Efficiencies of thermodynamics when temperature-dependent energy levels exist

2016 ◽  
Vol 18 (10) ◽  
pp. 7011-7014 ◽  
Author(s):  
Takuya Yamano
Keyword(s):  
Entropy Generation ◽  
Energy Levels ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Temperature Dependent ◽  
Thermodynamic Processes

Based on a generalized form of the second law of thermodynamics, in which the temperature-dependent energy levels of a system are appropriately included in entropy generation, we show that the effect reasonably appears in efficiencies of thermodynamic processes.

Thermodynamic Processes

2019 ◽  
pp. 132-147
Author(s):  
Robert H. Swendsen
Keyword(s):  
Real World ◽  
Heat Engine ◽  
Second Law Of Thermodynamics ◽  
Heat Pumps ◽  
Second Law ◽  
Carnot Cycle ◽  
Heat Engines ◽  
Negative Temperatures ◽  
Special Case ◽  
Thermodynamic Processes

This chapter begins by defining terms critical to understanding thermodynamics: reversible, irreversible, and quasi-static. Because heat engines are central to thermodynamic principles, they are described in detail, along with their operation as refrigerators and heat pumps. Various expressions of efficiency for such engines lead to alternative expressions of the second law of thermodynamics. A Carnot cycle is discussed in detail as an example of an idealized heat engine with optimum efficiency. A special case, called negative temperatures, where temperatures actually exceed infinity, provides further insights. In this chapter we will discuss thermodynamic processes, which concern the consequences of thermodynamics for things that happen in the real world.

scholarly journals From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 361 ◽  
Author(s):  
Giedrė Streckienė ◽  
Vytautas Martinaitis ◽  
Juozas Bielskus
Keyword(s):  
Heat Pump ◽  
Entropy Generation ◽  
Energy Demand ◽  
Dynamic Modelling ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Second Law ◽  
Air Handling Unit ◽  
Individual Character ◽  
Environment Temperature

The continuous energy transformation processes in heating, ventilation, and air conditioning systems of buildings are responsible for 36% of global final energy consumption. Tighter thermal insulation requirements for buildings have significantly reduced heat transfer losses. Unfortunately, this has little effect on energy demand for ventilation. On the basis of the First and the Second Law of Thermodynamics, the concepts of entropy and exergy are applied to the analysis of ventilation air handling unit (AHU) with a heat pump, in this paper. This study aims to develop a consistent approach for this purpose, taking into account the variations of reference temperature and temperatures of working fluids. An analytical investigation on entropy generation and exergy analysis are used, when exergy is determined by calculating coenthalpies and evaluating exergy flows and their directions. The results show that each component of the AHU has its individual character of generated entropy, destroyed exergy, and exergy efficiency variation. However, the evaporator of the heat pump and fans have unabated quantities of exergy destruction. The exergy efficiency of AHU decreases from 45–55% to 12–15% when outdoor air temperature is within the range of −30 to +10 °C, respectively. This helps to determine the conditions and components of improving the exergy efficiency of the AHU at variable real-world local climate conditions. The presented methodological approach could be used in the dynamic modelling software and contribute to a wider application of the Second Law of Thermodynamics in practice.

Thermodynamics as a fundamental science of reliability

2016 ◽  
Vol 230 (6) ◽  
pp. 598-608 ◽  
Author(s):  
Anahita Imanian ◽  
Mohammad Modarres
Keyword(s):  
Energy Dissipation ◽  
Entropy Generation ◽  
Damage Model ◽  
Second Law Of Thermodynamics ◽  
Reliability Function ◽  
Cumulative Damage ◽  
Life Assessment ◽  
Irreversible Processes ◽  
Second Law ◽  
Cumulative Hazard

