Development of a New Ejector Performance Map for Design of an Automotive Air Conditioning System 2020-01-1244
Ejector as a work recovery device offers potential for developing energy efficient heating and cooling systems based on vapor compression technology. For applications like automobile air conditioning, the operating conditions vary significantly which can lead to considerable performance degradation when the system is operated in off-design conditions. Therefore, system designing warrants development of accurate ejector performance models for a wide range of operating conditions.
In this paper, a novel methodology for ejector performance maps is proposed using ejector efficiency as performance parameter and volumetric entrainment ratio as characterization parameter. The proposed performance map is developed after conducting experiments to find appropriate performance representation where ejector driven flow can be characterized using ejector motive flow. The developed performance map can predict ejector pressure lift within an accuracy of 20% using an iterative solver.
In a later part of the paper, a component selection analysis is conducted considering two ejectors, two compressors and two evaporators. The selection analysis mimics a typical system design process for selecting a combination of system components that give the optimum system. Ejectors are modeled using proposed performance maps. Variable speed compressors are modeled using 10-coefficient polynomial for each of three compressor efficiencies. Heat exchangers are modeled using thermodynamic state analysis.
The study shows the proposed performance map can be used in selecting appropriate ejector for an application. This is encouraging as these performance maps along with more detailed heat exchanger models can be employed in future studies to select the optimum system configuration for an automobile air conditioning system using ejector as a work recovery device.