Özet:

This experimental investigation was performed to improve heat transfer in the heat exchanger (tube of shell and helically coiled (using nanoparticles for turbulent parallel flow and counter flow of distilled water (Dw) and ethylene glycol (EG) fluids. Six types of nanofluids have been used namely: copper – distilled water, copper – distilled water and ethylene glycol, copper – ethylene glycol, titanium oxide – distilled water, titanium oxide – distilled water and ethylene glycol, titanium oxide – ethylene glycol with 0.5%,1%,2%,3% and 5% volume concentration as well as the range of Reynolds number are 4000 – 15000. The experimental results reveal that an increase in coefficient of heat transfer of 50.2 % to Cu – Dw, 41.5% to Cu – ( EG + Dw ), 32.12 % for Cu – EG , 36.5% for TiO2 – Dw, 30.2 % to TiO2 – ( EG + Dw) and 25.5%, to TiO2 – EG . The strong nanoconvection currents and good mixing caused by the presence of Cu and TiO2 nanoparticles. The metal nanofluids give more improvement than oxide nanofluids. The shear stress of nanofluids increases with concentration of nanoparticles in the case of parallel and counter flow. The effect of flow direction is insignificant on coefficient of overall heat transfer and the nanofluids behave as the Newtonian fluid for 0.5%,1%,2%,3% and 5%. Good assent between the practical data and analytical prediction to nanofluids friction factor which means the nanofluid endure pump power with no penalty. This study reveals that the thermal performance from nanofluid Cu – Dw is higher than Cu – (EG + Dw) and Cu – EG due to higher thermal conductivity for the copper and distilled water compared with ethylene glycol.

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