| The rapid development of automobile industry and the improvement of livingstandard, people’s requirement for comfort of automobile passenger compartment is alsomore and more higher, automobile air conditioning has become the importantcomponent of automobile. The HVAC assembly is a key part of automobile airconditioning system, usually the evaporator and heater core is contained in the HVACassembly. It has a great influence on flow field that the internal channel of HVACassembly has arranged, and then affects the air-conditioning effect.In the paper, automotive air conditioning double evaporator system was researchedby computational fluid dynamics (CFD). Respectively, in the vent full cold, defrost fullhot, vent full hot and feet full hot four working modes are studied by numericalsimulation on the front HVAC system, review the internal flow field, temperature field;the vent full cold mode on overhead HVAC is computing, and analyse its internal flowfield, temperature field. According to the front HVAC system in the various modes ofvelocity distribution, analyse the HVAC assembly structure is reasonable, and putforward the optimized scheme. According to the internal flow field, temperature field ofoverhead HVAC, analyse the air outlet is uniform, and bring forward optimized solution.In order to investigate the feasibility of model optimization, optimized model is studiedby CFD, and the simulation result is compared with the original model, analysesimilarities and differences before and after optimization of flow field, temperature field,and shows the feasibility of the optimized scheme. In addition to the HVAC assembly,the defrosting duct is simulated, for two different air ducts, according to the results,select a duct which defrosts better.Specific work and results include: firstly, based on the characteristic of the doubleevaporator assembly system, the numerical model is simplified and reasonable meshing,three-dimensional numerical simulation of double evaporator system is done by usingFLUENT; secondly, according to the simulation results of the front HVAC system,analyze the characteristics of internal flow field of front HVAC assembly, foundexistence of vortex before entering the front HVAC system evaporator, affected theuniformity of flow field, and then presents an optimized project, namely adding guideplates and a guide device in the vent before entering the evaporator; and then accordingto the optimized program to modify the numerical model and simulated, compared the results with the original model, found that flow field is more uniform after optimization.According to the simulation results of overhead HVAC system, it is found that thedistribution of evaporator inlet wind is very uniform, there is not the phenomenon of theevaporator entrance of front HVAC system, but because of the air outlet structure, leadsto a wind uneven phenomenon, in view of this problem, according to the characteristicsof the model, change outlet angle, and calculate, the calculation results of optimizedmodel and the original model are compared, found that the wind is more uniform afterthe outlet angle modifying, and the air temperature of outlet is lower than the old model;finally, on the two duct A and B were analyzed by CFD, through the analysis of staticpressure contours, velocity vector diagram and pathlines chart of air duct, and thevelocity vector diagram, pathlines chart of front windshield glass and window of the car,compare the defrosting effect of the two air ducts, and get the air duct B which defrostsbetter, it will assemble in automobile air conditioning system. |
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