Fluid In Pipe Research Articles

Numerical study on the heat transfer performance of coaxial shallow borehole heat exchanger

l CFD simulations on the coaxial shallow borehole heat exchanger without grouting. l Analyzing the effect of design parameters on the heat transfer performance. l Investigating the effect of thermal short-circuiting. l Providing some guidelines for the coaxial shallow borehole exchanger design. In the present work, a numerical investigation on the coaxial shallow borehole heat exchanger based on Computational Fluid Dynamics (CFD) technique in Hefei city of China has been performed. The effects of design parameters, including inlet flow rate, inlet fluid temperature, inner pipe material and outer pipe diameter, on the heat transfer performance were systematically studied. Besides, the thermal behavior along the pipe has been carefully examined with focus on the thermal short-circuiting phenomena. When the fluid inlet velocity is less than the critical value, the turbulence intensity increases and the Nusselt number increases with the inlet flow rate increasing. However, there is sufficient time for heat transfer between the fluid in inner pipe and outer pipe because of low flow rates, leading to large heat loss, i.e., thermal short-circuiting phenomenon. It is found that with the inlet flow rate increasing, the heat transfer increases first and then decreases, and the rate of reduction slows down gradually. When the inlet flow rate increases, the pumping power undergoes exponential growth. As the inlet temperature increasing, the heat transfer decreases almost linearly. Moreover, when the soil temperature at the top of the casing is lower than that of the fluid in the casing, heat is transferred from the fluid in the casing to the soil, and the heat loss increases with the increase of the inlet fluid temperature. The material of inner pipe with high heat conductivity would result in large heat loss under the influence of thermal short-circuiting. The heat load increases while the pumping power required decreases with the increasing of outer pipe diameter. This study is very beneficial for the coaxial shallow borehole exchanger designs and energy conservation of buildings.

Heat Transfer Characteristics of Nano Suspension Type Latent Heat Transport Heat Transfer Fluid in Straight Pipe

Heat Transfer Characteristics of Nano Suspension Type Latent Heat Transport Heat Transfer Fluid in Straight Pipe

Configuration Optimization of Ultrasonic Descaling Device for Condenser Based on Solidworks-Fluent

As a key component of the open circulation cooling system, the condenser of the power plant is very prone to fouling. After the condenser cooling pipe is scaled, the heat transfer resistance increases, which reduces the heat transfer coefficient and heat exchange efficiency of the heat exchange equipment, which is not conducive to improving the energy efficiency. Therefore, the research on condenser descaling technology has attracted widespread attention. Ultrasonic descaling is a new type of online descaling technology. Its application effect in descaling of condensers in power plants has been verified by actual engineering, but it lacks optimization of the arrangement and configuration of ultrasonic devices. In order to explore the influence of various ultrasonic parameters on the descaling effect, this paper builds a 3D geometric model of the condenser in Solidworks based on the relevant structural parameters of the N-20910 condenser, meshing the model reasonably and setting the boundary conditions. Then, in Fluent, the descaling effect is characterized by the pressure change curve of the specific position of the fluid in the condenser pipe. By setting three different ultrasonic inlet modes and different ultrasonic sound pressure functions, the effects of the quantity, power, frequency and distribution of ultrasonic descaler on the internal flow field and descaling effect of the condenser are compared and analyzed. The simulation results can provide effective help for the optimization and parameter setting of the ultrasonic descaling device of the power plant condenser.

Improvement of Thermal Performance using Spineloxides/Water Nanofluids in the Heat Recovery Unit with Air-to-Air Thermosiphone Mechanism

