Characterization of nanofluids formed by fumed Al 2 O 3 in water for geothermal applications Sergio Bobbo, Laura Colla, Antonella Barizza, Stefano Rossi, Laura Fedele Istituto per le Tecnologie della Costruzione Consiglio Nazionale delle Ricerche, Italy July 11 -14, 2016
Outline • Background • Experimental apparatus and procedure • Experimental results • Conclusions 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 2
European Project Cheap-GSHPs The present work developed in the frame of the EU Project CHeap and Efficient APplication of reliable Ground Source Heat exchangers and PumpS (Cheap-GSHPs), funded by the European Union’s Horizon 2020 Research and Innovation Programme. It started in 2015 and will last for four years. Basic idea to substantially reduce the total cost of ownership (investment and operating costs), increase the safety of shallow geothermal systems during installation and operation and increase the awareness of this technology throughout Europe. 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 3
European Project Cheap-GSHPs A multidisciplinary and complementary consortium, composed by specialists in different disciplines (physics, climatology, chemistry, mechanics, engineering, architecture, drilling and GSHE technology) will work on the project. The proposal will focus on • the development of more efficient and safe shallow geothermal systems; • the reduction of the installation costs. • Firstly, improving an existing, innovative vertical borehole installation technology and the design of coaxial steel GSHE • Secondly, newly designed basket type GSHE’s with novel installation methodologies will be developed. The proposal will develop a decision support system (DSS) covering geological, economic and technological aspects. 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 4
European Project Cheap-GSHPs To reduce the total cost of shallow geothermal systems by 20-30 %, the project will improve actual drilling/installation technologies and designs of Ground Source Heat Exchangers (GSHEs) in combination with a holistic engineering approach to optimize the entire systems for building and district heating and cooling applications across the different underground and climate conditions existing within the EU. The safety and regulatory aspects will also be addressed. The developments will be demonstrated in six sites whilst the tools will be applied to several virtual demo cases. 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 5
Demo cases Real demo sites 1. Belfield House at University College Dublin, Ireland 2. Residential ecohouse, Putte bij Mechelen, Belgium 3. Universidad Politécnica de Valencia, Spain 4. Test Site Erlangen, Erlangen-Eltersdorf, Germany 5. Bioclimatic office building of CRES, Pikermi, Greece 6. Technical Museum of Zagreb, Croatia Virtual demo sites 1. Ballyroan Library, Dublin, Ireland 2. Residential Retrofit Glencree, Wicklow, Ireland 3. Complex of Santa Croce, Florence, Italy 4. Ca’ Rezzonico and Ca’ Lupelli, Venice, Italy 5. Manens-Tifs S.p.A. Headquarter, Padua, Italy 6. Grupo Ortiz Office Buildings, Vallecas – Madrid, Spain 7. Historical building, Bucharest, Romania 8. Historical Museum, Sarajevo, Bosnia and Herzegovina 9. The Serbian Orthodox Bođani Monastery, Bodjani, Serbia 10. Office building of Brogeda-Chiasso, Switzerland 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 6
Alternative secondary fluids In this frame, the efficiency of the system heat pump/GSHE will be an important task analyses of possible alternative secondary fluids Nanofluids, i.e . suspensions of nanometric solid particles in liquids proposed, due to their thermal, rheological and tribological properties • In particular, in the geothermal field, some nanofluids considered as possible thermal vectors, promising high heat transfer efficiency and better performance. Recently, a project, called Improve the heat transfer “Improving the Efficiency of Fumed alumina (Al 2 O 3 ) in and the overall efficiency of Geothermal Heat Pumps”, water or water and the geothermal heat pumps funded by the U.S. propylene glycol mixtures (GHPs) systems Environmental Protection Agency's Small Business Innovation Research Program 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 7
