This article presents a thermodynamic framework based on the second law of thermodynamics for predicting overpotential irreversibilities in a lithium-mediated electrochemical cell for ammonia synthesis. It analyzes experimental data from prior studies, in terms of the overpotential entropy generation, and identifies regions where entropy generation is minimized. Overpotential models for the activation kinetics, nucleation, mass transport, and ohmic resistance of the electrochemical cell are developed as functions of the operating current density. Analysis of potentiodynamic and impedance data was used to determine the key electrochemical parameters of the system. A differential analysis identified the charge transfer coefficients, and improvements were found when comparing its correlation coefficient to that obtained through logarithmic analysis in a previous study. The predictive model allows for minimizing the entropy generation attributed to the thermodynamic overpotentials, wherein the second law captures the irreversibilities in the electrochemical system. The new model is applied to a lithium-mediated electrochemical cell with high Faradaic efficiency, and the entropy generation of the system is evaluated within the framework. Predicted results are compared against past experimental data. The approach analyses entropy generation across various overpotential components, including ohmic losses, activation and nucleation energy barriers, as well as mass transport limitations during electrodeposition. By considering these overpotential contributions to the overall entropy generation, the study provides new insight into thermodynamic irreversibilities of lithium-mediated electrochemical systems and proposes ways to reduce them. The paper advances the theoretical understanding of electrochemical irreversibilities in lithium-mediated electrochemical systems and provides a practical tool for assessing and improving the performance of electrochemical cells including with nucleation and electrodeposition.

This article presents a second law analysis of a lithium-mediated electrochemical ammonia production cell with internal thermodynamic irreversibilities attributed to ohmic losses and activation energy. A Tafel analysis is first applied to potentiostatic data from past experimental studies to determine relevant electrochemical parameters of the cell. The predictive thermodynamic model provides an entropy-based perspective to quantify and minimize irreversibilities of the electrochemical cell thereby delineating the optimal regions of operation and improving its overall energy efficiency. The thermodynamic analysis based on the second law is then applied to a lithium-mediated electrochemical ammonia production cell with a high Faradaic efficiency. A formulation for the entropy generation of the cell is developed and calculated across the separate overpotential components attributed to the ohmic losses and the kinetic activation energy barriers of the cell. By considering these overpotential contributions to the overall entropy generation of the cell, the study provides unique insight into the inherent inefficiencies in lithium-mediated electrochemical systems and presents alternative pathways to reduce and quantify irreversible losses. The paper advances the theoretical understanding of electrochemical systems and provides a useful tool for assessing and improving the performance of lithium-mediated electrochemical ammonia production cells with ohmic losses and activation energy barriers.

The hydrolysis reaction of the copper-chlorine (Cu-Cl) cycle is examined in this paper to better understand the corresponding reaction kinetics and mass transfer resistance. The experiment was operated at a temperature of 390 degrees C at atmospheric pressure. The reaction is heterogeneous in which solid reactant CuCl2 and gaseous reactant H2O produce Cu2OCl2 (s) and HCl(g). Heterogeneous behaviour of the reaction causes a resistance to mass transfer of gaseous reactant H2O. The resistance in internal diffusion and a surface reaction with mass transfer was analyzed with respect to the initial solid reactant particle size using a shrinking core model (SCM). The experimentally determined reaction and conversion rates of hydrolysis reaction with respect to time are presented.

Geothermal-based flash steam power plants are promising systems for clean power generation. A comprehensive thermodynamic analysis through energy and exergy approaches is presented here to investigate the optimum flashing pressures for multistep plants, including single-, double-, triple-, and quadruple-flash systems with reinjection. A new methodology is presented to investigate the optimum pressure levels for the flashing process, which can be considered as a suitable range of operation in power-generating geothermal plants. The present methodology is combined with a family of curves representing power output vs flashing pressure to determine the maximum available power for the system. The performances of the proposed systems are evaluated from both energy and exergy perspectives. It is shown that an energy efficiency analysis alone is insufficient to differentiate between the systems. The results of the exergy approach indicate a significant improvement in terms of efficiency as the quantity of flashing steps has risen. The potential performance enhancement in terms of power output becomes smaller as the quantity of flashing steps becomes four or more.

