Coiled Pipe Research Articles

Experimental Study of Single and Two-Phase Flow and Heat Transfer Characteristics in Helical Tube under Motion Condition

The unique structural characteristic of the helical coiled pipe causes some special phenomena such as the secondary flow effect inside the tube, and the heat transfer characteristics are more complicated than those in circular pipe. There have been few published papers about experimental research of flow and heat transfer characteristics of helical tube under motion conditions. An experimental loop was built based on the background above. An experimental study of single-phase and saturated boiling two-phase heat transfer characteristics and flow instability in helical tubes under multiple motion conditions was carried out. In which the maximum system pressure was 4 MPa, mass flux was 550 kg/(m2·s), and heat flux of the test section was 360 kW/m2. The results show that the heat transfer capacity of the side close to the central axis of the helical tube is significantly lower than that of the side away from the central axis under rocking and inclination conditions. An empirical correlation of the heat transfer coefficient in helical tube under static and motion conditions was drafted based on the experiment data of single-phase conditions. The influence of motion conditions on two-phase heat transfer characteristics was similar to that of a single phase but much weaker.

Enhanced thermal management of electric vehicle lithium-ion batteries with Al2O3–MWCNT–ethylene glycol hybrid nanofluid-based helical coiled pulsating heat pipe (HC-PHP)

Enhanced thermal management of electric vehicle lithium-ion batteries with Al2O3–MWCNT–ethylene glycol hybrid nanofluid-based helical coiled pulsating heat pipe (HC-PHP)

Effect of two different peritoneal dialysis modalities on wound infection in peritoneal dialysis patients: A meta-analysis.

Peritoneal dialysis(PD) is one of the most efficient methods in end-stage kidney disease, and it is very important for PD to perform well. No research has been conducted to evaluate the effect of various types of PD catheters on the prognosis of post-operative wound complications. While recent meta-analyses are in favour of straight tubing, there is still uncertainty as to whether direct or coiled PD is beneficial. The purpose of this meta-analysis was to compare the efficacy of direct and coiled PD catheters on the incidence of post-operative wound infection, bleeding and peritonitis. A comprehensive search was carried out on three databases, including PubMed and Embase, and a manual search was carried out on the links in the paper. The results showed that the incidence rate of bleeding after operation and the degree of infection among the straight and coiled pipes were compared. The results showed that there were no statistically significant differences in the incidence of post-operative wound infection among straight PD patients with coiled PD (OR, 0.79; 95% CI, 0.58-1.08 p = 0.13). No statistical significance was found in the case of PD with coiled tubing compared with that of straight PD group in wound leakage (OR, 1.17; 95% CI, 0.71-1.93 p = 0.55). No statistically significantly different rates of post-operative peritonitis were observed for coiled tubing compared with straight ones in PD patients (OR, 1.06; 95% CI, 0.78-1.45 p = 0.7). There is no statistical significance on the rate of wound infection, wound leakage and peritonitis among coiled and straight tube in PD.

Advanced Thermo-Hydraulic Assessment of Helical Pipes with Different Shapes of Jackets Using Single-Phase and Hybrid Nanofluids

This study investigates the efficiency and flow characteristics of helical pipes with different jacket shapes, utilizing single and hybrid nanofluids to enhance heat transfer. The research work presented here provides a unique, coherent method to enhance heat transfer efficiency by concurrently incorporating geometrical alterations and improving operating fluid efficiency. A computational framework analyzes turbulent flow in three-dimensional helical pipes with Reynolds numbers ranging from 5000 to 30,000 and a constant heat flux of 1000 W/m2. This investigation involves evaluating the thermo-hydrodynamic performance of spiral pipes with circular, triangular, and square-shaped jackets, using various volume fractions of single-phase nanofluids (water-based Al2O3 and CuO nanofluids) and a water-based hybrid nanofluid comprising Al2O3/Cu. The results indicate that using different nanofluids significantly improves the Nusselt number value and heat transfer coefficients, ranging from 36 % to 60 % compared to water in a smooth coiled pipe. The strategic design of the jacket enhances the Nusselt number values by generating vortices and increasing turbulence. The Bejan number indicates greater irreversibility in the heat transfer process, leading to substantial energy dispersion. The performance evaluation criterion (PEC) value exceeding one suggests that the modified geometries have the potential to outperform smooth channels.

