Investigations Of Air Handling Unit Heat Transfer And Air Distribution In Winter For The Improved Induction Air-conditioning System

Building energy consumption increases rapidly with the development of urbanization process,air-conditioning system used in building energy consumption accounts for the largest proportion.People pay attention to the research of the new air-conditioning system.This paper provides the theoretical basis for an improved induction air-conditioning system(IIAS)to the popularization and application,researches the heat transfer process of the oval-tube fin heat exchanger in the air handling unit(AHU)from the point of energy saving;analyzes the feature of the indoor air distribution supplied by the terminal air inductive unit(IAU)in the winter from the point of the comfort.IIAS consists of three components:medium temperature heat pump(MTHP),intensive AHU and terminal IAU.Comparing to the conventional air-conditioning system,this system has obvious advantages of energy saving for integrating the air and water supply in the large temperature difference,characteristics of high heat transfer performance and low resistance of oval-tube fin heat exchangers,inductive air supply technology.For oval-tube fin heat exchangers in the intensive AHU of IIAS,computational fluid dynamics(CFD)method was used for numerical simulation on the basis of reasonable model simplification,and the oval-tube fin heat exchanger was compared with circular-tube fin heat exchanger with the same equivalent diameter.This paper studied and analyzed the differences between two kinds of heat exchangers in the term of comprehensive performance,and the distribution feature of the air-side velocity and temperature field.The result show that the average temperature at the outlet of oval-tube heat exchanger is high;vortex and high temperature area at the tail is small;the comprehensive heat exchange performance is superior to circular-tube heat exchanger.The application of the oval-tube heat exchanger in AHU can reduce the resistance losses and enhance the heat transfer,improving the overall efficiency of air-conditioning system.Increasing the fin distance can improve the performance of the oval-tube fin heat exchangers,but increase the width of the unit as well.There is an optimum point for the effect of fin thickness on the comprehensive heat transfer performance.Reasonable selection of fin thickness can make the heat transfer performance high while saving manufacturing material.There is also an optimum point for the effect of tube distance on the heat transfer performance,when designing the distance of the heat exchanger in the unit,it can ensure high heat transfer performance and reduce the size and area of the unit by considering this optimum point.ThisStudy provides guidance for the operation and performance optimization of oval tubes in AHU.Used Airpak software to simulate the indoor air distribution by terminal IAU air supply in the winter,and verified the reliability of the simulation by the experimental measurement.The results show that IAU has poor heating effect and low applicability in the winter.The indoor air will not cause a draft sensation for its small velocity,but the indoor air distribution shows the characteristics of the high upper temperature,the low bottom temperature and lager vertical temperature difference,which affecting the comfort of the human body.Furthermore,research the influence of different factors on the air distribution.It pointed out that increasing the temperature and velocity of IAU supply-air can increase the temperature of indoor human activity area.The inducer was suitable for the room about low load in the winter and low height.This study will provide reference and improvement measures for IAU heating effect in the winter.