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RESEARCH PAPERS

J. Energy Resour. Technol. 1987;109(3):101-104. doi:10.1115/1.3231333.

Storage of thermal energy due to latent heat involved during outward radial melting of a phase-change material contained in a spherical shell is solved using variational, integral and quasi-steady methods. At uniform temperature heat is applied to inner surface. These methods provide closed-form solutions in the Stefan number, an independent parameter. The results for total energy storage, the phase-change depth and their rate obtained from these approximate analyses do not vary significantly.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):105-111. doi:10.1115/1.3231334.

Marine risers are modeled as thin-walled, slender, extensible or inextensible, tubular beams subject to nonlinear three-dimensional hydrodynamic loads of interactive nature, torsion and distributed couples, inertia forces and varying axial tension. A finite element, time-incremental algorithm is developed which utilizes equilibrium and kinematic constraints to reduce the required computational time. Iterations are used within each increment to assure convergence of deformation, stiffness matrices and external loads. The algorithm is implemented numerically and the developed computer code is used in several numerical applications to show that a structurally linear model may not be accurate enough and may occasionally be nonconservative in predicting the dynamic riser response.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):112-118. doi:10.1115/1.3231335.

This paper provides an analysis of the non-Darcian effect on transient natural convection of a vertical flat plate embedded in a high-porosity medium. The plate surface is either maintained at an uniform wall temperature (UWT), or subjected to an uniform heat flux (UHF), and convective, boundary and inertia effects are considered. The local volume-averaged principles and certain empirical relations have been utilized to establish the governing equations. The coupled nonlinear partial differential equations are solved with a numerical integration technique using a cubic spline. Along with transient mean and local Nusselt numbers at the plate, representative transient velocity and temperature profiles are presented. Both effects for non-Darcian flow model are shown to be more pronounced in high-porosity medium and, hence, reduce the heat transfer rate.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):119-123. doi:10.1115/1.3231336.

The problem of natural convection of a non-Newtonian power-law fluid about a horizontal impermeable surface in the porous medium is considered, where the plate is assumed with a nonuniform heat flux distribution. The present study is based on the boundary layer approximation and only suitable for a high Rayleigh number. Similarity solutions are obtained by using the fourth-order Runge-Kutta method and the Nachtsheim-Swigert iteration scheme. The effects of the nonuniform wall heat flux q w (x) and the new power-law index n on the heat transfer characteristics are discussed.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):124-128. doi:10.1115/1.3231337.

This paper describes a thermodynamically based correlation between coal ash fusion temperatures and ash composition. A wide range of data from the literature was used to obtain the values of model parameters. A seven-parameter correlation is proposed which permits predicting the ash fusion temperature with a standard error ± 65°C or better.

Topics: Temperature , Coal , Errors
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):129-141. doi:10.1115/1.3231338.

Wood is a highly flexible fuel which can be used in a variety of ways for energy generation. Direct combustion of wood is the oldest method of utilization of this renewable energy source. This paper presents an analysis of wood combustion based on the first and second laws of thermodynamics, using a computer program developed for this study. Since the moisture content of the available wood fuels vary over a wide range, special attention is given to the effects of moisture content on the exergy and energy content of the wood. Because of the wide variation in particle size and moisture content of the wood fuels, different types of combustion systems have been designed and are utilized in industry. Each combustion system uses a certain amount of combustion air and is designed for a certain range of combustion air temperatures and wood fuel moisture contents. The effects of these variables on wood combustion and the efficiencies of the process have been studied and are presented in this paper. To point out the importance and differences between efficiencies that are commonly used, several efficiencies based on the first and the second laws of the thermodynamics are calculated and compared. Based on the results presented in this report, it is concluded that, over the range of variables studied, the most efficient conditions for wood combustion can be achieved by using the minimum amount of excess air at highest permissible temperature. It is also concluded that the lower moisture contents result in higher combustion efficiencies.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):142-147. doi:10.1115/1.3231339.

The trend toward offshore oilfield development schemes which utilize relatively long, large diameter, multiphase flowlines has resulted in a need for better design techniques for such systems. In order to validate these new and improved design methods it is necessary to compare them with good quality field data obtained from a variety of different multiphase lines. Therefore trials to determine the characteristics of the multiphase flow through 150 mm NB (6 in. NB) lines from four of the satellite wells in BP’s Magnus field were carried out during October, 1985. Using two gamma ray density gages, the flow regimes, and where possible the characteristics of slug flow, were identified over a range of flowrates in the different lines. Comparison of the data is made with the predictive techniques widely used in the industry.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):148-154. doi:10.1115/1.3231340.

The literature of FBC solid wastes has been critically evaluated and solid wastes from Canada’s first atmospheric fluidized bed combustion (AFBC) boilers at the Canadian Forces Base (CFB) Summerside, Prince Edward Island have been investigated in order to determine possible uses for AFBC wastes. Scanning electron microscopy (SEM), electron microprobe, and chemical and physical tests were employed to determine the suitability of the material for pollution control, construction, and other uses. SEM and ancillary techniques have shown that the chemical and physical properties of the bed material and the elutriated streams are significantly different. Agricultural use, pollution control, soil stabilization (where freezing and thawing are not significant problems), asphaltic concrete, and specialized construction applications such as low strength backfill appear to be potential uses for FBC solid wastes.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(3):155-160. doi:10.1115/1.3231341.

The purpose of this paper is to review the progress made during the past two decades towards the structural modeling and the numerical approaches of a more realistic riser analysis. Two or three-dimensional, linear or nonlinear, either static or dynamic riser modelings are reviewed. Suitable numerical solution techniques for different kinds of modelings are discussed and compared.

Commentary by Dr. Valentin Fuster

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