A New Approach to Understanding Engineering Thermodynamics From Its Molecular Basis

2012 ◽  
Author(s):  
W. John Dartnall ◽  
John A. Reizes
Keyword(s):  
Working Fluid ◽  
Combustion Engines ◽  
New Approach ◽  
Heat Engines ◽  
Molecular Behavior ◽  
Modern Engineering ◽  
Prime Concern ◽  
And Performance ◽  
General Physical ◽  
External Combustion

Engineering Thermodynamics is that engineering science in which students learn to analyze dynamic systems involving energy transformations, particularly where some of the energy is in the form of heat. It is well known that people have difficulty in understanding many of the concepts of thermodynamics; in particular, entropy and its consequences. However, even more widely known concepts such as energy and temperature are not simply defined or explained. Why is this lack of understanding and clarity of definition prevalent in this subject? Older engineering thermodynamics textbooks (often containing the words “heat engines” in the title) had a strong emphasis in their early chapters on the general physical details of thermodynamic equipment such as internal and external combustion engines, gas compressors and refrigeration systems. The working fluid in these systems might expand or contract while heat, work and mass might cross the system boundary. The molecular workings within the thermodynamic fluid are not of prime concern to the engineer even though they are to a physicist or chemist. Modern engineering thermodynamics textbooks place great emphasis on mathematical systems designed to analyze the behavior and performance of thermodynamic devices and systems, yet they rarely show, at least early in their presentation, graphical images of the equipment; moreover, they tend to give only passing reference to the molecular behavior of the thermodynamic fluid. This paper presents some teaching strategies for placing a greater emphasis on the physical realities of the equipment in conjunction with the molecular structure of the working fluid in order to facilitate a deeper understanding of thermodynamic performance limitations of equipment.

Thermodynamics From a Few Dynamic Particles Raises Questions as to How Temperature and Entropy Should Be Perceived and Defined

2007 ◽  
Author(s):  
W. John Dartnall ◽  
John Reizes
Keyword(s):  
Kinetic Energy ◽  
Single Particle ◽  
Heat Engine ◽  
Working Fluid ◽  
Second Law ◽  
Piston Engine ◽  
New Approach ◽  
Particle Mechanics ◽  
Mechanics Model ◽  
Heat Engines

In a recently developed simple particle mechanics model, in which a single particle represents the working fluid, (gas) in a heat engine, (exemplified by a piston engine) a new approach was outlined for the teaching of concepts to thermodynamic students. By mechanics reasoning, a model was developed that demonstrates the connection between the Carnot efficiency limitation of heat engines, and the Kelvin-Planck statement of Second Law, requiring only the truth of the Clausius statement. In a second paper the model was extended to introduce entropy. The particle’s entropy was defined as a function of its kinetic energy, and the space that it occupies, that is analogous to that normally found in classical macroscopic analyses. In this paper, questions are raised and addressed: How should temperature and entropy be perceived and defined? Should temperature be proportional to average (molecular) translational kinetic energy and should entropy be dimensionless?

Modeling of a New Crank-Less Rotary Heat Engine Concept for Solar Power Utilization

2018 ◽  
Author(s):  
Muhammad I. Rashad ◽  
Hend A. Faiad ◽  
Mahmoud Elzouka
Keyword(s):  
Degrees Of Freedom ◽  
Unit Cost ◽  
Heat Engine ◽  
Structure Design ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Heat Engines ◽  
And Performance ◽  
Engine Concept

This paper presents the operating principle of a novel solar rotary crank-less heat engine. The proposed engine concept uses air as working fluid. The reciprocating motion is converted to a rotary motion by the mean of unbalanced mass and Coriolis effect, instead of a crank shaft. This facilitates the engine scaling and provides several degrees of freedom in terms of structure design and configuration. Unlike classical heat engines (i.e. Stirling), the proposed engine can be fixed to the ground which significantly reduce the generation unit cost. Firstly, the engine’s configuration is illustrated. Then, order analysis for the engine is carried out. The combined dynamics and thermal model is developed using ordinary differential equations which are then numerically solved by Simulink™. The resulting engine thermodynamics cycle is described. It incorporates the common thermodynamics processes (isobaric, isothermal, isochoric processes). Finally, the system behavior and performance are analyzed along with studying the effect of various design parameters on operating conditions such as engine speed, output power and efficiency.

