Research On The Method Of Determining The Outdoor Design Dry-and Wet-bulb Temperature Of Air Conditioning Based On The Binary Over Threshold Model

Outdoor dry-and wet-bulb temperature parameters of air conditioning act on buildings at the same time,which is an important parameter affecting the thermal environment of buildings.In the design of air conditioning system,it is the initial calculation meteorological condition for load calculation and equipment capacity selection.At present,the method of determining the outdoor design dry-and wet-bulb temperatures of air conditioners is mainly one-dimensional probability statistics of a single meteorological parameter,without considering the simultaneous occurrence of the two.Therefore,it is necessary to study the method of determining the simultaneous occurrence of dry-and wet-bulb temperatures to determine a more scientific and reasonable outdoor calculation of dry-and wet-bulb temperatures for air conditioning.Based on the knowledge of mathematical statistics and extremum statistics,this paper proposes a method to determine the outdoor dry-and wet-bulb temperature based on binary super threshold model.The optimal solution of dry-and wet-bulb temperature is obtained by penalty function artificial firefly swarm optimization algorithm,which meets the simultaneously non-guarantee rate of the dry-and wet-bulb temperature.Finally,the outdoor dry-and wet-bulb temperature parameters are obtained.Based on the meteorological observation data of Urumqi city for 30 years from 1978 to 2016,this paper discusses the existing determination methods in China and the outdoor calculation of dry-and wet-bulb temperature in Urumqi in summer determined by various national methods.The main research contents and results are as follows:1.This paper introduces the method of determining the outdoor design parameters of air conditioning in summer based on the single parameter uncertainty rate(duration)of China,ASHRAE and CIBSE.,and compares the outdoor design dry-and wet-bulb temperatures determined by the methods of China,the United States and the United Kingdom in the same area of Urumqi.2.According to a pair of designed dry-and wet-bulb temperatures obtained by the method of our country,the scatter plot of the 30-year hourly dry-and wet-bulb temperature data in Urumqi is divided into four regions.The air state points located in Area I are the fully guaranteed areas under the designed wet and dry bulb temperatures,and the areas II,III and IV are the actual air state points which are not guaranteed areas.The calculation results show that the actual air state points of dry-and wet-bulb temperatures obtained by Chinese method are not guaranteed for 84 hours,exceeding the required 50 hours.The ASHRAE outdoor design parameters,which are defined by the main parameters and the adjoint parameters,are too low compared with the unsafe rate of the main parameters,which is also unreasonable.3.It is proved that the data of dry-and wet-bulb temperatures exceeding a certain threshold generally obey the generalized Pareto distribution(GPD).The model fits well through the model test.Through calculation,there is a strong tail correlation between the two indicators of dry-and wet-bulb temperatures.After determining the threshold of dry-and wet-bulb temperature,symmetrical Logistic model is selected as the correlation structure function between dry-and wet-bulb temperature.Finally,a binary super-threshold model of dry-and wet-bulb temperature is established.4.Outdoor dry-and wet-bulb temperature is a random variable in the same time dimension.The problem of not guaranteeing rate at the same time of dry-and wet-bulb temperature can be transformed into studying the binary distribution regularity of dryand wet-bulb temperature.The design dry-and wet-bulb temperatures divide the air state distribution into four zones.Area I is a fully guaranteed area,and area III is a completely non-guaranteed area.The joint frequency distribution of the dry-and wet-bulb temperature distribution in region III is taken as the non-guarantee rate of the dry-and wet-bulb temperature,which is taken as the constraint condition,and the joint frequency distribution in region I is taken as the objective function.Through the penalty function firefly optimization algorithm to optimize the objective function under certain constraints,we can get the simultaneous design wet and dry bulb temperature values.Through the penalty function firefly optimization algorithm to optimize the objective function under certain constraints,we can get the simultaneous design dry-and wet-bulb temperature values.5.Taking Urumqi as an example,the outdoor design dry-and wet-bulb temperature of air conditioning system is 31.5 and 19.9?,which are obtained by the new method with a simultaneous non-guarantee rate of 0.57%(50h).It is compared with the design parameters calculated by our method and ASHRAE method.The unguaranteed time of each parameter under the new method is between the Chinese method and the ASHRAE method.The unguaranteed time of single parameter under the new method is much lower than that of the ASHRAE method.Compared with the Chinese method,the parameters obtained by the new method are the simultaneous dry-and wet-bulb temperature,and the dry-and wet-bulb temperature is interrelated.The design dry-and wet-bulb temperature under the new method is concentrated in late July in the statistical year,which reflects the simultaneity of the design dry-and wet-bulb temperature,and further verifies the rationality of the method.Through the above research,it provides a more scientific and reasonable method for the selection of design dry-and wet-bulb temperature for air conditioning system.