Pipe Inclination Angle Research Articles

Dynamic response of inclined pipe conveying fluid under thermal effect

This study treats with the transverse vibration of polypropylene random-copolymer (PP-R) pipes caused by fluid flow inside them assuming pinned connections at both ends. The effect of inclination angle, aspect ratio (the ratio of length to outside diameter) and temperature variation on dynamic response of inclined pipe containing flowing fluid with different velocity was investigated. The Euler–Bernoulli formula for beam theory was adopted to model the inclined pipe. An analytical model has been prepared to calculate the dynamic response of the pipe, taking into account pipe weight, thermal effect, inclination angle, aspect ratio, and fluid flow velocity, using the integral transform techniques (ITT) by utilizing a combining of Laplace and Fourier transforms and their inverses. The results demonstrate that the prepared analytic model is a powerful tool to obtain the dynamic characteristic of pipe conveying fluid. Moreover, the results showed that the dynamic deflection was strongly affected by the change in the values of inclination angle, pipe temperature, aspect ratio, and fluid velocity, where there was a significant increase in pipe deflection with increasing temperature and aspect ratio. and fluid velocity, while a decrease in the deflection value is observed with an increase in the angle of inclination in the range of 0-90°. The findings proved that the thermal effect becomes more important than the fluid velocity at high aspect ratios. The same case applies to the angle of inclination, as its effect on the pipe deflection increases at high aspect ratios. These results were limited to the fundamental (first) mode and can be useful for engineering component design. The main contributions of this work are to find the combined effect of inclination angle, thermal loading, and aspect ratio on the deflection of the pipe, in addition to preparing an analytical model to calculate this deflection.

Thermal Performance and Numerical Simulation of the 1-Pyrene Carboxylic-Acid Functionalized Graphene Nanofluids in a Sintered Wick Heat Pipe

Experimental and numerical modeling of a heat pipe included with a phase change heat transfer was developed to assess the effects of three parameters of nanofluid, heat pipe inclination angles, and input heating power. Distilled water (DW) and 1-pyrene carboxylic-acid (PCA)-functionalized graphene nanofluid (with concentrations of 0.06 wt%) were used as working fluids in the heat pipe. A computational fluid dynamic (CFD) model was developed for evaluation of the heat transfer and two-phase flow through the steady-state process of the heat pipe. It was found that inclination significantly affects the heat transfer of the heat pipe. Maximum increment of thermal performance in the heat pipe reached 49.4% by using 0.06 wt% of PCA-functionalized graphene as working fluids. The result associated with this comparison indicates that the highest deviation is less than 6%, consequently confirming that the CFD model was successful in reproducing the heat and mass transfer processes in the DW and nanofluids charged heat pipe. The results of CFD simulation have good agreement between predicted temperature profiles and experimental data.

Experimental Investigation of Heat Transfer Depending on Inclination Angle of Unfinned, Axial Finned and Radial Finned Heat Exchangers

In this study, effects of axial and radial fins on a circular pipe and inclination angle were investigated experimentally for natural convection heat transfer. An unfinned circular pipe was utilized as reference. Experiments were carried out at 00,300,600 and 900 pipe inclination angles to measure natural convection heat transfer. Hot water was used as heat source during the experiments. The water in a storage tank was kept at a constant temperature and it was circulated through heat exchanger. Radiation heat transfer was also taken into consideration. Rayleigh number varied between Ra≈10 × 106 and 60 × 106. The highest calculated Nusselt number was found as about Nu≈408 for axial finned heat exchanger. All finned surfaces and inclination angles lead to better heat transfer performances comparing to the unfinned heat exchanger.

