Research On Ejector Performance Of Air-conditioning System Driven By Automobile Waste Heat

Energy consumption on transportation has risen sharply with the increase of automobiles. Automobile exhaust has become one of the important cause leading to the haze weather, therefore, the car energy saving and emission reduction are urgently required. This paper studies the usage of the car waste heat and the structure of automotive refrigeration system. Ejector refrigerating system driven by the waste heat of car is researched, which is of more significance for energy saving and emission reduction.The compressor in conventional refrigeration system is replaced by ejector which is driven by low-grade renewable waste heat. The ejector is a key component of ejector cooling system, which has the advantages of simple structure, stable operation and lower cost. But the low COP (Coefficient of Performance) of ejector limits its popularization and application. Aiming at this problem, this paper analyzes the internal fluid flow of the ejector, optimizes its structure according to the different working conditions, effectively improves the working efficiency of the ejector cooling system.Firstly, the paper proposes a new ejector control equation of one dimensional model based on the constant pressure mixing theory and then builds the single-stage ejector model and two-stage ejector model. Refprop software is adopted to collect saturation characteristic of related refrigerants. Through comparing saturated characteristic curve of temperature and pressure, stability and security, the paper ultimately choose the suitable refrigerant (R134a). The polynomial fitting of the physical parameters enhances the theory basis of the experimental data, thus increasing the applicability of the system. In addition, this paper selects appropriate turbulence model through analysis.Secondly, using commercial CFD software package FLUENT, discrete control equations for the flow field using control volume method. Using Gambit2.2.30 and Fluent6.3.26 respectively for meshing and solving the ejector model, for single-stage ejector and two-stage ejector performance analysis and comparison. Using Fluent 2D and 3D flow simulation, adjusting and optimizing the system parameters, effectively improved the performance of the system.Finally, constructing platform of ejector refrigeration system for the experimental study. Based on Labview, the paper has set up an automatic control and measurement system for the ejector refrigeration system. A large number of experimental data show that the proposed ejector model is effective and has high promotion of practical value.The studies of ejector performance in theory, simulation and experiment aspects show that the structure of the proposed ejector model has better performance and higher practicability under normal condition and extreme conditions, which meets the requirements of automobile air conditioning refrigeration.