Conceptual issues related to reversibility and reversible work produced in closed and open flow systems

Pal, Rajinder

doi:10.1016/j.ece.2017.04.001

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…Thermodynamics is a difficult subject to learn and teach. It is considered to be one of the most abstract disciplines of the physical sciences [1]. Students all over the world face difficulties in learning thermodynamics.…”

Section: Introductionmentioning

confidence: 99%

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

Pal

2019

Fluids

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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.

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Section: Introductionmentioning

confidence: 99%

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

Pal

2019

Fluids

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“…Since much of the energy used in industry is provided by the combustion of fossil fuels, a reduction in energy use will also reduce production of the 'greenhouse gas' carbon dioxide with its contribution to global warming. In thermodynamic terms, optimum processes-those requiring least energy-are performed under reversible conditions [1,2]. In this paper, we consider the generalised thermodynamics of industrial production and show how production may be optimised towards reversibility by judicious application of material transfers, heat transfers and performances of work.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic optimization of steady-flow industrial chemical processes

et al. 2018

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Industrial steady-flow chemical processes are generally organised as a sequence of individually optimised operations. However, this may not achieve overall optimization since material (as recycle), heat and work transfers overall may not be well balanced. We introduce the idea of a preliminary overall thermodynamic balance to produce a reversible process, with the objective of minimising, for both economic and environmental reasons, the quality and quantity of energy used. This balance may later require adjustment to account for the realities of available materials and equipment. For this purpose, we introduce (i) a Carnot temperature, T Carnot , by which a Carnot machine (an engine which can operate as either a heat pump or a turbine) can supply the required heat at the correct temperature for a process to operate reversibly, that is with least energy, and (ii) the GH Diagram on which Carnot temperature-based processes are plotted in ∆G-∆H space. We demonstrate the utility of this analysis by simple application to the Haber-Bosch process for ammonia synthesis and by a sequence of operations for the synthesis of methanol. We also briefly introduce the state function exergy, which uses the natural environment as the reference base for energy in place of pure elements under standard conditions.

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Towards the meaningful learning of thermodynamics: A proposal for teaching exergy

Gatti

Perez

Horst

et al. 2023

Education for Chemical Engineers

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Conceptual issues related to reversibility and reversible work produced in closed and open flow systems

Cited by 3 publications

References 9 publications

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

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

Thermodynamic optimization of steady-flow industrial chemical processes

Towards the meaningful learning of thermodynamics: A proposal for teaching exergy

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