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The Laws of Thermodynamics
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
One final way to visualize the thermodynamic state of a system is a pressure–volume or P–V diagram. An example of such a diagram is presented in Figure 6.18. When we look at the physical state of a system in this way, we can gain an additional insight into how the volume and the pressure are related. On a high level, a P–V diagram looks very similar to a T–V diagram. The primary difference is that the vertical axis now contains the pressure rather than the temperature. A P–V diagram still possesses a vapor dome where the material to the left of the dome is a liquid and the material to the right of the dome is a vapor. However, instead of constant pressure lines, the lines across the dome are constant temperature lines or isotherms. A second difference is that the constant temperature lines start out much higher in the liquid region of the diagram, and end much lower in the vapor region of the diagram. In a T–V diagram, the lines run in the opposite way. The temperature still increases in the vertical direction—just as the pressure in a T–V diagram does. Otherwise, the diagrams are quite similar.
Development of a Novel Miniature Power Converter for Low-Power Radioisotope Heat Sources: Numerical and Experimental Results
Published in Nuclear Technology, 2021
Francisco I. Valentín, Gregory Daines
Figure 15a displays an example of piston position versus time data. This information was then combined with pressure versus time data (Fig. 15b) to obtain accurate pressure versus position data (Fig. 16). As is evident from Fig. 16, our breadboard assembly generated positive work because the PV diagram enclosed an area while moving clockwise in the PV diagram. This demonstrates that the converter is able to extract heat energy from the HX and transform it into pressure energy, which then produces positive work on the gas. As shown in Fig. 16, the data were consistent and highly repetitive throughout multiple tests.
Mathematical modeling of the Fontan blood circulation supported with pediatric ventricular assist device
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Ekaterina Rubtsova, Aleksandr Markov, Sergey Selishchev, Jamshid H. Karimov, Dmitry Telyshev
The single ventricular circulation interaction with the pediatric VAD Sputnik was simulated (Figure 3). The pressure distribution and the PV diagram of the ventricle are shown in Figure 4. Comparison of cases with and without VAD support reveals that the pump allows normalized circulation parameters; both vena cava pressure and systemic output increase to the normal value. Pump implantation leads to necessary pressure difference between the pulmonary artery and the systemic veins. In addition, the pump increases venous return, which, according to the Frank-Starling mechanism, entails an increase in stroke volume.
Thermodynamics from Lagrangian theory and its applications to nanosize particle systems
Published in Molecular Physics, 2021
Eduardo Hernández-Huerta, Ruben Santamaria, Tomás Rocha-Rinza
The following goal is to evaluate the changes of the internal energy U, enthalpy H, and entropy S in a cyclic thermodynamic process, which involves changes of P, and T. The thermodynamic cycle consists of four stages illustrated in the PV diagram of Figure 7. The isothermal curves are essentially straight lines and . The values of the independent variables and energy functions are given in Table 5.