Explaining Exergy: A Cycle Approach

2012 ◽  
Author(s):  
Daisie D. Boettner ◽  
Michael J. Benson ◽  
James E. Bluman ◽  
Bret P. Van Poppel ◽  
A. Őzer Arnas
Keyword(s):  
Heat Pump ◽  
Closed System ◽  
System State ◽  
Visual Interpretation ◽  
Power Cycle ◽  
Dead State ◽  
System Temperature ◽  
Temperature And Pressure ◽  
The Dead ◽  
Definition Of

The exergy of a system at a given state traditionally is defined as the maximum potential useful work available from the system as it reaches equilibrium with its surroundings or a specified state (dead state). Boettner, et al. [1] demonstrate consideration of work required to restore the system to its original state is inherent in the definition of exergy. They provide a visual interpretation for the concept of exergy of a closed system whose temperature and pressure are above those of the dead state: closed system exergy corresponds to the sum of net work associated with a power cycle and a heat pump cycle with both cycles incorporating the system state and the dead state. On further investigation, the second cycle is not limited to a heat pump cycle and can be modeled as either a power cycle or a refrigeration/heat pump cycle. This paper simplifies the analysis such that one can immediately graph on a pressure-volume diagram and a temperature-entropy diagram a cycle whose enclosed area represents the exergy of a closed system at state i interacting with its surroundings (dead state). This paper also examines the case in which the closed system temperature and pressure are below those of the dead state.

Graphical Interpretation of Exergy

2011 ◽  
Author(s):  
Daisie D. Boettner ◽  
James Bluman ◽  
Matthew Rowland ◽  
Jonathan Bodenhamer ◽  
A. O˝zer Arnas
Keyword(s):  
Thermodynamic Property ◽  
Heat Pump ◽  
Closed System ◽  
Abstract Concept ◽  
System State ◽  
Power Cycle ◽  
Graphical Interpretation ◽  
Dead State ◽  
The Dead

Exergy is a system thermodynamic property defined only with respect to the system’s surroundings. For a specified system state, exergy is the maximum potential useful work available from the system as it achieves equilibrium with the surroundings. For students exergy can be a very abstract concept. This paper presents a graphical means to clarify the concept of exergy for a closed system, demonstrating exergy at any state i corresponds to the sum of the net work of a power cycle that incorporates a process from system state i to the dead state and the net work of a refrigeration/heat pump cycle required to move the system from the dead state to state i.

Towards an Exergy-Based Explosion Energy Model for Boiling-Liquid Expanding-Vapor Explosions

2011 ◽  
Author(s):  
Juan C. Ramirez ◽  
Suzanne A. Smyth ◽  
Russell A. Ogle
Keyword(s):  
Pressure Vessel ◽  
Ambient Pressure ◽  
Maximum Energy ◽  
Explosion Energy ◽  
Superheated Liquid ◽  
Boiling Liquid ◽  
Dead State ◽  
Vapor Explosions ◽  
The Dead ◽  
Definition Of

A boiling liquid, expanding vapor explosion (BLEVE) occurs when a pressure vessel containing a superheated liquid undergoes a catastrophic failure, resulting in a violent vaporization of the liquid. The exposure of a pressure vessel to a fire is a classic scenario that can result in a BLEVE. The thermomechanical exergy of a pressure vessel’s contents provides — by definition — an upper bound on the work that can be performed by the system during the explosion. By fixing the values of ambient pressure and temperature (i.e., the dead state), exergy can be interpreted as another thermodynamic property. This rigorous and unambiguous definition makes it ideal to estimate the maximum energy of explosions. The numerical value of exergy depends on the definition of the dead state. In this paper we examine the effect of different definitions for the dead state on the explosion energy value. We consider two applications of this method: the contribution of the vapor head-space to the explosive energy as a function of the fractional liquid fill of the vessel, and the effect of the vessel burst pressure.

