Study On Calculation Of Design Flow For Distribution System Of Building Water Supply System Based On Probability Method

The design flow for distribution system directly determines the size of the diameter of the indoor water supply pipe network and the flow and head of the pump.If the design flow for distribution system is greater than the actual required design flow,it will cause the overall pipe diameter is too large,the pump flow is too large,and energy consumption will therefore increase;If the design flow is too small,it will cause insufficient water supply capacity,unable to meet the residents’ normal water demand,thus resulting in water supply safety accidents.Therefore,it is of great significance to explore the design flow value of water supply which is closer to the law of actual water use in the whole life cycle of a building.(1)According to the actual situation,when to use what kind of sanitary appliances,which belongs to the probability problem,has it’s uncertainty.Therefore,it is more scientific and reasonable to use probability theory to study the design flow for distribution system.Combined with the use characteristics of sanitary appliances,the design flow formula calculation model of water supply was established on the basis of binomial distribution theory.At the same time,Python language is used to write the solution program for the established calculation model,and the final calculation results are output in the form of Qg～Ng curve.(2)Based on the analysis of the characteristics of China’s residential water use and the actual situation in China,the calculation formula of the probability "p" of water use for residential building sanitary appliances is finally determined.The "p" value of residential buildings is calculated based on the relevant provisions of the domestic water quota in the"Design Standard for Building Water Supply and Drainage"(GB50015-2019),and the results mainly focus on 1.0～4.0%.According to the engineering practice,select p=1.0%,1.5%,2.0%,2.5%,3.0%,3.5%,4.0%respectively into the calculation program to calculate,and get the corresponding Qg～Ng curve.In order to be convenient to use,the calculation formula with uniform form,simple structure and convenient use is obtained by piecewide fitting of the calculation results based on the provisions of water supply zoning in the standard,the variation trend of Qg～Ng curve and the principle of curve fitting.(3)The calculation results of the method in this paper are compared with those specified in the "Design Standards for Water Supply and Drainage in Buildings"(GB50015-2019).Before the intersection of the two curves,the design flow calculated according to the method specified in the "Building Water Supply and Drainage Design Standards"(GB50015-2019)is too large,which will cause the pipe network diameter is too large,leading to the increase of the project cost,and will also cause the flow of the selected water supply equipment to be greater than the actual need of the flow;After the intersection point of the two curves,the design flow calculated according to the method specified in the "Building Water Supply and Drainage Design Standards"(GB50015-2019)is too small,which will lead to insufficient water supply capacity,low water supply safety and unable to meet the water demand of residents.(4)Residential communities in the south,middle and north of China were selected as the research objects,and long-term water consumption data were obtained through long-term monitoring of their water consumption changes.The "p" value was calculated according to the number of people,the measured water consumption quota,the measured variation coefficient,and the quantity of sanitary appliances.Then,the "p" value was substituted into the calculation formula obtained in this paper and the calculation formula stipulated in the "Design Standards for Building Water Supply and Drainage"(GB50015-2019)respectively for calculation.By comparison,it was found that the calculation result obtained by the method in this paper was more close to the measured flow rate.