Experimental study on heat transfer limit of high temperature potassium heat pipe for advanced reactors

Heat pipe cooled reactor (HPR) is widely applied in various environment due to its remarkable advantages compared with other nuclear power systems, such as high reliability, low noise level and compact structure. As one of the essential components in HPR, the high temperature heat pipe has an important effect on HPR operation performance. In this paper, an experimental study was carried to investigate the thermal–hydraulic characteristics and heat transfer limit of potassium heat pipe. Under the steady-state conditions, heating power and inclination angle of heat pipe were taken as sensitivity parameters. By increasing heating power, the heat transfer capacity was enhanced. For inclination angle, an increase in inclination angle would enhance heat transfer for low filling ratio heat pipe, while it does not make obvious effect on high filling ratio heat pipe. As for heat transfer limit, by analyzing the axial wall temperature distribution and predicting the vapor flow pressure drop, the particular phenomena is classified to four heat transfer limits including viscosity, sonic, entrainment and condensation limit. When heat pipe is cooled by natural air convection, the accurate prediction of condensation limit under effect of inclination is performed by air convection heat transfer relationship. Because of the friction force influence on viscosity limit when operating at low temperature state, the temperature at inlet of condenser section is 11℃ lower than adjacent position. The same reason for sonic limit when operating at low temperature state, the temperature at outlet of evaporator section is 17 ℃ higher than adjacent position. The occurrence of local dryout which lead evaporator temperature increasing sharply to 632 ℃ is entrainment limit. The experimental results provide guidance for the engineering application of high temperature heat pipe.

DEM study of monodisperse granular flow in a pipe

Flow of granular material through a pipe has several industrial applications but maintaining a uniform mass flux is quite challenging. In this work, monodisperse granular flow (non-turbulent and non-dense phase particle transport) through a vertical pipe was simulated using discrete element method (DEM). Effects of different geometric and granular parameters on mass flux of cohesive and non-cohesive solids were analyzed and evaluated. Several important parameters and their effects on mass flux were studied like: L/D ratio, pipe diameter to particle diameter ratio (D/Dp), Poisson ratio, and pipe inclination angle. Furthermore, effects of moisture content and Bond number on mass flux were also investigated. These parameters influenced mass flux except Poisson ratio which showed no significant improvement in mass flux upon increasing the value of this ratio.

An improved drift-flux correlation for gas-liquid two-phase flow in horizontal and vertical upward inclined wells

Drift-flux model has been diffusely applied to characterize two-phase flow in pipes and wellbores owing to its accuracy and simplicity. The constitutive correlations used in the drift-flux model specifying the relative motion between the phases have been extensively investigated leading to the development of multitudinous correlations. However, previous studies reveal that most of the correlations can either be proper for limited two-phase flow conditions or the applicability is extended by increasing the complexity of the correlation. This study attempts to propose an improved drift-flux correlation concerning the distribution coefficient and drift velocity applying for a wide range of fluid properties, pipe orientations, and flow patterns without complicating the correlation. In this study, the drift velocity is defined in terms of pipe diameter, inclination angle, and void fraction while the distribution coefficient is correlated as a function of mixture Reynolds number and a Yield-Power-Law correlation in terms of void fraction. A comprehensive experimental database consisted of 1865 data records collected from 13 distinct sources is used for correlation parameterization and performance estimation. The proposed correlation shows comparable or even better performance in comparison to the other three well-established drift-flux correlations for predicting void fraction. The proposed correlation has also demonstrated outstanding performance in case where high liquid viscosity is involved.

Parametric studies on interacting parameters influencing heat pipe performance

The performance of a heat pipe is governed by many parameters, the effects of which may influence each other. Hence, it is utmost important to optimize the combination of these parameters for an effective energy transfer in a heat pipe. In the present study, the interacting effects of four different parameters affecting the effectiveness of heat pipe are studied namely the fluid filling ratio (20%, 30%, 40%), the pressure inside the heat pipe (0.2 bar, 1 bar, 1.8 bar), the number of wick layers (0, 1, 2) and the inclination angle of heat pipe (0°, 45°, 90°). The response surface method based on central composite design approach is applied to optimize the number of experiments. The effects of interacting parameters on the effectiveness of heat pipe are discussed. Among the various parameters, the pressure inside the heat pipe was found to be the most important parameter followed by the fluid filling ratio, the inclination of heat pipe and the number of wick layers. From the analysis, the optimum combination of parameters was obtained as 40% filling ratio, 0.2 bar pressure, 2 wick layers and 0° inclination. At this point, the effectiveness predicted with the model and obtained through experiments was found to be 0.630 and 0.649 respectively. Based on the experimental results, a quadratic empirical model is developed which predicts the effectiveness of heat pipe within [Formula: see text]% of the experimental results for different operating conditions of heat pipe.

