Silvio de Oliveira Junior

Thermodynamic Model of a Twin-Screw Multiphase Pump

The twin-screw multiphase pump has been studied as an alternative system to substitute the conventional one (fluid separation, liquid pumping and gas compression) in petroleum boosting. By “pumping” simultaneously gas and liquid, the multiphase pump could reduce production costs in deepwater activities. This paper presents a thermodynamic model of a twin-screw multiphase pump to determine performance parameters such as: absorbed power, discharge conditions and efficiency. To overcome problems with the complex flow field inside of this novel equipment, the multiphase flow was divided into a sequence of simpler processes. Such approach helps determine energy and mass balances and enables the use of a process simulator (Hysys.Process v2.1) to construct the model. The model prediction when compared to the literature show that the assumption of a smooth turbulent flow, considering the pressure loss in the entrance and discharge of the gap, fits better the phenomena than the turbulent flow when calculating the flow through the gaps. In addition, the comparison for absorbed power indicates that the assumption of gaps filled only with liquid is not valid under all operation conditions.Copyright

ENERGY AND EXERGY PERFORMANCE OF THREE FPSO OPERATIONAL MODES

Floating, Production, Storage and Offloading (FPSO) is a floating facility used in primary petroleum processing. In Brazil, most FPSOs have been installed in Campos Basin and new facilities may be implemented in the pre-salt area are projected to boost the Brazilian oil production. Crude oil composition has a significant influence on the operational mode of the FPSO. In this study, three operational modes of a FPSO are assessed: the first mode is used when the crude oil has the maximum water and CO2 contents, the second mode is implemented for a composition of 50% basic sediment and water (BSW) in the crude oil, and the third mode is operated when the crude oil has the maximum oil and gas fractions. The FPSO facility configuration changes with the operational mode, and it is possible to have gas export, gas injection, and CO2 injection, in order to achieve the functional conditions established by the FPSO operator. Energy and exergy criteria have been applied to evaluate and compare the performance of components and systems of the three operational modes of the FPSO. The processing and utilities plants have been modeled and simulated by using Aspen HYSYS. Results indicate that higher oil content in the crude oil increases the power consumption, the exergy requirement and the destroyed exergy of the FPSO.

Exergy Analysis and Human Body Thermal Comfort Conditions: Evaluation of Different Body Compositions

This article focuses on studying the effects of muscle and fat percentages on the exergy behavior of the human body under several environmental conditions. The main objective is to relate the thermal comfort indicators with exergy rates, resulting in a Second Law perspective to evaluate thermal environment. A phenomenological model is proposed of the human body with four layers: core, muscle, fat and skin. The choice of a simplified model is justified by the facility to variate the amount of mass in each tissue without knowing how it spreads around the body. After validated, the model was subjected to a set of environmental conditions and body compositions. The results obtained indicate that the area normalization (Watts per square meter) may be used as a safe generalization for the exergy transfer to environment. Moreover, the destroyed exergy itself is sufficient to evaluate the thermal sensation when the model is submitted to environmental temperatures lower than that considered for the thermal neutrality condition (and, in this text, the thermal comfort) . Nevertheless, for environments with temperatures higher than the calculated for the thermal neutrality, the combination of destroyed exergy and the rate of exergy transferred to the environment should be used to properly evaluate thermal comfort.

Exergy Analysis and Environmental Impact

This chapter is concerned with the definition and application of exergy indexes to assess the performance of environmental impact mitigation technologies. These parameters are employed to evaluate the performance of air emission treatment systems, procedures to remediate contaminated sites, management of solid wastes, and technologies of wastewater treatment technologies. Initially it is proposed that the cumulative consumption of materials and utilities for construction and operation of environmental treatment systems can be quantified in terms of exergy. In addition, the exergy content of the emissions of a given production process, as well as the exergy of by-products of the treatment process, can be quantified to develop an exergy balance, focused on the treatment process. Thus, a methodology is described to compare different process alternatives in two situations: in the former the main task of the process is to eliminate the exergy content of a given emission, and in the latter the objective of the process is to maximize the utilization of the exergy content of a given emission. The environmental performance of wastewater treatment technologies is conducted by calculating the environmental exergy efficiency and complemented with the determination of the renewability exergy index. This approach is applied to compare three wastewater treatment plants based on biological (aerobic and anaerobic) and physicochemical processes.

Modeling and Simulation of Artificial Lifting Methods on Offshore Oil Platforms

The objective of the following paper is to present a model for the artificial lifting mechanism known generally as gas-lift and a comparison between its correlates. The comparison between lifting mechanisms can be performed directly, through experiments, or indirectly, through computational simulation. It has been chosen to develop a closer to the state-of-the-art model for the gas-lift, in order to compare it with the results of the multiphase pump simulation contained in the bibliography and included in this paper. Initially a flow pattern has been established, so that the boundary conditions would be known and the control volume would be therefore established as well; in which the intrinsic equations of the flow could be applied. Then, simplifying and adequate hypothesis were formulated, and the geometry, of the high depth riser, in which the mechanism would be simulated, was created, these were inputted into a numerical simulation CFD software. Inputting these geometrical and fluid data along with several controlling equations in the CFX® 5.7 software demonstrated the behavior of the gas lift, both in the transient, as an illustration, and in the steady state flow, and permitted an evaluation and graphical analysis of relevant parameters of the gas lift mechanism. Finally a comparison, between the results obtained by the SMPS (Submarine Multiphase Pumping System) and the above has been performed, showing in which situations the mechanisms presented a higher performance in a real high depth offshore well located in the Campos Basin, Rio de Janeiro.© 2008 ASME