Drop-in Replacement of Conventional Automotive Refrigeration System to Hybrid-Ejector System with Environment-Friendly Refrigerants

Ejector refrigeration system (ERS) is a propitious cooling skill for automobiles with a reduced fuel consumption along with structural simplicity, low cost, and driven by engine waste heat. Conversely, the lower coefficient of performance (COP) of standalone ERS is the major drawback for automotive applications, which can be overcome by hybridizing with a conventional compression system. Therefore, an indigenously designed hybrid cooling system is proposed to switch in three different cooling modes based on required thermal comfort- compressor, ejector, and hybrid. A real gas property-based theoretical model of this hybrid system is established under critical and sub-critical modes with a variable area ejector for a better entrainment ratio. In parallel, the performance of the proposed system is explored with two environment-friendly hydrofluorocarbon (HFC) refrigerants R152a, R440a and four extremely low global warming potential (GWP) hydrofluoroolefin (HFO) refrigerants R1234yf, R1243zf, R1234ze(E) and R513a, as an immediate replacement of commonly used R134a. The thermodynamic performance variation is compared for an extensive choice of the evaporator, generator, and condenser temperatures. Due to the conversion of waste heat into work in the hybrid mode, the compression ratio reduces maximum by 54% and cooling capacity increases by almost 22% more than in the conventional compressor mode. Moreover, compared with the standalone ejector system, the hybrid system improves the cooling capacity and COP by up to 4 times. Irrespective of the circumstances, the maximum entrainment ratio and COP are achieved with refrigerant R1234yf in hybrid mode, claiming ideal replacement of R134a for automotive air conditioning applications.

Automated summary

The Ejector refrigeration system (ERS) is a promising cooling technology for automobiles. However, the lower coefficient of performance (COP) of standalone ERS is a major drawback. This study proposes a hybrid cooling system that can switch between different cooling modes to overcome this drawback. A theoretical model of this hybrid system is established, and its performance is explored with different refrigerants. The results show that the hybrid system improves the cooling capacity and COP compared to the standalone ejector system.