Study On Contaminant Distribution Characteristics And Control In Negative Pressure Ward Under Radiation Air Conditioning

Negative pressure ward,as the main place for admission and treatment of respiratory infectious patients,plays a very important role in preventing the spread of virus and protecting the life and health of doctors and patients.At present,negative pressure wards generally use split air conditioners,fan coils+fresh air systems and other heat and humidity coupling treatment and mixed ventilation modes to ensure the thermal comfort and air quality of the ward environment.However,split air conditioners and fan coils have problems such as indoor air circulation flow and condensation collection.Radiant air-conditioning system relies on radiant panels to bear part of the indoor sensible heat load,and fresh air to bear the latent heat load and part of the sensible heat load.Fresh air is direct current operation,which can avoid the virus diffusion problem caused by indoor air circulation flow,and effectively guarantee the indoor air quality.At the same time,the direct current fresh air also makes the indoor airflow simpler,through the reasonable airflow organization design can inhibit the spread of viruses,reduce the risk of infection of health care workers.In this paper,the indoor environment,contaminant distribution characteristics and infection risk of healthcare workers in negative pressure ward under two modes of fan coil system and radiant air-conditioning system are investigated through a combination of experiments and simulations.The thermal comfort,contaminant distribution characteristics and contaminant removal efficiency of negative pressure ward by different airflow organizations under the mode of radiant air-conditioning system are further analyzed.A prediction method of indoor contaminant concentration distribution based on machine learning was proposed to provide a basis for the optimization of indoor air flow organization.The above research can provide reference for the design of new negative pressure ward.The specific work is as follows:Firstly,a full-size laboratory for negative pressure ward based on radiant air conditioning was designed and constructed.According to the‘Code for design of infectious diseases hospital’and the‘Technical guidelines for construction of negative pressure area for COVID-19 emergency Treatment Facilities’,etc.,design calculations were made for the position of air outlets,fresh air volume and exhaust air volume inside the laboratory to ensure that the negative pressure ward laboratory meets the functional requirements.At the same time,measurement points are arranged at different locations inside the laboratory to measure the temperature,wind speed and contaminant concentration inside the laboratory,which provides a basis for subsequent simulation and analysis.Secondly,a mathematical model of the indoor environment of the negative pressure ward based on radiant air conditioning was established.The mathematical model of indoor environment in negative pressure ward was established,and the Reynolds time-averaged simulation was used to solve the indoor flow field to obtain the distribution of indoor temperature,velocity and contaminant concentration in the negative pressure ward.The simulation results were compared with the experimental results to verify the accuracy of the simulation.Compared with the experimental results and simulation results,the error of indoor temperature is less than 5.00%,the error of indoor wind speed is less than 0.1 m/s,and the error of indoor contaminant concentration is less than 10%.Thirdly,the indoor environmental characteristics of the negative pressure ward in the mode of radiant air-conditioning system and fan coil air-conditioning system were comparatively analyzed.A mathematical model of the negative pressure ward under the fan coil air-conditioning system mode was established,and a comparative analysis was conducted with the negative pressure ward based on the radiation air-conditioning mode in terms of the indoor temperature field,the velocity field and the distribution of contaminant concentrations and the risk of infection for healthcare workers.The results showed that the use of radiant air-conditioning system not only reduces the indoor vertical temperature difference and the sense of blowing,but also reduces the indoor contaminant concentration and the infection risk of indoor personnel.The maximum reductions in indoor contaminant concentration,exposure risk and infection probability were 29.85%,29.63%and 15.79%,respectively,for radiant air-conditioning compared with fan coils.Fourthly,the impact of different airflow organization forms on the indoor environment of the negative pressure ward under the radiant air conditioning mode was analyzed.The thermal comfort,contaminant distribution characteristics,contaminant removal efficiency and infection probability of healthcare workers in negative pressure wards under three airflow organization forms:downward ventilation,stratum ventilation and ceiling-attached jets under radiant air conditioning mode were studied.The results showed that the application of radiant air-conditioning system in negative-pressure wards can ensure the thermal comfort of patients;both stratum ventilation and ceiling-attached jets can effectively reduce the concentration of contaminant and the risk of infection of healthcare workers.When the number of fresh air changes was 6 ACH,the indoor contaminant concentration was reduced by 10.73%and7.73%,the contaminant removal efficiency was increased by 12.50%and 10.42%,and the probability of infection was reduced by 23.18%and 20.78%,respectively,for ceiling-attached jets and stratum ventilation compared with downward ventilation.Finally,the prediction method of indoor contaminant distribution in negative pressure ward under radiant air conditioning mode was studied.Rapidly obtaining the distribution pattern of indoor contaminant concentration is conducive to rationally regulating indoor airflow organization,improving indoor air quality,and ensuring the safety of healthcare workers.A study on the prediction of indoor contaminant concentration distribution based on a limited number of measurement points was carried out,and the convolutional neural network method was used to predict the indoor contaminant distribution.the results were compared with those of multiple linear regression,support vector regression and BP neural network.The results show that both BP neural network and convolutional neural network can effectively predict the indoor contaminant concentration distribution,in which convolutional neural network has the highest accuracy,and the R~2,RMSE,MAE and MAPE of convolutional neural network are 0.92,6.31 ppm,3.18 ppm and 8.33%,respectively.