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A saturation dome uses the projection of a P–v–T diagram (pressure, specific volume, and temperature) onto the P–v plane. The points that create the left-hand side of the dome represent the saturated liquid states, while the points on the right-hand side represent the saturated vapor states (commonly referred to as the “dry” region).
A PV diagram plots the change in pressure P with respect to volume V for some process or processes. Typically in thermodynamics, the set of processes forms a cycle, so that upon completion of the cycle there has been no net change in state of the system; i.e. the device returns to the starting pressure and volume.
The pressure on a pressure-temperature diagram (such as the water phase diagram shown above) is the partial pressure of the substance in question. A phase diagram in physical chemistry , engineering , mineralogy , and materials science is a type of chart used to show conditions (pressure, temperature, etc.) at which thermodynamically distinct ...
This is the case, for example, for liquid water at atmospheric pressure and room temperature. In a plot that compares pressure and specific volume (commonly called a p-v diagram), compressed fluid is the state to the left of the saturation curve. Conditions that cause a fluid to be compressed include:
Thermodynamic diagrams are diagrams used to represent the thermodynamic states of a material (typically fluid) and the consequences of manipulating this material. For instance, a temperature– entropy diagram ( T–s diagram ) may be used to demonstrate the behavior of a fluid as it is changed by a compressor.
Because the net variation in state properties during a thermodynamic cycle is zero, it forms a closed loop on a P-V diagram. A P-V diagram's abscissa, Y axis, shows pressure (P) and ordinate, X axis, shows volume (V). The area enclosed by the loop is the net work done by the processes, i.e. the cycle:
The critical point of water occurs at 647.096 K (373.946 °C; 705.103 °F) and 22.064 megapascals (3,200.1 psi; 217.75 atm; 220.64 bar). [ 3 ] In the vicinity of the critical point, the physical properties of the liquid and the vapor change dramatically, with both phases becoming even more similar.
The PV diagram is a particularly useful visualization of a quasi-static process, because the area under the curve of a process is the amount of work done by the system during that process. Thus work is considered to be a process variable , as its exact value depends on the particular path taken between the start and end points of the process.