitchens——All kitchens are equipped with frying stoves;59.02%kitchen area in the range of 30-70 m~2;The number of stoves in the 30-70 m~2 kitchen is usually 5-7;There are also more kitchens where the hood is against the wall on both or three sides;There are often 7 stoves when three sides are against the wall,and two sides against the wall are 6;About every 3 stoves correspond to 2 suction ports inside the extract hood.(3)Ventilation simulation of the typical kitchen——When the ventilation system is mainly used to remove heat,the extract air flow rate needs to be at least 9000 m~3/h(1286 m~3/h for one stove);When it is mainly used to eliminate pollutants from cooking fume,the extract air flow rate needs to be 12000 m~3/h(1714 m~3/h for one stove).Therefore,for kitchens with small pollutants emission,it is recommended to refer to the calculation method based on extractor hood area in England and Japan,as well as the air change rate method in China.On the contrary,it is recommended to use the calculation method based on the extractor hood area in JSCS,or the baseline cooker method based on the area of the cooker,or the American method based on thermally induced airflow.In addition,extract air flow rate based on extractor hood area is always greater than that based on the smoking side length.It is suggested that the average value of the two calculations is used when the simultaneity factor of stoves is small or the pollutants emission is not large.For the baseline cooker method,it is suggested to reduce the value of 46.39 k W corresponding to one standard stove,or increase the extract air flow rate of the corresponding one standard stove. |
PDF Full Text Request