Performance Characteristics of a Class of External Combustion Engines

2013 ◽  
Vol 732-733 ◽  
pp. 199-203
Author(s):  
Shi Yan Zheng ◽  
Hui Shan Yang
Keyword(s):  
Optimal Design ◽  
Heat Loss ◽  
Power Output ◽  
Combustion Engines ◽  
Heat Reservoir ◽  
Cycle Model ◽  
Heat Engines ◽  
Output Efficiency ◽  
Adiabatic Processes ◽  
External Combustion

The general cycle model of a class of external combustion engines is established in which the influence of the multi-irreversibilities mainly resulting from the linear heat-loss model between the high and low heat reservoir, and the irreversible adiabatic processes. Some important parameters such as the power output, efficiency and the temperatures of the working substance are calculated and some important characteristic curves are given. The results obtained in this paper may provide some theoretical guidance for the optimal design of the Carnot, Brayton, Braysson and some new heat engines.

A Novel Approach to the Teaching of Etropy Based on a Recent Single Particle Heat Engine Model

2006 ◽  
Author(s):  
W. John Dartnall ◽  
John Reizes
Keyword(s):  
Single Particle ◽  
Heat Engine ◽  
Working Fluid ◽  
Second Law ◽  
Piston Engine ◽  
New Approach ◽  
Engine Model ◽  
Mechanics Model ◽  
Heat Engines ◽  
Novel Approach

In a recently developed simple particle mechanics model in which a single particle represents the working fluid (gas) in a heat engine (exemplified by a piston engine) a new approach was outlined for the teaching of concepts to thermodynamic students. By mechanics reasoning a model was developed that demonstrates the connection between the Carnot efficiency limitation of heat engines and the Kelvin-Planck statement of Second Law requiring only the truth of the Clausius statement. In this paper the model is extended to introduce entropy. Here the particle's entropy is defined as a function of its kinetic energy and the space that it occupies that is analogous to that normally found in classical macroscopic analyses.

scholarly journals Optimal Stroke Path for Reciprocating Heat Engines

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Mahmoud Huleihil
Keyword(s):  
Internal Combustion Engines ◽  
Control Variable ◽  
Building Blocks ◽  
Power Production ◽  
Combustion Engines ◽  
Piston Motion ◽  
Heat Engines ◽  
Sinusoidal Motion ◽  
Frictional Dissipation ◽  
External Combustion

By testing piston motion in reciprocating heat engines as a control variable, one could find piston trajectories, different from the conventional near sinusoidal motion that should increase power production. This results from minimizing frictional losses. The purpose of this study is to determine piston trajectories that are optimal for noncombustion strokes in reciprocating engines, in the sense of minimizing frictional dissipation and hence maximizing efficiency and power. The optimal piston traces for noncombustion strokes are determined by using a combination of optimal control theory and models for the thermodynamic irreversibilities. Hence, the results are germane to external combustion engines and to the noncombustion strokes of internal combustion engines. The optimal piston traces or trajectories obtained here can be viewed as some of the building blocks from which optimal overall cycles can be constructed.

Optimal Configuration and Performance of Heat Engines with Heat Leak and Finite Heat Capacity

2002 ◽  
Vol 09 (01) ◽  
pp. 85-96 ◽  
Author(s):  
Lingen Chen ◽  
Shengbing Zhou ◽  
Fengrui Sun ◽  
Chih Wu
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Low Temperature ◽  
Heat Engine ◽  
Optimal Configuration ◽  
Working Fluid ◽  
Heat Leak ◽  
Heat Engines ◽  
And Performance ◽  
Maximum Work Output

