scholarly journals Progress in Carnot and Chambadal Modeling of Thermomechanical Engine by Considering Entropy Production and Heat Transfer Entropy

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1232 ◽  
Author(s):  
Michel Feidt ◽  
Monica Costea
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Industrial Revolution ◽  
Mechanical Energy ◽  
Optimization Procedure ◽  
Maximum Energy ◽  
Transfer Entropy ◽  
Coefficient Of Performance ◽  
Environmental Criteria

Nowadays the importance of thermomechanical engines is recognized worldwide. Since the industrial revolution, physicists and engineers have sought to maximize the efficiency of these machines, but also the mechanical energy or the power output of the engine, as we have recently found. The optimization procedure applied in many works in the literature focuses on considering new objective functions including economic and environmental criteria (i.e., ECOP ecological coefficient of performance). The debate here is oriented more towards fundamental aspects. It is known that the maximum of the power output is not obtained under the same conditions as the maximum of efficiency. This is shown, among other things, by the so-called nice radical that accounts for efficiency at maximum power, most often for the endoreversible configuration. We propose here to enrich the model and the debate by emphasizing the fundamental role of the heat transfer entropy together with the production of entropy, accounting for the external or internal irreversibilities of the converter. This original modeling to our knowledge, leads to new and more general results that are reported here. The main consequences of the approach are emphasized, and new limits of the efficiency at maximum energy or power output are obtained.

Performance Optimization of a Modified Wells Turbine Using Non-Symmetric Airfoil Blades

2008 ◽  
Author(s):  
M. H. Mohamed ◽  
G. Janiga ◽  
D. The´venin
Keyword(s):  
Power Output ◽  
Performance Optimization ◽  
Mechanical Energy ◽  
Tangential Force ◽  
Optimization Procedure ◽  
Optimized Design ◽  
Wells Turbine ◽  
Force Coefficient ◽  
Airfoil Blades ◽  
Two Stages

A Wells turbine is a self-rectifying air flow turbine employed to convert the pneumatic power of the air stream induced by an Oscillating Water Column into mechanical energy. Standard Wells turbines have several well-known disadvantages: a very low tangential force, leading to a low power output from the turbine; a high undesired axial force; usually a low aerodynamic efficiency and a limited range of operation due to stall. In the present work we investigate extensively the potential of non-symmetric airfoil blades to improve the tangential force induced by a two-stage modified Wells turbine. Since these two stages are mirrored, the system stays globally symmetric. Non-symmetric blades allow to increase considerably power output from the turbine and the global efficiency of the system. The optimization of the gap between the two stages as well as of the shape of the airfoils is considered. The automatic optimization procedure is carried out by coupling an in-house optimization library (OPAL) with an industrial CFD code (ANSYS-Fluent). The multi-objective optimization taking into account both tangential force coefficient and efficiency relies on Evolutionary Algorithms. Detailed comparisons are finally presented between the optimized design performance and the classical monoplane Wells turbine using symmetric airfoils, demonstrating the superiority of the proposed solution.

scholarly journals Effect of Machine Entropy Production on the Optimal Performance of a Refrigerator

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 913 ◽  
Author(s):  
Michel Feidt ◽  
Monica Costea
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Optimal Allocation ◽  
Minimum Energy ◽  
Transfer Entropy ◽  
Coefficient Of Performance ◽  
Environmental Constraints ◽  
Minimum Energy Consumption ◽  
Control Command ◽  
Internal Irreversibility

The need for cooling is more and more important in current applications, as environmental constraints become more and more restrictive. Therefore, the optimization of reverse cycle machines is currently required. This optimization could be split in two parts, namely, (1) the design optimization, leading to an optimal dimensioning to fulfill the specific demand (static or nominal steady state optimization); and (2) the dynamic optimization, where the demand fluctuates, and the system must be continuously adapted. Thus, the variability of the system load (with or without storage) implies its careful control-command. The topic of this paper is concerned with part (1) and proposes a novel and more complete modeling of an irreversible Carnot refrigerator that involves the coupling between sink (source) and machine through a heat transfer constraint. Moreover, it induces the choice of a reference heat transfer entropy, which is the heat transfer entropy at the source of a Carnot irreversible refrigerator. The thermodynamic optimization of the refrigerator provides new results regarding the optimal allocation of heat transfer conductances and minimum energy consumption with associated coefficient of performance (COP) when various forms of entropy production owing to internal irreversibility are considered. The reported results and their consequences represent a new fundamental step forward regarding the performance upper bound of Carnot irreversible refrigerator.

Cyclic Processes in Closed Regenerative Gas Machines Analyzed by a Digital Computer Simulating a Differential Analyzer

1962 ◽  
Vol 84 (1) ◽  
pp. 165-178 ◽  
Author(s):  
T. Finkelstein
Keyword(s):  
Heat Transfer ◽  
Mechanical Energy ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Computational Techniques ◽  
Practical Case ◽  
Cyclic Processes ◽  
Prime Movers ◽  
Set Up ◽  
Differential Analyzer

A complete thermodynamic analysis of closed, reversible, regenerative gas cycles is developed which among other refinements takes into account heat-transfer limitations, regenerator inefficiency, and flow losses. This results in a set of equations for the cyclic variations of temperatures, pressures, and flow rates in different parts of the system. A heat balance is set up for the integrated heat transfer and mechanical energy conversions per cycle and an accurate figure for the efficiency of prime movers or the Coefficient of Performance of heat pumps or refrigerators is derived from this. Special computational techniques simulating a differential analyzer on an IBM 704 electronic computer are described and the results of a typical practical case are given in graphs and figures.

Internet of Things as Engine of Economic Growth in Indonesia

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Bambang Widagdo ◽  
Mochamad Rofik
Keyword(s):  
Economic Growth ◽  
Internet Of Things ◽  
Industrial Revolution ◽  
The Internet ◽  
Economic Diversification ◽  
Great Opportunity ◽  
Economic Basis ◽  
Network Quality ◽  
The Internet Of Things

The economic diversification concept gives hope for a country with rich natural resources to strengthen its economic basis. Thus industrial revolution era of 4.0 provides great opportunity to fasten the process. A study by McKensey in 2011 proved that the internet in the developing country contributes around 3.4% towards its GDP which means that the internet has become a new hope for the economy in the future. Indonesia is one of the countries that is attempting to maximize the role of the Internet of Things (IoT) for its economic growth.� The attempt has made the retail and tourism industries as the two main sectors to experience the significant effect of IoT. In the process of optimizing the IoT to support the economic growth, Indonesia faces several issues especially in the term of the internet network quality and its distribution, the inclusive access of financial access and the infrastructure

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