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However, the liquid–vapor boundary terminates in an endpoint at some critical temperature T c and critical pressure p c. This is the critical point. 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]
The water temperature drops below the critical point as it does work in a high pressure turbine and enters the generator's condenser, resulting in slightly less fuel use. The efficiency of power plants with supercritical steam generators is higher than with subcritical steam because thermodynamic efficiency is directly related to the magnitude ...
This pressure is given by the saturated vapour pressure, and can be looked up in steam tables, or calculated. [9] As a guide, the saturated vapour pressure at 121 °C is 200 kPa, 150 °C is 470 kPa, and 200 °C is 1550 kPa. The critical point is 21.7 MPa at a temperature of 374 °C, above which water is supercritical rather than superheated ...
As wet steam is heated further, the droplets evaporate, and at a high enough temperature (which depends on the pressure) all of the water evaporates and the system is in vapour–liquid equilibrium. [5] When steam has reached this equilibrium point, it is referred to as saturated steam.
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 ...
At the critical point, (304.1 K and 7.38 MPa (73.8 bar)), there is no difference in density, and the 2 phases become one fluid phase. Thus, above the critical temperature a gas cannot be liquefied by pressure. At slightly above the critical temperature (310 K), in the vicinity of the critical pressure, the line is almost vertical.
There is no generation of steam bubbles within the water, because the pressure is above the critical pressure at which steam bubbles can form. It passes below the critical point as it does work in a high-pressure turbine and enters the generator's condenser. This results in slightly less fuel use and therefore less greenhouse gas production ...
The SCWR operates at supercritical pressure. The reactor outlet coolant is supercritical water.Light water is used as a neutron moderator and coolant. Above the critical point, steam and liquid become the same density and are indistinguishable, eliminating the need for pressurizers and steam generators (), or jet/recirculation pumps, steam separators and dryers ().