| Air distribution is the final link between a heating,ventilation and air conditioning(HVAC)system and the human body.Thus,the difficult technical issues of evaluating and optimizing air distribution and thermal comfort are important and worthy of further study.In this paper,a proposed target value in the form of a standard deviation is presented.The existing and new indicators were analyzed in the evaluation of the temperature field and the velocity field under different air supply modes.Different air distributions were optimized based on the target value in typical building spaces.The optimized air distributions in typical office buildings were obtained.This paper expounds a new method for air distribution design and optimization based on target value evaluation,summarizes the relevant design processes based on an orthogonal test and by decoupling effect of the tuyere size,airflow temperature,air-supply angle and velocity on air distribution,and then presents the design case.It was found that in the five different air supply modes,the optimal values of the air supply velocity and air supply temperature exist only for the proposed evaluation indicator,i.e.,the target value.That is,compared with other evaluation indicators,the target value is a more effective means of evaluating the optimization of air distribution and thermal comfort.On the basis of the optimization of the target value,the velocity in the working area is approximately 0.3 m/s for each air supply mode,and the temperature is approximately 26℃,indicating that the target value can effectively guide the optimization process.In the stratified ventilation mode,the optimal velocity target value Tv(min)is 0.164,which is smaller than that in the displacement ventilation mode(Tv(min)=0.185),which means that stratified ventilation is more suitable than displacement ventilation for meeting the velocity field requirements in the given building.With regard to the temperature field,the Tt(min)of displacement ventilation is 0.671.This value is the lowest Tt(min)among the different ventilation modes,indicating that displacement ventilation is most suitable ventilation mode for meeting the temperature field requirements in the given building.In the configuration of lateral air supply in high-and large-space buildings in winter,the change in the axial trajectory of the jet with the diameter of the air-supply outlet follows(?yi)/(?d0)<0;thus,the axial trajectory of the jet decreases monotonically with increasing outlet diameter.The change in the axial trajectory of the jet along with the deflection angle of the air-supply outlet follows(?yi)/(?β)>0;thus,the axial trajectory of the jet increases monotonically with increasing incident angle.The change in the axial velocity of the jet with the outlet diameter follows(?ux)/(?d0)>0;thus,the axial velocity of the jet increases monotonically with increasing outlet diameter and also with increasing average velocity of the jet outlet.The jet temperature diffusion is similar to that of the velocity.When optimizing the distribution of lateral air supply in winter,deflection angle,velocity and temperature of air supply can be determined in turn.For the high and large-space building type addressed in this paper,the optimal air-supply angle is 2°,optimal air-supply velocity is 8 m/s,the optimal air-supply temperature is 19℃,the final velocity target value is T=0.138,and the temperature target value is T=5.50. |