Fumed Al 2 O 3 in H 2 O Amongst others, first tests have been performed Two different commercial suspensions Fumed Al 2 O 3 nanoparticles in H 2 O concentrations 30% or 40% Then diluted at 3 wt% and 5 wt% • Stability and thermal conductivity carefully characterized • Dynamic viscosity analysed in order to evaluate the nanofluids performance as geothermal fluid • Mouromtseff numbers (Mo) considered to estimate the thermal effectiveness of the these nanofluids compared with water 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 8
Stability characterization A Zetasizer Nano ZS (Malvern), based on the Dynamic Light Scattering (DLS), used to analyse the average dimension of the nanoparticles in solution. 136 nm Zeta potential 149 nm 49.6 mV for 30 wt% 47.5 mV for 40 wt% STABLE FLUIDS 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 9
Stability characterization STABLE FLUIDS 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 10
Thermal Conductivity Thermal conductivity measured at ambient pressure and between 283 K and 323 K by means of a TPS 2500 S (Hot Disk) declared instrument accuracy 5% tests performed on water within 1% 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 11
Thermal Conductivity 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 12
Dynamic Viscosity Some preliminary viscosity measurements performed between 303 K and 323 K at atmospheric pressure for the suspensions W440 at 40 wt% and W630 at 30 wt%. A rotational rheometer with a plate-cone geometry (AR-G2 rheometer TA Instruments) employed. declared instrument accuracy 5% tests performed on water within 2% 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 13
Dynamic Viscosity 40 wt% 30 wt% m m T T m exp / m water m exp / m water (K) (Pa·s) (K) (Pa·s) 313 0.01130 17.3 313 0.06717 102.9 323 0.00965 17.6 323 0.07656 140.0 3 wt% 5 wt% m m T T m exp / m water m exp / m water (K) (Pa·s) (K) (Pa·s) 303 0.000839 1.05 303 0.000915 1.15 323 0.000571 1.04 323 0.000656 1.20 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 14
Thermal conductivity 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 15
Mouromtseff number A theoretical evaluation of the heat transfer behaviour performed by calculating the Mouromtseff number, applying the general expression, valid for single phase forced convection 𝑁𝑝 = 𝑏 𝜍 𝑐 𝑑 𝑞 𝑑 𝜈 𝑒 For a fluid flowing in a fixed geometry at given velocity, the larger the Mouromtseff number the larger will be the heat transfer rate. For nanofluids 𝜍 𝑜𝑔 = · 𝜍 𝑜𝑞 + 1 − · 𝜍 𝑐𝑔 𝜍 𝑜𝑔 · 𝑑 𝑞 𝑜𝑔 = · 𝜍 𝑜𝑞 · 𝑑 𝑞 𝑜𝑞 + 1 − · 𝜍 𝑐𝑔 · 𝑑 𝑞 𝑐𝑔 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 16
Mouromtseff number In case of internal laminar regime, the ratio is given simply by: = 𝑜𝑔 𝑁𝑝 𝑜𝑔 𝑥 𝑁𝑝 𝑥 In case of internal turbulent flow, the Mo number is given by the following expression: 𝑁𝑝 = 0.67 𝜍 0.8 𝑑 𝑞 0.88 𝜈 0.47 Mo nf /Mo w 3 wt% 5 wt% T Laminar Turbulent Laminar Turbulent (K) flow flow flow flow 303 1.04 1.01 1.05 0.99 323 1.08 1.05 1.09 0.99 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 17
Conclusions • Under the European Project Cheap-GSHPs, several nanofluids will be tested as possible secondary fluids in the heat pump-geothermal probe system. • Here, two different commercial suspensions of fumed Al 2 O 3 nanoparticles in H 2 O were studied (at 30% or 40%). • The less penalising in terms of viscosity (40%) was considered for additional dilution (3% and 5%). • Stability, thermal conductivity and dynamic viscosity were analysed. • Mouromtseff numbers for nanofluids at 3% and 5% were calculated. • 3 wt% seems to have some possibility to be applied, at least at temperatures higher than 40-50°C. • Additional measurements, in particular viscosity and heat transfer coefficient, are necessary and will be performed in the near future. 16 th International Refrigeration and Air Conditioning Conference at Purdue July 14, 2016 18
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