Interfacial structure of upward gas–liquid annular flow in inclined pipes

Temporal and spatial-resolved data on the interfacial structure in upward vertical and inclined two-phase annular flows were accumulated using a novel non-intrusive multilayer conductance sensor. The sensor provides simultaneous measurement of the film thickness across the entire pipe circumference, enabling a three dimensional reconstruction of the wavy interface. Measurements were performed for two liquid (water) flow rates and a single high gas (air) flow rate. Three types of interfacial waves were identified, including ripples, disturbance and rogue waves. Rogue waves can be described as an infrequent solitary disturbance wave propagating over a ripple-dominant interface. Detailed statistical properties of the interfacial shape, such as the mean film thickness, wave height distribution, wave frequency spectra, wave propagation velocities and more, were obtained as a function the pipe inclination and azimuthal angle. The statistical analysis of the wavy interface presented in this study sheds light on a complex flow pattern of annular flow in inclined pipes, which has remained relatively unstudied experimentally.For inclined pipes, gravity imposes an asymmetric film distribution resulting in the thickest film at the bottom of the pipe. At this location, waves attain larger amplitudes while maintaining slower propagation velocities as compared to smaller amplitude waves at the top of the pipe. Generally, the wave frequency throughout the pipe circumference increases with inclination angle. For a larger liquid flow rate, the interface was found to be primarily dominant by disturbance waves. For a lower liquid velocity, the interfacial structure was found to be highly dependent on both the azimuthal and the inclination angles. An interface wave type map is presented as a function of those angles.

Modeling and prediction of slug characteristics utilizing data-driven machine-learning methodology

Slug liquid holdup, translational velocity, and slug length are representative slug characteristics. The precise prediction of these parameters is essential for the accurate calculation of the average liquid holdup and pressure gradient in pipes. Nevertheless, existing correlations have mainly been developed by an empirical approach. Each correlation can only be applied to a restricted fluid property and geometrical condition, preventing people from selecting a suitable one without professional knowledge. In this study, slug characteristics were predicted by several machine learning methodologies with 2590 experimental data to overcome the limitation of selecting the proper model or correlation. The experimental dataset includes −10° ≤ θ (pipe inclination angle) ≤ 10°, 0.0258 m ≤ I.D. (pipe inner diameter) ≤ 0.0780 m, 0.01 m/s ≤ vSL (superficial liquid velocity) ≤ 3.4 m/s, 0.03 m/s ≤ vSg (superficial gas velocity) ≤ 20 m/s, 769 kg/m3 ≤ ρL ≤ 998 kg/m3, 1.12 kg/m3 ≤ ρG ≤ 7.36 kg/m3, 0.001 Pa s ≤ μL ≤ 4.65 Pa s, and 6 ≤ ReM (mixture Reynolds number) ≤ 863,920. The existing dataset has been preprocessed to pursue better machine learning performance. The random forest results reveal a better training performance and prediction than that of a deep neural network and present a competitive prediction compared with the existing correlations, indicating a great potential of utilizing the data-driven machine learning methodology.

Viscoplastic displacements in axially rotating pipes

We investigate experimentally the effects of a pipe axial rotation on buoyant miscible displacement flows in an inclined pipe. The displacing Newtonian fluid (salt-water solution) is heavier than the displaced viscoplastic one (Carbopol solution). Via image processing techniques and ultrasound Doppler velocity measurements, we analyze the key flow features such as the flow patterns, the velocity and concentration fields, and the leading front velocity (Vˆf) as well as the trailing front velocity (Vˆt) of the displacement flow. The main flow parameters in our experiments are the pipe inclination angle, the small density difference between the two fluids, the yield stress of the displaced fluid, the imposed mean flow velocity (Vˆ0), and most importantly the pipe rotation speed. We find that increasing the pipe rotation speed enhances the transverse mixing between the two fluids and, above a critical transition, leads to a complete removal of the displaced viscoplastic fluid. We classify the flow regimes into efficient and inefficient displacement flows, using appropriate dimensionless groups, i.e. the Rossby number (Rb) and the Froude number (Fr). We find that the critical transition between the two flow regimes can be roughly described by a critical Rossby number (Rbc), as a function of Fr, independent of the other flow dimensionless numbers. For Rb≤Rbc, we find that Vˆf≈1.6Vˆ0 and Vˆt≈Vˆ0, while for Rb>Rbc we propose an empirical relation for the leading front velocity versus the Rossby number. These findings can offer new insight to control viscoplastic displacement flows using rotational motion.

