The origin of irreversibility and thermalization in thermodynamic processes

Thermodynamic processes involve energy exchanges in the forms of work, heat, or particles. Such exchanges might be reversible or irreversible, and they might be controlled by barriers or reservoirs. A cyclic process takes a system through several states and eventually back to its initial state; it may convert heat into work (engine) or vice versa (heat pump). This chapter defines work and heat mathematically and investigates their respective properties, in particular their impact on entropy. It discusses the roles of barriers and reservoirs and introduces cyclic processes. Basic constraints imposed by the laws of thermodynamics are considered, in particular on the efficiency of a heat engine. The chapter also introduces the thermodynamic potentials: free energy, enthalpy, free enthalpy, and grand potential. These are used to describe energy exchanges and equilibrium in the presence of reservoirs. Finally, this chapter considers thermodynamic coefficients which characterize the response of a system to heating, compression, and other external actions.

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Defining the Thermodynamic Efficiency in a Wave Rotor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4033508 ◽

2016 ◽

Vol 138 (11) ◽

Cited By ~ 4

Author(s):

Shining Chan ◽

Huoxing Liu ◽

Fei Xing

Keyword(s):

Gas Turbine ◽

Control Volume ◽

Thermodynamic Efficiency ◽

Wave Rotor ◽

Wave Rotors ◽

Compression And Expansion ◽

Efficiency Estimation ◽

Parametric Analyses ◽

Control Volumes ◽

Thermodynamic Processes

A wave rotor enhances the performance of a gas turbine with its internal compression and expansion, yet the thermodynamic efficiency estimation has been troubling because the efficiency definition is unclear. This paper put forward three new thermodynamic efficiency definitions to overcome the trouble: the adiabatic efficiency, the weighted-pressure mixed efficiency, and the pressure pre-equilibrated efficiency. They were all derived from multistream control volumes. As a consequence, they could correct the efficiency values and make the values for compression and expansion independent. Moreover, the latter two incorporated new models of pre-equilibration inside a control volume, and modified the hypothetical “ideal” thermodynamic processes. Parametric analyses based on practical wave rotor data demonstrated that the trends of those efficiency values reflected the energy losses in wave rotors. Essentially, different thermodynamic efficiency definitions indicated different ideal thermal cycle that an optimal wave rotor can provide for a gas turbine, and they were recommended to application based on that essence.

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Thermodynamic processes expressed in terms of nonlinear maps

Quantum Studies Mathematics and Foundations ◽

10.1007/s40509-018-0165-y ◽

2018 ◽

Vol 6 (1) ◽

pp. 83-88

Author(s):

Yehuda Roth

Keyword(s):

Nonlinear Maps ◽

Thermodynamic Processes

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Determination of bulk density of the source of heat in the analysis of thermodynamic processes in the quartz piezoelectric element

2014 24th International Crimean Conference Microwave & Telecommunication Technology ◽

10.1109/crmico.2014.6959599 ◽

2014 ◽

Cited By ~ 9

Author(s):

A. A. Taranchuk ◽

S. K. Pidchenko ◽

R.P. Khoptinskiy

Keyword(s):

Bulk Density ◽

Piezoelectric Element ◽

Thermodynamic Processes

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Summer Westerly Jet in Northern Hemisphere during the Mid-Holocene: A Multi-Model Study

Atmosphere ◽

10.3390/atmos11111193 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1193

Author(s):

Chuchu Xu ◽

Mi Yan ◽

Liang Ning ◽

Jian Liu

Keyword(s):

Temperature Gradient ◽

Northern Hemisphere ◽

Hadley Cell ◽

Dynamic Processes ◽

Jet Stream ◽

Meridional Temperature Gradient ◽

The North ◽

Westerly Jet ◽

Poleward Shift ◽

Thermodynamic Processes

The upper-level jet stream, a narrow band of maximum wind speed in the mid-latitude westerlies, exerts a considerable influence on the global climate by modulating the transport and distribution of momentum, heat and moisture. In this study by using four high-resolution models in the Paleoclimate Modelling Intercomparison Project phase 3, the changes of position and intensity of the northern hemisphere westerly jet at 200 hPa in summer during the mid-Holocene (MH), as well as the related mechanisms, are investigated. The four models show similar performance on the westerly jet. At the hemispheric scale, the simulated westerly jet has a poleward shift during the MH compared to the preindustrial period. The warming in arctic and cooling in the tropics during the MH are caused by the orbital changes of the earth and the precipitation changes, and it could lead to the weakened meridional temperature gradient and pressure gradient, which might account for the poleward shift of the westerly jet from the thermodynamic perspective. From the dynamic perspective, two maximum centers of eddy kinetic energy are simulated over the North Pacific and North Atlantic with the north deviation, which could cause the northward movement of the westerly jet. The weakening of the jet stream is associated with the change of the Hadley cell and the meridional temperature gradient. The largest weakening is over the Pacific Ocean where both the dynamic and the thermodynamic processes have weakening effects. The smallest weakening is over the Atlantic Ocean, and it is induced by the offset effects of dynamic processes and thermodynamic processes. The weakening over the Eurasia is mainly caused by the dynamic processes.

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Properties of nickel-based superalloys of equiaxial crystallization

Innovative Materials and Technologies in Metallurgy and Mechanical Engineering ◽

10.15588/1607-6885-2021-2-3 ◽

2021 ◽

pp. 19-23

Author(s):

O. Glotka ◽

V. Olshanetskii

Keyword(s):

Mechanical Properties ◽

Chemical Composition ◽

Regression Models ◽

Computational Prediction ◽

Integrated Approach ◽

Experimental Data Processing ◽

Predictive Regression ◽

Heat Resistant ◽

First Time ◽

Thermodynamic Processes

Purpose. The aim of the work is to obtain predictive regression models, with the help of which, it is possible to adequately calculate the mechanical properties of nickel-based superalloys of equiaxial crystallization, without carrying out preliminary experiments. Research methods. To find regularities and calculate the latest CALPHAD method was chosen, and modeling of thermodynamic processes of phase crystallization was performed. Results. As a result of experimental data processing, the ratio of alloying elements Kg¢ was proposed for the first time, which can be used to assess the mechanical properties, taking into account the complex effect of the main alloy components. The regularities of the influence of the composition on the properties of heat-resistant nickel alloys of equiaxial crystallization are established. The analysis of the received dependences in comparison with practical results is carried out. The relations well correlated with heat resistance, mismatch and strength of alloys are obtained. Scientific novelty. It is shown that for multicomponent nickel systems it is possible with a high probability to predict a mismatch, which significantly affects the strength characteristics of alloys of this class. The regularities of the influence of the chemical composition on the structure and properties of alloys are established. A promising and effective direction in solving the problem of predicting the main characteristics of heat-resistant materials based on nickel is shown Practical value. On the basis of an integrated approach for multicomponent heat-resistant nickel-based alloys, new regression models have been obtained that make it possible to adequately predict the properties of the chemical composition of the alloy, which made it possible to solve the problem of computational prediction of properties from the chemical composition of the alloy. This allows not only to design new nickel-based alloys, but also to optimize the composition of existing brands.

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