Friction losses of Newtonian and non-Newtonian fluids flowing in laminar regime in a helical coil

Abstract

a b s t r a c tThis study aimed to carry out experimental work to determine, for Newtonian and non-Newtonian fluids, the friction factor (f c ) with simultaneous heat transfer, at constant wall temperature as boundary condition, in fully developed laminar flow inside a vertical helical coil. The Newtonian fluids studied were aqueous solutions of glycerol, 25%, 36%, 43%, 59% and 78% (w/w). The non-Newtonian fluids were aqueous solutions of carboxymethylcellulose (CMC), a polymer, with concentrations of 0.2%, 0.3%, 0.4% and 0.6% (w/w) and aqueous solutions of xanthan gum (XG), another polymer, with concentrations of 0.1% and 0.2% (w/w). According to the rheological study done, the polymer solutions had shear-thinning behavior and different values of viscoelasticity. The helical coil used has an internal diameter, curvature ratio, length and pitch, respectively: 0.00483 m, 0.0263, 5.0 m and 11.34 mm. It was concluded that the friction factors, with simultaneous heat transfer, for Newtonian fluids can be calculated using expressions from literature for isothermal flows. The friction factors for CMC and XG solutions are similar to those for Newtonian fluids when the Dean number, based in a generalized Reynolds number, is less than 80. For Dean numbers higher than 80, the friction factors of the CMC solutions are lower those of the XG solutions and of the Newtonian fluids. In this range the friction factors decrease with the increase of the viscometric component of the solution and increase for increasing elastic component. The change of behavior at Dean number 80, for Newtonian and non-Newtonian fluids, is in accordance with the study of Ali [4]. There is a change of behavior at Dean number 80, for Newtonian and non-Newtonian fluids, which is in according to previous studies. The data also showed that the use of the bulk temperature or of the film temperature to calculate the physical properties of the fluid has a residual effect in the friction factor values.

Experimental Investigation of Coil Curvature Effect on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

“…Re sh ¼ 4 _ m sh pD sh;h l sh (16) The Fanning friction factor for the fluid in circulation inside the HCT, f c , was calculated with the following equation:…”

“…This wide use of HCTs is because they are compact and promote good mixing of the fluids that increase the heat transfer coefficients. In addition, this equipment is low cost and of easy construction and maintenance [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Due to the extensive application of the HCTs in these fields, knowledge about the heat transfer and pressure drop characteristics is very important.…”

“…Generalized pressure drop correlations were developed in terms of the Euler and Reynolds numbers and geometrical group. Pimenta and Campos [36] determined f c experimentally with simultaneous heat transfer for Newtonian and non-Newtonian fluids at constant wall temperature as boundary condition for fully developed laminar flow inside vertical HCT. It was concluded that f c for non-Newtonian fluids was similar to those for Newtonian fluids when De < 80.…”

A numerical study of flow characteristics in a helical pipe

“…Cioncolini and Santini 8 and Hayamizu et al 9 experimentally clarified the curvature and torsion effect on the flow in helical pipes from laminar to turbulent flow, respectively. Gupta et al, 10 Pimenta and Campos, 11 and Amicis et al 12 all measured the pressure drop for helical pipe under laminar flow condition. However, Gupta et al 10 applied the experimental data to obtain a new fiction factor correlation, Pimental and Campos 11 employed them to analyze the fiction factor of non-Newtonian fluids, and Amicis et al 12 used them as a comparison group to compare with calculation results from different codes.…”

Non-Newtonian flow of highly-viscous oils in hydraulic components

“…Tsang and James [17] proposed that the dampening mechanism of the streamwise counter-rotating Dean vortices under the presence of additives is an analogue for laminar flow conditions of the turbulence-reducing effects through dissipation of near-wall quasi-streamwise vortices. In the study of Pimenta and Campos [18], different shear-thinning liquids also exhibiting certain degrees of viscoelastic behaviour were comparatively examined in a helical-coil layout under laminar flow conditions. The liquids exhibited reduced friction losses compared to Newtonian flow.…”