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Abstract

Close-coupled pipes can be applied to a number of HVAC systems. This paper discusses the local drag reduction achieved by components placed in elbow and T-junction close-coupled pipes. The components are necessary to reduce or even eliminate vortices produced by turning flow patterns. It includes a numerical study of drag reduction effects of seven components with different shapes. The shear stress transport (SST) k–ω turbulence model is applied. The local pressure loss coefficients and the drag reduction rate are introduced to compare drag reduction effects. The results show that the drag reduction components studied in this paper all have varying degrees of an effect for most of the cases. Also, the drag reduction effect of components was influenced by the specific flow cases. Therefore, the selection of a suitable shape for the drag reduction component should consider the flow pattern.

Practical application: This paper has studied the local drag reduction achieved by components placed in elbow and T-junction close-coupled pipes, which can be used in the building industry. In order to find the suitable component shapes, we designed seven kinds of drag reduction components. The designs came from drag reduction technologies used in different applications such as commercial, high performance automobiles and aerofoil designs.

Keywords

drag reduction elbow and T-junction close-coupled pipe

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References

Choi

. European drag-reduction research-recent developments and current status. Fluid Dyn Res 2000; 26: 325–335.

Toms BA. Some observations on the flow of linear polymer solutions through straight tubes at large Reynolds numbers. Amsterdam, North Holland: First Intl. Congress on Rheology, 1949.

Lumley

. Drag reduction by additives. Annu Rev Fluid Mech 1969; 1: 367–384.

Virk

. Drag reduction fundamentals. AIChE J 1975; 21: 625–656.

Sureshkumar

Beris

Handler

. Direct numerical simulation of the turbulent channel flow of a polymer solution. Phys Fluids 1997; 9: 743–755.

Al-Sarkhi

Hanratty

. Effect of pipe diameter on the performance of drag-reducing polymers in annular gas-liquid flows. Chem Eng Res Des 2001; 79: 402–407.

Al-Sarkhi

Soleimania

. Effect of drag reducting polymers on two-phase gas-liquid flows in a horizontal pipe. Chem Eng Res Des 2004; 82: 1583–1588.

Walsh MJ. Turbulent boundary layer drag reduction using riblets. AIAA paper 1982; 82–0169.

Walsh

. Riblets as a viscous drag reduction technique. AIAA J 1983; 21: 485–486.

10.

Bechert

Bruce

Hage

. Experiments on drag reducing surfaces and their optimization with an adjustable geometry. J Fluid Mech 1997; 338: 59–87.

11.

Bechert

Bruce

Hage

. Experiments with three-dimensional riblets as an idealized model of shark skin. Exp Fluids 2000; 28: 403–412.

12.

Wang

Lan

Chen

. Experimental study on the turbulent boundary layer flow over riblets surface. Fluid Dyn Res 2000; 27: 217–229.

13.

Lafleur

Langston

. Drag reduction of a cylinder/endwall junction using the ice-formation method. J Fluids Eng-T ASME 1993; 115: 26–32.

14.

Zhao

Luo

. Turbulent drag reduction by traveling wave of flexible wall. Fluid Dyn Res 2003; 34: 175–198.

15.

Hartmut

. A simple model for gas bubble drag reduction. Phys Fluid 1984; 27: 2788–2790.

16.

Shatrov

Gerbeth

. Magnetohydrodynamic drag reduction and its efficiency. Phys Fluids 2007; 19: 1–12.

17.

Anderson

Rohr

Stanley

. The combined drag effects of riblets and polymers in pipe flow. J Fluids Eng 1993; 115: 213–221.

18.

Mizunuma

Ueda

. Synergistic effects in turbulent drag reduction by riblets and polymer additives. J Fluids Eng 1999; 121: 533–540.

19.

Gan

Riffat

. K-factors for HVAC ducts: Numerical and experimental determination. Building Serv Eng Technol 1995; 16: 133–139.

20.

Shao

Riffat

. Accuracy of CFD for predicting pressure losses in HVAC duct fittings. Appl Energ 1995; 51: 233–248.

21.

Koskinen

Pättikangas

Manninen

. CFD modelling of drag reduction effects in pipe flows. Comput Aided Chem Eng 2003; 14: 737–742.

22.

Sami

Cui

. Numerical study of pressure losses in close-coupled fittings. HVAC&R Res 2004; 10: 539–552.

23.

Zhang

. Experiments on the pressure loss coefficient of pipe sections around elbow and tee junction. J.HV&AC 2009; 10: 39–44. (In Chinese).

24.

Iaccarino

Shaqfeh

ESG

Dubief

. Reynolds-averaged modeling of polymer drag reduction in turbulent flows. J Non-Newton Fluid 2010; 165: 376–384.

25.

Resende

Kim

Younis

. A FENE-P k–ɛ turbulence model for low and intermediate regimes of polymer-induced drag reduction. J Non-Newton Fluid 2011; 166: 639–660.

26.

Pinho

Younis

. A low Reynolds number k–ɛ turbulence model for FENE-P viscoelastic fluids. J Non-Newton Fluid 2008; 154: 89–108.

27.

Chen

Gao

. Study on local drag reduction effects of wedge-shaped components in elbow and T-junction close-coupled pipes. Build Simulation 2014; 7: 175–184.

28.

Fluent. FLUENT user’s guide, version 6.3, USA: Fluent Inc, 2006.

29.

Ünal

Gören

. Effect of vortex generators on the flow around a circular cylinder: computational investigation with two-equation turbulence models. Eng Appl Comp Fluid 2011; 5: 99–116.

30.

Rahmeyer

. Pressure loss coefficients of threaded and forged weld pipe fittings for ells, reducing ells and pipe reducers. ASHRAE Transact 1999a; 105: 334–354.

31.

Rahmeyer

. Pressure loss coefficients of threaded and forged weld pipe Tees. ASHRAE Transact 1999b; 105: 355–385.

32.

Rahmeyer

. Pressure loss coefficients for close-coupled pipe ells. ASHRAE Transact 2002; 108: 390–406.

33.

Zhang X. Study on the fluid flow in elbow, Junction closed-coupled pipes by 2DPIV and CFD. PhD thesis. Xi’an: Xi’an University of Architecture and Technology, 2008.

34.

Fang

. Aircraft aerodynamic configuration design, Beijing: Aviation Industry Press, 1997.

Numerical investigations on effects of seven drag reduction components in elbow and T-junction close-coupled pipes

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