applications; expanded tube count tables for shell-and-tube heat exchangers; a practical approach to design against tube bundle vibration; and a comparative synopsis of the various national wind codes. Topics included in the text are considered to be those typically encountered in engineering practice. For reasons of time and space the dynamic analyses of seismic response spectra and an extensive discussion on pulsation response spectra in piping induced by acoustic pulsation are not discussed. However, a short discussion is given on pulsation response spectra induced by acoustic pulsations. Single-phase flow is much more common in mechanical systems than two-phase flow, so because of time and space two-phase flow is not discussed. This book is not intended to be a substitute or a replacement of any accepted code or standard. The reader is strongly encouraged to consult and be knowledgeable of any accepted standard or code that may govern. It is felt that this book is a valuable supplement to any standard or code used. The book is slanted toward the practices of the ASME vessel and piping codes and the TEMA standard for shell-and-tube heat exchangers. The intent is not to be heavily prejudiced toward any standard, but to discuss the issue—engineering. If one feels that a certain standard or code should be mentioned, please remember that there are others who may be using different standards and it is impossible to discuss all of them. The reader's academic level is assumed to be a bachelor of science degree in mechanical engineering, but engineers with bachelor of science degrees in civil, chemical, electrical, or other engineering disciplines should have little difficulty with the book, provided, of course, that they have received adequate academic training or experience. Junior or senior undergraduate engineering students should find the book a useful introduction to the application of mechanical engineering to process systems. Professors should find the book a helpful reference (and a source of potential exam problems), as well as practical textbook for junior-, senior-, or graduate-level courses in the mechanical, civil, or chemical engineering fields. The book can also be used to supplement an introductory level textbook. The French philosopher Voltaire once said," Common sense is not very common," and unfortunately, this is sometimes the case in engineering. Common sense is often the by-product of experience, and while both are essential to sound engineering practice, neither can be learned from books alone. It is one of this book's goals to unite these three elements of "book learning," common sense, and experience to give the novice a better grasp of engineering principles and procedures, and serve as a practical design reference for the veteran engineer.

This study examines the suppression of liquid slugs in the transport and separation of multiphase flows in pipelines. Two well-known slug control approaches are evaluated in this paper. The methods are employed to control and stabilize an undesired and unstable flow regime, optimize flow production, reduce operating costs, and in general, improve overall safety requirements of oil and gas pipelines. Unlike designs with an additional flowline to separate gas upstream, this study shows that active topside choking can suppress slugs and stabilize the system flowrates and pressures without the requirement of separation upstream of the topside valve. Careful choking is required to minimize production losses that can result from excess back pressure. A riser-based, gas-lift method reduces system instability and increases production. This study also reveals that negligible improvement in stability is achieved when large volumes of gas are injected. The system shifts into an annular flow regime when the injection is further increased. A large separator may be required to accommodate high gas volumes. This study shows that gas-lift not coordinated with choking is not effective for slug mitigation through pipeline bends. This paper also presents and discusses new non-dimensional correlations, including slug control inputs in the pipelines such as choke openings, based on new experimental data.

A numerical study is presented in this paper to investigate blade sections (NACA 4415) with a scaling analysis.For variable rotational speeds (up to 60 RPMs) and operating/icing conditions for both similar models, the effects on the flow field, droplet impingement and ice accretion process are obtained.The numerical simulations are conducted using ANSYS FENSAP ICE software.Effects of the relative flow Reynolds number and speed ratio over two similar blade sections are investigated.Flow velocity contours, pressure distributions, droplet impingement/collection efficiencies and ice shapes/quantities are presented.The results of this paper provide useful insight to predict icing on wind turbine blades including scaling effects among different blade configurations.

In this study, an experimental lab-scale copper-chlorine (Cu–Cl) cycle of hydrogen production is examined and optimized in terms of exergy efficiency and operational costs of produced hydrogen. The integrated process is modeled and simulated in Aspen Plus incorporating the reaction kinetic parameters with a sensitivity analysis of a range of operating conditions. An artificial neural network (ANN) method with machine learning is used to generate a mathematical function that is optimized based on a multi-objective genetic algorithm (MOGA) method. A sensitivity analysis of variations of each design parameter for both the objective functions and the effectiveness of exergy performance relative to operational costs of produced hydrogen is demonstrated. The sensitivity analysis and optimization results are presented and discussed.

An entropy-based error indicator is presented to assess the solution accuracy of fluid flow simulations with heat transfer using the second law of thermodynamics. This paper presents a new approach for the characterization of numerical error using a parameter called an "apparent entropy production difference." A control-volume-based finite-element method is used to discretize and solve the governing equations and the second law. The procedure involves the computation and comparison of local entropy production rates obtained from two forms of the discretized second law: transport and positive-definite forms of the entropy generation. The computed local entropy generation rates from both methods are compared and related to expected numerical errors from benchmark solutions. The results of the numerical studies indicate that there is a relationship between the solution error in the computed scalar variables and the apparent entropy production difference.

This paper examines the transport phenomena and optimal performance of an integrated concentrated photovoltaic and photoelectrochemical hydrogen reactor. Individual components and the overall system are studied experimentally including the performance of the concentrator, spectrum-splitting mirror, electrolyser, reactor, and photovoltaic module. Integrating the solar concentration with a spectrum-splitting mirror allows simultaneous photovoltaic electricity generation and direct photonic energy conversion to produce hydrogen via electrolytic and photoelectrochemical water splitting. A multi-objective optimization of the integrated system is performed with machine learning and integration of a neural network. This yields a relationship between the system inputs and outputs. The neural network is used to optimize the overall system through a genetic algorithm. Numerical and experimental results are presented and discussed in the paper.