Experimental Friction Factor Research Articles

Experimental investigation of two-phase water–oil flow pressure drop in inclined pipes

In this experimental work the effect of inclination on the pressure gradient in two phase oil–water flow is investigated. The experiments were performed in a 6m long, 20mm inner diameter and inclinable acrylic pipe using oil (3mPas viscosity and 830kg/m3 density) and water (1mPas viscosity and 990kg/m3 density) as test fluids. Pressure gradients between inlet and outlet of flow in pipe were measured for inclination angles of 0°, ±5°, ±15°, ±30° and ±45° with respect to the horizontal plane. The experimental results were compared with Homogeneous and Two-Fluid models. It was observed that in high mixture velocities, where dispersed flow prevails, there is a peak pressure gradient which is related to phase inversion. It was also found that, phase inversion appears at higher inlet water cut values in inclinations of −30° and −45° compared with other inclinations. However the two-fluid model and homogeneous model both over-predicted the pressure drop, but two-fluid model predicted the pressure drop with less average deviation. Several correlations for effective mixture viscosity in a homogeneous model were considered and the results were compared with experimental results. Acceptable agreement was seen between the computed and measured data.The experimental two-phase friction factors were compared with the friction factors for single phase flow of oil and water, at the same velocities as the two phase mixture and it was found that the experimental friction factors were less than the predicted friction factors of single phase flow.

Laminar Flow Through a Circular Tube Having Transverse Ribs and Twisted Tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral transverse rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral transverse rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Thermal and friction characteristics of laminar flow through a circular duct having helical screw-tape with oblique teeth inserts and wire coil inserts

Helical screw-tape inserts and wire coil inserts both individually are enhancement techniques. Naturally, therefore, it is worthwhile to try their combinations as a potential enhancement technique. The experimental friction factor and Nusselt number data for laminar flow through a circular duct having helical screw-tape and wire coil inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with wire coil inserts perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter.

CFD analysis of heat transfer and pressure drop in helically coiled heat exchangers using Al2O3 / water nanofluid

In this investigation, the heat transfer coefficient and pressure drop of a helically coiled tube heat exchanger handling Al2O3/ water nanofluids is made by using computational fluid dynamics fluent (CFD) software package. This was done under laminar flow condition in the Dean number (De) range of 1650–2650 and the nanoparticles volume concentration of 0.1%, 0.4% and 0.8%. The effect of some important parameters such as nanoparticle volume concentration and Dean number (De) on heat transfer and pressure drop is studied. The coiled tube side Nusselt number (Nu) is found to be 30% higher than water at maximum De. The maximum pressure drop is found to be 9% higher than water. It is also found that the Nu and pressure drop significantly increase with increasing particle volume concentration and De. It is also found that the experimental friction factor increases with increasing the particle volume concentration and De. The CFD Nu and pressure drop results have been compared with the experimental and theoretical results. On comparison, it is found that the CFD simulation results show good agreement with the experimental and theoretical results. It is concluded that the CFD approach gives good prediction for heat transfer coefficient and pressure drop in a shell and helically coiled tube heat exchanger using Al2O3/ water nanofluids. The average relative error between experimental Nu, pressure drop results and CFD results are found to be 8.5% and 9.5% respectively.

Experimental investigation of laminar flow of viscous oil through a circular tube having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral axial corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

微管道内液体低速流动的实验研究

研究微尺度条件下的液体流动规律对于高效开发低渗透油气资源有着重要意义。本文实验研究了低速条件下去离子水和正十六烷在内径分别为18.5 μm、9.6 μm和4.1 μm的石英微圆管内的流动特性。实验结果显示当流速范围在0.01 mm/s~1 mm/s时，微管道内的液体压降与平均流速呈线性关系，微圆管内的实际流动阻力与经典流体力学的层流流动理论基本吻合，该结果说明对于直径大于4 μm的微管道内的牛顿流体流动，固壁不动边界层的影响可以忽略，并没有出现流动阻力随着流速降低而减小的达西非线性现象以及明显的启动压力现象。 The research on the liquid flow at micro-scale is of great significance to develop low permeability oil/gas reservoirs at high efficiency. In this paper, the flow characteristics of de-ionized water andn-Hexadecane flowing through quartz microtubes with inner diameter of 18.5 μm, 9.6 μm and 4.1μm were investigated in experiments. The experimental results show that the pressure drop has linear relationship with average velocity of the fluid in the microtubes. The experimental friction factor is consistent with the classical laminar flow theory when the flow velocity ranges in 0.01 mm/s - 1 mm/s, which indicates that the influence of the stationary boundary layer could be neglected when the diameter of the microtube exceeds 4 μm. The nonlinear Darcy phenomenon that the flow resistance increases as the reduction of flow rate and the obvious phenomenon of the starting pressure do not occur for the Newton fluid flow in microtubes.

