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RESEARCH PAPERS

J. Energy Resour. Technol. 1993;115(3):151-161. doi:10.1115/1.2905987.
Abstract
Topics: Multiphase flow
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):162-167. doi:10.1115/1.2905988.

This paper describes a method for estimating the position of a detected leak by applying a fluid transient model to a real-time pipeline system. The method takes into account flow rate and pressure profiles along a pipeline in a transient condition based on an assumption of quasi-steady-state flow. The result of case studies using a hypothetical gas pipeline system shows that, even in a transient condition, the method gives a more accurate estimation of a leak position than conventional methods which do not consider flow rate or pressure profiles along a pipeline. The method is also applicable to a pipeline having consumer stations which cause abrupt changes of flow rate profile along the pipeline. Furthermore, the influence of instrument accuracy on the result of the method is examined. The result also shows the advantage of the method compared to the conventional methods.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):168-174. doi:10.1115/1.2905989.

A laboratory-scale experimental study of the basic processes and controlling parameters involved in the spontaneous heating of a pile of ferrous metal turnings during their marine transport is presented. The results indicate that the salinity of seawater, the amount of moisture coming in contact with the turnings, the surface area of turnings, the volume of container, and the bulk density of the pile affect the temperature rise in the ferrous material.

Topics: Heat , Iron alloys
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):175-182. doi:10.1115/1.2905990.

The influence of flow rotation on droplet combustion and evaporation are experimentally studied by using a burning liquid-pool system, and numerically investigated by considering a nonreactive, rotating, stagnation-point flow, respectively. The experiment involves measurements of flame temperature, flame position and evaporation rate of the liquid pool, observations of the recirculation zone and the soot layer, and identification of flame extinction. A finite-volume method is employed to numerically solve the corresponding transport equations. Calculated results show that in the vicinity of the liquid surface, both convection and diffusion transports are weakened by the flow rotation, resulting in the suppression of the evaporation strength of liquid; the recirculation zone can be identified and compared with experimental observation. For the steady burning of an ethanol pool in a swirling air jet, it is found that as the angular velocity increases, the diffusion flame shifts closer to the upper burner, has a larger flame thickness, experiences a smaller flame stretch, but suffers from the reduction of mass diffusion of ethanol vapor to the flame. However, the evaporation rate of ethanol is usually decreased with increasing angular velocity. In the flame extinction experiment, the critical volumetric oxygen concentration at extinction first decreases to a minimum value and then increases with angular velocity. It is generally concluded that flow rotation reduces the rates of both droplet combustion and evaporation.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):183-189. doi:10.1115/1.2905991.

An experimental study of the effects of the orientation of the liquid fuel stream relative to the air stream from a twin fluid atomizer located in an open-jet wind tunnel is presented. The orientation angle was set at 0 (concurrent), 45, 90, 135, and 180 deg (directly opposed). At 45 and 90 deg, the flame length, the radiation emission, and the concentrations of carbon monoxide, carbon dioxide, nitric oxide, and soot are higher than those at co-flow conditions. At 135 deg, all these quantities decrease markedly from their values at 90 deg and again increase when the fuel and air streams are directly opposed (180 deg). These changes are discussed in terms of the influx of air and recirculation of combustion products into the salient zones of the flame.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):190-195. doi:10.1115/1.2905992.
Abstract
Topics: Wells , Pipes , Buckling
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):196-201. doi:10.1115/1.2905993.
Abstract
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):202-207. doi:10.1115/1.2905994.

This paper focuses on the use of the 3-D drilling trajectory equations derived from the concept of constant curvature. It is shown that the constant curvature equations are specially useful for horizontal drilling. Three examples of using the constant curvature method are presented to demonstrate the practical usefulness of the proposed concept. The results obtained reveal that the well trajectory with constant curvature is not only consistent with directional performance of deflection tools, but also yields less dogleg severity. This, in turn, should increase the fatigue life of drillstring elements passing through the curved segments of the hole. Finally, drag and torque computations show that, thanks to less dogleg severity, the drag and torque are expected to be less in holes designed to have constant wellpath curvature.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):208-212. doi:10.1115/1.2905995.

