Analysis and Design of a Steam Ejector Structure
By adjusting structures of the nozzle and mixing-chamber , effects of the structure on the steam ejector performance were analyzed. An improved CFD program which was proved suitable for simulating flow profile in a steam ejector formerly was used here. The results of this study would be useful for designing a steam ejector with high performance when working condition was given.
Analysis of an ejector with environment friendly refrigerants
When an ejector is operated at choking-mode, it gives a better performance with higher entrainment ratio. To obtain this better performance at different operating conditions, area ratio of the ejector is varied. A computer code based on existing one-dimensional ejector theory is written to analyze performance of the ejector. The code includes effects of friction at the constant-area mixing chamber and change in specific heat of the working fluid besides internal irreversibility of the ejector. The simulated performance is compared with the available experimental data from the literature for validation. The effects of operating parameters on critical ejector area ratio and critical entrainment ratio are studied. Comparison of performance of ejector with environment friendly refrigerants, R134a, R152a, R290, R600a and R717 is made.
Performances d'une machine tritherme à éjecteur utilisant des mélanges de fluides frigorigènes
Resume On etudie le remplacement des fluides frigorigenes purs par des melanges dans les machines frigorifiques trithermes a ejecteur, en vue de leur optimisation. L'etude est menee theoriquement, pour des conditions de temperature de sources definies, en utilisant un modele de comportement du systeme base sur des modeles simples de chaque composant. Les caracteristiques thermodynamiques des melanges, en phase gazeuse ou a l'equilibre liquide–vapeur, sont determinees par la methode de l'equation d'etat et de l'egalite des fugacites de chacune des phases. L'equation d'etat utilisee est celle de Peng–Robinson. Les fluides consideres sont les suivants : pour les corps purs, R142b, R152a, RC318, R124, R134a, R22; pour les melanges binaires, R22/RC318, R22/R142b, R22/R124, R22/R152a, R22/R134a, R134a/R142b, R152a/R142b et R134a/R152a. L'etude montre que l'emploi d'un melange peut conduire aussi bien a une amelioration qu'a une degradation des performances de la machine. Ainsi, en general, quand le melange est fortement zeotropique (par exemple : R22/RC318), l'efficacite du systeme diminue. En revanche, quand le melange est legerement zeotropique (par exemple : R134a /R142b) ou quasi azeotropique (R134a/R152a), l'efficacite et le rendement exergetique augmentent.