Using CONTAM to design ventilation strategy of negative pressure isolation ward considering different height of door gaps

Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air volumes.The door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the room.There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building.In this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department.The results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air volumes.Pressure fluctuations in the medical and patient corridors are greater than in other rooms.The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients.It is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.

Void fraction for random loose packing of the cylindrical particles considering filling rate,material and shape

Particle packing is widely applied in organic pollutant adsorption,catalytic reaction.biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void fraction of the cylindrical particles are not as thorough as the spherical particles.This study investigated the influence of the flling rate,material properties and sphericity on the void fraction of cylinders through experiments and simulation.DEM(discrete element method)was validated by the internal structures of the packing obtained by CT(computed tomography).Based on the logarithmic correlation between the void fraction and flling rate,an ingenious framework for predicting the void fraction of cylindrical particles was presented with two intermediate coefficients.By correlating the coefficients with the material property and sphericity,a novel void-fraction prediction model was established with R-squared of 0.996.The mechanism of void fraction under random loose packing for cylinders was eventually found in this study.

Pressure and flowrate distribution in central exhaust shaft with multiple randomly operating range hoods

Central flues are now commonly adopted in high-rise residential buildings in China for cooking oil fumes(COF)exhaust.Range hoods of all floors are connected to the central shaft,where oil fumes were gathered and exhausted through the outlet at the building roof.As households may cook and use their range hood at random periods,there is great uncertainty of the amount of COF being exhausted.In addition,users can often adjust the exhaust rate of the range hood according to their needs.As a result,thousands of possible operating conditions consisting of distinct combinations of on/off conditions and fan speed occur randomly in the central COF exhaust system,causing the exhaust performance to vary considerably from condition to condition.This work developed a mathematical model for characterizing the operation of the central COF exhaust system in a high-rise residential building as well as its iterative solving method.Full-scale tests coupled with CFD simulation referring to a real 30-floor building were conducted to validate the proposed model.The results show that the model agreed well with the CFD and experimental data under various system operating conditions.Moreover,the Monte-Carlo method was introduced to simulate the random operating characteristics of the system,and a hundred thousand cases corresponding to distinct system operating conditions were sampled and statistically analyzed.