The Dead State According to the Available Energy of Gibbs

2000 ◽  
Author(s):  
David M. Paulus ◽  
Richard A. Gaggioli
Keyword(s):  
Heat Pump ◽  
Environmental Conditions ◽  
Ambient Conditions ◽  
Available Energy ◽  
Dead State ◽  
Energy Concept ◽  
Partial Interaction ◽  
The Dead ◽  
Reference Environment

Abstract For exergy calculations, it is necessary to choose a reference environment. Typically the ambient conditions surrounding the system are chosen. It will be argued here that the outdoor environmental conditions are not always correct as a reference “dead state” for evaluating a system or accounting. The constraints on the system must be considered when choosing this “dead state”. Gibbs’ original available energy concept allows a proper dead state to be chosen, especially when a system has no or only partial interaction with the environment. The application of this theory is demonstrated in this paper through the example of a hypothetical plant, which serves as both a chiller and a heat pump.

scholarly journals Patterns of Memory in Askold Melnyczuk’s Novels as an Example of Ukrainian-American Émigré Fiction

2020 ◽  
Vol 47 (2) ◽  
pp. 125-137
Author(s):  
Marta Koval
Keyword(s):  
North America ◽  
20Th Century ◽  
European History ◽  
Family Stories ◽  
Traumatic Memories ◽  
The Past ◽  
History Of ◽  
The Dead ◽  
Definition Of

Although Ukrainian emigration to North America is not a new phenomenon, the dilemmas of memory and amnesia remain crucial in Ukrainian-American émigré fiction. The paper focuses on selected novels by Askold Melnyczuk (What is Told and Ambassador of the Dead) and analyzes how traumatic memories and family stories of the past shape the American lives of Ukrainian emigrants. The discussion of the selected Ukrainian-American émigré novels focuses on the dilemmas of remembering and forgetting in the construction of both Ukrainian and American narratives of the past. The voluntary amnesia of the Ame- rican-born Ukrainians in Melnyczuk’s novels confronts their parents’ dependence on the past and their inability to abandon it emotionally. Memories of ‘the old country’ make them, similarly to Ada Kruk, ambassadors of the dead. The expression becomes a metaphoric definition of those wrapped by their repressed, fragmentary and sometimes inaccessible memories. Crucial events of European history of the 20th century are inscribed and personalized in the older generation’s stories which their children are reluctant to hear. For them, their parents’ memories became a burden and a shame. Using the concept of transgenerational memory, the paper explores the challenges of postmemory, and eventually its failure. 

What Is Behavior?

2019 ◽  
pp. 1-13
Author(s):  
Christopher M. Furlow
Keyword(s):  
Living Organism ◽  
The Dead ◽  
Definition Of ◽  
Measurable Change

Prior to implementing interventions, practitioners must first develop definitions of behavior that are objective. This chapter first provides a definition of behavior and provides three criteria for determining whether something is a behavior: it is demonstrated by a living organism, in interaction with the environment, and the interaction results in measurable change within the environment. Next, the chapter outlines how practitioners should develop operational definitions of behaviors of interest. Then, the chapter provides a description of the dead man’s test, a heuristic that practitioners often utilize when determining if something qualifies as a behavior suitable for intervention. Finally, the chapter describes the meaningful operant dimensions of behavior, such as frequency, duration, latency, and magnitude.

scholarly journals Landscape—A Review with a European Perspective

Land ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 85 ◽  
Author(s):  
Katia Talento ◽  
Miguel Amado ◽  
Josè Carlos Kullberg
Keyword(s):  
Literature Review ◽  
Life Cycles ◽  
European Perspective ◽  
A Value ◽  
Terrain Vague ◽  
The Dead ◽  
Definition Of ◽  
Present Text

This article aims to act as a general literature review regarding the landscape, analyzing it through a synthesis of the main concepts and processes that have generated, and subsequently developed, the word “Landscape”. It is a versatile theme, because it has always been studied by various disciplines, through different theories, which sometimes even conflict with each other. Through the present text, we understand the importance and the unique value of the landscape, a value that has nowadays been transfigured by the strong industrialization and strong brand of man in the territory. Thus, the first part of the research is, to some extent, a reflection on current issues that are related to the landscape. It is also a tool for integration, including in the definition of “Landscape”, even those heavily humanized, exploited, degraded, abandoned, and residual; the so-called “Drosscape”, “Friche”, and “Terrain Vague”. The solution is not to negatively interpret these types of scenarios, but rather to enhance them as they are, filled with potential and creativity. This concept is achieved by means of an operation of recycling or reuse of waste, which is capable of germinating new life cycles within the “dead nature” of our increasingly cemented territories.

