Monitoring Analysis And Simulation Of Carbon Dioxide Concentration In College Classrooms In Harbin

Since China entered the 21st century,researches related to indoor air quality have been emerging one after another.With the increase of the national construction of colleges,the learning and working environment of teachers and students in colleges is gradually getting more and more attention.Therefore,it is of great significance to study the indoor air quality of public buildings in colleges.In this paper,a method which combined theoretical model research,field testing and simulation study is carried out to understand the pollution level of CO₂ concentration in certain college classrooms in the cold region representative city——Harbin,which indirectly reflects the indoor air quality in the college classrooms.At the same time,the rules and influencing factors of CO₂ concentration change were explored,and suggestions for reasonable improvement of indoor air quality in classrooms were put forward.In the part of theoretical model research,two kinds of CO₂ concentration prediction models for natural ventilation classrooms,the steady-state and dynamic models for predicting the number of people in classrooms are both summarized and deduced,the advantages and disadvantages of each model are compared and analyzed.Accuracy is only compared from the applicable conditions and parameters of the model,DA model is better than HB model,while the dynamic model is better than the steady-state model,but the model with higher accuracy requires more effort to calculate.Meanwhile,the parameters needed to be used in the model,air change rate ACH and the rate of personal CO₂ emission g,were both calculated and explained.Secondly,continuous on-site monitoring was carried out for three types of classrooms in the main building of the college.The monitoring results showed that the CO₂ concentration in the classrooms exceeded the standard seriously,and the time of exceeding the standard in a day is at least 68%,and the highest is 90%.According to the field test data,the characteristic analysis of CO₂ concentration in the classrooms during the class was conducted to explore the relationship between CO₂ and the characteristic parameter?=N/V of the classroom,and the characteristic model was established.The average error between the characteristic model and the measured value is about 5.3%,by using this model,the reasonable occupancy density?_reasonableeasonable that makes the CO₂concentration does not exceed the limit value was calculated as 0.065 person/m³.We also validated the accuracy of the prediction model in the second chapter with the data of field test,results show that the two types of prediction model with high accuracy are respectively DA model and the dynamic model.Using DA model for calculation,In a full classroom with 60 minutes of class,in order to make the CO₂ concentration not exceed the standard,the required air change rate should be around 6¹0h^-1.Finally,in order to fully understand the distribution field of various parameters in the indoor environment,the steady-state simulation was carried out for the classroom under the typical class condition,and the transient simulation was also carried out for the classroom under the condition of window opening.The steady state simulation showed that the CO₂ concentration distribution,mean age of air,the value of the PMV and PPD is affected by temperature field and velocity field,and the transient simulation found that the window opening time during class break in winter is ideal within1²min.In the simulation process,the simulation value was also compared with the field test value,and the results showed that Airpak simulation had a high accuracy and could play a role in studying the rule of indoor environment change,and the simulation results had certain value.