Research And Analysis Of Air Flow Organization In Negative Pressure Isolation Ward Based On CFD

Isolation wards are significant for dealing with public health emergencies,and negative pressure design can prevent pollutants from spreading to the external environment and indoor clean areas under static isolation conditions.In the design of a negative pressure isolation ward in an infectious disease hospital or in the renovation of a common ward combined with epidemic prevention,reasonable planning of the negative pressure gradient in the ward and the air flow organization in the ward can minimize the leakage of pollutants and reduce the risk of infection among medical personnel.This paper takes the negative pressure isolation ward unit and negative pressure ward area of a hospital infection building in Xinxiang City in winter as the research object.Based on the project design and construction drawings,the physical models of the negative pressure isolation ward unit and negative pressure ward area are established using ICEM CFD and structured grids are divided.After verifying the accuracy of the physical and numerical models,determine external boundary conditions such as patient body surface heat dissipation and ward wall temperature for winter conditions.Based on the relevant specifications for environmental control requirements in negative pressure isolation wards,combined with pollutant propagation characteristics and airflow organization optimization analysis,various air supply and exhaust outlet locations and air supply parameters are determined;To achieve negative pressure design,the air volume in the negative pressure ward and ward unit areas is checked.Based on the above,using the CFD numerical simulation method,using speed,temperature,air age,contaminant content,and other airflow organization evaluation indicators as quantitative evaluation criteria,under the conditions of constant fresh air ventilation times,and constant supply air temperature,the advantages and disadvantages of airflow organization under different combinations of exhaust location,number and location of air supply openings,and number and location of air exhaust openings were compared in pairs;Patient corridors and medical corridors are used as pressure boundary conditions to analyze the directional airflow direction and negative pressure gradient in negative pressure wards.After analyzing and comparing the numerical simulation results,the following conclusions are drawn.(1)For negative pressure isolation ward: adopt the layout of two wards sharing a buffer room,with a negative pressure value of-9.85 Pa in the buffer room,which can form a reasonable directional airflow and negative pressure gradient;The negative pressure gradient and the door crack seepage velocity are related to the door crack size,and the negative pressure gradient is the best when the door crack width is 3mm.(2)For negative pressure isolation ward units: When vertical jet air supply is used,the flow velocity in the lower part of the hospital bed and the upper part of the ward is relatively large,about0.3～0.4m/s,and the flow velocity near the patient’s face is 0.1～0.15m/s,which meets the comfort requirements;The single exhaust arrangement produces a short circuit of air flow,with a ventilation efficiency of 0.82,which is lower than other double exhaust arrangement conditions;The ventilation on both sides of the hospital bed is better than that under the bed.The average concentration of respiratory pollutants in medical personnel is 15.3% lower,and the ventilation efficiency in the ward is 5.8% higher.The arrangement of double air supply outlets and ventilation on both sides of the bed can significantly improve the uniformity of temperature and velocity fields in the ward.Compared to the arrangement of single air supply outlets,the average temperature of the upper part of the hospital bed is 1.5 ℃ higher,and the ventilation efficiency reaches 1.34,which is higher than other combinations of air outlet arrangements.The average air age of the patient’s breathing area and the respiratory height of medical personnel are 215 s and 245 s,respectively;A relatively close distance between the air outlets of the dual air supply arrangement will form an upward reflux with a flow rate of about 0.4m/s,and the reflux trend will weaken when the position of the exhaust outlet is changed.