Ejectors - Research and thesis proposals - 2015
** BT – bachelor thesis, MT – master thesis, DT – doctoral thesis
1 – Development of a Supersonic Ejector Cycle working with refrigerants, SEC:
Goal: The aim is to develop and optimize a standard supersonic ejector cycle for industrial use. The system may operate on waste heat and solar power resources. Further advantages are the low production costs and the high reliability of the system due to the absence of the gas compressor.
Status of research and critical aspects:
Currently a test bench of 40kW of cooling power is running at Frigel S.p.a. (Scandicci, Italy) which is partner on this research. The plant COP has reached 0.5 but the condensing temperature is still too low for summer use. An optimization of the supersonic ejector design is required to increase the cycle efficiency and condensing temperature. Passive configurations are also attempted by substitution of the pump by means of injectors. Training periods within Frigel are available. In addition, possible partners on this research may be Georgia-Tech (USA) and Politecnico of Milano (Italy).
Future research and thesis proposals:
a) Tests of new refrigerants inside the plant. Experimental and CFD analysis of alternative refrigerants on the existing geometry (BT, MT). Design of a new ejector profile suitable to the refrigerant properties (BT, MT).
b) Installation of injector to substitute centrifugal pump. Literature research on the method to design two-phase injector (BT). Selection of a proper design method, construction of the injector and experimental tests (MT). CFD analysis of the injector (MT, DT).
c) Optimization of the existing supersonic ejector profile. Development of a theoretical 1D model of the supersonic ejector to give a first approximated profile (MT). Detailed numerical optimization by means of CFD analysis coupled with a suitable optimization algorithm (MT, DT).
Relevant publications (in order of appearance):
Grazzini, G., Milazzo, A., Paganini, D., 2012. Design of an ejector cycle refrigeration system, Energy Conversion and Management 54, 38-46
Eames, I.W., Milazzo, A., Paganini, D., Livi, M., 2013. The design, manufacture and testing of a jet-pump chiller for air conditioning and industrial application. Appl. Therm. Eng. 58, 234-240
Mazzelli, F., Milazzo, A., 2015. Performance analysis of a supersonic ejector cycle working with R245fa. Int. J. Refrigeration 49, 79-92
Grazzini, G., Mazzelli, F., Milazzo, A., 2015. Constructal design of the mixing zone inside a supersonic ejector, Constructal Law & Second Law Conference 2015, Parma – Selected for publication (Download)
Milazzo, A., Mazzelli, F., 2016. Ejector Chillers for Solar Cooling, in: Renewable Energy in the Service of Mankind Vol II, Springer
2 – Development of a Steam Ejector Cycle, StEC:
Goal: The aim is to project and build a new supersonic ejector cycle working with steam. The main advantage is the fluid environmental safety, low costs and large availability which make it suitable for use in developing countries and integration with existing power and solar plants working with water.
Status of research and critical aspects:
Of importance in this research is the development of reliable numerical tools. In this respect, the prediction and analysis of condensation shocks is a complex but fundamental aspect. Furthermore, the description of the steam properties in metastable regions and the prediction of ice formation are critical for the correct operation of the system. Partner of this research is the Université Catholique de Louvain (Belgium) as well as the Ural Federal University (Russia). Exchange programs and International PhD degree are available.
Future research and thesis proposals:
a) Construction of a new Steam Ejector Cycle inside the Fisica Tecnica Laboratory. Project and sizing of the main components of the system as well as the measurement apparatus (MT). Design of the Two-Phase steam ejector by testing and comparison of various design techniques (BT, MT).
b) CFD analysis of the supersonic steam ejector. Literature research on the modelling of condensation shocks and prediction of ice formation (BT). Extension of the steam property libraries inside the meta-stable region (MT). CFD analysis of various ejector profiles (BT, MT).
Relevant publications (in order of appearance):
Grazzini, G., Rocchetti, A., 2002. Numerical optimisation of a two-stage ejector refrigeration plant, International Journal of Refrigeration 25, 621-633.
Grazzini G., Rocchetti A., 2008. Influence of the objective function on the optimisation of a steam ejector cycle, International Journal of Refrigeration 31, 510-515
Grazzini, G., Milazzo, A., Piazzini, S., 2011. Prediction of condensation in steam ejector for a refrigeration system, International Journal of Refrigeration 34, 1641-1648.
Milazzo, A., Rocchetti, A., Eames, I.W., 2014. Theoretical and experimental activity on Ejector Refrigeration. Energy Procedia, 45, 1245 – 1254
Milazzo, A., Rocchetti, A., 2015. Modelling of ejector chillers with steam and other working fluids. International Journal of Refrigeration, 57, 277-287
3 – Development of an Ejector Expansion Cycles, EEC
Goal: The recover of expansion losses inside conventional refrigeration systems can lead to COP increase of the order of 5 to 20% depending on the specific application and refrigerant. This may produce a substantial impact if applied on a worldwide scale. The aim of this research is to exploit the simplicity and reliability of supersonic ejector to replace the expansion valve without recurring to complex rotary and turbo-machinery solutions. Possible partners on this research subject may be Dorin Compressori (Firenze), Prof. Ferrara research group (Unifi), Université Catholique de Louvain (Belgium).
Status of research and critical aspects:
Currently the research is still at a preliminary explorative phase
Future research and thesis proposals:
a) Experimental activity on a CO2 trans-critical compression Cycle. Literature research on design procedures for the ejector (BT). Design, construction and tests of the supersonic flashing ejector (MT).
b) CFD analysis of the two-phase flashing flow inside the ejector. Literature research on the physics and models of the high speed cavitation and related fields like supersonic propulsion (BT, MT). Development of new numerical procedure by means of open source software, like OpenFoam or dedicated software from aerospace research (MT, DT).
For more information contact
Ing. Adriano Milazzo (adriano.milazzo@unifi.it)
Ing. Federico Mazzelli (federico.mazzelli@unifi.it)
Ultimo aggiornamento
15.04.2021