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Entropy
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
The isentropic process is a process in which entropy is constant. It has been observed that the entropy of a closed system can be varied by heat transfer and irreversibilities. If the process is reversible and adiabatic, the entropy remains constant and it is called an isentropic process. The entropy of a substance will be the same at the end of the process and the beginning, if the process is carried out isentropically. The term efficiency is frequently used by engineers in many engineering applications. Generally, it is defined as the ratio of output to the input. In this section, the isentropic efficiencies for steady-flow devices such as nozzles, turbines, and compressors are presented. Isentropic efficiency is derived by comparing the actual performance of a device and the performance under idealized conditions for the same inlet and the exit conditions. It is defined differently for work-producing and work-consuming devices.
Compressible Flow
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
For an isentropic process, p/ργ = a constant, or pργ=ptρtγ
Symbols, Terminology, and Nomenclature
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Inductance - The ratio of the electromagnetic force induced in a coil by a current to the rate of change of the current. Inductive coupled plasma mass spectroscopy (ICPMS) - See Techniques for Materials Characterization, page 12-1. Inertial defect - In molecular spectroscopy, the quantity Ic-Ia-Ib for a molecule whose equilibrium configuration is planar, where Ia, Ib, and Ic are the effective principal moments of inertia. The inertial defect for a rigid planar molecule would be zero, but vibration-rotation interactions in a real molecule lead to a positive inertial defect. Insulator - A material in which the highest occupied energy band (valence band) is completely filled with electrons, while the next higher band (conduction band) is empty. Solids with an energy gap of 5 eV or more are generally considered as insulators at room temperature. Their conductivity is less than 10-6 S/m and increases with temperature. Intercalation compounds - Compounds resulting from reversible inclusion, without covalent bonding, of one kind of molecule in a solid matrix of another compound, which has a laminar structure. The host compound, a solid, may be macromolecular, crystalline, or amorphous. [5] International System of Units (SI)* - The unit system adopted by the General Conference on Weights and Measures in 1960. It consists of seven base units (meter, kilogram, second, ampere, kelvin, mole, candela), plus derived units and prefixes. [1] International Temperature Scale (ITS-90)* - The official international temperature scale adopted in 1990. It consists of a set of fixed points and equations which enable the thermodynamic temperature to be determined from operational measurements. [9] Ion - An atomic or molecular particle having a net electric charge. [3] Ion exchange - A process involving the adsorption of one or several ionic species accompanied by the simultaneous desorption (displacement) of one or more other ionic species. [3] Ion neutralization spectroscopy (INS) - See Techniques for Materials Characterization, page 12-1. Ionic strength (I) - A measure of the total concentration of ions in a solution, defined by I = 1/2i zi2mi, where zi is the charge of ionic species i and mi is its molality. For a 1-1 electrolyte at molality m, I = m. Ionization constant* - The equilibrium constant for a reaction in which a substance in solution dissociates into ions. Ionization potential* - The minimum energy required to remove an electron from an isolated atom or molecule (in its vibrational ground state) in the gaseous phase. More properly called ionization energy. [3] Irradiance (E) - The radiant energy flux incident on an element of a surface, divided by the area of that element. [1] Isentropic process - A thermodynamic process in which the entropy of the system does not change. Ising model - A model describing the coupling between two atoms in a ferromagnetic lattice, in which the interaction energy is proportional to the negative of the product of the spin components along a specified axis. Isobar - A line connecting points of equal pressure on a graphical representation of a physical system. Isochore - A line or surface of constant volume on a graphical representation of a physical system.
Creep life prediction for a nickel-based single crystal turbine blade
Published in Mechanics of Advanced Materials and Structures, 2022
Zhen Li, Zhixun Wen, Haiqing Pei, Xiaowei Yue, Pu Wang, Changsheng Ai, Zhufeng Yue
As is known to all, the isentropic process is also called the reversible adiabatic process. The adiabatic process is a thermal process in which the gas does not exchange heat with the external environment. When the process is proceeding very fast, the working fluid are too late to exchange heat with the external environment or the exchange of heat is very little. It can be approximately regarded as an adiabatic process. The compression process of the gas in the compressor of the turbine engine and the expansion process in the turbine as well as the exhaust nozzle can be regarded as an adiabatic process. The inlet boundary condition is a pressure inlet. The gas inlet angle, total pressure distortion intensity, and total temperature are shown in Figure 8. Among them, the definition of total pressure distortion intensity is shown in equation (10).
Coupled heat transfer model for the combustion and steam characteristics of coal-fired boilers
Published in Engineering Applications of Computational Fluid Mechanics, 2021
Yan Xie, Xin Liu, Chaoqun Zhang, Jun Zhao, Heyang Wang
The SH steam out of the SSH is discharged to drive the HP turbine. The specific enthalpy of steam out of the HP turbine, , can be obtained according to where is the isentropic efficiency of the HP turbine and is the specific enthalpy out of the HP turbine for the isentropic process. The isentropic efficiency of the HP turbine, , can be determined based on the SH and RH steam parameters from the plant operating data as listed in Table 3. The specific enthalpy of steam out of the HP turbine, , is then used as the inlet enthalpy of the reheaters, Using the steam extraction rate estimated based on the SH and RH steam flow rates of the plant data, the reheat steam flow, , can be determined as The first stage of the reheaters is the wall reheater (WRH). Then the specific enthalpy of RH steam out of the WRH, , can be obtained according to where is the heat absorption of WRH. Then, following the same procedure as that for the superheaters, the specific enthalpies of the RH steam at the outlets of the CRH and the HRH can be solved sequentially.
Performance analysis of a membrane dehumidifier system subject to component characteristics – a numerical model
Published in Science and Technology for the Built Environment, 2020
Shao-Ming Li, Yu-Lun Lai, Shaw-Yi Yan, Chi-Chuan Wang
The heat transfer (Qsys) of this system includes latent heat and sensible heat based on enthalpy change in the condenser. is the amount of water vapor being removed by the condenser. The power consumption (W) of this system is the combination of power consumption of the vacuum pump and water pump responsible for transporting coolant. The work of vacuum pump (Wvac) is estimated by the isentropic process and corrected by a mechanical efficiency η. Besides, the work of water pump (Wcool) can be evaluated by Equation 23. where η is mechanical efficiency which is 0.65 (Xing et al. 2013) and ηcool is also mechanical efficiency which is 0.85 (Majoumerd et al. 2012). Besides, the criterion of membrane performance is presented by the separation factor (S.F.) as shown below (Bynum 2012): where y represents mole fraction at the permeate side, z presents mole fraction in the feed side, and the subscripts in this equation denote the species (w is water vapor, and a is air). Normally the higher the S.F. is, the greater separation the membrane can perform.