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Fluid containing nanometer-sized particles (i.e. nanoparticles) is known as nanofluid. Three different nanofluids flowing in a pipe with heat source at the inlet and sink in the walls are studied. The base fluid is water. 20 nm size nanoparticle Al2O3 is mixed with base fluid with volume concentrations of 0.1%, 0.2% and 0.5%. Simulation is done using ANSYS Workbench 17.1. The result shows correlation between concentration of nanoparticle and temperature gradient at the outlet of the pipe.

Nanofluids (nanoparticles fluid suspensions) [

Transfer of heat energy has become a major task in industrial processes [

In this study, three different nanofluids were studied inside a pipe with flow and heat transfer.

A situation is considered where fluid is flowing through a pipe. The pipe is connected with both source and sink. Then three different types of nanofluids are investigated in respect to their temperature distribution at the outlet. The base fluid is water, which has been investigated at first to compare the nanofluids results. Nanoparticle aluminum oxide is mixed with base fluid at volume concentrations (0.1%, 0.2%, and 0.5%) to create three different nanofluids. These liquid-solid nanofluids are treated as single fluid in Fluent using their representative thermal and physical properties. Experimental values [

At the beginning a situation following the Example 8-3 [

At the inlet fluid is flowing with a constant temperature. The pipe wall is always at 273.15 k temperature as according to Example 8-3 [

Property | Volume Concentration of Al_{2}O_{3} | ||
---|---|---|---|

0.1% Al_{2}O_{3} | 0.2% Al_{2}O_{3} | 0.5% Al_{2}O_{3} | |

Density ρ (kg/m^{3}) | 1038 | 1042 | 1060 |

Specific heat C_{p} (j/kg∙k) | 3200 | 2600 | 500 |

Thermal conductivity K (W/m∙k) | 0.6 | 0.615 | 0.65 |

Viscosity µ (kg/m∙s) | 0.0007 | 0.00068 | 0.0006 |

Continuity (Equation (1)), momentum (Equation (2)) and energy equations (Equation (3)) are solved to get result.

( ∂ ρ / ∂ t ) + ∇ ⋅ ( ρ V ) = 0 (1)

ρ ( ∂ V / ∂ t ) + ρ ( V ⋅ ∇ ) V = − ∇ ρ + ρ g + ∇ ⋅ τ i j (2)

( ∂ / ∂ t ) ∫ e * ρ d ∀ + ∫ ( u ^ + P / ρ + V 2 / 2 + g z ) ρ V ⋅ n ^ d A = Q ˙ n e t i n + W ˙ n e t i n (3)

After reproducing, the result of Example 8-3, the properties of the fluid are changed to mimic nanofluids. Temperature gradient at the outlet of the pipe is studied and trend is identified with the volume concentrations of nano particles in the base fluid.

Considered geometry is two-dimensional planar. For simplicity, 3D geometry is avoided, which is a consideration for future cases. 2500 × 15 mesh grid is used for this simulation. Simulation parameters are provided in

The flow is calculated laminar for every case studied in this paper. Reynolds number is less than critical Reynolds number 2300 in all cases considered.

In order to avoid inaccurate result due to poor mesh density, different element numbers were used to analyze the mesh sensitivity. Three different element numbers (i.e., 1250, 3750, 37,500) have been used to compare temperature at the outlet of the pipe. It is found the element number converges after 3750 (

Hagen-Poiseuille equation (Equation (4)) is used to compare the pressure drop along the pipe.

Δ p = 8 μ L Q π R 4 (4)

Solver-Type | Pressure based |
---|---|

Solver-Time | Steady |

Energy Model | On |

Viscous Model | Laminar |

Wall | Stationary |

Constant temperature | |

Solution method | Scheme: SIMPLE |

Energy: 2^{nd} order upwind | |

Momentum: 2^{nd} order upwind |

Here, µ (for water) = 0.001003 kg/m∙s, L (pipe length) = 200 m, v (fluid velocity) = 2 m/s, R (pipe radius) = 0.15 m, Q (=area of pipe cross section × v) represents discharge rate. The pressure drop along the pipe (Δp) is found 142.65 Pa. The simulated result from Fluent is in close proximity of the calculated value (

Noticeably pressure fluctuates at the end of the pipe length. This happens due to the local back flow.

Equation (5) is used to calculate temperature at the end of pipe.

T e = T s − ( T s − T i ) exp [ − h A s / m ˙ C p ] (5)

h = 10.45 − v + 10 v 1 / 2 (6)

Here, T_{e}, T_{s} and T_{i} represent temperatures of outlet, surface and inlet of the pipe respectively; h―convective heat transfer coefficient of water, A_{s}―surface area of pipe, m ˙ ―mass flow rate.

The calculated value of the temperature at the end of pipe is 302.93 K (

Flow is fully developed at some downstream distance of inlet (

At this point, the properties of the fluid are changed to mimic nanofluids. Experimental thermophysical properties of nanofluids were taken from [

smaller values. This shows that with a very small amount of addition of nanoparticles, these nanofluids’ thermal properties can be varied to a large extent.

After investigating three nanofludis in a pipe flow in terms of their temperature distribution at the outlet, it is found that with increasing volume fraction of aluminum oxide, temperature at the outlet wall decreases. The initial conclusion suggests that nanofluids have a potential to work as an industrial thermal fluid with superior thermophysical properties.

Bhuiyan, Md.E.K., Khan, M.M.R. and Mahmud, I. (2017) Water Based Nanofluids: A Computational Study on Temperature Distribution in a Pipe Flow. Advances in Nanoparticles, 6, 141-147. https://doi.org/10.4236/anp.2017.64012