For a nonchemical-equilibrium state of an isolated system A that has r constituents with initial amounts n a = {n1a , n2a , [[ellipsis]], nra } , and that is subject to τ chemical reaction mechanisms, temperature, pressure, and chemical potentials cannot be defined. As time evolves, the values of the amounts of constitutents vary according to the stoichiometric relations ni (t) = nia + Σj=1 τ νi (j) εj (t) , where νi (j) is the stoichiometric coefficient of the i th constituent in the j -reaction mechanism and εj (t) the reaction coordinate of the j th reaction at time t . For such a state, we approximate the values of all the properties at time t with the corresponding properties of the stable equilibrium state of a surrogate system B consisting of the same constituents as A with amounts equal to ni (t) for i = 1, 2, [[ellipsis]], r , but experiencing no chemical reactions. Under this approximation, the rate of entropy generation is given by the expression Ṡ irr = ε̇ · Y , where ε̇ is the row vector of the τ rates of change of the reaction coordinates, ε̇ = { ε̇1 , [[ellipsis]], ε̇τ }, Y the column vector of the τ ratios a j /T off for j = 1, 2, [[ellipsis]], τ, a j = −Σi=1 r νi (j) μ i ,off , that is, the j th affinity of the stable equilibrium state of the surrogate system B , and μ i ,off , and T off are the chemical potential of the i th constituent and the temperature of the stable equilibrium state of the surrogate system. Under the same approximation, by further assuming that ε̇ can be represented as a function of Y only that is, ε̇(Y ) , with ε̇(0) = 0 for chemical equilibrium, we show that ε̇ = L·Y + (higher order terms in Y ), where L is a τ × τ matrix that must be non-negative definite and symmetric, that is, such that the matrix elements Lij satisfy the Onsager reciprocal relations, Lij = Lji . It is noteworthy that, for the first time, the Onsager relations are proven without reference to microscopic reversibility. In our view, if a process is irreversible, microscopic reversibility does not exist.

Topics: Entropy
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):213-220. doi:10.1115/1.2905996.

A quasi-three-dimensional numerical procedure is proposed to simulate the fluid flow and heat transfer in the shell-side of steam surface condensers. The proposed procedure is applied to an experimental steam surface condenser to evaluate its predictive capability. The predicted results give good general agreement with the experimental data. The governing equations are solved in primitive variable form using a semi-implicit consistent control-volume formulation in which a segregated pressure correction linked algorithm is employed. The modeling of the geometries of condensers, including tube bundles and baffle plates, is carried out based on porous media concepts using flow, heat and mass transfer resistances.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):221-227. doi:10.1115/1.2905997.

This paper reports on analyses and optimization studies of problems associated with liquid hydrogen thermal stratification and self-pressurization in cryogenic vessels. Three different pressure rise models were employed to calculate the self-pressurization and boil-off rates. These are a homogeneous model, a surface-evaporation model, and a thermal stratification model. The first two models are based on the assumption that no temperature gradients exist in the tank, while the thermal stratification model takes the temperature distribution into account. Employing the thermal stratification model, temperature gradients and their effect on the pressure rise rates in liquid hydrogen tanks are analyzed.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1993;115(3):232-236. doi:10.1115/1.2905999.

Binary-flashing units utilize new types of geothermal power cycles, which may be used with resources of relatively low temperatures (less than 150°C) where other cycles result in very low efficiencies. The thermodynamic cycles for the binary flashing units are combinations of the geothermal binary and flashing cycles. They have most of the advantages of these two conventionally used cycles, but avoid the high irreversibilities associated with some of their processes. Any fluid with suitable thermodynamic properties may be used in the secondary Rankine cycle. At the optimum design conditions binary-flashing geothermal power plants may provide up to 25 percent more power than the conventional geothermal units.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster

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