Heat recovery units are used for pre-heating the fresh air in waste heat plants. The nanofluid used as working fluid in the heat pipe will allow the heat recovery unit to benefit from the waste heat at lower temperatures, since it can evaporate at a temperature lower than the temperature of the base fluid. Therefore, the range of the operating temperature of the heat recovery unit will be increased. Different temperatures and flow rates of waste heat were used to find the optimum conditions for the evaporation of spinel nanofluid in the evaporator region of the heat pipe. Similar conditions were investigated for both of the cold fluid and optimal conditions on the condensation of nanofluid in the condenser region. In this study, an experimental setup was designed to improve the thermal performance of the air-to-air containing heat pipe heat recovery unit. The experiments were carried out using pure water-based nanofluids containing nano-sized ZnOAl2O3, MgOAl2O3, FeOAl2O3 particles, and the efficiencies of the heat transfer were investigated in this experiment. A thermosiphon mechanism that consists of five heat pipes, the length of each one is equal to 1 m, and the inner and the outer diameter of them is equal to 23.4 mm and 25.4 mm, respectively, those pipes are vacuumed, without wick and copper material. Heat pipes in the experimental setup; the evaporation zone is positioned to form 450 mm, the condensation zone 400 mm and the middle 150 mm parts to form the adiabatic region. At the beginning of the experiments, the working fluid charged to fill the 1/3 of the evaporation zone volumes of the heat pipes. Two different cooling air flow rates, 30 g·s−1 and 60 g·s−1, and three different heating air flow rates, 50 g·s−1, 70 g·s−1, 90 g·s−1 have been used, to calculate the heat obtained from the condensation zone. All the experiments were carried out by applying two different heaters with a power of, 1000 W and 2000 W, in the evaporation zone. Thus, the optimum temperatures and flow rates were found for all Reynolds numbers in the hot and cold fluid region, and its helps to determining the ranges of the operating temperature in the heat recovery unit. The experimental results that obtained from the two different working fluids (pure water and nanofluid) are compared. The best thermal performance of the system was found in the hot and cold air duct, when the Reynolds number was equal to 12 000. The thermal performance improvement rate was found as 92.8 % when the FeOAl2O3/water nanofluid used as working fluid, and 1000 W heater power and 60 g·s−1 cooling air flow applied.

Application of ANN to the water-lubricated flow of non-conventional crude

An annular water-film lubricates an oil-core by functioning as a barrier between the core and the pipe wall in the water-lubricated flow of non-conventional viscous oil. A dependable model for appraising the frictional energy losses in such a core annular flow system is necessary to ensure its widespread implementation in the industry. In the current study, the modeling was conducted using an artificial neural network (ANN) based on 223 data sets. Seven input variables applied in the current ANN model are pipe diameter, average velocity, fluid properties, and water fraction. The optimum architecture was identified as a feed-forward neural network with backpropagation technique involving two hidden layers, each of which was consisted of 20 neurons or nodes. Comparative statistical analysis demonstrated promising accuracy of the current model, the coefficient of determination was 0.992, and the root mean square error was 0.111. In addition to validating the model, the relative significance of the input parameters was evaluated with a sensitivity analysis.

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.

Transient flow of evaporating fluid in multiple parallel pipes, theory and experiments

The model of Barnea et al. [1] for an evaporating liquid flow in a system of parallel heated pipes with common inlet and outlet headers was modified, taking into account fluctuations in the flow rates during the transient process. The experimental system of two horizontal parallel mini channels presented in Barnea et al. [1] was expanded to include four pipes.New quantitative data on the steady state flow rate distribution and the transient response of the system to changes in the inlet flow rate and in the heating power are presented. The degree of complexity of three and four parallel heated pipes increases significantly compared to the case of two pipes. Several stable steady state flow rate distributions may be obtained for the same inlet flow rate, as well as various transient trajectories towards these steady states.The experimental results compare fairly well with the modified model simulations. The possibility of having multiple transient routs for the same constraint in the operational conditions is illustrated.

Large Eddy Simulation of turbulent fluid mixing in double-tee junctions

Double-Tee junctions serve as building blocks of pipe network systems and fluid mixing occurring in them is complex due to excessive eddying of flow. In this paper a LES model with pure advection was used on a double-Tee junction turbulent mixing phenomena problem. This kind of approach does not require the turbulent Schmidt number which is problem specific and needs to be calibrated with experimental data. When applying the LES-WALE turbulence model in conjunction with the pure advection transport of a scalar quantity on the double-Tee mixing problem it is achieved that the resolved turbulent flow field accurately transports the scalar when compared to experimental data from literature. This approach enables accurate mixing predictions in double-Tee junctions for the purpose of correcting simpler 1D numerical mixing models without the need of obtaining new experimental data since no turbulent Schmidt number calibration is needed. The approach can be applied to biological or chemical agent transport in a fluid and the model was tested and shown to be valid for a Reynolds number range of 20,000–400,000 on three different types of double-Tee junction configurations and five double-Tee distances with a constant inlet and outlet pipe diameter.