Pressure drop and heat transfer characteristics of nanofluids in horizontal microtubes under thermally developing flow conditions

This study presents pressure drop and heat transfer characteristics of water based nanofluids with TiO2 and Al2O3 nanoparticles of various mass fractions in horizontal smooth hypodermic microtubes with an outer diameter of ∼717μm and an inner diameter of ∼502μm over a wide variety of Reynolds numbers under hydrodynamically fully developed and thermally developing conditions. For this purpose, TiO2 and Al2O3 nanoparticles of 20nm average solid diameters were added to deionized water to prepare nanofluids with mass fractions of 0.01–3wt.%, and prepared nanofluids were characterized by standard methods such as Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and zeta potential measurements. Experimental friction factor coefficients were predicted within ±10% and are in good agreement with existing analytical predictions, while experimental heat transfer coefficients were predicted within ±15% with existing correlations for single phase flow. Our results show that there is no considerable heat transfer enhancement for Re<1000. A consistent enhancement in heat transfer was observed (for average heat transfer coefficient up to 25%), once Reynolds number goes beyond 1500. At low Reynolds numbers, flow is mainly laminar. However, at higher Reynolds numbers, flow starts to transition to turbulent flow, when heat transfer enhancement is also observed. Under these conditions, the enhancement in heat transfer increases with mass fraction.

Laminar fluid flow and heat transfer through a circular tube having spiral ribs and twisted tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral spiral rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

EFFECT OF TUBE DIAMETER AND SURFACE ROUGHNESS ON FLUID FLOW FRICTION FACTOR

Experiments have been performed to investigate the effect of channel roughness and diameter on fluid friction. Three different diameters and roughness of tubes were used to examine the friction factor. The first tube made of stainless steel with an inner diameter of 1.14 mm was investigated at Brunel University, whilst the others made of PVC with diameters of 17 mm and 15.5 mm rough were tested at Mataram University. The stainless steel was equipped with a 200 mm calming section and smooth one. The 15.5 mm diameter tube was coated internally with sand that had an average grain size of 0.5 mm so that the tube had a relative roughness of 0.032. The last tube with a diameter of 17 mm was smooth as explained in the H408 Fluid Friction Experimental Apparatus manual. The results indicate that the flow in the stainless steel tube still obeys the theory and in the 17 mm tube shows a deviation in friction factor with the theory. However, this was due to no calming section installed in the test rig. Flow in the rough tube (15.5 mm diameter) demonstrates that the Reynolds number does not affect the friction factor in turbulent regimes and the experimental friction factors were reasonably in a good agreement with the theory or Moody diagram. Hence, the effect of decreasing in diameter of channels on friction factor is insignificant.

Laminar flow and heat transfer through a circular tube having integral transverse corrugations and fitted with centre-cleared twisted-tape

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral transverse corrugation and fitted with centre-cleared twisted-tape has been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the centre-cleared twisted tapes in combination with integral transverse corrugation perform better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain amount of twisted-tape centre-clearance.

Experimental investigation of laminar flow of viscous oil through a circular tube having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Experimental heat transfer and friction factor studies through a square duct fitted with helical screw tapes

AbstractExperimental investigations of friction factor and heat transfer characteristics through a square duct fitted with helical screw tapes of various twist ratios have been studied under nearly uniform wall temperature conditions. The experimental results reveal that the use of helical screw tapes leads to a considerable increase in heat transfer and friction loss over those of a plain square duct. The Nusselt number increases with the rise of Reynolds number and the reduction of twist ratio. The Performance evaluation criteria have been presented and maximum performance ratio was observed for minimum twist ratio.

Thermally Developing Single-Phase Flows in Microtubes

The pressure drop and heat transfer due to the flow of de-ionized water at high mass fluxes in microtubes of ∼ 254 μm and ∼ 685 μm inner diameters is investigated in the laminar, transition and the turbulent flow regimes. The flow is hydrodynamically fully developed and thermally developing. The experimental friction factors and heat transfer coefficients are respectively predicted to within ±20% and ±30% by existing open literature correlations. Higher single phase heat transfer coefficients were obtained with increasing mass fluxes, which is motivating to operate at high mass fluxes and under thermally developing flow conditions. The transition to turbulent flow and friction factors for both laminar and turbulent conditions were found to be in agreement with existing theory. A reasonable agreement was present between experimental results and theoretical predictions recommended for convective heat transfer in thermally developing flows.

Enhancement of heat transfer of laminar flow through a circular tube having integral helical rib roughness and fitted with wavy strip inserts

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral helical rib roughness and fitted with way strip inserts have been presented. The heat transfer test section was electrically heated and uniform wall heat flux boundary condition was imposed. Friction factor and Nusselt number correlations have been developed by log-linear regression analysis. The performance of the present fin geometry has been evaluated. The major findings of this experimental investigation are that the wavy strip inserts in combination with integral helical rib roughness perform better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain range of parameters.

