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RESEARCH PAPERS

J. Energy Resour. Technol. 1988;110(2):59-67. doi:10.1115/1.3231367.

At the beginning of the eighties, the offshore technology relevant to thermally insulated pipelines did not offer a cost-effective and technically challenging solution. Nowadays, the oil industry requires an ever-increasing use of thermally insulated pipelines with improved reliability in the offshore and, more particularly, for the exploitation of arctic fields. The present solution has been developed on the basis of easy handling, conventional laying procedures and long-term integrity criteria adopting a special field joint connector. This type of connector allows the two coaxial pipes to be assembled in a workshop and the individual double pipe sections to be connected in the field by means of a standard butt weld. This paper includes: the presentation of the DPIS (Double Pipe Insulated System) concept, which deals with the structural and thermal insulation aspects relevant to this new system; and a brief description of the first application of the DPIS for a pipeline connecting an unloading terminal for heavy oils to onshore plants.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):68-76. doi:10.1115/1.3231368.

The results of the two and three-dimensional, nonlinear analyses of a caisson retained island in the Beaufort Sea are presented. A hyperbolic stress-strain relation for soils has been implemented in a general purpose finite element program, ADINA, to carry out the analysis. Based on the comparisons of the results, conclusions were drawn about whether a two-dimensional analysis can be safely used to replace a three-dimensional analysis.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):77-84. doi:10.1115/1.3231369.

Because the average ocean depth is four kilometers, seafloor investigations are mostly remote sensing operations. The primary means to determine the morphology, the structure, and the texture of the seafloor are acoustic. This paper considers the current seafloor remote sensing approaches involving acoustic backscattering. The physical constraints imposed by the ocean as a propagation medium, by the seafloor as a backscattering boundary, and by the measuring instruments are briefly reviewed. The sonar systems currently used by the oceanographic community for deep seafloor acoustic backscattering measurements deal with these constraints differently, depending on their specific application and on whether they are towed behind a ship or mounted on her hull. Towed sidescan systems such as Gloria II (U.K.), the Sea Mapping and Remote Characterization (Sea MARC) I and II, the Deep Tow system of the Marine Physical Laboratory (MPL), and hull-mounted systems, such as Swathmap all give a qualitative measure of backscattering by converting echo amplitudes to gray levels to produce a sidescan image of the seafloor. A new approach is presented which uses a Sea Beam multibeam echo-sounder to produce similar acoustic images. Quantitative measurements of backscattering have been attempted in recent experiments using the Deep Tow system and Sea Beam. Such measurements provide some insight into the geological processes responsible for the acoustic backscatter, with useful applications for geologists as well as designers and operators of bottom-interacting sonars.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):85-92. doi:10.1115/1.3231370.

Finite element analyses were conducted of the threaded marine riser connector which has the main, internal, and external shoulder seals. The objectives of the analyses are to evaluate the fatigue resistance, strength, and seal capability of the connector under the bending, tensile, internal and external pressure loads. An element which models the bending effect in an axisymmetric body is developed and implemented into the computer program ADINA. Using the program, stress concentration factors at the corner and threaded parts of the connector under these loads are obtained. The large contribution of both shoulders to the reduction of the stress concentration factors is found to be quite clear. The seal mechanism and the stress response of the connectors are also clarified. The fatigue evaluation based on ASME Boiler and Pressure Vessel Code, Sec. III, Rules for Construction of Nuclear Power Plant Components, Division 1, Subsection NB are compared with the experimental results.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):93-101. doi:10.1115/1.3231371.

A new method is developed to analyze transient gas-liquid two-phase flow in natural gas pipelines. This method utilizes the two velocity mixture model to derive the basic equations. Also, a new model, which expresses phase conditions for multicomponent natural gas-condensate system, is presented to derive mass conservation equations for each hypothetical component. Transient air-water two-phase flow experiments were conducted using a test pipeline 105.3 mm in diameter and 1436.5 m long. Experimental conditions include, increasing or decreasing air flow rate with constant water flow rate, and transition from single-phase air flow to air-water two-phase flow. Experimental data were compared with calculated results, and the agreement was very good. Furthermore, calculated results agreed very well with a published field data.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):102-108. doi:10.1115/1.3231362.

The vital role of logistic support for maintaining uninterrupted drilling operations is well known to offshore petroleum engineers. Moreover, its importance is growing as exploration and production activities are extended to progressively deeper water and harsher weather conditions. However, no systematic approach for ensuring effective logistic support has yet been realized. A method of studying the characteristics of logistic support and of designing a system for securing effective supply to an offshore rig is proposed. It is based on event simulation modeling of offshore supply operations, together with more conventional technical and economic models for yielding economic criteria which take into account a possible interruption of drilling operations. The method has been developed through a detailed investigation of each component of the supply operation and of the inherent problems. To evaluate the feasibility of the approach, an example has been provided.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):109-113. doi:10.1115/1.3231363.

The evolutionary process of system synthesis and the mathematical process of system optimization are integrated in one do-it-yourself software. A large number of flowsheet arrangements can be conveniently evaluated and optimized. The interactions among dissipations and dissipators can be monitored and analyzed to establish leading indicators to optimal configuration. The software is briefly described. An example problem demonstrates the integration of synthesis and optimization. The distribution of dissipations of the considered solutions to the problem are discussed.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):114-118. doi:10.1115/1.3231364.

Flow diagrams for exergy have been made for Unit 2 at the Umm Al Nar West power plant in Abu Dhabi. This unit is one of six in a combined power and desalination facility, each delivering 60 MW of electricity and 18000 metric tons per day of freshwater at design conditions. The diagrams show the rates of exergy flow between all of the components in the facility as well as the consumption in each. For the desalination facility, diagrams were developed for both summer and winter operation, at design conditions. The steam generation and power plant diagrams were made for full and three-quarter electrical loads, and full-load delivery of steam to the desalination plant. Furthermore, detailed exergy costing diagrams have been constructed for the steam/power facility, at both full and three-quarter electrical load conditions. Conclusions are drawn regarding means for improving the existing plant and future designs.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):119-123. doi:10.1115/1.3231365.

Combustion efficiency and flue-gas drying of solid fuels are analyzed. A simple, universal arithmetic expression for combustion efficiency is developed. This expression involves four primary dimensionless parameters which relate to (and are fixed for given) fuel and ambient conditions, and three secondary dimensionless parameters which relate to (and vary with) fuel moisture content, excess air, and flue-gas temperature. Additional expressions involving the same primary parameters are developed to calculate the decrease in fuel moisture content due to flue-gas drying with and without entrainment of air into the dryer system and the decrease in flue-gas temperature with air entrainment. Values for the four primary parameters are presented for various fuels; their values do not vary much for most biomass fuels.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1988;110(2):124-132. doi:10.1115/1.3231366.

A comprehensive computer code is developed for the calculation of pulverized coal combustion and is evaluated against a series of IFRF experimental data. An improved stochastic model for turbulent particle dispersion is implemented together with a phenomenological fast chemistry eddy breakup model for coal-off gas combustion. The predicted and measured values show good agreement with each other. However, model deficiencies are noted in the prediction of nonequilibrium phenomena such as local flame extinction and minor species (e.g., CO) formation.

Commentary by Dr. Valentin Fuster

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