The ejector expansion refrigeration cycle is a modified vapor compression cycle in which a two phase ejector is used to recover a portion of the work otherwise lost in the expansion valve. The ejector improves cycle performance by increasing compressor inlet pressure and by lowering the quality of the fluid entering the evaporator. Theoretically, a cooling COP improvement of approximately 21 % is achievable for a typical refrigerating cycle and an ideal ejector. If the ejector performed as well as typical single-phase ejectors, an improvement of 12% could be achieved. Previous tests have demonstrated a smaller 3.7% improvement; the difference is in the poor performance of the two-phase ejector. The purpose of this research is to understand the operating characteristics of the two phase ejector and to improve design. A two-phase ejector test rig has been constructed and tested. Preliminary data show performance superior to previously tested two-phase ejectors, but still inferior to single phase ejectors. Ejector performance corresponds to refrigeration cycle COP improvements ranging from 3.9010 to 7.6%. This performance was obtained with an ejector designed from single-phase ejector and wet steam ejector design methods. The poor performance indicates the design methods must be improved for two-phase ejectors. This research has begun the development of design methods for the two-phase ejectors and this research has developed models to describe the fluid dynamics and thermodynamics of the ejector. / Ph. D.

<p>Electrostatic spray is a spray that is induced by an interaction between the surface charge on the liquid meniscus and the externally applied electrical field that forms a conical shape known as the Taylor Cone. Electrostatic spray can be seen in a variety of different fields in modern times, such as, agriculture, combustion, space propulsion, and medical applications. The experimental setup for any electrostatic spray consists of the following components: a syringe pump filled with an ionic fluid, a high voltage power supply, and a ground source. The orientation of the nozzle, set to a horizontal or vertical orientation, and the interface that is examined, liquid/air or liquid/liquid interface are two parameters that can vary from one setup to another while still using the same components to form the electrostatic spray. In this experimental study, the characteristic of the electrostatic spray of two immiscible fluids, liquid/liquid interface, with a horizontal nozzle orientation, was analyzed. The two immiscible fluids that were chosen for this experiment were olive oil, the ambient fluid, and pure ethanol, the working fluid. A set range of 0 – 5 kV with an increment of 0.5 kV was applied to the working fluid with a flowrate of 0.1 mL/min. The distance between the nozzle and the copper disk was also altered for three different distances, 22.09, 14.6 and 10.33 mm. Different patterns and trajectories were captured and analyzed using both a high-speed camera and a long exposure camera. Formation of vortices was recorded in the induced flow. The general trend was found was an increase in the droplets’ velocity with the increase of the applied voltage. Additionally, there was an increase in the droplets’ velocity was recorded as the copper disk was moved closer to the nozzle. A dimensional number, Jowaiser’s number Jo, has been proposed where it relates the electric forces to the inertial forces. It can be used to predicts the phase that the flow experiences. The four phases that a flow can experience are the droplet phase, transition phase, spray phase, and the shorting phase.  </p>

This study was regarding the waterjets in the water atomization process. This is because the understanding of the waterjets is not complete and with a greater understanding the production of metal powder could be improved. The waterjets were going to be categorized according to their wave function, size and distribution of the droplets and the three regimes that Höganäs had divided up the jets into was also analyzed. The three regimes depend on the jets characteristics and the regimes are the transparent, milky and the droplet jet. The purpose was to get a better understanding of the correlation between velocity, temperature, waves, size and distribution of the droplets in a 50 cm long waterjet. The method to enhance the understanding of this project was to first do theoretical solution with the help of fluid dynamics. Weber, Reynolds and Ohnesorge number were calculated and evaluated to get a better understanding of the waterjet. Secondly, experiments were conducted where a waterjet with different nozzles and temperatures was filmed with a highspeed camera and the videos were analyzed with the help of a software package called ImageJ. The results show the correlation between increasing temperature and decreasing droplet size and a less cohesive waterjet core. The conclusion from the study was that with the help of temperature one can help control the droplet size. / Denna studie angår vattenstrålar i en vattenatomiserings process vid tillverkning av metallpulver och en bättre förståelse skulle förbättra tillverkningen av metallpulver. Vattenstrålen skulle kartläggas enligt dess vågfunktion, storlek och spridning av dropparna och de tre regionerna som Höganäs har delat upp vattenstrålen i skulle analyseras. Regionerna är beroende av strålens karaktäristiska utseenden vid olika delare av vattenstrålen och är genomskinlig, mjölkig och dropp stråle. Syftet med studien var att få en bättre förståelse av sambandet mellan hastighet, temperatur, vågor, storlek och spridning av dropparna i en 50 cm lång vattenstråle. Metoden som användes för att öka förståelsen av vattenstrålen var först en teoretisk del med hjälp av fluidmekanik. Weber, Reynolds och Ohnesorge tal beräknades och utvärderades för att ge en teoretisk förståelse för vattenstrålen. Sedan utfördes vattenflödesexperiment, där vattenstrålen filmades med olika munstycken och temperaturer med en höghastighetskamera och videon analyserades med hjälp av mjukvaran kallad ImageJ. Resultaten visar ett samband mellan ökad temperatur och minskad droppstorlek och en mer uppbruten kärna av vattenstrålen. Slutsatsen från studien var att man med hjälp av temperaturen kan reglera droppstorleken.

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