Numerical Study of Turbulent Convective Heat Transfer of Aviation Kerosene in Coiled Pipes

Abstract Turbulent flow and convective heat transfer of kerosene in coiled pipes with different wall boundary conditions and curvature radii of coiled pipes are numerically studied. The Reynolds-averaged Navier–Stokes equations are solved by finite volume method and the realizable k–ε model is applied for turbulence modeling. The fluid media is aviation kerosene with an inlet supercritical pressure of 3 MPa and an inlet temperature of 400 K. The present results provide temperature and velocity fields as well as distributions of turbulence kinetic energy and streamlines at different axial locations along the flow direction. The Nusselt number at the outer side of the pipe wall is higher than that at the inner side by 75%. Compared to a straight pipe with the same pipe radius of 6 mm and inlet flow conditions, the coiled pipe with a curvature radius of 192.5 mm can increase the averaged heat transfer coefficient by 28.5%. Meanwhile, it is found that when the curvature ratio increases, the effect of secondary flow in the cross section of pipe is more significant and the heat transfer effect at different locations of the pipe wall also changes significantly. In addition, the present results also reveal that heat transfer deterioration takes place for the kerosene flow in coiled pipe with an increased wall heat flux due to the state change of kerosene from liquid to supercritical.

Angular segregation of fibres in pipe flow: floc formation and utilization for length-based fibre separation

Cellulose fibres are prone to flocculate and form aggregates that are deformable by the hydrodynamic stress. In this work I document for coiled pipe flow, known to have secondary motion in the pipe cross-sectional plane, an accumulation of fibre flocs and fibre aggregates at the outer bend. That is the segregation into a section in the pipe cross-section and hence presents a case of angular segregation. The segregation was studied for non-coherent crowded fibre flocs. For that, segregation benefited from fibre concentration and suffered from increased hydrodynamic stress expressed by increasing Reynolds number. Based on the observed segregation of fibres a flow splitter was designed that separated the flow at 1/3 of the tube diameter measured from the inner bend. The outer bend suspension length-weighted fibre length was found to increase. For the best case in this work, the difference between outer and inner bend relative to the feed fibre length was 22%. As for radial and axial segregation, which are known, also angular segregation is fibre-length sensitive. As such it can be exploited for length fractionation of networking and aggregating elongated particles, for example fibres.

Comparison between simulations and experiment for heat transfer characteristics in the re-burning kiln heat exchanger

Waste heat from the combustion process that is left unused may cause pollution problems and adversely affect health. This waste heat should be recovered. In this research, the simulation and experimental data on heat transfer characteristics of the pipe coiled inside the re-burning kiln heat exchanger were studied. The main objective of this study was to compare heat transfer coefficients obtained from the simulation using water as the working fluid with those obtained experimentally from the re-burning kiln heat exchanger for the drying system. The re-burning kiln heat exchanger was of coil-pipe-type with an outside diameter of 38 mm. The coiled pipe set up on the re-burning kiln heat exchanger was 80 cm in width and 173 cm in height. The flow rate of the cold water used as a working fluid was varied from 10 to 20 LPM, while the surface temperature of the coil pipe was varied from 200±20°C to 400±20°C, respectively. Thermal conductivity and outlet temperature of the water were also measured as a function of the internal temperature and water flow rate. The experimental results were validated against the simulation. The results showed that when the flow rate of water inlet decreased from 20 LPM to 10 LPM, the temperature of the water outlet was increased from 52.4 °C to 76.3 °C respectively. An increase in the temperature of the water outlet because of increased the re-burning kiln heat exchanger temperature and reduced the mass flow rate of supply water. The obtained simulated heat transfer coefficient in the re-burning kiln heat exchanger was in agreement with the experimental results.

Welding Thermal Accumulation During Butt-welding of Coiled Tubing

As a kind of advanced continuous coiled pipe, coiled tubing is widely used in oiled well engineering, it has high strength and good corrosion resistance. But unfortunately, its outstanding properties will be intensively affected by butt welding process. The welding thermal accumulation during butt-welding was studied in this paper. Based on double ellipsoid source model, a finite element model for butt welding process was developed and the temperature distribution was analyzed. The results show that for bead on plate welding, the weld pool size of tubing welding is smaller than that of plate welding because of dispersion of arc. Thermal accumulation can be observed around start point, where two peak temperatures appeared and cooling time is a little longer than plate welding.

