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Thermodynamic Processes
Published in S. Bobby Rauf, Thermodynamics Made Simple for Energy Engineers, 2021
An isobaric process is a thermodynamic process in which the pressure remains constant. See Figure 8-4, where the curve represents an isobar. Even though the temperature varies as a function of the entropy in this graph, the pressure stays constant.
Fundamental concepts
Published in W. John Rankin, Chemical Thermodynamics, 2019
In thermodynamics, a process is said to occur when a system changes from one state of equilibrium to another, for example, an ice cube in a glass (state 1) melting to form water in the glass (state 2) or a piece of zinc reacting with sulfuric acid to form hydrogen and zinc sulfate. Processes are classified according to the conditions under which they occur as follows: An isothermal process is one that occurs at constant temperature.An adiabatic process is one that occurs with no heat exchange with the surroundings.An isobaric process is one that occurs at constant pressure.An isochoric process is one that occurs at constant volume.
Thermodynamics of Gases at Low Pressures
Published in Igor Bello, Vacuum and Ultravacuum, 2017
Heating or cooling a gas while gas pressure is maintained constant (p = constant) is called the isobaric process. In the isobaric process, the pressure change is zero (dp = 0). Thus, heating of ideal gas raises the temperature and internal energy of the gas, which consequently causes a volumetric expansion of the gas. Since a part of the supplied heat is used for the gas expansion, the gas also performs a work. Accordingly, the first law of thermodynamics applied to the isobaric process leads to the equation dQ=CpdT=dU+pdV where Cp is the molar heat capacity at constant pressure. The substitution of dU = CVdT and the ideal gas law applied to 1 kmol: pdV = R0dT into Equation 3.21 gives the well-known Mayer’s formula: Cp=CV+R0 named after German physician and physicist, Julius Robert von Mayer. The Mayer’s formula gives the relationship between the heat capacities at constant pressure and constant volume. Accordingly, the molar heat capacity at constant volume of an arbitrary gas is smaller than the molar heat capacity at constant pressure by the value of the universal gas constant.
A numerical study of supercritical carbon dioxide as a medium for thermal energy storage applications under natural convection
Published in Numerical Heat Transfer, Part A: Applications, 2022
T. D. Luz, F. G. Battisti, A. K. da Silva
Furthermore, the results of Figure 9 enable additional discussions. First, concerning constant-volume and constant-pressure operations, for an equal temperature variation, the energy density of the isochoric process is much lower. Nevertheless, the isobaric process results in an engineering challenge to maintain such a constant system’s pressure. Besides, an aspect that still requires further consideration for isochoric operation is the pressure increase within the storage tank, which requires thicker walls. Hence, it is advisable to evaluate if the gains enabled by such TES application justify its implementation regarding costs and energy density.