Effects of tube flattening on the fluid dynamic and heat transfer performance of nanofluids

• The effects of the simultaneous use of nanofluids and flat tubes are numerically investigated.
• The results show that with increasing the flattening, the heat transfer and wall stress increase.
• With increasing the flattening, the non-uniformity of nanoparticles in the flat tubes is strengthened.
• The symmetry feature with respect to the horizontal plane is strengthened with increasing the flattening value in tubes.

In the present article, numerical simulation of Al2O3–water nanofluid flow in different flat tubes are performed to investigate the effects of tube flattening on the fluid dynamic and heat transfer performance of nanofluids. The numerical simulations of nanofluids are performed using two phase mixture model by FORTRAN programming language. The flow regime and the wall boundary conditions are assumed to be laminar and constant heat flux respectively. The simulated results are compared with previously published data and good agreement is observed. The effects of tube flattening on different parameters such as heat transfer coefficient, wall shear stress, nanoparticles distribution, temperature distribution, secondary flow and velocity profiles are presented and discussed. The results show that with increasing the flattening, the heat transfer coefficient and wall shear stress increase. The rate of increasing is soft for all flat tubes except for the tube with the most flattening which has a severe increasing in heat transfer and wall shear stress values.

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