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Corresponding Author

Saad El-Din, M.

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

Forced convective heat transfer and friction factor for nanofluid flows inside circular horizontal tube with inserting helical tape, is experimentally studied. Electric heater is wrapped around the outer surface of the tube to obtain a constant and uniform heat flux at the tube wall. Experiments are conducted with adding nano-particles (Al2O3) to water up to 0.35% by volume to obtain different concentrations of nanofluids. An experimental test loop equipped with the required measuring instruments was designed and constructed to assess the effects of nano-particles concentration, mass flow rate, and applied heat flux on the convection heat transfer process and pressure drop. The tested tube fitted with screw helical tape inserts to evaluate its effects on heat transfer rate and friction factor with nanofluid and pure water as a working fluid. The measurements of temperature, flow rate, applied volt and pressure drop are recorded and manipulated to calculate the convective heat transfer coefficient and friction factor. The obtained experimental results show that, wall temperature is reduced by using nanofluid compared with pure water. Accordingly, the convection heat transfer coefficient increased when using nanofluid and it also increased with increasing heat flux and mass flow rate (Reynolds number). Higher rates of heat transfer and pressure drop are obtained from the tube fitted with screw helical tape insert compared to flow in a plain tube under similar conditions. This improvement in the convection heat transfer coefficient characterized by a swirling flow as a result of the secondary flow of the fluid flow inside tube with helical tape and the area of the tape inserted. The average value for the thermal hydraulic performance (ŋ) for tube with inserting helical tape was 1.4 for water only, and 1.8 for nanofluid at concentration 0.2%. Comparison with the previous work shows fairly agreement. A correlation is obtained between Nusselt number and operating parameter.

Keywords

Nanofluid; Convective heat transfer, helical tape around rod inserted, Horizontal tube

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