Determination of the ejector dimensions using the CFD method for the bus air conditioner with ejector expansion

Almost all buses that are commonly utilized for passenger transportation have air conditioning systems. The air conditioner compressor takes its power from the bus engine. With the ejector system to be used in the air conditioner, some of the work spent on the expansion valve can be recovered and the compressor work can be reduced by increasing the inlet pressure of the refrigerant entering the compressor. Thus, by raising the input pressure of the refrigerant entering the compressor, the compressor workload may be decreased. In this study, the change in the performance of the system in the case of using an ejector in a midibus air conditioner using R134a as the refrigerant was investigated. First, the flow in the ejector was analyzed in one dimension using analytical and numerical methods. According to the results obtained from here, the ejector was dimensioned and a model suitable for Computational Fluid Dynamics (CFD) was created. Two-dimensional analyzes of the flow in the ejector were performed with the help of CFD. In the analysis, it was observed that the compressor inlet pressure increased by 26% in the system with ejector. The effects of nozzle position, throat diameter, mixing zone diameter, nozzle length, mixing zone length, diffuser length, and nozzle and diffuser angles on flow rate and pressure boosting amounts were investigated using CFD models. As a result, the NXP value is between 0 and 1, the throat diameter is 2mm, the mixing zone diameter is 6mm to 7mm, the diverging nozzle angle ranges between 0.6 and 0.67, the mixing zone length is 150mm, and the diffuser length ranges between 100mm and 120mm, the diffuser angle is between 0.65 and 0.7 are the optimal ejector dimensions. According to the CFD findings, making suitable adjustments to the aforementioned parameters may result in an improvement in ejector performance.