A coupled Computational Fluid Dynamics and Wells-Riley model to predict COVID-19 infection probability for passengers on long-distance trains

Energy efficiency and exergy destruction of supersonic steam ejector based on nonequilibrium condensation model

Steam ejector plays a key role in the refrigeration system. The water has been used as a working fluid because water is more economical and non-toxic. The operating fluid often enters the evaporator as a water liquid and droplets evaporate by absorbing heat. Cooling load changing causes the vapor in the outlet of the evaporator to be accompanied by droplets. Therefore, there are droplets at the inlet of secondary nozzle and flow should be simulated as a wet steam flow with injection droplets at the secondary flow. In this paper, the effects of droplets injection at secondary flow have been investigated on the performance of the refrigeration cycle. For this purpose, the Eulerian-Eulerian method has been used and the results have been validated with experimental data. Six cases are considered with different wetness and number of droplets in the secondary flow. The results of case 6 show COP, T¯outlet, and ER decrease about 22.93%, 15.66%, and 22.93%, respectively. In addition, the steam accompanies by droplets at the outlet of ejector. Therefore, it is essential for designers and operators to model and consider the effects of the droplets on the wall erosion to optimize the wet steam ejector and refrigeration cycle performance. 

Numerical modeling of droplets injection in the secondary flow of the wet steam ejector in the refrigeration cycle

Optimization variables of the injection of hot-steam into the non-equilibrium condensing flow using TOPSIS method

In this research, the improvement of an ejector performance has been studied as crucial part of an ejector refrigeration system by means of applying changes in its geometry. Water steam is taken as a non-expensive, non-toxic, and available refrigerant and wet steam model has been employed to more accurate numerical simulation and analysis. It is investigated the effect of changing geometric parameters according to the presence of wetness in the flow field. The geometric parameters are the length and diameter of the constant area section of the ejector and the diameter of primary nozzle throat. In addition to entrainment ratio (ER) and critical compression ratio (CR) of the ejector as conventional design criteria, COP of the refrigeration system and the total entropy generation (EG) in the flow inside the ejector are also used; which results in a novel EEC ( E ntropy generation, E ntrainment ratio, and C oefficient of performance) method for ejector design in the ejector refrigeration systems. The impact of changing each geometry parameter is examined in a separate process. Finally, the increment in the length and diameter of the constant area section and decrement in the diameter of the primary nozzle throat are considered as desirable changes. Consequently, by applying these changes ER and COP have improved by 32% and total entropy generation is decreased.

Improvement of the wet steam ejector performance in a refrigeration cycle via changing the ejector geometry by a novel EEC (Entropy generation, Entrainment ratio, and Coefficient of performance) method.

An applicable surface heating in a two-phase ejector refrigeration

Steam ejector, as a heat pump, plays a key role in ejector refrigeration system which operates with water vapor as an available, economic and environmentally friendly refrigerant. In this research, supersonic steam flow through the ejector is simulated by CFD methods to investigate effects of ejector geometry on its performance. Basic design criteria are entrainment ratio (ER) and critical compression ratio so that the former affects COP of the refrigeration system and the latter changes the temperature at which condenser is operated. For more accurate design, we also investigate the effect of ejector geometry (non-dimensional parameters consist of D/L and d/D) on the entropy generation rate as a design criterion. In fact, increase in ER and COP and decrease in the entropy generation rate are desirable changes in the present work. Among all geometric parameters which affect the entropy generation, the diameter of the throat of the primary nozzle is more effective than the rest. Finally, the ejector geometry has been proposed that make improvement in the ejector ER and COP of the refrigeration cycle up to 32% and 38%, respectively, and reduction of 28% in total entropy generation rate.

Farzaneh Foroozesh

Papers

Improvement of the wet steam ejector performance in a refrigeration cycle via changing the ejector geometry by a novel EEC (Entropy generation, Entrainment ratio, and Coefficient of performance) method.

An applicable surface heating in a two-phase ejector refrigeration

Investigation on the effects of water steam ejector geometry in the refrigeration systems using entropy generation assessment