Feasibility study of a new attached multi-loop CO2 heat pipe for bridge deck de-icing using geothermal energy

Heated bridge using CO2 heat pipe with geothermal energy as its heating source is a sustainable and environmentally friendly alternative to conventional chemical de-icers, which corrode the bridges and pollute the environment. However, in previous studies, the heat pipe was embedded in the bridge deck for heating and is only applicable to new bridges. In this study, a new attached multi-loop heat pipe system was developed to be used with ground heat exchangers for heating existing bridges. The heat pipe system, using CO2 as the heat transfer fluid, consists of an evaporator pipe and a manifold pipe with five pipe branches. A parametric study was first conducted on the system in a freezer box at controlled freezing temperatures to determine the optimum CO2 pressure and pipe inclination angle. Then the optimized heat pipe system was attached to the bottom surface of a concrete slab and covered with fiberglass and geofoam insulation. A water bath capable of supplying hot water similar to that from the ground heat exchanger was connected to the evaporator pipe as the heating source. The slab was heated at two freezing temperatures of −3.89 °C and −6.67 °C with the water bath temperature ranging from 25 to 45 °C. A 1-D heat transfer model using a finite difference method (FDM) was developed for the heat transfer analyses of the concrete slab. The average convective heat transfer coefficient (h value) of each test was back-calculated from the FDM model. Results show that an average 28.3% of the supplied heat energy was transferred to the slab surface, and the surface heat flux ranged from 92.8 to 140.3 W/m2. Compared with previous studies, the new CO2 heat pipe is feasible and efficient as a heating system attached to existing bridge decks for de-icing.

Numerical modeling of the critical pipeline inclination for the elimination of the water accumulation on the pipe floor in oil-water fluid flow

In this work, numerical models were developed to investigate the critical inclination of a pipeline to eliminate the water accumulation at the floor of the pipe carrying oil-water fluid. Computational fluid dynamics software was used to establish a geometric model of the pipe with various inclination angles, and a grid-independent verification was conducted to determine a reasonable meshing method. Quantitative relationships were determined between the pipe inclination angle and the affecting factors including the flow velocity, viscosity and the pipe diameter, where the water accumulation would not be able to occur. Generally, the critical inclination angle increases with the fluid flow velocity. The refluxing of water is the key mechanism causing the water accumulation at the bottom of the pipe. In addition to the fluid flow velocity, an increase in fluid viscosity and a decrease in the pipe diameter cause an increase of the critical inclination angle that the water phase can be carried away by oil. The model can be used to determine the critical inclination of pipelines carrying oil-water fluid to cause the water accumulation and the operating conditions that can eliminate the accumulation of water phase at the pipe floor.

Injection of a heavy fluid into a light fluid in a closed-end pipe

We report experimental results on the injection of a heavy fluid into a light one in a closed-end pipe, inclined at intermediate angles. The injection of the heavy fluid is made using an inner duct with a smaller diameter than that of the pipe in which the light fluid is placed. The fluids used are miscible and Newtonian, and they have the same viscosity. Our observation shows that, during the removal/replacement of the light fluid by the heavy fluid, at least four distinct flow stages can be identified: (i) initial buoyant jet of the heavy fluid, (ii) development of a mixing region, (iii) slumping flow of the heavy fluid, and (iv) heavy fluid front reaching the pipe end and returning toward the mixing region. Using high-speed camera images along with the ultrasound Doppler velocimetry and laser induced fluorescence data, the flow characteristics in these flow stages are quantified, and they are described in detail vs the dimensionless groups that govern the flow dynamics, namely, the Froude number (Fr), the Reynolds number (Re), the Archimedes number (Ar), and the pipe inclination angle (β). While our findings are of fundamental importance, they can also be used to provide a fluid mechanics understanding of the dump bailing method in the plug and abandonment (P&A) of oil and gas wells.