Depressurization System by Coiled Pipes Applied to a High Pressure Process: Experimental Results and Modeling

Background:The use of backpressure regulator valves is widespread in high-pressure processes both at laboratory and pilot plant scales, but being a single step for effluent depressurization, such valves may have some limitations at industrial scale. In an effort to improve the depressurization step, this work studies a system based on the pressure drop of a fluid that circulates through coiled pipes.Method:The equipment, based on three series of variable length coiled pipes, was installed to achieve depressurization of 240 bars in a SCWO pilot plant.Results:The experimental results were compared with those obtained by the modeling carried out using different friction factor correlations from the literature.Conclusion:Among all the correlations tested, the Lockhart–Martinelli correlation showed the best agreement with experimental data. However, it was necessary to obtain an appropriate C parameter to achieve a good agreement with experimental data.

Secondary vortex-based analysis of flow characteristics and pressure drop in helically coiled pipe

This article presents an investigation for the secondary flow characteristics and associated pressure loss in fluid flow through helically coiled pipe. Computational fluid dynamics is employed to analyze the pipe flow with various geometries, and the accuracy of the numerical methodology is validated by conducting corresponding experiments. The analysis performs a detailed parametric study involving the pressure loss, the secondary vortex motion, and the secondary vortex intensity for a range of coil diameters ( D; ranging from 300 to 3000 mm) and pipe diameters ( d; ranging from 50 to 90 mm). The pipe flow develops to a stable state with increase in coil diameter, while an increase in pipe diameter delays this development. Then, the secondary flow characteristics are analyzed to explore the pressure loss mechanism. The distorted streamline of secondary vortices and the enlarged deflection angle of secondary vortices are both factors contributing to the enhanced pressure loss. Furthermore, the effects of pipe flow development on the following flow characteristics such as the turbulence dissipation rate and the secondary vortex intensity are revealed. These characteristics all distribute regularly and reach lower values when pipe flow begins to a stable state.

Experimental Study of the Transient Flow in a Coiled Pipe Using PIV

AbstractA comprehensive knowledge of energy dissipation during the accelerations and decelerations in transient flow is essential to develop robust and accurate hydraulic transient solvers. Currently, most transient solvers are not accurate enough to describe the physical phenomenon, tending to underestimate observed energy dissipation. The current paper aims to contribute to a better understanding of transient flow by measuring instantaneous velocities using 2D particle image velocimetry (PIV) and discussing key features of the mean and of the turbulent flow. Measurements were carried out at the middle section of a coiled copper pipe for Reynolds and Dean numbers of 7,000 and 1,040, respectively. In steady-state flow, the time-averaged velocity profiles have shown a strong asymmetry, with maximum axial velocity in the outer bend region of the pipe, caused by the centrifugal force. During transient flow, the ensemble-averaged velocity profiles have clearly shown regions with strong gradients near the pipe...

Experimental investigation of the condensation of R134a and R404A refrigerants in a long, water-cooled, serpentine coils

The subject of the present analysis is the condensation of the environmentally friendly refrigerants R134a and R404A in long, serpentine pipe coils, for Lc/d>800–1000, where Lc is the total length of the coiled pipe, and d is its internal diameter. During condensation in a coiled-pipe condenser, heat exchange occurs in three regimes, i.e., the superheat removal regimes, the two-phase condensation regimes and the condensate subcooling regimes. The length L of the two-phase area significantly affects the values of the average heat transfer coefficient α and the flow resistance (Δp/L) in this area. On the basis of experimental investigations of the condensation process in a long, water-cooled serpentine coil with five pipe coils of differing dimensions, it was established that the condensation mechanism in a long coil pipe differs substantially from that in a horizontal pipe. New experimental correlations were developed to calculate the average heat transfer coefficient and flow resistance in the two-phase area. In these correlations, the dimensions of the two-phase area are characterized by the geometric index L/d. The correlations developed in this study may be useful in the design of water-cooled serpentine-coil condensers.

