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Presented by: Mohamed Hamda
M.A.Sc Candidate Supervisor: Dr. M. Hamed
On The Effect of Initial Surface Condition on Pool Boiling of
Nanofluids
Outline
• Pool Boiling.
• Nanofluids.
• Literature review.
• Recent Research in TPL.
• Current research.
• Conclusion.
• Future work.
• Publications.
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Why Pool Boiling?
• Free Convection - Water: 20 - 100 (W/(m2K))
• Forced Convection - Water: 50 - 10.000 (W/(m2K))
• Boiling Water : 3.000 - 100.000 (W/(m2K))
Boiling Heat transfer coefficients are the highest among different heat convection mechanisms.
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Pool Boiling Curve
7 * Heat and Mass Transfer: Fundamentals & Applications,Fourth Edition, Yunus A. Cengel
Thermal conductivity of different materials
Liquids Metals
k - W/(m.K)
Steel, Carbon 1% 43
Aluminium 205
Copper 401
k - W/(m.K)
Alcohol 0.17
Engine Oil 0.15
Water 0.58
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• The thermal conductivity of liquids is three orders of magnitude less than of metals.
• The idea is to increase the thermal conductivity of liquids.
How can we do that?
• Powder of metal has particles of certain size (10 ~ 100 nm) dispersed into liquid.
• This mixture is now called Nanofluid or Nanoparticles suspension.
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Is Nanofluid a novel idea?
• Maxwell model (1881) – Effective thermal conductivity increases with the
volume fraction of the solid particles as well as the ratio of the surface area to volume of the particle.
– Confined to millimeter-sized particles.
– Not practical (severe clogging problems).
• Lee, Choi and et al. (1999) – Reported 20% increase in the thermal conductivity of
CuO nanoparticles (10 nm) suspended in ethylene glycol.
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Literature Review
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* O. Ahmed, M.S. Hamed, Experimental investigation of the effect of particle deposition on pool boiling of nanofluids
Recent Research in TPL
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Researcher (Year)
Experiment Type
Ra (nm) Concentration
% Nanofluid Material
Particle size
pH Remarks
Osama Ahmed (2011)
Pool Boiling 100 ~ 150 50
0.01 0.1 0.5
Al2O3
40 ~ 50 nm
5 and 6.5
Enhancement &
deterioration
Ahmed Abd El-
hady (2013)
Pool and Jet Impingement
Boiling
20, 80 and 420
0.005 0.01
Al2O3
CuO 10 nm 50 nm
6.5
Enhancement &
deterioration
Findings from Literature Review
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• Contradicting results!
• Heat transfer deterioration is always noticed with nanoparticles deposition on heated surface.
• Most enhancement results were reported for heated wires.
• Deterioration is more likely to happen with flat or horizontal heated surfaces.
• Heater geometry affects Nano fluid heat transfer.
What is new in this research?
Old technique
• Polishing by emery paper.
• Inconsistent surface texture.
New technique
• High precision machining.
• Consistent surface texture.
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1. Surface Preparation
What is new in this research?
2. Using surfactants to enhance the stability of nanofluids.
• Surfactant is a compound that lowers the surface tension.
• Sodium dodecylbenzenesulfonate (SDBS).
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Nanofluid Preparation
• Deionized water.
• Al2O3 , Particle size =40 nm ,(0.05%wt)
• Sodium dodecylbenzenesulfonate “SDBS” (0.1%wt).
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1. Li et al, Evaluation on dispersion behavior of the aqueous copper nano-suspensions.
2. Wang et al, Influence of pH and SDBS on the Stability and Thermal Conductivity of Nanofluids.
Experimental Setup
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q”
Boiling curves on Ra=60 nm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14
q”
MW
/m2
ΔT
Water Before
NF,SDBS(0.1%)
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Boiling curves on Ra=60 nm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14
q”
MW
/m2
ΔT
Water Before
NF,SDBS(0.1%)
NF,SDBS(1.0%)
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Boiling curves on Ra=60 nm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14
q”
MW
/m2
ΔT
Water Before
NF,SDBS(0.1%)
NF,SDBS(1.0%)
Water After
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Boiling curves on Ra=60 nm
• Heat transfer enhancement in natural convection regime and deterioration in nucleate boiling regime.
• Nanoparticles deposition has been noticed. • ONB has been delayed using Nanofluids. • Increasing SDBS concentration has effectively
eliminated deposition and thus heat transfer enhancement is achieved.
• No deposition was confirmed by boiling pure water on the same surface from the Nanofluid experiment.
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Water boiling curves
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14 16 18 20
q”
MW
/m2
ΔT
Ra=6 nm
Ra=60 nm
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Boiling curves on R=6 nm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14 16 18 20
q”
MW
/m2
ΔT
Water Before
NF,SDBS(0.1%)
NF,SDBS(0.0%)
Water After
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Boiling curves on R=6 nm
• Heat transfer is affected by the surface roughness.
• SDBS accelerates Onset of Nucleate Boiling(ONB).
• Heat transfer enhancement is achieved with and without adding SDBS.
• No deposition is noticed.
• Nanoparticle size is larger than surface roughness.
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Boiling at 0.2 MW/m2
Nanofluid Water
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Boiling at 0.4 MW/m2
Nanofluid Water
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Boiling at Critical Heat Flux
Nanofluid Water
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Conclusions
• Modern manufacturing technologies introduced new types of fluids.
• Nanofluid heat transfer is greatly affected by initial surface conditions.
• Surfactants enhance stability of Nanofluids.
• Heat transfer deterioration results from Nanoparticles deposition.
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Future Work
• Develop a matrix to quantify the contribution of each component used in Nanofluid preparation.
• Test the performance of Nanofluid on very rough surface.
• Understanding the Nanofluid interactions with active nucleation sites using engineered Nano-indentation.
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Publication
• N.A. Almalki, M. Hamda, M. S. Hamed, On The Effect of Initial Surface Condition on Pool Boiling of Nanofluids,9th International Conference on Boiling and Condensation Heat Transfer, April 26-30, 2015 – Boulder, Colorado. (Extended Abstract Accepted)
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Acknowledgement
• Alex Yip • M. Tauhiduzzaman
