Friction Factor Directly From Roughness Measurements

Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness.

Possible Detection of Multiple Blockages Using Transients

This work explores the possibility of utilizing the interaction between a pressure pulse propagating in a pipe with the blockages therein, as a means of blockage detection and characterization. Whereas an earlier work focused on a single blockage, the present work attempts to extend the strategy to multiple blockages. A one-dimensional isothermal non-compositional single-phase Eulerian model was used to describe the propagation of a pressure pulse through a pipe with multiple blockages. Pressure variations at the inlet caused by reflections of the propagating transient are monitored and analyzed. This analysis is used to make deductions about the internal configuration of the pipe. The results demonstrate that the technique is feasible and that accurate characterization of multiple blockages is possible.

An Investigation of Slug Flow in Hilly Terrain Pipelines

Two-phase flow in hilly terrain pipelines can cause significant practical operating problems. When slugs flow in a hilly terrain pipeline that contains sections of different inclinations they undergo a change of length and slug flow characteristics as the slug move from section to section. In addition, slugs can be generated at low elbows, dissipate at top elbows and shrink or grow in length as they travel along the pipe. A mathematical model and a computer program was developed to simulate these phenomena. The model was based on the sink/source concept at the pipeline connections. A connection between two pipeline sections of different slopes was conveniently called elbow. An elbow accumulates liquid as a sink, and releases liquid as a source. The sink/source has a characteristic capacity of its own. This capacity is positive if the liquid can indeed be accumulated at the elbow or negative if the liquid is actually drained away from the elbow. This type of treatment effectively isolates the flow upstream from an elbow from that downstream, while still allowing flow interactions between two detailed pipeline sections. The hydrodynamic flow model was also used to calculate the film liquid holdup in horizontal and inclined pipelines. The model can successfully predict the liquid film holdup if the liquid film height is assumed to be uniform through the gas pocket. Many other models were used to calculate all the needed parameters to perform the sink/source model. The overall effect of a hill or terrain on slug flow depends on the operating flow rates and pipeline configurations. For special case of near constant slug frequency corresponding to moderately high superficial liquid and gas velocities, this effect was found to be small. The changes in the film characteristics between two adjacent pipeline sections were found to be mostly responsible for the pseudo-slug generation, slug growth and dissipation in the downstream pipeline sections. The film liquid holdup decreased with increasing pipe diameter. The unit slug length increased at the upstream inclined pipes and decreased at the downstream inclined pipes with increasing pipe diameter. The possibility of pseudo-slug generation was increased at large pipe diameters even at high sink capacities. At low sink capacities, no pseudo-slugs were generated at high superficial velocities. The slug flow characteristics was more effected by low superficial gas and liquid velocities, large pipe diameters and shallow pipeline inclinations.

Platform Equipment and Operations for Extended Reach Remediation

A discussion of the equipment and preparation necessary to be made on an offshore platform for effective extended reach services.

Thermal Analysis of Curing Process of Epoxy Prepreg

The curing process of epoxy prepreg was studied by means of Differential Scanning Calorimeter. The dynamic, isothermal, and combinations of dynamic and isothermal measurements were done over selected temperature ranges and isothermal cure temperatures. The heats of reaction for dynamic and isothermal cure were determined. The results show that the heat of isothermal-cure reaction increased with the increment of temperature. The degree of cure was calculated from the heat of isothermal-cure reaction. The complete cure reaction could be achieved at 220 °C within the very short cure time. The changes of cure rate with time were given for the studied isothermal cure temperatures. To simulate the relationship between the cure rate and degree of cure, the autocatalytic model was used and the four parameters were calculated. Except in the late stage of cure reaction, the model agrees well with the experimental data, especially at high temperatures. To account for the effect of diffusion on the cure rate, a diffusion factor was introduced into the model. The modified model greatly improved the predicated data at the late stage of cure reaction.

Deformation and Fracture Characteristics of Cenosphere Filled Epoxies Under Compressive Loading Conditions

Close cell structured foams are made by incorporation of cenospheres in polymeric materials. Low moisture absorption characteristics and considerably higher compressive strength of these materials compared to open cell structured foams make them suitable for use as core materials in sandwich structured materials. Incorporation of cenospheres in the epoxy resins enhances their impact strength and damage tolerance, especially if these materials are used in sandwich configurations. Present study analyzes and compares the effect of incorporation of cenospheres like flyash and glass microballoons in the epoxy resins on the deformation and fracture behavior of the material. Approach based on determination of local stress intensity factors is used to obtain estimate of the stresses in the material.

Experimental Verification of Fractal Geometry of Tool-Chip Contact in Machining

The tool-chip interface in machining often consists of sliding and sticking islands of varying geometry intertwined within each other. Preliminary experimental evidence verifying the fractal geometry of the sticking/sliding profiles is presented in this paper.

Models for Inspected Systems Under General Degradation

Many protective devices, as well as spare and standby systems, exhibit what are known as non self-announcing failures; that is, failures can be observed only by inspection. Inspections can usually reveal only whether the device is operational or not, and not the level of deterioration of the device. This paper considers the availability of such systems when degradation is driven by an exogenous random environment. We allow this environment to be quite general; it includes both continuous (graceful) degradation and degradation due to discrete shocks. For periodic inspection schemes, we compute the limiting average availability and discuss opportunities for more effective inspection policies.

Real-Time Multiphase Metering Using Non-Intrusive Microwave Sensor

At the University of Liverpool we have developed a real-time, non-intrusive multiphase dielectric meter capable of measuring the dielectric properties of different mixtures of oil, gas and water in full well stream flow. The design of such a microwave cavity using a range of rf and microwave is described. The experimental results with a wide range of multiphase mixtures from 0 to 100% are reported. In this paper we also present the implementation of a neural network to simulate the response of the meter under all conceivable conditions. Other parameters including pump speed, temperature, salt and sand are also discussed.

Comparison of the Performance of Drag Reducing Agent Between 2.5 cP Oil and 6.0 cP Oil in Multiphase Flow in Horizontal Pipes

Experimental studies have been performed in a 10 cm diameter, 36 m long, multiphase flow loop to examine the effect of drag reducing agents using 6 cP oil. Studies were performed for superficial liquid velocities of 0.5, 1.0 and 1.5 m/s and superficial gas velocities between 2 and 12 m/s. Carbon dioxide was used as the gas phase. The drag reducing agent (DRA) concentrations were 20 and 50 ppm. The system was maintained at a pressure of 0.13 MPa and a temperature of 25 °C. The comparison of the conditioning of flow with DRA between 2.5 cP oil and 6 cP oil is presented. The results show that pressure drop in both 2.5 cP oil and 6 cP oil was reduced significantly in multiphase flow with addition of DRA. A DRA concentration of 50 ppm was more effective than 20 ppm DRA for all cases. As the oil viscosity was increased from 2.5 cP to 6 cP oil, the transition to annular flow was observed to occur at lower superficial gas velocities. For slug flow and lower superficial gas velocities, the effectiveness in 2.5 cP oil was much higher than that in 6 cP oil with addition of DRA. However, for higher superficial gas velocities, the effectiveness in both oils was similar. For annular flow, the effectiveness in 2.5 cP oil was higher than in 6 cP oil with 50 ppm DRA. At low superficial gas velocities, DRA in 2.5 cP oil was more effective in reducing the slug frequency. This led to a higher average pressure drop reduction in 2.5 cP oil. However, at higher superficial gas velocities, the slug frequency decreased in both oils almost the same magnitude.