Effect of Nanoparticles Aspect Ratio on the Two Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of Refrigerant and Nanolubricants Mixtures in a 9.5 mm Micro-fin Tube. Paper # 2098 author: Pratik S. Deokar Auburn University pratik.deokar@auburn.edu co-author: Lorenzo Cremaschi Auburn University lorenzo.cremaschi@auburn.edu
I. Objectives a) To learn the effects of nanoparticles shape, concentration, heat flux, and mass flux on heat transfer coefficient (α) and pressure drop (ΔP) during two-phase flow boiling of refrigerant R410A and POE mixture in 9.5 mm micro-fin tube evaporator. b) To provide new data of two-phase flow boiling heat transfer coefficient and pressure drop for model development and validation. c) Verify the hypothesis that the heat transfer coefficient and pressure drop are not proportional to the nanolubricant thermal conductivity and viscosity. 2 / 16
II. Introduction needs lubricant (e.g. POE, Compressor Nanoparticle Motivation suspension Mineral oil) in lubricants Vapor compression systems Velocity profile Nanoparticles in Heat exchangers Nanolubricants few studies and intriguing results small portion of oil circulates up to 50% k with the refrigerant Are there shear induced opportunities motion to transform a lubricant (a contaminant) 29 up to 63% heat transfer. Work good on system with up to 26% in in an effective mean for oil is energy a contaminant, savings may reduce HT and increase ΔP up to 101% during two phase flow boiling. The authors reported negligible effect on the two-phase pressure drops energy efficiency promoter? 3 / 16
III. Experimental Facility O.D. α O.D. (360/N) t t Micro-fin tube Adapted from: Thome, J. R. (2004) Engineering data book III. Wolverine Tube Inc., Chapter 11 Micro-fin tube dimensions Outer diameter O.D. = 9.53 mm Wall thickness t = 0.3 mm fin height t = 0.2 mm Number of fins N = 60 Helical angle α = 18. 4 / 16
III. Experimental Facility 5 / 16
III. Experimental Facility Tested conditions Nanolubricants Lubricant [ (wt. %)] Heat flux (kw/m 2 ) (%) Mass flux (kg/m 2 -s) Heat flux - () 12 kw/m 12, 15 2 0.5, 15 1, 3kW/m 2 183, 255, 350, 425 γ-al 2 O 3 in POE [ 2 wt.%, 12 10 wt.%, and 3 20 wt.% 255, ] 350 POE Alumina (γ-al2o3) nanoparticles: Mass flux ( ) 180 - Spherical kg/m 2 3 -s 250 kg/m 2 255 15 0.5, 1, 3 -s 350 γ-al 2 O 3 [2 wt. %, 10 wt. %] in - 40 nm 12 nom. particles diameter 1, 3 350 POE 350 kg/m 2 -s 1, 425 3 kg/m 2 -s 183, 255, 425 12 γ-al 2 O 3 [20 wt. %] in POE 3 350 Oil mass fraction ( ZnO ) in 15 POE 0.5% [ 20 wt.% 1, 1% 3] 3% 350 12 1, 3 183, 255, 350, 425 ZnO [20 wt. %] in POE ZnO nanoparticles: 15 0.5, 1, 3 350 - elongated hexagonal wurtzite shape - 20 to 40 nm nom. particles diameter Refrigerant reference temperature, = 3.5±0.9 C 6 / 16
IV. Data reduction Derived Variables Oil mass fraction ( ) Nanoparticle mass concentration (" #$# ) Refrigerant reference temperature ( ) (Sawant et al., 2007) = + = $% $% + =& '( *+ +,. +- Measured Variables Accuracy Surface temperature ( ) ± 0.1 C Pressure ( ) ± 1.0 kpa Refrigerant quality () ± 1.8% Mass flux ( ) ± 0.1% Heat flux () ± 0.53% Details to control and measure these parameters are described in authors previous work (Smith & Cremaschi, 2014) 7 / 16
IV. Data reduction Figure of Merits Accuracy Test Repeatability Flow Boiling Heat Transfer Coefficient (/) = " / 6 and 6 ~ representative baselines at no ± 10.7% oil, ( ) ± 0.5 kw/m 2 -K (=0.8) and at same mass flux ( ), heat flux (), and refrigerant quality ( ), as that of / and Pressure Drop across ± 1 kpa (0.3<<0.6) =Δ ± 0.07 kpa the micro-fin tube ± 2 kpa (=0.8) ± 0.13 kw/m 2 -K (0.3<<0.6) Heat Transfer Factor (4) = / / 6 100 ± 14.5% / 6 ± 5% (0.3<<0.6) ± 18% (=0.8) Pressure Drop Factor (:) = 6 100 ± 1.0% ± 9.5% (0.3<<0.6) 6 ± 16% (=0.8) 8 / 16
F. Results and Discussion Nanolubricant Thermal Conductivity Flag NP conc NP (wt.%) POE - γ-al 2 O 3 2 γ-al 2 O 3 10 γ-al 2 O 3 20 ZnO 10 ZnO 20 9 / 16
V. Results and Discussion # Flag NP NP conc OMF mass flux heat flux (wt. %) (%) (kg/m 2 -s) (kw/m 2 ) O - - 3 250 12 P γ-al 2 O 3 20 3 250 12 Q ZnO 20 3 250 12 10 / 16
V. Results and Discussion +30% ~ 0% # Flag Flag NP NP NP NP conc conc (wt. (wt. %) %) OMF OMF mass mass flux flux heat heat flux flux (%) (%) (kg/m (kg/m 2 2 -s) -s) (kw/m (kw/m 2 2 ) ) A - - - - 3 350 350 12 12 B γ-al γ-al 2 2 O 3 3 2 1 350 350 12 12 C γ-al γ-al 2 O 2 3 2 3 3 350 350 12 12 D γ-al γ-al 2 2 O 3 3 10 10 1 350 350 12 12 E γ-al γ-al 2 O 2 3 10 3 10 3 350 350 12 12 F γ-al γ-al 2 2 O 3 3 20 20 3 350 350 12 12-30% ~ 5% 11 / 16
V. Results and Discussion => < = 0.35 < = 0.52 < = 0.78 # NP NP conc OMF heat flux (wt. %) (%) (kw/m 2 ) V POE - 3 12 W γ-al 2 O 3 20 3 12 X ZnO 20 3 12 Y POE - 3 15 Z γ-al 2 O 3 20 3 15 Nanoparticles spinning & shear induced motion? 12 / 16
VI. Conclusions The effect on the heat transfer coefficient was more marked, (and more important measurable!) Alumina, γ-al 2 O 3, based nanolubricants provided an enhancement of the heat transfer coefficients up to 40% with no or very small penalization of the pressure drop. ZnO based nanolubricants with high thermal conductivity had lower heat transfer coefficient than POE or γ-al 2 O 3 based nanolubricants. Proves that thermal conductivity was not the main property responsible for the heat transfer coefficient intensification. ZnO based nanolubricants had significantly higher pressure drop when compared to POE oil and γ-al 2 O 3 nanolubricants. 13 / 16
Acknowledgements I would like to acknowledge and thank Thiam Wong paper co-author (MS, Oklahoma State University, USA) Gennaro Criscuolo paper co-author (MS, Milan Polytechnic Institute, Italy) Andrea A. M. Bigi (Ph.D student, Auburn University, USA) Dr. Harry W. Sarkas and Nanophase Technologies Corporation The Chemours Company Dr. Thomas J Leck, TJLeck Consulting, LLC ASHRAE (Irg-021) 14 / 16
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Questions? Pratik S. Deokar pratik.deokar@auburn.edu 16 / 16