Cooling Water for pre-commissioning Operations in Subsea Fields

Pre-commissioning in subsea oil and gas fields ensures the readiness for operation and integrity of the valves, pipelines, and various components installed on the seabed. A critical task in this process is the pressure testing of pipelines, which involves flooding them with fluids such as freshwater, seawater, or water-glycol mixtures. The testing fluid, initially stored in vessel tanks, is typically at ambient temperature. The high insulation in the subsea pipelines creates a significant temperature difference between the internal fluid used for pressure testing and the pipeline surroundings. This condition creates a false impression of pressure decrease due to temperature stabilization. Consequently, it becomes challenging to accurately identify leakages during pressure testing, resulting in prolonged offshore campaigns. This study aims to investigate different solutions for efficiently cooling large amounts of water within a reasonable time frame under different spread configuration cases. Five different alternatives were studied: 1) Installation of a subsea spool with low insulation to allow for natural and forced convection cooling from the sea currents. 2) Single heat exchanger on the vessel deck. 3) Water chiller on the vessel deck. 4) Producing seawater using a desalination system and pumping the water from the seabed. 5) Theoretical reviews of developed patents for subsea heat exchangers. Heat transfer calculations indicate the first two alternatives won't cover the objectives. First, The required length of the spool piece renders this alternative unfeasible. As for the heat exchanger, using seawater as a cold fluid limits the process final temperature. Two technologies are found to be more suitable for this application due to their extensive utilization in marine applications. First, the installation of a system similar to an RSW chiller, commonly used in fishing vessels to cool seawater and preserve the catch. Capacity calculations for this project result in average ranges for this type of equipment. Alternatively, the installation of a desalination system provides a different approach to the problem, however, the outlet temperature of the water is limited to the minimum achievable seawater temperature, which, in turn, is restricted by the capacity and installed depth of a subsea pump. Considering the advantages of using a chiller system on a vessel, an economic evaluation was performed using quotations for this system. The interviewed providers offered the option to purchase the system instead of renting when compared to the assumed daily rate of a diving vessel, acquiring a unit like this becomes profitable. The initial investment can even be recouped in a single project, and operational time in offshore campaigns will be significantly reduced while decreasing at the same time the company's CO2 emissions

Water Management in PEM Fuel Cells: Controllability Analysis and Steady-state Optimization for Temperature Control

This paper presents a controllability study of the water management inside anode channel by regulating the stack temperature for PEM fuel cell systems with dead-ended anode. Moreover, this work includes the design of a steady-state target optimizer which calculates the temperature set-point profiles that minimize the stack degradation and the hydrogen leaks. The control architecture is successfully simulated and the results show promising performanc

Right to Quality University Education

Tener acceso a la escuela es un primer paso para ejercer el derecho a la educación. Sin embargo, su pleno ejercicio exige la participación equitativa de los estudiantes en un proceso educativo de calidad capaz de promover el pleno desarrollo de sus múltiples potencialidades, más aún en la universidad, a través de aprendizajes socialmente relevantes y experiencias educativas pertinentes a las necesidades y características de los individuos, y de los contextos en los que se desenvuelven. La calidad educativa exige además equidad en los resultados de aprendizaje y un uso eficiente de los recursos.Abstract: Access to school is a first step to exercise the right to education. However, its full realization requires the equitable participation of students in an educational process quality able to promote the full development of its multiple potentialities, especially in university through learning socially relevant and appropriate educational experiences to the needs and characteristics of individuals, and the contexts in which they operate. The quality of education also requires equity in learning outcomes and efficient use of resources

Multidimensional Costas Arrays and Their Periodicity

A novel higher-dimensional definition for Costas arrays is introduced. This definition works for arbitrary dimensions and avoids some limitations of previous definitions. Some non-existence results are presented for multidimensional Costas arrays preserving the Costas condition when the array is extended periodically throughout the whole space. In particular, it is shown that three-dimensional arrays with this property must have the least possible order; extending an analogous two-dimensional result by H. Taylor. Said result is conjectured to extend for Costas arrays of arbitrary dimensions

LA ENFERMERA. CONOCIMIENTOS Y COMPETENCIAS PARA DIRIGIR HOSPITALES

Com o objetivo de determinar se a enfermagem possui conhecimentos e competências para dirigir os hospitais, desenvolveu-se está pesquisa qualitativa, sustentada pela teoria de pensamento estratégico, abordando a categoria acadêmica, com o método de estudo de caso. Os sujeitos foram quatro enfermeiras diretoras gerais de hospital. A pesquisa evidencia que a enfermeira possui competências que respondem ao campo de atuação caracterizado por um conjunto de conhecimentos e práticas que permitem a realização de uma tarefa significativa, sua visão holística faz a diferença profissional constatada pela humanização, ao reconhecer no processo de comunicação dentre o profissional, a pessoa subordinada e o usuário no contexto hospitalar. Suas habilidades administrativas foram consideradas em seus planos e programas de estudos. As competências da enfermeira respondem às expectativas requeridas pela instituição e na contribuição esperada para cada cargo

Solar Thermal Plants Integration in Smart Grids

Solar energy penetration has been increasingly growing in recent years. Since solar energy is intermittent its integration in existing grids is difficult. This paper deals with the optimal integration of solar power plants in grids. The paper proposes a modification of energy hubs which allows to solve the optimization problem with a mixed integer programming algorithm in a distributed way. An introductory simulation study case is givenMinisterio de Educación DPI2008-05818Junta de Andalucía P07-TEP-02720Comisión Europea HD-MP

The Liquidity Premium in Equity Pricing under a Continuous Auction System

The paper shows that the cost of illiquidity is not (positively) priced over all months in the Spanish continuous auction system, where liquidity is provideh in the absence of market makers. Two distinct approaches are employed. Both the two-step traditional cross-sectional method and the pooled cross-section time series analysis tend to indicate that the liquidity premium is negative during months other than January. Morever, the liquidity premium in January is positive (although not significant) and at the 10% level it seems to be significantly higher than the liquidity premium over the rest of the year. Therefore, given the previous results for the US market, we conclude that, independently of the market trading mechanism with the exception of NASDAQ, the behaviour of the relationship between the bid-ask spread and stock returns is rather similar.Publicad