Experimental study and numerical analysis of fluid-structure coupling vibration characteristics for the reciprocating compressor pipeline

The fluid-structure coupling has been one of the hot issues of academic research in recent years, the achievements in various fields of study also emerge in an endless stream, but on the current research status, The study of fluid structure interaction in the field of dynamic equipment, especially compressor, is not very common. With the development of industrial compressors in the direction of large-scale and high-parameters, the analysis of coupling characteristics represented by fluid-solid coupling can evaluate the safe and stable operation of the system, and the evaluations are ofen more close to the actual situation. Therefore, it has gradually been valued. Through the comparison and analysis of the vibration test system of the reciprocating compressor before and after the pipeline inflation, the vibration response caused by the coupling factor is obtained, for the correctness verification of the fluid-structure coupling simulation. the numerical model of the experimental system is established based on ANSYS WORKBENCH, and the boundary conditions of the model are simulated by the experimental data, verified the feasibility of simulation program. Finally, the effects of medium density, pressure, flow rate, elastic modulus of pipe and Poisson’s ratio on fluid solid coupling vibration are discussed by using the verified simulation model. The results show that the medium density, dynamic fluid flow rate and pipe Poisson’s ratio have relatively little influence on the fluid-solid coupling vibration of the pipeline, while the medium pressure and the elastic modulus of the pipe have a great influence.

Analyzing the Fluid Flow of Transit-Time Ultrasonic Flowmeter with Image Processing Technique and Developing a Quality Metric Depending on Pipe Profile

The ultrasonic transit-time method measures the velocity and quantity of fluids in circular type pipes by using the difference of transit time between the ultrasonic pulses propagating with and against the flow direction. This method gives the average velocity of the fluid along a particular acoustic path. At least two ultrasonic transducers are used for an acoustic path. The multipath ultrasonic flowmeters have more acoustic paths. In this paper, the acoustic path between two transducers is described as pixels for the turbulent flow and formed a flow map for ideal flow conditions such as no elbow or bend depending on pipe profile. Using the obtained pixel values, the average fluid velocity is calculated between two transducers. Finally, a quality metric that calculates the ideal average fluid velocity ratio between the acoustic paths for the turbulent flow is developed. Thus, researchers can evaluate their designs with this quality metric.

Performance assessment and techno-economic optimization of ground source heat pump for residential heating and cooling: A case study of Nanjing, China

This study implemented the performance assessment and techno-economic optimization of residential ground source heat pump (GSHP). First, a detailed numerical model integrating the ground heat exchanger and heat pump and economic model considering economic indicators were developed to analyze the thermal and economic efficiency of residential GSHP. Then, Taguchi method was proposed to investigate the impacts of five parameters on the thermal and economic performance of GSHP and obtain the optimal parameters set. After that, the sensitivity of optimal parameter to the drilling costs, pipe prices, and interest rate were performed. Lastly, the analysis of variance approach was implemented to find out the relative significance of parameters. Results revealing that the superiority of individual GSHP can be maintained in the vast majority of time and the capital investments are relatively high within the range of 13034.4 to 18199.2 CNY. The optimal parameters combination was of great discrepancies when taking the economic indicators into account. The most economical choice of pipe size remains unchanged, despite the optimization objectives and varying pipe prices. The relative importance of fluid velocity, borehole depth, and pipe material towards the variation of economic efficiency largely depends on the drilling costs, pipe prices, and the interest rate.