Cumulative hazard and cumulative damage are important models for reliability and structural integrity assessment. This article reviews a previously developed thermodynamic entropy–based damage model and derives and demonstrates an equivalent reliability function. As such, a thermodynamically inspired approach to developing new definitions of cumulative hazard, cumulative damage, and life models of structures and components based on the second law of thermodynamics is presented. The article defines a new unified measure of damage in terms of energy dissipation associated with multiple interacting irreversible processes that represent the underlying failure mechanisms that cause damage and failure. Since energy dissipation leads to entropy generation in materials, it has been shown and experimentally demonstrated that the use of the total entropy generated in any degradation process is measurable and can ultimately be used to represent the time of failure of structures and components. This description therefore connects the second law of thermodynamics to the conventional models of reliability used in life assessment. Any variability in the entropic endurance to failure and uncertainties about the parameters of the entropic-based damage model lead to the time-to-failure distribution. In comparison with the conventional probabilistic reliability methods, deriving the reliability function in terms of the entropy generation can offer a general and more fundamental approach to representation of reliability. The entropic-based theory of damage and the equivalent reliability approach are demonstrated and confirmed experimentally by applying the complex interactive corrosion-fatigue degradation mechanism to samples of aluminum materials.

scholarly journals Diffusive Bejan number and second law of thermodynamics toward a new dimensionless formulation of fluid dynamics laws

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 4005-4022 ◽  
Author(s):  
Michele Trancossi ◽  
Jose Pascoa
Keyword(s):  
Fluid Dynamics ◽  
Entropy Generation ◽  
Fluid Dynamic ◽  
Second Law Of Thermodynamics ◽  
Integral Form ◽  
Second Law ◽  
Bejan Number ◽  
Definition Of ◽  
New Formulation ◽  
Dimensionless Formulation

In a recent paper, Liversage and Trancossi have defined a new formulation of drag as a function of the dimensionless Bejan and Reynolds numbers. Further analysis of this hypothesis has permitted to obtain a new dimensionless formulation of the fundamental equations of fluid dynamics in their integral form. The resulting equations have been deeply discussed for the thermodynamic definition of Bejan number evidencing that the proposed formulation allows solving fluid dynamic problems in terms of entropy generation, allowing an effective optimization of design in terms of the Second law of thermodynamics. Some samples are discussed evidencing how the new formulation can support the generation of an optimized configuration of fluidic devices and that the optimized configurations allow minimizing the entropy generation.

scholarly journals Teach Second Law of Thermodynamics via Analysis of Flow through Packed Beds and Consolidated Porous Media

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 116 ◽  
Author(s):  
Rajinder Pal
Keyword(s):  
Porous Media ◽  
Entropy Generation ◽  
Power Plants ◽  
Mechanical Energy ◽  
Fluid Velocity ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Packed Beds ◽  
Factors Affecting ◽  
Flow Through

The second law of thermodynamics is indispensable in engineering applications. It allows us to determine if a given process is feasible or not, and if the given process is feasible, how efficient or inefficient is the process. Thus, the second law plays a key role in the design and operation of engineering processes, such as steam power plants and refrigeration processes. Nevertheless students often find the second law and its applications most difficult to comprehend. The second law revolves around the concepts of entropy and entropy generation. The feasibility of a process and its efficiency are directly related to entropy generation in the process. As entropy generation occurs in all flow processes due to friction in fluids, fluid mechanics can be used as a tool to teach the second law of thermodynamics and related concepts to students. In this article, flow through packed beds and consolidated porous media is analyzed in terms of entropy generation. The link between entropy generation and mechanical energy dissipation is established in such flows in terms of the directly measurable quantities such as pressure drop. Equations are developed to predict the entropy generation rates in terms of superficial fluid velocity, porous medium characteristics, and fluid properties. The predictions of the proposed equations are presented and discussed. Factors affecting the rate of entropy generation in flow through packed beds and consolidated porous media are identified and explained.

scholarly journals Quantum Discord, Thermal Discord, and Entropy Generation in the Minimum Error Discrimination Strategy

