IT-FR seminar on nanotechnologies and advanced materials

Transcription

1 Marengo Research Group Thermal Physics Laboratory IT-FR seminar on nanotechnologies and advanced materials Grenoble, October 21 st 22 nd, 2013 ILEANA MALAVASI Engineering Department University of Bergamo Dalmine, Italy

2 2 Outlook Issues Idea Solutions

3 3 Issues

4 Issues (1) 4 EUROPE S GOALS: securing Europe s energy supplies; ensuring that energy prices do not make Europe less competitive; protecting the environment and combating climate change; improving energy grids. SAVING ENERGY ENERGY EFFICIENCY

5 Issues (2) 5 WHY SAVING ENERGY AND ENERGY EFFICIENCY ARE IMPORTANT? prevent CO 2 emissions => greenhouse issue; less dependent on energy imports; stimulating growth; Insulating homes, installing new energysaving equipment, refurbishing buildings, carrying out audits: they all create economic activity. Two million jobs could be created by 2020 if Europe s energy-saving objectives are achieved. Sustainable, secure and affordable energy for Europeans, European Union,

6 Issues (3) 6 Icing in aeronautics a serious problem leading to: excessive fuel usage due to increased drag excessive energy consumption to combat icing required power: order of kw/m 2, 1-2% total engine power aircraft crashes or engine damage 12 th Feb 2009: 49 people died in Buffalo. 1 st June 2009 : Air France Flight 447 from Rio de Janeiro to Paris, that crashed into the Atlantic Ocean on, killing all 216 passengers and 12 crew members. Icing probably caused failure of Pitot tube: incorrect speed measurement automatic speed reduction stall altitude loss Ice on the wing of the NASA Twin Otter research aircraft.

7 Issues (4) 7 Icing on Wind-turbine risks for safety (severance ice fragments) may be so high that some systems need to be stopped during all icing events; loss of productivity can be estimated between 5% and 10% in cold climate regions on annual basis (for a 50 turbine wind farm, with power rating of 100MW, stoppage due to icing costs up to 1.6M /yr);

8 Issues (5) 8 Ice formation on Heat pump evaporator In heating mode, the outdoor coil is an evaporator, while the indoor is a condenser. The outdoor unit. A simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor. When the outdoor radiator operates as evaporator, its surface is at low temperature when the outside air is cold (heating phase in the winter season). This involves the formation of ice on it, due to the presence of moisture in the outdoor air => reduction in the efficiency of heat exchange (the ice is insulating).

9 Issues (6) 9 Enhancement of the heat transfer rates in boiling phenomena at lower heat fluxes it requires hydrophobicity to promote nucleation at higher heat fluxes it requires hydrophilicity to maintain the liquid transport to the heated surface in the regime of slugs and columns A.M. Betz, J. Jenkins, C.-J. Kim, D. Attinger, Boiling heat transfer on superhydrophilic, superhydrophobic and superbiphilic surfaces, Int. J. Heat Mass Transf., vol 57, pp , Y. Takata, S. Hidaka, M. Kohno, Effect of surface wettability on pool boiling: enhancement by hydrophobic coating, Int. J. Air- Conditioning and Refrigeration, vol.20(1), , 2012.

10 10 Idea

11 Idea (1) 11 What is superhydrophobicity? LOTUS LEAF DUCK FEATHERS BUTTERFLY WINGS Photo: Ilaria Bernagozzi Water doesn t stick on surface, rolls away easily, allowing self cleaning

12 Idea (2) 12 IDEA: use SHS so that water rolls away before freezing PMMA (hydrophilic) D=2.8mm V=3.1m/s SHS-Teflon 1.1ms 2.1ms 3.2ms 8.5ms 13.7ms 1.1ms 9.5ms ms 21.1ms 25.7ms

13 Idea (3) 13 IDEA: use SHS and patterned surfaces at lower heat fluxes it is required hydrophobicity to promote nucleation Rioboo, R., Marengo, M., Dall'Olio, S., Voué, M., De Coninck, J. An Innovative Method to Control the Incipient Flow Boiling through Grafted Surfaces with Chemical Patterns, Langmuir, 25 (11), Bourdon, B., R. Rioboo, M. Marengo, E. Gosselin, J. De Coninck, "Influence of the wettability on the boiling onset", Langmuir, Vol. 28(2), pp , 2012

14 Idea (4) Superhydrophobic surfaces applications in saving energy Mitigation of ice formation (aerospace, offshore platforms, power lines, wind turbines). s/article/43489 Resistance to the growth of microorganisms (antifouling properties) => application as protective coatings on marine vessels, submarines and oil platforms. To repel water, dust, and dirt => easy-clean surfaces. Reduction of friction and pressure drops in pipes. Prevention of contamination and oxidation => corrosion and fouling en.wikipedia.org/wiki/ Freezing_rain Iced power lines threaten power outage after a powerful ice storm

15 15 Solutions

16 Solutions (1) 16 Marengo Research Group (MRG) is a multidisciplinary research and consulting group that works in the fields of thermofluidynamics, heat transfer, building energy, superhydrophobic surfaces and liquid interfaces. The group was established in 2007 at the Engineering Department of University of Bergamo.

17 Solutions (2) 17 Overview of our competences Thermal management Liquid interfaces and sprays Building physics Heat Pipes Drop impact Thermal plants Flow boiling Superhydrophobic surfaces Energy dynamic simulations Thermal control De-icing systems Energy saving

18 Solutions (3) Icing in aeronautics TECHNOLOGICAL DEVELOPMENT OF A PROTOTYPE FOR ICING MITIGATION SYSTEMS in collaboration with University of Alberta Ice on the wing of the NASA Twin Otter research aircraft. 18 Most interesting results: rough surfaces with high CA and low CAH can reduce ice adhesion; - application of superhydrophobic surface in the leading edge area entail a significant reduction of required heating power (approximately 80% compared to metallic sample) to avoid ice accretion and a significant reduction of runback ice. Example of ice accretion during IWC tests. Only the central part of the leading edge is heated. UNTREATED ALUMINUM SUPERHYDROPHOBIC COATING

19 Solutions (4) 19

20 20 Thank you for your attention! Contacts: Ing. Ileana Malavasi Via Galvani 2, Dalmine (BG) Italy