Scale-Up Correlation for the Flow of Surfactant-Based Fluids in Circular Coiled Pipes

This study involves experimental investigation on the flow properties of aqueous surfactant-based (SB) fluids in small and large-scale coiled tubing. It aims at understanding the viscoelastic properties and its effect on the flow behavior of SB fluids in coiled tubing. In spite of SB fluids wide use as friction reducer and/or fracturing fluid in the oil and gas industry, the flow data in large pipe sizes as well as coiled tubing are very scarce. Majority of the available flow data are gathered in straight pipes with small sizes. The scale-up of small-scale flow data is questionable due to the pronounced diameter effect. Furthermore, previous studies have correlated flow behavior of these fluids only through simple power-law model parameters. Limited work with polymeric fluids has been reported that includes fluid elasticity in scale-up procedure and it is nonexistent for highly elastic SB fluids. In this study, the properties of widely used Aromox APA-T, a highly active surfactant used as gelling agent in aqueous and brine base fluids, are thoroughly investigated. Rheological measurements are conducted using Bohlin rheometer for SB fluid concentration of 1.5 vol %, 2 vol %, 3 vol %, and 4 vol %. Flow data are gathered using 1.27 cm, 3.81 cm, 6.03 cm, and 7.30 cm OD coiled tubing with various curvature ratios. This study presents the first attempt to investigate the flow behavior SB fluids in large-scale coiled tubing. The results show that SB fluids exhibit non-Newtonian pseudoplastic behavior. Elastic and viscous properties of SB fluids are very sensitive to surfactant concentration. Friction losses in coiled tubing are significantly higher than those in straight pipes due to secondary flow effect. Increasing curvature ratio yields higher friction pressure loss. Also, small-scale data correlations using only simple power-law model fluid rheological parameters lead to erroneous results when scaled-up to large pipe sizes. New technique, based on the modified Deborah number, which includes fluid elasticity and pipe shear effect, has been developed to correlate data from the small laboratory-scale tubing and large field-scale pipes. Correlation to predict Fanning friction factor of SB fluids in coiled tubing as a function of Deborah number and fluid flow behavior index is presented. Correlation is validated by comparing predictions with the experimental data. It is shown that the new correlation accurately predicts friction factor of SB fluids and thus alleviates the scale-up issue.

Long-Range Pipeline Monitoring by Distributed Fiber Optic Sensing

Distributed fiber optic sensing presents unique features that have no match in conventional sensing techniques. The ability to measure temperatures and strain at thousands of points along a single fiber is particularly interesting for the monitoring of elongated structures such as pipelines, flow lines, oil wells, and coiled tubing. Sensing systems based on Brillouin and Raman scattering are used, for example, to detect pipeline leakages, to verify pipeline operational parameters and to prevent failure of pipelines installed in landslide areas, to optimize oil production from wells, and to detect hot spots in high-power cables. Recent developments in distributed fiber sensing technology allow the monitoring of 60 km of pipeline from a single instrument and of up to 300 km with the use of optical amplifiers. New application opportunities have demonstrated that the design and production of sensing cables are a critical element for the success of any distributed sensing instrumentation project. Although some telecommunication cables can be effectively used for sensing ordinary temperatures, monitoring high and low temperatures or distributed strain presents unique challenges that require specific cable designs. This contribution presents advances in long-range distributed sensing and in novel sensing cable designs for distributed temperature and strain sensing. This paper also reports a number of significant field application examples of this technology, including leakage detection on brine and gas pipelines, strain monitoring on gas pipelines and combined strain and temperature monitoring on composite flow lines, and composite coiled tubing pipes.

Friction and heat transfer in drag-reducing surfactant solution flow through curved pipes and elbows

A study of drag-reducing flow in curved pipes was conducted. In contrast to earlier studies we show that if we use a modified definition of drag reduction that includes only the turbulence effects, we observe indeed the same level of drag reduction in both coiled and straight pipes. More complex results showing reduced drag reduction compared to curved pipes were achieved with elbows. Two elbows of different size and type were tested in turbulent flow of both water and drag-reducing surfactant solution. A more elaborate analysis was conducted for a half-inch threaded elbow with a ratio of curvature radius to diameter of 1.2. The pressure drop and heat transfer were measured in a section downstream from the elbow over a distance of x/ D = 130 in order to investigate the hydrodynamic and thermal developments of the flow. The pressure drop coefficient of the elbow was calculated for water and a surfactant solution, based on the total increase in pressure drop in the system due to the presence of the elbow. For a larger welded elbow of 6″ diameter some drag reduction was measured for the surfactant solution.

