Free Convection Cooling in Modified L-Shape Enclosures Using Copper Water Nanofluid

Majid Saidi, Gholamreza KarimiDepartment of Chemical Engineering, Shiraz University, Iran

Sayed Rasul1015102008

Journal of Energy, 2014

IntroductionThe study examines the effect of various operating and design parameters such as

Rayleigh number, geometry and the volume fraction of copper nanoparticles on the free convection characteristics

within an L-shaped enclosure filled with nanofluids. The enclosure geometry was modified by insertion of a few round pins and by inclination to study their effects on

the rate of heat transfer.

ObjectiveThe aim of the present study is

investigation of free convection cooling in an L-shape enclosure filled with copper-

water nanofluid. The effects of the volume fraction of the Cu nanoparticles, Rayleigh

number and the aspect ratio of the L-shaped enclosure on the heat transfer coefficient, temperature and velocity

profiles are studied.

Physical Model

Mathematical Model

Non-Dimensional Form

Boundary Condition

Aspect Ratio

Results- IsothermsAR=0.2ᵠ=0.03

AR=0.2ᵠ=0.01

AR=0.2ᵠ=0.03

AR=0.2ᵠ=0.1

AR=0.4ᵠ=0.03

AR=0.4ᵠ=0.03

AR=0.4ᵠ=0.03

AR=0.2ᵠ=0.03

Velocity Profiles

AR=0.2ᵠ=0

AR=0.2ᵠ=0.03

AR=0.2ᵠ=0.1

AR=0.2ᵠ=0.06

AR=0.4ᵠ=0.06

AR=0.4ᵠ=0.03

AR=0.4ᵠ=0.1

Heat Transfer Coefficient

AR=0.2ᵠ=0.03

AR=0.2ᵠ=0.1

AR=0.2ᵠ=0.06

AR=0.2ᵠ=0.1

AR=0.4ᵠ=0.1

Performance analysis of the modified L-shape enclosureIsotherms

AR=0.4ᵠ=0.1

AR=0.4, ᵠ=0.1Velocity Profile

AR=0.4ᵠ=0.1

Heat transfer coefficient

AR=0.4ᵠ=0.1

Heat transfer coefficient at Inclination

45˚ 135˚

225˚ 315˚

Conclusion• Numerical results indicate that the presence of Cu

nanoparticles in pure water can significantly enhance heat transfer coefficient.

• At low Rayleigh numbers, the fluid in the horizontal section of the enclosure is almost stagnant and the dominant heat transfer mechanism is conduction.

• Transition from pure conduction to free convection occurs at Rayleigh number ranging from 105 to 106.

• Decreasing Rayleigh number and increasing aspect ratio can enhance the heat transfer coefficient in the enclosure.

• The results have revealed that the application of cylindrical pins inside the enclosure can enhance heat transfer rate.

• The study of the effect of inclination angle has shown that there exists an optimum angle (ω=225˚) for which the heat transfer coefficient is maximum.

Thanks to all for your kind

Attention