Analysis Of Biological Heat Transfer And Flow Characteristics Of Micro-environment Of Rabbits In Laboratory Animal Room

As an important foundation and supporting condition for life science research and development,high-quality laboratory animals have high requirements for the quality of their living environment in order to maintain their good physical and mental state.After more than two hundred years of development,people have a certain understanding of improving the welfare of laboratory animals,and have formulated relevant norms.However,the environmental indicators of laboratory animal facilities in the standard focus on the environment of animal room in the present,and pay little attention to the indicators of animal living micro-environment that we really need to care about.This paper takes an actual SPF rabbit laboratory animal room in Changsha as the research object,and the experimental animal facility micro-environment was included in the research scope for the first time.The airflow organization,temperature and humidity,and ammonia concentration distribution of the SPF rabbit laboratory animal room were analyzed by CFD method and the rabbit biological heat transfer model is added to this research.This paper analyzes the distribution of airflow,temperature,humidity,and ammonia concentration of laboratory animal rooms under three different conditions state: empty condition,layout cage and running state.The working conditions is in summer,and the air changes 15 times per hour.The temperature is 24 °C,and the relative humidity is 60%.The results show that in the numerical analysis of the laboratory animal room,ignoring the cage micro-environment and the biological heat transfer of the rabbit will seriously affect the reliability of the calculation results.At the same time,it is found that under current typical air distribution of ceiling diffuser supply and return in the corner,there are vortexes inside and outside the cage,so the heat and pollutants inside the cage especially the middle layer,are hard to be excluded.The temperature gradient of the rabbit near skin is as high as 600 °C / m.A larg e area of high humidity occurred on the back wall of the cages,and the relative humidity is above 63%.On this basis,the effects of different air exchange times,the number of air supply ports and the position of the cage on micro-environment in the cage are further studied.The results show that when the number of air changes is increased from 8 times per hour to 24 times per hour,the parameters of the indoor environment do not change much.The micro-environment temperature in the cage decreases with th e increase of the number of air changes,but the temperature around the first and second layers of the tray is still above 26 °C.The relative humidity of the back wall of the cage is reduced,but there is still a large area of high humidity.The re has little benefit on the temperature and humidity of the micro-environment in the cage when the number of air changes continues to increase.Instead,it will result in the high airflow speed.When the number of air changes reaches 24 times per hour,the airflow velocity around the rabbit at the bottom of the cage will reach to more than 0.2 m/s.At this time,the average total surface heat flux of the rabbit in the cage bottom reaches 35 W/m2,and there is a linear relationship between the heat flux and the number of air changes.When the air supply port is increased from one to two,the micro-environment parameters of the cage are changed significantly,and the internal environment temperature of the cage is reduced by 1 °C on average.The tempe rature gradient of the rabbit near skin is also significantly reduced.In the middle two columns of the cage,the relative humidity of large part of the back wall fell below 63%.The ammonia emission of the tray is more severe,but the ammonia concentration in the cage micro-environment and room is reduced due to the better airflow in room and the entire cage.When the cage is placed horizontally,the heat dissipation effect of the cage top layer is improved,and the heat dissipation effect of the bottom lay er is deteriorated.The high humidity of the back wall of the cage d oes not improve.The ammonia in the tray is diffused vigorously,and the ammonia concentration around the rabbit in the middle layer increases to 0.6~1.4 mg/m3.At present,there are few p aper analyses on the micro-environmental characteristics of laboratory animal rooms.The study on the biological heat transfer and flow micro-environment characteristics of experimental animal house rabbits provides a reference for the improvement of envir onmental indicators of experimental animal facilities.The research methods adopted for the biological heat transfer of laboratory animal rabbits also provide ideas for the subsequent biological heat transfer research.In addition,the basic work of analyz ing the micro-environmental characteristics of laboratory animals completed in this paper will also have a positive impact on improving the welfare of laboratory animals.