790 = 2420 + 103 = 2523 kJ/kgĪ pressurizer is a key component of PWRs.Ī pressurizer is a component of a pressurized water reactor. The enthalpy for the state C can be picked directly from steam tables, whereas the enthalpy for the state D must be calculated using vapor quality: Calculate the enthalpy difference between these two states. Steam leaves this stage of turbine at a pressure of 1.15 MPa, 186☌ and x = 0.87 (point D). V l = specific volume of saturated liquid water (m 3 /kg)Ī high-pressure stage of steam turbine operates at steady state with inlet conditions of 6 MPa, t = 275.6☌, x = 1 (point C). V s = specific volume of “dry” steam (m 3 /kg) V wet = specific volume of wet steam (m 3 /kg) In case of wet steam, the actual specific volume can be calculated with the vapor quality, x, and the specific volumes of saturated liquid water and dry steam: Similarly, the specific volume of saturated liquid water (x=0) and dry steam (x=1) can be picked from steam tables. S l = entropy of saturated liquid water (J/kg K) Specific Volume of Wet Steam In case of wet steam, the actual entropy can be calculated with the vapor quality, x, and the specific entropies of saturated liquid water and dry steam: Similarly, the specific entropy of saturated liquid water (x=0) and dry steam (x=1) can be picked from steam tables. H l = enthalpy of saturated liquid water (J/kg)Īs can be seen, wet steam will always have lower enthalpy than dry steam. In case of wet steam, the actual enthalpy can be calculated with the vapor quality, x, and the specific enthalpies of saturated liquid water and dry steam: The specific enthalpy of saturated liquid water (x=0) and dry steam (x=1) can be picked from steam tables. The exhausted steam is at a pressure well below atmospheric, and is in a partially condensed state (point F), typically of a quality near 90%. The reheater heats the steam (point D) and then the steam is directed to the low-pressure stage of steam turbine, where expands (point E to F). The steam must be reheated in order to avoid damages that could be caused to blades of steam turbine by low quality steam. In these turbines the high-pressure stage receives steam (this steam is nearly saturated steam – x = 0.995 – point C at the figure) from a steam generator and exhaust it to moisture separator-reheater (point D). Typically most of nuclear power plants operates multi-stage condensing steam turbines. Rankine Cycle – Thermodynamics as Energy Conversion Science Saturated liquid water, which has no latent heat and therefore 0% quality, will therefore only contain sensible heat. In the case of dry steam (100% quality), it contains 100% of the latent heat available at that pressure. At constant pressure, an addition of energy does not changes the temperature of the mixture, but the vapor quality and specific volume changes. Between these two states, we talk about vapor-liquid mixture or wet steam (two-phase mixture). On the other hand, when the vapor quality is equal to 1, it is referred to as the saturated vapor state or dry steam (single-phase). When the vapor quality is equal to 0, it is referred to as the saturated liquid state (single-phase). Wet steam is characterized by the vapor quality, which ranges from zero to unity – open interval (0,1).
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