Internal Corrosion in Pipes, Inspection and Analysis by Pulsed Thermography Using the Finite Element Method

In this work, the pulsed thermography process applied to inspect and analyze the internal corrosion defect in a pipe. The study carried out in two stages, the first one characterizes the control of the pipe at a standstill by considering the air inside the pipe, and the second one characterizes the control during operation by introducing a turbulent flow of seawater into the simulation. For this purpose, a 3D model of a fluid pipe containing three forms of internal rust defects performed using finite element software. The influence of parameters such as the size and penetration of rust into the tube evaluated by analyzing the contrast of the corresponding thermal images and the temporal and spatial variation of the temperature. The tube thickness introduced as a parameter influencing detection.

Viscous Heating Effects on Heat Transfer Characteristics of an Explosive Fluid in a Converging Pipe

Viscous dissipation is the production of heat due to the slip of fluid layers and can raise the temperature of the fluid that is affected by high shear stresses. This raise of temperature in fluids with explosive properties can cause the explosion during the processing. The present paper investigates the temperature distribution of an explosive fluid beside the wall of a converging tube. This study has been done by using the computational fluid dynamics and OpenFOAM software. The studied cases contain the fluid with two viscosities (50 and 500 kg/m × s) and two inlet conditions (constant and developed velocity profile). The results of this study show that at the end of a converging pipe, duo to the viscous dissipation effects, the temperature rise for high viscosity fluid is more intensive and this is a dangerous fact for high viscosity explosive fluids discharging. Also, it has been considered that the constant inlet velocity is safer in comparison with the developed profile, as the slope of temperature rise is less.

Morphometric scaling of subsurface vent complexes: implications for a new classification scheme

This paper provides a novel classification scheme for magma-induced subsurface vent complexes based on morphometric data and stacking patterns. The study area is the Naglfar Dome in the Voring Basin where the interaction between magmatic intrusions and vent complexes is well known. Seismic interpretation, characterization and morphometric analyses of 35 vent complexes observed within the Palaeocene-Eocene strata were done from a high-quality, three-dimensional seismic reflection data. The vent complexes have dome-shaped, eye-shaped, fault-controlled and reactivated upper termini, and are linked to their root zones by columnar, downward-tapered and fault-related fluid conduits or pipes. Statistical analyses and cross plots of L-A and Dmax-Hmax allowed the discrimination of vents and pipes into their genetic types. A new classification scheme based on the morphometric sub-division and structures of subsurface vent complexes is introduced to include S-P-V, S-P-F, V-P-V and V-P-F types. These combinations freshly demonstrate the importance of morphometric data at deciphering the nature, timing, classification and activity of subsurface fluid vent complexes.

FEA Analysis of Double Tube Heat Exchanger on Variable Baffle Pitch for Optimizing Thermal Efficiency

The main objective of this work is to compare different configurations of helical baffles in the cold fluid side of a double tube heat exchanger. For this analysis double pipe heat exchangers are divided into three different domains such as two fluid domains hot fluid in the inner tube and cold fluid in the outer pipe and a solid domain as helical baffles on inner tube of hot fluid. The hot water flows inside the heat exchanger tube, while the cold fluid flows in the outer side in the direction of counter flow. Mass flow rate cold fluid was varied from 0.1 kg/s to 0.3 kg/s while the flow rate in the inner tube i.e. hot water was kept constant at 0.1 kg/s. the inlet temperature of hot fluid taken as 40oC while Cold fluid inlet temperature taken as 15oC. The fluent software is used to calculate the fluid flow and heat transfer in the computational domains. The governing equations are iteratively solved by the finite volume formulation with the SIMPLE algorithm. Results show that that the maximum temperature drop of 10.9 oC for hot fluid and the maximum temperature rise of 11.9 oC for cold fluid are observed at 0.3 kg/sec mass flow rate for double pipe heat exchanger with double helical baffles. It has been also observed that the heat transfer coefficient increasing with the increasing in the mass flow rate of cold fluid. The overall heat transfer coefficients differ significantly by 20.4 % at same mass flow rate, because the considerable difference between heat transfer surface area on the inner and outer side of the tube resulting in a prominent thermal enhancement of the cold fluid.

