Analysis of laminar nanofluid forced convection heat transport through the CFD
Abstract
In the present paper, developing laminar forced convection flows were numerically investigated by using waterAl2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux (UHF) at the wall. The whole numerical experiments were processed under the Re = 1050 and the nano-fluid models were made by the Alumina volume fraction. Single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase model (mixture granular model) were processed in 100nm diameter. The results show that Nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show the increment of thermal transfer from the volume fraction concentration.
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Introduction
To enhance the heat exchangers energy transfer efficiency, Engineers have interested not only the development exchanger or enhanced its structure, but also improvement of heat transfer fluid itself. Maxwell [1] proved the possibility of increasing thermal conductivity of a mixture by higher volume fraction of solid particle. Nowadays available particle diameter is smaller than 100nm which is called ‘Nano-sized’. This effort makes particle mixture fluid would enhance the heat transfer performance of heat transfer fluids. [2] Moreover, solid nanoparticle colloids are highly stable and exhibit no significant settling under static conditions. Also, decreasing particle size makes suspending solid colloid easily. So that nano-fluid technology is expected to suitable of heat transfer fluid. [3] However, nano-fluid development is interrupted by the lack of agreement with different research group, theoretical understanding of the heat transfer mechanisms, different suspension conditions. [4]In this paper, Nano-fluid model assume that the Homogeneous flow mixture model [5] which is the dispersed and continuous phase with very strong coupling and the nano-particles is moving at the same inlet velocity. Therefore the dispersed granular mixture models are made by ‘Mixture model’ which is one of the Euler-Euler approaches. This numerical investigation purpose is an observation of heat transfer coefficient increment in a compact pipe and comparison between single-phase and multi-phase model. Geometry model size is as same as experimental pipe which will use in a university laboratory. Nano-particle volume fractions are less than 5 percent, and divided by 1 percent from 0 to 4 percent. The wall has constant surface heat flux as known as Uniform Heat Flux (UHF). The numerical simulation geometry is asymmetric twodimensional model. Through the limit of 2D model and assumption, implicit effect such as gravity and buoyancy force are excluded. The nano-particle material is an Aluminium Oxide with a spherical size of 100 nm diameter and simulations are processed in a steady state. The purpose of this study is comparing heat transfer ability between single and mixture model which have same heat transfer value except the particle presence.
Conclusion
Average heat transfer coefficient and Nusselt number are shown in Table 3 with relative increase of the total heat transfer rates and Nusselt number as a concentration of the nano-particle volume fraction 𝜑. Significant increases of the total heat transfer rates can be found with the use of fully dispersed nanoparticles multi-phase. These results have indicated the nanofluids beneficial effects of thermal properties improvement. The results showed that the nanoparticles inclusion produced considerable heat transfer with respect to base fluid. Heat transfer enhancement was increasing with concentration of particle volume. But the CFD should be progressed with constant and transient numerical investigation parallel and these numerical researches would be pace with the experiment especially.