THERMOHYDRAULICS OF LAMINAR FLOW THROUGH A CIRCULAR TUBE HAVING INTEGRAL HELICAL CORRUGATIONS AND FITTED WITH HELICAL SCREW-TAPE INSERT

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral helical corrugations and fitted with a helical screw-tape insert are presented. Predictive friction factor and Nusselt number correlations are also presented. The thermohydraulic performance was evaluated. The major findings of this experimental investigation are that the helical screw-tape insert in combination with integral helical corrugations performs significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter. This research finding is useful in designing tubes carrying solar thermal mass of viscous oil in a parabolic trough solar collector used in environmentally sound and increasingly cost-effective solar thermal electric power plants. The result is also useful in designing heat exchangers used in process industries.

An Experimental Investigation of the Reynolds Analogy and its Modifications Applied to Annular Condensation Laminar Flow of R134a in a Vertical Tube

The Reynolds analogy and its modifications are applied to forced convection laminar in-tube condensation to predict the heat transfer coefficient of R134a by means of well-known two-phase friction factors and agreed void fraction models and correlations explained in the authors’ previous works. The vertical test section is a 0.5 m long countercurrent flow double tube heat exchanger with refrigerant flowing in the inner smooth copper tube (8.1 mm i.d.) and cooling water flowing in the annulus (26 mm i.d.). The test runs are performed at average saturated condensing temperatures of 40 °C (Pr = 0.92) and 50 °C (Pr = 0.97). The heat fluxes are between 10.16 and 66.61 kW m−2 while the mass fluxes are between 260 and 515 kg m−2 s−1 for the vertical test sections. The Reynolds’ model is modified by various two-phase flow models and correlations to account for the partial condensation inside the tube. The refrigerant side heat transfer coefficients are determined within ±30% using the two-phase friction factors of Wallis, Moeck, Fore et al., while all the proposed friction factor correlations for the Reynolds analogy, Prandtl and Taylor analogy, and Colburn analogy predict the experimental friction factor within a ±20% deviation band. The importance of altering the Prandtl number to the Reynolds analogy (Pr = 1) is also shown in the paper.

Enhancement of heat transfer of laminar flow of viscous oil through a circular tube having integral helical rib roughness and fitted with helical screw-tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral helical rib roughness and fitted with helical screw-tape insert have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with integral helical rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Laminar Flow Heat Transfer and Pressure Drop in a Circular Tube Having Wire-Coil and Helical Screw-Tape Inserts

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having wire-coil and helical screw-tape inserts have been presented. Peripherally and axially local temperatures on the duct outside wall have been measured. The temperature drop across the duct wall has been calculated to obtain the duct inside wall temperatures. Peripherally averaged and axially local temperatures have been used to get axially local Nusselt numbers. These axially local Nusselt numbers have been averaged over the whole length of the duct to get the mean Nusselt number. Predictive friction factor and Nusselt number correlations developed by log-regression analysis have also been presented. Nusselt number correlation takes care of the thermal development length represented by the Graetz number, swirl and inertia force due to forced convection at large Reynolds number, buoyancy force due to natural convection at low Reynolds number represented by Rayleigh number and the geometrical parameters of wire-coil and helical screw-tape inserts. The thermohydraulic performance has been evaluated. The helical screw-tape inserts in combination with wire-coil inserts perform better than the individual enhancement technique acting alone for laminar flow through a circular tube up to a certain value of fin parameter.

G0605 高レイノルズ数における管摩擦係数(GS6 噴流・内部流)

New experimental data and new equation of friction factor in a fully developed turbulent pipe flow at high Reynolds number is presented in this paper. The experiments are performed using the water flow test facility for high Reynolds number in NMIJ, AIST. The Reynolds number range examined is from 4.69 X 104 to 1.77 X 107. The experimental friction factors are smaller than those by the Prandtl equation in high Reynolds number region, Re>1.0 X 105 and those do not agree with the previous experiment. Finally, new equation for the friction factor based on the experimental results is proposed.

A new approach to investigate real flow stress in micro-extrusion

The friction effect is very important in micro-forming process and differs from the usual forming process. A new method of evaluating the friction factor in tests by combining micro-compression was presented. The friction behavior and the flow stress were investigated in micro-expression by theory analysis and experiment. To investigate the effects of specimen size on the flow stress, a series of compression tests were carried out for specimens with different diameters. The results show that with the decrease of specimen size, the flow stress shows a gradually downward trend. The bulging value increases with increasing the friction factor. Combining the bulging method and theory analysis, the experimental friction factor was obtained and the flow stress was calibrated without friction. Thus, the real stress—strain curve was obtained, which provides the accurate material model for the subsequent finite element simulation on micro-forming.