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Introduction and Basic Concepts
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
There are three kinds of thermodynamic systems: closed, isolated, and open. A closed system refers to a fixed quantity of matter and it is also called control mass, as mass cannot cross its boundary, only energy can cross. Examples of closed systems are air trapped in a piston-cylinder device and gas inside a closed balloon. An isolated system is the one in which neither energy nor mass can cross the boundaries of the system. It is a special case of closed system. Although it seems that a system that doesn’t interact with the surroundings has no significance, if the combination of two or more systems, interacting with each other, is surrounded by a boundary, then they can be regarded as an isolated system for the analysis. A thermos with a lid used to keep the things either cold or hot is an example of an isolated system since it doesn’t allow either mass or energy transfer across it. An open system, also called as control volume, is a region of space through which mass and energy can cross the boundaries of the system. Examples of open systems are air and fuel entering and exhaust gases leaving an internal combustion engine, and the engineering devices that involve mass flow such as turbines, compressors, and nozzles can be considered as control volume. Figures 1.1–1.3 show how the closed system, isolated system, and open system interact with their surroundings, respectively.
The Laws of Thermodynamics
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
This expression is called the Clausius inequality, and it has profound implications on the process of nuclear heat transfer and fluid flow. In other words, the entropy of an isolated system will always increase or stay the same, it but neverdecreases over time. This is a reminder of the fact that the molecular disorder of a system always increases over time and that the entropy of an isolated system will continue to increase until the entropy reaches a maximum value SMAX. At this point, the system is said to be in thermodynamic equilibrium with its environment, and the molecular disorder cannot increase any further. The energy distribution of the particles when this occurs is given by what is known as a Maxwell–Boltzmann probability distribution, and in a Maxwell–Boltzmann probability distribution, the average energy E of each particle is only a function of the absolute temperature T (which is assumed to be uniform everywhere). In a Maxwell–Boltzmann distribution, the average energy of a particle is 〈E〉 = 3/2 kT and the most probable energy is E = ½ kT, where k is Boltzmann’s constant.
Phase and State Transitions and Transformations in Food Systems
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Thermodynamics is the study of transformations of energy. Energy transformation in relation to phase transitions may occur within a system or between a system and its surroundings. A closed system has no transfer of matter between the system and its surroundings. An open system exhibits transfer of matter through a boundary between the system and its surroundings. Both closed and open systems can transfer energy between the systems and their surroundings. If there is transfer of neither energy nor matter between a system and its surroundings, the system is an isolated system. The state of a single system can be characterized according to its internal energy, U, temperature, T, volume, V, pressure, p, number of moles, N, and mass, M. Internal energy, volume, number of moles, and mass are extensive functions of state, which means that they are proportional to the amount of matter. Temperature and pressure are independent of the amount of matter, and they are defined as intensive functions of state. The basic thermodynamics of phase transitions can be found in books of Physical Chemistry, such as Atkins and de Paula (2006), and an excellent summary is available in Singh and Heldman (2001).
A multicomponent multitemperature model for simulating laminar deflagration waves in mixtures of air and hydrogen
Published in Numerical Heat Transfer, Part B: Fundamentals, 2023
We are interested now in the properties of Proposition 2.3, in particular the third one (item (iii)). The second law of thermodynamics applied to a closed and isolated system states that the concave mixture entropy must increase: and that it can reach an asymptotic equilibrium state which is defined as the maximum of the entropy η. Since the latter is strictly concave for fixed (V, M, E), this equilibrium state is unique. Let us denote the equilibrium state by: and for which is uniquely defined for a given (V, M, E) as: with:
Entropy generation and mixed convection of CuO–water near an oblique stagnation point: modified Chebyshev wavelets approach
Published in Waves in Random and Complex Media, 2022
Tabinda Sajjad, Rizwan Ul Haq, Muhammad Usman
The second law of thermodynamics asserts that the state of entropy of the entire universe, as an isolated system, will always increase over time. ‘The process of heat transfer occurs in a specific direction from hotter region to colder region.’ Bejan and Kestin [36] were the first who discuss about entropy generation in fluids. Entropy is responsible for the loss of useful energy during the heat transfer process. It is important in application of any engineering model. Minimization of entropy can produce more economic models [37]. The production of system may increase by diminishing factors responsible for entropy generation [38]. Approximate entropy (ApEn) of blood pressure gives more clear results about higher and low risks of hypertensive crises [39]. Entropy analysis is used in facial electromyogram. It uses entropy change to discuss the tension and stress in human facial nerves. Entropy change could be considered as the composite measure in change in physiological behavior toward a stimulus or stressor [40]. Entropy of system increases when heat supply increases, e.g. entropy increases when solid is converted to liquid.
Intelligent computing through neural networks for entropy generation in MHD third-grade nanofluid under chemical reaction and viscous dissipation
Published in Waves in Random and Complex Media, 2022
Muhammad Asif Zahoor Raja, Rafia Tabassum, Essam Roshdy El-Zahar, Muhammad Shoaib, M. Ijaz Khan, M. Y. Malik, Sami Ullah Khan, Sumaira Qayyum
Entropy is a measurable physical attribute mostly linked with a condition or disorder, unpredictability, or uncertainty. It has many applications in biological systems, economics, sociology, meteorology, climate change, cosmology, and information systems, including telecommunications data transmission. Entropy has the effect of making specific processes irreversible. The second law of thermodynamics holds that the entropy of an isolated system left to spontaneous development cannot decrease with time because it always reaches a state of thermodynamic equilibrium, where the entropy is greatest. Using entropy optimisation, Alsaedi et al. [21] investigated the MHD TGNF flow by considering binary chemical reaction and activation energy past a stretching sheet. Hayat et al. [22] exemplified heat transmission in a mixed convective stream of carbon nanotubes with entropy generation subjected to a curved stretching surface. Under the influence of magnetic and electric fields, Khan et al. [23] explored EG in electro-magneto dynamical mixed convection flow. Nayak et al. [24] used EG to explore an MHD Hamilton’s Crosser flow by considering the Darcy-Forchheimer. The Jeffrey nanofluid stream under the effects of entropy generation was studied by Le et al. [25]. Using the Buongiorno model, Adnan et al. [26] evaluated the EG in a convective stream of hybrid nanofluid fluid using magnetic force impact. The EG was presented by Adnan et al. [27] in a nanofluid flow passing through convergent and divergent channels.