Simulation Analysis Of Air Duct Performance Of Automobile Air Conditioning

The air duct of automobile air conditioning is an important part of air conditioning system.It is engineering significance and practical value to study the influence of air duct on the defrosting performance of windshield and the thermal comfort of occupant compartment,so as to further ensure the driving safety and improve the driving environment of occupant compartment.In this paper,a light truck air-conditioning duct in research and development is taken as the object to study its influence on windshield defrosting effect in the whole air-conditioning system of the vehicle,as well as on the thermal comfort of the passenger cabin.Firstly,the defrosting performance of air duct of automobile air conditioner is analyzed.The defrosting principle and process of automobile air conditioning are analyzed in detail,and the defrosting geometry model,mesh model and mathematical model of automobile air conditioning are established.It is analyzed that the air distribution ratio of each defrosting outlet is 3.14%,40.96%,48.72%and 7.18%for the left,left middle,right and right air outlets respectively.The results of steady-state defrosting analysis show that the wind speed distribution and coverage area near the wall in the field of vision area of the windshield,the wind speed?2m/s near the wall in area a only accounts for 22.40%of the area in area A,and the wind speed?1.5m/s near the wall in area B only accounts for 51.75%of the area in area B,which fails to meet the industry standard.Therefore,three defrosting air duct structure improvement schemes are proposed to jointly implement to improve the air duct structure.The results show that the air distribution ratio of the air outlets of each defrosting air duct is 9.04%,41.68%,41.33%,7.95%respectively,which meets the use requirements.The area of wind speed?2m/s near the wall of zone A accounts for 90.51%of the area of zone A,the area of wind speed?2m/s near the wall of zone A~?accounts for 100%of the area of zone A~?,the area of wind speed?1.5m/s of zone B accounts for 95.15%of the area of zone B,and the area of wind speed?1m/s near the wall of the glass vision area of both sides of the door reaches 100%,which meets the standard of steady-state defrosting.After the defrosting duct structure meets the steady-state defrosting,the transient defrosting analysis is carried out to determine whether the defrosting system can meet the regulatory requirements.The results show that when t=215s,the frost layer on the outer surface of the windshield begins to melt,and the first place where the frost layer melts is the place where the air flow at the outlet of the defrosting duct first collides with the windshield.When t=1110s,the frost layer in area~?has all melted.When t=1200s,the defrosting area in area a reaches more than 80%;when t=1240s,the frost layer in area B has all melted;when t=1710s,the frost layer in area a has all melted,All frost layers of the front windshield have melted,and the transient defrosting results can meet the defrosting standards stipulated by the national regulations.Then,the influence of air duct of automobile air conditioning on the thermal comfort of human body in passenger cabin is analyzed.Firstly,the geometric model,grid model and mathematical model of human thermal comfort in passenger cabin are established respectively.According to the external environment in summer and winter and the test conditions,the environmental parameters and boundary conditions in two modes are set up respectively.The air distribution proportion of the air outlet on each blowing surface of the air conditioning duct is analyzed.The results show that the air volume of the left middle air outlet and the right middle air outlet of the blowing surface duct account for 28.76%and27.71%respectively,slightly higher than the ideal distribution ratio,which can meet the use requirements.The wind speed of each air outlet is between 6m/s-8m/s,meeting the use standard.Then considering the human body comfort,the paper analyzes the characteristics of various current human body thermal comfort evaluation indexes,and determines the equivalent temperature and national regulatory standards as the human body thermal comfort evaluation indexes in summer and winter respectively.It analyzes the human body thermal comfort in the passenger cabin in summer and winter,and the results show that the human body thermal comfort in winter can meet the regulatory standards,However,under summer cooling conditions,the head of the driver and passenger exceeds the upper limit of comfort.Therefore,by optimizing the air inlet temperature and air volume at the entrance of the blowpipe,the head is within the comfortable range.The analysis results show that the optimized defrosting duct and face blowing duct meet the relevant specifications and requirements.The optimal design analysis can be used to predict and guide product development,design,manufacturing and engineering test.