China
Africa
Explore chapters and articles related to this topic
Theoretical Foundations of Energy Conversions and Thermodynamics
Published in Alexander V. Dimitrov, Introduction to Energy Technologies for Efficient Power Generation, 2017
As proposed by Carnot, an isothermal process is the first step of an ideal efficient cycle, since the total external heat q1 (temperature T1) is consumed to expand the system and do mechanical work (see Section 1.3.3). At this stage (point 1–point A), the hot source (HS) supplies heat q1 to the TDS—Figure 1.23a. Keeping the energy balance of the isothermal process (Equation 1.52), the form of the mechanical work is lM1−A=RT1lnvAv1=RμT1∗lnp1pA, since T1 = const and du = 0. The necessary amount of heat supplied is q1 = T1 (sA − s1).
B
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[atomic, fluid dynamics, mechanics, nuclear] For an isothermal process, the pressure–volume relationship can be defined as PV = constant. During an adiabatic process (T ≠ constant), the pressure will drop faster with increasing volume than for an isothermal process and a correction is required, which has been established empirically as PVγ = constant, where the exponential factor γ depends on the process and the medium. For a monoatomic gas, γ = 1.67, while for a diatomic and polyatomic gas, the values are, respectively, γ ≅ 1.4 and γ ≅ 1.3. The “ideal gas law” still hold true. The correlation between volume and pressure at constant temperature was described earlier by Edme Mariotte (1620–1684) from France in 1650, hence also known as Mariotte’s law. Since it was introduced by Robert Boyle (1627–1691), it is also known as Boyle’s gas law (see Figure B.57).
The Ideal Gas
Published in Irving Granet, Jorge Luis Alvarado, Maurice Bluestein, Thermodynamics and Heat Power, 2020
Irving Granet, Jorge Luis Alvarado, Maurice Bluestein
and from the first law, it can be deduced that both the changes in enthalpy and internal energy for this process are zero (q−w=0) because the temperature is constant. Therefore, the work of the isothermal process must exactly equal the heat transferred. Thus, q=wJ
Treatment of solid objects in the Pencil Code using an immersed boundary method and overset grids
Published in Geophysical & Astrophysical Fluid Dynamics, 2020
Jørgen R. Aarnes, Tai Jin, Chaoli Mao, Nils E. L. Haugen, Kun Luo, Helge I. Andersson
The governing equations of the flow are the continuity equation and the momentum equation where and μ are the density, time, velocity vector, pressure and dynamic viscosity (, with kinematic viscosity ν), respectively, and is the material derivative operator. The compressible rate of strain tensor is given by where is the identity matrix. The pressure is computed by the isothermal ideal gas law, where is the speed of sound. With a constant speed of sound (for the isothermal case) and a constant kinematic viscosity, the momentum equation (2) can be rewritten as which is the form solved in the computations performed in this study.
Research on the mechanism of drag reduction and efficiency improvement of hydraulic retarders with bionic non-smooth surface spoilers
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Yuanyuan An, Wei Wei, Shuangshuang Li, Cheng Liu, Xianglu Meng, Qingdong Yan
ANSYS CFX software was used to conduct the steady-state simulation. The air ideal gas was used and the isothermal model was considered. The Reynolds number of the studied flow is in the order of 104–105, which means that it is a fully developed turbulent flow, so the SST turbulent model was selected, which takes into account the turbulent shear stress transfer with accurate prediction of boundary layer separation under a pressure gradient to capture tiny eddies. The boundary conditions were set according to the geometries and operating conditions of the impellers. The mixed plane theory was applied to exchange data between the rotor and the stator, and rotationally periodic boundaries were assumed on each side of the flow passage. Other surfaces were assumed to be no-slip rigid walls. Residuals of 1 × 10−6 for the flow-field parameters were used as the iteration convergence targets.
Backflow air and pressure analysis in emptying a pipeline containing an entrapped air pocket
Published in Urban Water Journal, 2018
Mohsen Besharat, Oscar E. Coronado-Hernández, Vicente S. Fuertes-Miquel, Maria Teresa Viseu, Helena M. Ramos
A polytropic expression is used to simulate the air pocket behaviour using the polytropic equation, i.e. , which relates the air pocket pressure with the air volume (). The polytropic exponent or polytropic index (n) can vary from 1 for the isothermal process to 1.4 for adiabatic process depending on temperature change and heat transfer (Besharat and Ramos 2015). An algebraic-differential system (ADS) describes the entire process, which is composed by the momentum equation, a moving interface air-water position, and the polytropic model. The resolution of the ADS gives the information of the hydraulic variables (air pocket pressure, water velocity and length of the water column). To solve the ADS a constant friction coefficient was considered (f= 0.018) with a non-variable polytropic coefficient of n = 1.1. The minor loss coefficients were calibrated based on the experiments. The Simulink tool in Matlab was used to solve the algebraic-differential equations system.