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 263 ◽  
Author(s):  
Omar Jiménez ◽  
Miguel Solís-Prosser ◽  
Leonardo Neves ◽  
Aldo Delgado
Keyword(s):  
Entropy Generation ◽  
Quantum Discord ◽  
Success Probability ◽  
Second Law Of Thermodynamics ◽  
Thermodynamic Cycle ◽  
Quantum Correlations ◽  
Quantum States ◽  
Second Law ◽  
Minimum Error ◽  
Accessible Information

We study the classical and quantum correlations in the minimum error discrimination (ME) of two non-orthogonal pure quantum states. In particular, we consider quantum discord, thermal discord and entropy generation. We show that ME allows one to reach the accessible information between the two involved parties, Alice and Bob, in the discrimination process. We determine the amount of quantum discord that is consumed in the ME and show that the entropy generation is, in general, higher than the thermal discord. However, in certain cases the entropy generation is very close to thermal discord, which indicates that, in these cases, the process generates the least possible entropy. Moreover, we also study the ME process as a thermodynamic cycle and we show that it is in agreement with the second law of thermodynamics. Finally, we study the relation between the accessible information and the optimum success probability in ME.

scholarly journals From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit

2019 ◽  
Author(s):  
Giedrė Streckienė ◽  
Vytautas Martinaitis ◽  
Juozas Bielskus
Keyword(s):  
Heat Pump ◽  
Entropy Generation ◽  
Energy Demand ◽  
Dynamic Modelling ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Second Law ◽  
Air Handling Unit ◽  
Individual Character ◽  
Environment Temperature

The continuous energy transformation processes in heating, ventilation and air conditioning systems of buildings are responsible for 36% of global final energy consumption. Tighter thermal insulation requirements for buildings have significantly reduced heat transfer losses. Unfortunately, this has little effect on energy demand for ventilation. On the basis of the First and the Second Law of Thermodynamics, the concepts of entropy and exergy are applied to the analysis of ventilation air handling unit (AHU) with a heat pump in this paper. This study aims to develop a consistent approach for this purpose, taking into account the variations of reference temperature and temperatures of working fluids. An analytical investigation on entropy generation and exergy analysis are used, when exergy is determined by calculating coenthalpies and evaluating exergy flows and their directions. The results show that each component of the AHU has its individual character of generated entropy, destroyed exergy and exergy efficiency variation. However, the evaporator of heat pump and fans have unabated quantities of exergy destruction. The exergy efficiency of AHU decreases from 45-55% to 12-15% when outdoor air temperature is within the range of –30°C…+10°C, respectively. This helps to determine conditions and components of improving the exergy efficiency of the AHU at variable real-world local climate conditions. The presented methodological approach could be used in the dynamic modelling software and contribute to a wider application of the Second Law of Thermodynamics in practice.

scholarly journals Beyond the classical theory of heat conduction: a perspective view of future from entropy

2016 ◽  
Vol 472 (2194) ◽  
pp. 20160362 ◽  
Author(s):  
Xiaowei Tian ◽  
Xiang Lai ◽  
Pingan Zhu ◽  
Liqiu Wang
Keyword(s):  
Heat Conduction ◽  
Entropy Generation ◽  
Classical Theory ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Perspective View ◽  
One Dimensional ◽  
First Law Of Thermodynamics ◽  
Concise Review ◽  
The Future

Energy is conserved by the first law of thermodynamics; its quality degrades constantly due to entropy generation, by the second law of thermodynamics. It is thus important to examine the entropy generation regarding the way to reduce its magnitude and the limit of entropy generation as time tends to infinity regarding whether it is bounded or not. This work initiates such an analysis with one-dimensional heat conduction. The work not only offers some fundamental insights of universe and its future, but also builds up the relation between the second law of thermodynamics and mathematical inequalities via developing the latter of either new or classical nature. A concise review of entropy is also included for the interest of performing the analysis in this work and the similar analysis for other processes in the future.

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