**Commenced**in January 2007

**Frequency:**Monthly

**Edition:**International

**Paper Count:**30761

##### Evaluation of Heat Transfer and Entropy Generation by Al2O3-Water Nanofluid

**Authors:**
Houda Jalali,
Hassan Abbassi

**Abstract:**

In this numerical work, natural convection and entropy generation of Al_{2}O_{3}–water nanofluid in square cavity have been studied. A two-dimensional steady laminar natural convection in a differentially heated square cavity of length L, filled with a nanofluid is investigated numerically. The horizontal walls are considered adiabatic. Vertical walls corresponding to x=0 and x=L are respectively maintained at hot temperature, T_{h }and cold temperature, T_{c}. The resolution is performed by the CFD code "FLUENT" in combination with GAMBIT as mesh generator. These simulations are performed by maintaining the Rayleigh numbers varied as 10^{3} ≤ Ra ≤ 10^{6}, while the solid volume fraction varied from 1% to 5%, the particle size is fixed at dp=33 nm and a range of the temperature from 20 to 70 °C. We used models of thermophysical nanofluids properties based on experimental measurements for studying the effect of adding solid particle into water in natural convection heat transfer and entropy generation of nanofluid. Such as models of thermal conductivity and dynamic viscosity which are dependent on solid volume fraction, particle size and temperature. The average Nusselt number is calculated at the hot wall of the cavity in a different solid volume fraction. The most important results is that at low temperatures (less than 40 °C), the addition of nanosolids Al_{2}O_{3} into water leads to a decrease in heat transfer and entropy generation instead of the expected increase, whereas at high temperature, heat transfer and entropy generation increase with the addition of nanosolids. This behavior is due to the contradictory effects of viscosity and thermal conductivity of the nanofluid. These effects are discussed in this work.

**Keywords:**
Heat Transfer,
Nanofluid,
natural convection,
entropy generation

**Digital Object Identifier (DOI):**
doi.org/10.5281/zenodo.1128143

**References:**

[1] Choi SUS, Eastman JA (1995) “Enhancing thermal conductivity of fluids with nanoparticles,” IntMechEng Cong Exp, ASME, FED 231/MD 66, pp. 99–105

[2] Nader Ben-Cheikh, Ali J. Chamkha, Brahim Ben-Beyaand Taieb Lili (2013), “Natural Convection of Water-Based Nanofluids in a Square Enclosure with Non-Uniform Heating of the Bottom Wall,” Journal of Modern Physics, 4, pp. 147-159.

[3] Bouhalleb M. and Abbassi H. (2014) “Natural convection of nanofluids in enclosures with low aspect ratios,” Int J Hydrogen Energ 39, pp. 15275-15286.

[4] Oztop F. H and Abu-Nada E (2008) “Numerical study of natural convection in partially heated rectangular enclosures ﬁlled with nanoﬂuids,” Int J Heat Fluid Fl 29, pp. 1326–1336.

[5] Ghasemi B. and Aminossadati M. S. (2009) “Natural convection heat transfer in an inclined enclosure filled with a water-Cu Onanofluid,” Numer Heat Tr A-Appl 55, pp. 807-823.

[6] Arifin N. M, Nazar Rand PoP I. (2011) “Non-isobaric Marangoni boundary layer flow for Cu, Al2O3 and TiO2 nanoparticles in a water based fluid,” Meccanica 46, pp. 833–843.

[7] Nasrin R, Alim M. A and Chamkha A. J (2012) “Buoyancy-driven heat transfer of water–Al2O3nanofluid in a closed chamber: Effects of solid volume fraction, Prandtl number and aspect ratio,” Int J Heat Mass Tran 55, pp. 7355–7365.

[8] Saleh H, Roslan Rand Hashim I. (2011) “Natural convection heat transfer in a nanofluid-filled trapezoidal enclosure,” International Journal of Heat and Mass Transfer, 54, pp. 194–201.

[9] Santra AK, Sen S and Chakraborty N. (2008), “Study of heat transfer characteristics of copper-water nanofluid in a differentially heated square cavity with different viscosity models,” J Enhanced Heat Transf; 15(4), pp. 273–287.

[10] GH.R. Kefayati, S.F. Hosseinizadeh, M. Gorji and H. Sajjadi (2012) “Lattice Boltzmann simulation of natural convection in an open enclosure subjugated to water/copper nanofluid,” International Journal of Thermal Sciences 52, pp. 91-101.