Finding the Thermal Characteristics of a Heat Pipe using Hybrid Nano Fluid

In this experiment, work was carried out to infer the thermal characteristics of a heat pipe containing nano fluid inside in it. Various Parameters were considered in this experiment, some of them are inlet temperature at one end, mass flow rate (mfr) to evaporator section and inclination angle of heat pipe. In this work three numbers of heat pipes were used and hybrid nanofluid of Al2O3 – TiO2 has been used as cooling fluid in all three heat pipes. The thermal efficiency of the usage of hybrid nanofluidic working system is found to be highest and also this makes the system to get worse in terms of thermal resistance. The flow rate of condenser section was modified to the various ratios from 1:1 to 1:3 as that of evaporator section. To find the thermal characteristics of the heat pipe, many experiments have been carried out by considering many operating conditions. Evaluation on the heat pipe effectiveness was made on basis of gravity assistance to the condenser. The better productiveness of heat pipe when using the hybrid nanofluid has attained when Ch/Cc = 2 and 100 LPH for all operating conditions.

A novel lift-off diameter model for boiling bubbles in natural gas liquids transmission pipelines

The pipeline is a convenient and safe way to transport natural gas liquids (NGLs). However, the NGL is easy to boil due to the variations of pressures and temperatures along the pipeline. The bubble lift-off diameter is an essential parameter to calculate the mass and heat transfer rates between vapor and liquid phases for the NGL two-phase saturated boiling flow. This paper proposed a novel bubble lift-off diameter model based on the force-balance principle of bubbles, which considers the effects of the pressure, shear lift force, unstable drag force, surface tension, gravity force, buoyancy force, gas-phase density, bubble volume, bubble flow velocity, and bubble growth time on the bubble’s lift-off diameters at various pipe inclination angles. A total of 136 experimental data points are applied to validate the new model. Results demonstrate that the average relative deviation (ARD) between the experimental bubble’s lift-off diameters and calculated values based on the new model is in the range from 5.75% to 29.95%. In contrast, for horizontal and vertical pipes, the minimum ARDs of seven existing models (Fritz, Kocamustaf, Zeng, Lee, Situ, Hamzekhani, Chen models) are in the range from 19.42% to 42.58%, respectively. Moreover, the in-depth force analysis results reveal that the shear lift force, buoyancy force, drag force and surface tension force are dominant factors affecting the bubble lift-off diameters in inclined pipes. The new model provides an effective method to calculate the bubble lift-off diameter in the pipe at various inclination angles, overcoming the deficiencies of most existing models that only can be applied to either horizontal or vertical pipes.

A Novel, Coupled CFD-DEM Model for the Flow Characteristics of Particles Inside a Pipe

This study developed a novel, 3D coupled computational fluid dynamics (CFD)-discrete element method (DEM) model by coupling two software programs, OpenFOAM and PFC3D, to solve problems related to fluid–particle interaction systems. The complete governing equations and the flow chart of the coupling calculations are clearly presented herein. The coupled CFD-DEM model was first benchmarked using two classic geo-mechanics problems, for which the analytical solutions are available. Then, the CFD-DEM model was employed to investigate the flow characteristics of a particle heap subjected to the effects of water inside a pipe under different conditions. The results showed that particle size and pipe inclination angle can significantly affect the particle flow morphology, total kinetic energy and erosion rate for mono-sized particles, whereas polydisperse particles had a slight effect. This model can accurately describe the flow characteristics of particles inside a pipe, and the results of this study were consistent with those of previous studies. The reliability of this model was further demonstrated, which showed that this model can provide valuable references for solving similar problems such as soil erosion and bridge scour problems.