scholarly journals Investigating the Effect of Solid Boundaries on the Gas Molecular Mean-Free-Path

2009 ◽  
Author(s):  
Erik J. Arlemark ◽  
Jason M. Reese
Keyword(s):  
Molecular Dynamics ◽  
Boundary Conditions ◽  
Free Path ◽  
Mean Free Path ◽  
Gas Flows ◽  
Standard Temperature ◽  
Binary Collisions ◽  
The Mean ◽  
Temperature And Pressure ◽  
Definition Of

A key parameter for micro-gas-flows, the mean free path, is investigated in this paper. The mean free path is used in various models for predicting micro gas flows, both in the governing equations and their boundary conditions. The conventional definition of the mean free path is based on the assumption that only binary collisions occur and is commonly described using the macroscopic quantities density, viscosity and temperature. In this paper we compare the prediction by this definition of the mean free paths for helium, neon and argon gases under standard temperature and pressure conditions, with the mean free paths achieved by measurements of individual molecules using the numerical simulation technique of molecular dynamics. Our simulation using molecular dynamics consists of a cube with six periodic boundary conditions, allowing us to simulate an unconfined gas “package”. Although, the size of this package is important, since its impact on computational cost is considerable, it is also important to have enough simulated molecules to average data from. We find that the molecular dynamics method using 20520 simulated molecules yields results that are within 1% accuracy from the conventional definition of the mean free paths for neon and argon and within 2.5% for helium. We can also conclude that the normal approximation of only considering binary collisions is seemingly adequate for these gases under standard temperature and pressure conditions. We introduce a single planar wall and two parallel planar walls to the simulated gas of neon and record the mean free paths at various distances to the walls. It is found that the mean free paths affected by molecular collisions with the walls corresponds well with theoretical models up to Knudsen numbers of 0.2.

Structures of care in the Iliad

1996 ◽  
Vol 46 (1) ◽  
pp. 1-26 ◽  
Author(s):  
M. Lynn-George
Keyword(s):  
Funeral Rites ◽  
The Dead ◽  
Definition Of ◽  
Structures Of Care

When Andromache emerges from the inner chamber in Book 22, ascends the walls of Troy and looks out over the plain, she beholds a spectacle of ruthless brutality. She who has not been aware of the final combat, nor of the slaying of her husband, is suddenly confronted by the receding trail of utter defeat. Swift horses drag her husband's corpse into the distance, the cherished head disfigured as it is dragged, raking the dust of what was once their homeland. The violence of the scene is forcefully conveyed by one word in particular. The swift horses drag Hektor ⋯κηδ⋯στως (22.465)—without κ⋯δος without care, ‘sans soucier de, brutalement’. In itself the word ⋯κηδ⋯στως provides a definition of violence, one captured in Shakespeare's phrase ‘careless force’. Violence is, in its harsh brutality, specifically heedlessness, an absence of any form of care. When Achilles hurls the slain suppliant Lykaon into the river he utters the taunt, ‘the fish, ⋯κηδ⋯ες, will lick clean your wound's blood’ (21.122–3). The discarded corpse is denied funeral rites: in place of the care that the relations of the dead traditionally bestow in tending, washing, enshrouding, lamenting, and burying the dead, here the heedless creatures of nature, fleeting visitors, will attend to the corpse, ‘clean’ it, but utterly without care, completely oblivious to the oblivion they create by destroying. In Book 24 Achilles will describe the gods themselves as ⋯κηδ⋯ες (526).

The Dead State

2012 ◽  
Vol 15 (4) ◽  
Author(s):  
Richard Gaggioli
Keyword(s):  
Dead State ◽  
The Dead
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