China
Africa
Explore chapters and articles related to this topic
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.
Thermo-economic analysis and multi-objective optimization of a solar dish Stirling engine
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Mohsen Rostami, Ehsanolah Assareh, Rahim Moltames, Tohid Jafarinejad
Also, Figure 3 shows the Entropy-Temperature (T-S) diagram of the engine. The presented model is comprised of two isothermal and two isochoric processes. Through (1–2) process, the fluid is isothermally compressed and its temperature is decreased due to the convection heat transfer in the TC condenser heat exchanger. In the process, the temperature of the low-temperature source is increased from TL1 to TL2. Through the process (2–3), the operating fluid’s temperature is increased through an isochoric process during the passage within the regenerator. As for the isothermal process (3–4), the operating fluid is expanded by absorbing solar energy. During the process, the temperature of the high-temperature source is decreased from TH2 to TH1. Finally, as work is produced within the expansion chamber, the fluid’s high temperature is decreased (absorbed) by passing through the regenerator.
Quantitative and qualitative analysis for isochoric heating method during pressure development of phase change process
Published in International Journal of Ambient Energy, 2019
P. Sivamurugan, Irudayaraj Sebastin, N. Lenin
Increasing the fluid pressure is essential, particularly in phase change processes like evaporation and condensation. Two different methods are commonly adopted for increasing the vapour pressure. The first method is reducing the volume occupied by the substance, keeping the mass constant, in compressors working on the polytropic process using electrical or mechanical energy. The second method is increasing the temperature of the substance, keeping the volume constant. The former method is more reliable as it works with high-grade energy and can handle dry and superheated vapour. The latter approach uses low-grade energy; here addition of mass of the working medium ensures pressure increment through boosting of density. A domestic pressure vessel is a utensil working on the isochoric process to develop steam pressure and to ensure reduction of cooking time and energy. This concept of increasing pressure may establish new applications either to conserve energy or to harvest the potential of low-grade energy. The first law of thermodynamics provides a solution to the expected performance of a cycle and helps to assess the overall efficiency of the cycle in terms of energy. Exergy analysis aims to identify the magnitudes and the locations of exergy losses to establish improvements to an existing system, or to develop new processes or systems (Tekin and Bayramoglu 1998). Analysis of the second law offers a meaningful evaluation by indicating the association of irreversibility or exergy destruction with heat transfer processes (Aphornratana and Eames 1995; Khaliq and Kaushik 2004).
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.