Research On Angle Factor Between Human Body And Radiant Surfaces In Radiant Air-conditioning Rooms

With the development of building energy conservation and the improvement o f human demand for indoor environment,the design and application of HVAC system is facing great challenges.In recent years,more and mo re buildings use radiant air-conditioning system,which is more comfortable and energy-saving.In order to calculate radiant heat transfer,average radiant temperature and cooling or heating load,we need to calculate the angle factor between human body,r adiant panel and each surface accurately.In addition,the indoor items will also affect angle factor and radiation heat transfer.Firstly,the research status of radiant air-conditioning and the angle factor at home and abroad is introduced.The necessity and deficiency of the research on the angle factor are analyzed.Secondly,describe the definition and basic propertie s of angle coefficient.Compare the advantages and disadvantages of common calculation methods.Then,establish 3D models of standing and sitting human body.Also,Simplify the human body into a cube.The calculation method of the angle factor between the human body and the envelope surfaces is derived.When there is one or more obstacles in the room,the calculation method is proposed.The simplified algorithm is programmed by Python.Based on human 3D model size,establish the numerical model by FLUENT,which prove the validity of the simplified algorithm.In non-obstruction condition,the relative error is less than 10%,except the angle factor between sitting posture and the ceiling.In one-obstruction condition,the relative error is less than 10%.In two-obstruction condition,the relative error is less than 5%.The main factors affecting the size of the Angle coefficient are: room sur face(position,size,distance),human body posture,obstacle surface(number,position,size,distance).In non-obstruction condition,the angle factor between human body and the envelope surface(wall,ceiling,floor)is related to t he surface position,size,distance and human posture.The angle factor increases with the increase of surface size,and decreases with the increase of d istance.The closer the envelope surface is to the center of human body,the more obvious the effect is.In one-obstruction condition,the angle factor between human body and the front wall is related to the obstruction form,position,size,distance and human posture.The farther the distance between the obstacle surface and the human body is,or the large r the offset is,the closer the angle factor is to the value in no-obstruction condition.The larger the size of the obstacle surface is,the larger the the occluded amount is.However,the effect of obstruction is limited,and the occluded amount has a maximum.In multiple obstructions condition,they can be simplified into parallel or vertical planes according to the relative distance and shape characteristics of the objects,which can reduce the computation in the range of allowable error.