[11] G.A. Sheikhzadeh et al. (2011), “Natural convection of Cu–water nanofluid in a cavity with partially active side walls,” European Journal of Mechanics B/Fluids 30, pp. 166–176.

[12] M. Magherbi, H. Abbassi and A. Ben Brahim (2003), “Entropy generation at the onset of natural convection,” Int. J. Heat Mass Tran46, pp. 3441–3450.

[13] G.G. Ilis, M. Mobedi and B. Sunden (2008), “Effect of aspect ratio on entropy generation in a rectangular cavity with differentially heated vertical walls,” Int. Commun. Heat Mass Trans35, pp. 696–703.

[14] Rejane De C. Oliveski, Mario H. Macagnan, Jacqueline B. Copetti (2009) “Entropy generation and natural convection in rectangular cavities,” ApplThermEng 29, pp. 1417–1425.

[15] O. Mahian, A. Kianifar, C. Kleinstreuer, M.A. Al-Nimr, I. Pop, A.Z. Sahinand S. Wongwises (2013), “A review of entropy generation in nanofluid flow,” Int. J. Heat Mass Tran 65, pp. 514–532.

[16] H.F. Oztop and K. Al-Salem “A review on entropy generation in natural and mixed convection heat transfer for energy systems” Renewable and Sustainable Energy Reviews 16 (2012), pp. 911– 920.

[17] F. Selimefendigil and H.F. Öztop (2015) “Natural convection and entropy generation of nanofluid filled cavity having different shaped obstacles under the influence of magnetic field and internal heat generation” Journal of the Taiwan Institute of Chemical Engineers 56, pp. 42–56.

[18] Ching-Chang Cho (2014), “Heat transfer and entropy generation of natural convection in nanofluid-filled square cavity with partially-heated wavy surface,” Int. J. Heat Mass Tran 77, pp. 818–827.

[19] H. Saleh, R. Roslan and I. Hashim (2011) “Natural convection heat transfer in a nanofluid-filled trapezoidal enclosure,” International Communications in Heat and Mass Transfer 38, pp. 972–983.

[20] Nguyen C, Desgranges F, Roy G, Galanis N, Mare T, Boucher Sand Mintsa A. H (2007) “Temperature and particle-size dependent viscosity data for water-based nanofluids – hysteresis phenomenon,” Int J Heat Fluid Fl 28, pp. 1492–1506.

[21] Pastoriza G. M. J, Casanova C, Legido J. LandPiñeiro M. M (2011) “CuO in water nanofluid: influence of particle size and polydispersity on volumetric behaviour and viscosity,” Fluid Phase Equilibr 300, pp. 188–196.

[22] Kulkarni D. P, Das D. K and Vajjha R.S (2009) “Application of nanofluids in heating buildings and reducing pollution,” ApplEnerg 86, pp. 2566–2573.

[23] Teng T, Hung Y. H, Teng T. C, Mo H. E and Hsu H. G (2010) “The effect of alumina/water nanofluid particle size on thermal conductivity,” ApplThermEng30, pp. 2213-2218.

[24] Li H, He Y, Hu Y, Jiang B and Huang Y (2015) “Thermophysical and natural convection characteristics of ethylene glycol and water mixture based ZnO nanofluids,” Int J Heat Mass Tran 91, pp. 385–389.

[25] Brinkman H. C (1952) “The viscosity of concentrated suspensions and solution,” JChemPhys 20, pp. 571-581.

[26] Batchelor G (1977) “The effect of Brownian motion on the bulk stress in a suspension of spherical particles,” J Fluid Mech 83, pp. 97–117.

[27] Abu-Nada E, Masoud Z, Oztop H. F and Campo A (2010) “Effect of nanofluid variable properties on natural convection in enclosures,” Int J Therm49, pp. 479–491.

[28] Khanafer K and Vafai K (2011) “A critical synthesis of thermophysical characteristics of nanofluids,” Int J Heat Mass Tran 54:4410-4428.

[29] A. Bejan, “Entropy generation through heat and fluid flow”, Wiley, NewYork,1982.

[30] Lai F, Yang Y (2011) “Lattice Boltzmann simulation of natural convection heat transfer of Al2O3/water nanofluids in a square enclosure,” Int J ThermSci 50, pp. 1930-1941.

[31] Kahveci K (2010) “Buoyancy driven heat transfer of nanofluids in a tilted enclosure,” J Heat Transf 132, pp. 062501-7.