R744, refrigeration application, two-phase ejector, heat transfer numerical model, experimental investigation
The proposed three dimensional CFD model to simulate the influence of the heat transfer on the R744 two-phase ejector performance is presented. The numerical model was developed based on the homogeneous real fluid flow assumption with the enthalpy-based formulation of the energy equation. The R744 two-phase ejector was designed to evaluate the temperature profile within the ejector walls. The prototype R744 ejector for experimental investigation was manufactured by Institute of Thermal Technology and ATM in Poland. The performance measurements were carried out at a R744 test facility at SINTEF/NTNU in Norway. The foregoing ejector was equipped with the thirteen thermocouples located inside the ejector to measure the wall temperature in different ejector section i.e. the motive nozzle, the suction nozzle, the mixing section and the diffuser. The experimental test campaign at different operating conditions typical for refrigeration application was carried out and the uncertainty of the measurement was defined. Moreover, the experimental data are applied to validate the CFD results at defined operating conditions. The numerical results were set to evaluate the influence of the wall temperature on the two-phase flow parameters. In addition, the heat transfer coefficient of the two-phase flow within the ejector was estimated. The analysis of the heat transfer process within the R744 two-phase ejector let to investigate the influence of the ambient conditions and the different temperature levels of the motive and suction streams on the ejector performance.