Numerical Investigation of Heat Transfer Performance of Rectangularly Coiled Pipes

A numerical simulation was conducted to investigate convective heat transfer from small and compact coiled pipes heat exchangers using computational fluid dynamics (CFD) software Fluent V6. One fluid (air) moves over the coiled pipe while a second fluid (refrigerant R141B) at different temperature flows through the pipe. The studied heat exchanger is composed with bends and straight tubes. Calculations were done for two cases with different outside flow arrangements. The simulation results showed remarkable differences in the flow characteristics and heat transfer rate of different single tubes of the entire heat exchangers. The temperature distribution and heat transfer are mainly influenced by temperature gradient, backflow conditions, exterior flow velocity, and surface area. The results also show the effect of the bends on the flow in straight tubes and vice-versa.

Particle Distribution and Erosion During the Flow of Newtonian and Non-Newtonian Slurries in Straight and Coiled Pipes

Straight and coiled tubing are frequently used in the petroleum industry in operations such as fracturing, cementing, drilling and perforation. Most of these operations involve flow of slurries during which erosion of tubing is a major problem and its prediction becomes important for the safe and economical execution of oilfield operations. Erosion due to slurry flow depends on a number of factors, several of which are interdependent which makes the process more complex. Various experimental and modeling techniques have been in use to evaluate the erosion resulting from the flow of particles. These experimental and modeling techniques, however, have their limitations due to the deficient experimental data and computational restrictions. This study presents the results of Computational Fluid Dynamics (CFD) analyses conducted on straight and curved tubing sections under various flow conditions and different Newtonian and non-Newtonian base fluids commonly used in the petroleum industry. The particle distribution and shear stress for simulated flow cases have been evaluated and compared to comprehend the nature of particle interaction with the flow boundaries and resulting frictional erosion. The study highlights the effect of lubrication forces and viscosity of the base fluid.

Heat transfer in a horizontal coiled pipe in a transient regime and at a near-critical pressure of a fluid

It has been established that in the region of pressures close to a critical one, heat transfer in a transient regime of motion of a single-phase flow in a horizontal coil pipe changes nonuniformly over the cross section of the perimeter. The main factors here are the influence of inertia forces and of free convection. Equations to calculate the heat-transfer coefficient are suggested.

Heat transfer of high thermal energy storage with heat exchanger for solar trough power plant

High temperature thermal energy storage was studied by a lab-scale cylindrical storage tank experiment. A heat exchanger of thermal energy storage is used for separating two fluids, storage medium, and heat transfer fluid (HTF). There are two types of pipe in the heat exchanger, a vertical straight pipe and a helical coiled pipe. The experimental results were validated with the created mathematical model of nonsteady state heat exchanger. The highest storage efficiency is 0.631 at the HTF flow rate of 0.1 kg/s in a helical coiled pipe heat exchanger. The HTF and storage medium temperatures were measured for validating the model at various HTF flow rates. The agreement between model and experiment was presented with the error below 10%. This model is able to calculate the storage temperature of solar thermal power plants that performs in the liquid temperature range of selected HTF and storage medium.

Subcooled and saturated water flow boiling pressure drop in small diameter helical coils at low pressure

Experimental pressure drop results on boiling water flow through three helical coils of tube inner diameter of 4.03 mm and 4.98 mm and coil diameter to tube diameter ratio of 26.1, 64.1 and 93.3 are presented. Both subcooled and saturated flow boiling are investigated, covering operating pressures from 120 to 660 kPa, mass fluxes from 290 to 690 kg m −2 s −1 and heat fluxes from 50 to 440 kW m −2. Existing correlations for subcooled flow pressure drop are found not capable to fit the present subcooled database, while the measurements in saturated flow conditions are successfully reproduced by existing correlations for both straight and coiled pipe two-phase flow. The experimental database is included in tabular form.