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.

Shaft Pump Power - Effect of Pipe Network Configuration

Building design has often many engineering challenges to achieve the best possible energy and economic efficiencies. It is necessary to use technological tools capable of predicting with a high degree of accuracy the behavior of a pipe network system in order to obtain good designs that avoid problems in the future. This study is focused on the analysis of three pipe networks with different floors and the same configuration on each level. Four case studies have been developed in order to analyze the energy requirements and the outlet pressure of a pump for multiple pipe diameters, various floors, and fluid flow rates. The effects of the pipe diameter and the flow rate on the energy cost have been also analyzed. It has been observed that an increase in the flow rate in a pipeline of one inch of diameter causes a huge increase in the pump power when working on the net with a single floor. In addition, it has been found out that the higher the number of the floors is, the higher the pump powder is. However, this effect has not been significant when using pipelines with high diameters. Besides, it has been found out that the higher the number of the floors is, the higher the pressure drop in the system is. This effect is highly significant when using pipelines with small diameters. The total pump power cost had an exponential decay with the increase in pipe diameter.

Condition for the Incipient Motion of Non-Cohesive Particles Due to Laminar Flows of Power-Law Fluids in Closed Conduits

The results of an experimental study on the condition of incipient transport of non-cohesive particles due to the flow of a power-law fluid in a rectangular pipe are presented in this article. The pipe can change its inclination, and experiments were carried out with positive and negative slopes. From a dimensional analysis, the parameters that define the condition of incipient motion were found and validated with experimental data. Thus, the threshold condition is well defined by a particle Reynolds number and a Galileo number, properly modified to take into account the power-law rheology of the fluid. The experimental data are also presented in a standard Shields diagram, including the data obtained in other studies carried out in open-channel laminar flows of Newtonian and power-law fluids.

Numerical investigation on the mechanism of geyser in cryogenic fluid pipes

In order to study the mechanism of geyser in cryogenic fuel system, a CFD model based on VOF method for two-phase heat and mass transfer process is established and validated. The detailed transient behavior and the whole formation process of geyser in a cryogenic pipe are successfully captured and predicted. The prediction performance of 3-D, 2-D axisymmetric and 2-D planar model is evaluated. The formation and development of the whole geyser process are clearly revealed by visualization and macroscopic parameter analysis, and a contrastive study is performed to investigate the mechanism of the pressure peak in a geyser. It is found that: The incubation stage occupies the largest portion of geyser period up to 95% in the presented condition and there is a dramatic pressure fall in the eruption stage and a pressure spike in the refilling stage, which leads to a periodic shock of pressure. The violent depressurization boiling is the main cause of the eruption. Moreover, the water hammer induced by vapor condensation will bring about a huge pressure increase, and it becomes the main mechanism for the pressure spike in the refilling stage.

Topology optimization for heat transfer enhancement in thermochemical heat storage

Thermochemical heat storage has a promising application prospect due to its high energy density and ability of seasonal energy storage with little heat loss. However, most of thermochemical heat storage systems suffer from very poor thermal conductivity that limit the heat transfer rate and hinder the implementation of this technology. This study presents a novel solution to the poor heat transfer problem in a multi-tube thermochemical heat storage unit through topology optimization of highly conductive fins. For the formulation of the topology optimization problem, the dehydration process of Ca(OH)2 was considered, and a density-based approach was employed. Results indicated that the topology optimized geometry had a superior heat transfer performance and a 43% improvement was achieved with respect to the normally used longitudinal design in terms of reaction time. It was found that during the dehydration process of Ca(OH)2, heat conduction was the dominant factor while convection heat transfer was only observed in a small region near the porous gas channel. Furthermore, the effects of the number of heat transfer fluid (HTF) pipes were explored. It was shown that bifurcations of intermediate branches tend to vanish with the increase of the number of HTF pipes and the charging process can be further enhanced through a more uniform HTF pipe distribution. Finally, the reconstructed model was validated, and the optimized fins were tested under the hydration process of CaO, which further confirmed the superiority of the topology design.