Comparison of models to predict air infiltration rate of buildings with different surrounding environments

The air infiltration rate of buildings strongly influences indoor environment and energy consumption.In this study,several traditional methods for determining the air infiltration rate were compared,and their accuracy in different scenarios was examined.Additionally,a method combining computational flow dynamics(CFD)with the Swami and Chandra(S-C)model was developed to predict the influence of the surrounding environment on the air infiltration rate.Two buildings in Dalian,China,were selected:one with a simple surrounding environment and the other with a complex surrounding environment;their air infiltration rates were measured.The test results were used to validate the accuracy of the air infiltration rate solution models in different urban environments.For the building with a simple environment,the difference between the simulation and experimental results was 0.86%–22.52%.For the building with a complex environment,this difference ranged from 17.42%to 159.28%.We found that most traditional models provide accurate results for buildings with simple surrounding and that the simulation results widely vary for buildings with complex surrounding.The results of the method of combining CFD with the S-C model were more accurate,and the relative error between the simulation and test results was 10.61%.The results indicate that the environment around the building should be fully considered when calculating the air infiltration rate.The results of this study can guide the application of methods of determining air infiltration rate.

Prediction model of air infiltration in single-zone buildings with high airtightness

Air infiltration through building envelopes has a considerable impact on the comprehensive performance of build-ings,especially in terms of their energy demand and indoor air quality.Therefore,it is important to accurately predict building air infiltration rates under various scenarios.High airtightness is one of the typical character-istics of passive ultra-low energy buildings.With the rapid application of passive technology in building energy efficiency,the airtightness of new urban buildings has been significantly improved.The centralized air leakage path distribution assumption of current prediction model for building air infiltration rate is inconsistent with the actual situation of high airtightness buildings,which reduces its prediction accuracy and application range.Therefore,it is of great practical significance and academic value to carry out the research on the prediction model of air infiltration rate of buildings with high airtightness.This paper presents an air infiltration prediction model for single-zone buildings with adventitious openings.The building envelope was broken down into permeable parts and impermeable parts,and the air leakage path-ways were assumed to be uniformly and continuously distributed in the permeable envelope.A linear pressure distribution over the building facade was assumed,and the airflow rate was integrated in the vertical and hori-zontal planes to theoretically predict the air infiltration rate.The feasibility of the proposed model was tested by comparing the air infiltration rates simulated by this model with those determined using the tracer gas attenua-tion method of an airtight building.The initial test results suggest that this model is mathematically robust and is capable of modeling the air infiltration of a building in a wide variety of scenarios.Reasonable agreement was found between the tested and simulated results.This study can provide basic theoretical support for the coupling performance analysis of high airtightness buildings.

Research on air infiltration predictive models for residential building at different pressure

The pressure difference in buildings under natural state is usually below 10 Pa,and the air change rate at 50 Pa(ACHso)is often used to evaluate building airtightness.There is a dearth of research on air infiltration predictive model at different pressures in China.Moreover,the airflow coefficient(C),a key parameter for air infiltration,is necessary to determine ACHso.Based on prior experimental data,several methods including ordinary least squares(OLS),stepwise regression,partial least squares(PLS)and nonlinear fitting with independent variable screening methods,were employed to establish an airflow coefficient model.The determination coefficient(ft2)and the variation coefficient of the root-mean-square error(CV(RMSE))of these models were compared.The simulation results show that ft2 of the airflow coefficient models for apartments and villas increased by a maximum of 25.9%and 2.3%,respectively,using PLS method.The improvement with nonlinear fitting was weaker.Based on K-P model,a conversion model between ACHso and ACH4 was developed as an air infiltration predictive model under natural state.Blower door and tracer gas tests were conducted to verify the conversion model.The expected error was approximately 10%,which may be caused by measurement errors and shielding from surrounding obstructions.Further studies need to focus on obtaining more experimental data for building airtightness and developing a conversion model for high-rise residential buildings.

Study on the conversion coefficient between ACH_(50)and ACH in typical zones of public buildings

The air infiltration of buildings is closely related to its indoor and outdoor environment and energy consumption.However,measuring air infiltration of a building under natural conditions is time-consuming,easily affected and expensive,so it’s often inferred based on building airtightness in practical engineering.Empirical models can nevertheless make a rapid prediction without building parameters,which are widely applied in practical engineering.At present,most of the existing empirical models take residential buildings as objects,therefore they are difficult to be applied to public buildings.Hence,it is imperative to build an empirical model applicable to public buildings.In this study,the conversion coefficients between the airtightness(air change rate under the pressure difference of 50Pa)and the air infiltration rates under natural conditions of four typical zones of public buildings were analyzed.Firstly,the airtightness of four zones of public buildings in the cold region of China was measured.Secondly,their air infiltration rates under 1800 combined conditions of wind pressure and stack effect pressure were simulated based on the airtightness measured results.Finally,calculation and statistical analysis of the conversion coefficient were carried out based on the measured and simulated results,and the recommended value of conversion coefficient was proposed.Analysis results show that the CC of each zone is significantly affected by outdoor meteorological conditions and varies in a wide range(1#zone:3.21 to 188.44).It is advised to ignore the extreme data and take the mean value of the CC corresponding to 95%of the data volume as the recommended value(22.2).This study can provide theoretical basis for the formulation of standards for the performance evaluation of building airtightness.