The optimal configuration of a class of two-heat-reservoir heat engine cycles in which the maximum work output can be obtained under a given cycle time is determined with the considerations of heat leak, finite heat capacity high-temperature source and infinite heat capacity low-temperature heat sink. The heat engine cycles considered in this paper include: (1) infinite low- and high-temperature reservoirs without heat leak, (2) infinite low- and high-temperature reservoirs with heat leak, (3) finite high-temperature source and infinite low-temperature sink without heat leak, and (4) finite high-temperature source and infinite low-temperature sink with heat leak. It is assumed that the heat transfer between the working fluid and the reservoirs obeys Newton's law. It is shown that the existence of heat leak doesn't affect the configuration of a cycle with an infinite high-temperature source. The finite heat capacity of a high temperature source without heat leak makes the cycle a generalized Carnot heat engine cycle. There exists a great difference of the cycle configurations for the finite high-temperature source with heat leak and the former three cases. Moreover, the relations between the optimal power output and the efficiency of the former three configurations are derived, and they show that the heat leak affects the power versus efficiency characteristics of the heat engine cycles.

Music of Tragedy

2017 ◽  
Author(s):  
Naomi A. Weiss
Keyword(s):  
Cultural Context ◽  
Musical Language ◽  
New Approach ◽  
Late Work ◽  
Music Making ◽  
Dramatic Action ◽  
Instrumental Accompaniment ◽  
And Performance

The Music of Tragedy offers a new approach to the study of classical Greek theater by examining the use of musical language, imagery, and performance in the late work of Euripides. Drawing on the ancient conception of mousikē, in which words, song, dance, and instrumental accompaniment were closely linked, Naomi Weiss emphasizes the interplay of performance and imagination—the connection between the chorus’s own live singing and dancing in the theater and the images of music-making that frequently appear in their songs. Through detailed readings of four plays, she argues that the mousikē referred to and imagined in these plays is central to the progression of the dramatic action and to ancient audiences’ experiences of tragedy itself. She situates Euripides’s experimentation with the dramaturgical effects of mousikē within a broader cultural context, and in doing so, she shows how he both continues the practices of his tragic predecessors and also departs from them, reinventing traditional lyric styles and motifs for the tragic stage.

scholarly journals Sustainability Investigation of Vehicles’ CO2 Emission in Hungary

2021 ◽  
Vol 13 (15) ◽  
pp. 8237
Author(s):  
István Árpád ◽  
Judit T. Kiss ◽  
Gábor Bellér ◽  
Dénes Kocsis
Keyword(s):  
Energy Efficiency ◽  
Co2 Emissions ◽  
Energy Supply ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
The European Union ◽  
New Approach ◽  
Technology System ◽  
Low Co2

The regulation of vehicular CO2 emissions determines the permissible emissions of vehicles in units of g CO2/km. However, these values only partially provide adequate information because they characterize only the vehicle but not the emission of the associated energy supply technology system. The energy needed for the motion of vehicles is generated in several ways by the energy industry, depending on how the vehicles are driven. These methods of energy generation consist of different series of energy source conversions, where the last technological step is the vehicle itself, and the result is the motion. In addition, sustainability characterization of vehicles cannot be determined by the vehicle’s CO2 emissions alone because it is a more complex notion. The new approach investigates the entire energy technology system associated with the generation of motion, which of course includes the vehicle. The total CO2 emissions and the resulting energy efficiency have been determined. For this, it was necessary to systematize (collect) the energy supply technology lines of the vehicles. The emission results are not given in g CO2/km but in g CO2/J, which is defined in the paper. This new method is complementary to the European Union regulative one, but it allows more complex evaluations of sustainability. The calculations were performed based on Hungarian data. Finally, using the resulting energy efficiency values, the emission results were evaluated by constructing a sustainability matrix similar to the risk matrix. If only the vehicle is investigated, low CO2 emissions can be achieved with vehicles using internal combustion engines. However, taking into consideration present technologies, in terms of sustainability, the spread of electric-only vehicles using renewable energies can result in improvement in the future. This proposal was supported by the combined analysis of the energy-specific CO2 emissions and the energy efficiency of vehicles with different power-driven systems.

Sign in / Sign up

Export Citation Format

Share Document