Effect of Nanofluid and Surfactant on Thermosyphon Heat Pipe Performance

An experimental analysis is done to investigate the thermal performance of a thermosyphon heat pipe (THP) using three working fluids, namely, distilled water, nanofluid, and a mixture of nanofluid and surfactant. The working nanofluid is titanium dioxide and THP is made of copper tube with the outer diameter of 15 mm and length of 1000 mm. The effects of the input power and inclination angle on the THP performance are investigated. The experimental results indicated that with increasing the concentration of nanofluid, thermal efficiency increases and thermal resistance of the thermosyphon decreases. According to the results, mixing the nanofluid with the surfactant will decrease the evaporator wall temperature and the thermal resistance, while it increases the thermal efficiency of THP. Comparison between two nanofluids and a conventional fluid in a THP shows that the best pipe inclination angles are 60° for water and 90° for nanofluids. Adding the proper amount of surfactant increases THP’s thermal efficiency by 20%. The best thermal performance of THP achieved at the input power of 200 W for all the working fluids. The average deviation of 1% was observed between the experimental results of this study and those available in the open literature.

Thermal management system of CPU cooling with a novel short heat pipe cooling system

Due to the limited space and power available in computers or electronics devices, heat pipes are ideally suited for cooling the high power chips. The thermal management system of computer with CPU cooling with short heat pipe cooling system has been investigated. Effects of the relevant parameters; inclination angle of heat pipe, with and without porous media, working fluid types and operating conditions of computer on the variation of CPU temperature are considered. In the experiments, R11, R134a and ethanol are selected as working fluids inside the heat pipe with constant 50% fill ratio. The variations of CPU temperature obtained from the heat pipe cooling system are compared with those from the conventional cooling system. It can be seen that the inclination angles of the heat pipe and physical properties of working fluids have significant effect on the cooling capacity which results in the CPU temperature variations. The heat pipe with porous media gives the CPU temperature lower than without porous media. The obtained results are expected to lead to guidelines that will allow the design of the thermal management system with optimized heat pipe cooling system for CPU cooling system with maximum cooling capacity.

A Generalized Reduced-Order Dynamic Model for Two-Phase Flow in Pipes

Real-time monitoring of pressure and flow in multiphase flow applications is a critical problem given its economic and safety impacts. Using physics-based models has long been computationally expensive due to the spatial–temporal dependency of the variables and the nonlinear nature of the governing equations. This paper proposes a new reduced-order modeling approach for transient gas–liquid flow in pipes. In the proposed approach, artificial neural networks (ANNs) are considered to predict holdup and pressure drop at steady-state from which properties of the two-phase mixture are derived. The dynamic response of the mixture is then estimated using a dissipative distributed-parameter model. The proposed approach encompasses all pipe inclination angles and flow conditions, does not require a spatial discretization of the pipe, and is numerically stable. To validate our model, we compared its dynamic response to that of OLGA©, the leading multiphase flow dynamic simulator. The obtained results showed a good agreement between both models under different pipe inclinations and various levels of gas volume fractions (GVF). In addition, the proposed model reduced the computational time by four- to sixfolds compared to OLGA©. The above attribute makes it ideal for real-time monitoring and fluid flow control applications.

Heat transfer in a partially filled rotary evaporator

Heat transfer with evaporation in a partially-filled, rotating pipe with water flowing through it is experimentally investigated. The test section is a 32.8 mm ID, 1000 mm long stainless steel pipe with a wall thickness of 1.1 mm. The outer wall temperature distribution is captured using a thermal camera. Uniform wall heat flux (3348–21200 W/m2), water volume flow rate (100–400 ml/min), rotation rate (10–300 RPM) and pipe inclination angle (0°–6°) are varied to study their influence on the heat transfer characteristics of a rotary evaporator. Location of the onset of nucleate boiling is used to study the effect of various parameters on the rotary evaporator operation. With the increase in the pipe inclination angle and wall heat flux, the onset of nucleate boiling is achieved closer to the inlet of the rotary evaporator. Increasing liquid flow rate delays the onset of nucleate boiling for given wall heat flux and inclination angle. Rotation rate has no significant effect on the rotary evaporator performance in the subcooled boiling region. Local heat transfer coefficient along the length of the partially filled rotating test section is reported.