The difference between turbine workout WT and pump work input W p is defined as net work done W net. The efficiency of the ideal Rankine cycle is defined as the ratio of net work done by the steam turbine power plant W netand heat supplied to the boiler Q s. The efficiency of the Ideal Rankine Cycle The h-s and T-s diagrams for the ideal Rankine cycle are shown in Fig. h-s and T-s Diagram for Ideal Rankine CycleĪs we discussed above, reversible isobaric heat addition (1-2) takes place in a boiler, reversible adiabatic expansion or isentropic expansion (2-3) in a turbine, reversible isobaric heat rejection (3-4) in the condenser and reversible isentropic pumping (4-1) in the heat pump. Reversible adiabatic pumping (4-1) takes place in the pump. Steam is converted into the water in a condenser, and water is pumped into the boiler using a hydraulic pump. Steam is allowed to pass into the condenser, and reversible isobaric heat rejection (3-4) occurs in the condenser. Reversible adiabatic or isentropic expansion (2-3) occurs in the turbine. Reversible isobaric heat addition (1-2) takes place in the boiler, then the steam passes through the nozzle, and high-velocity steam impinges the turbine blades. The thermal efficiency of the Rankine cycle is given by:Ī steam turbine power plant consists of a boiler, turbine, condenser and pump.Work delivered by turbine: W T= h 3 – h 4Įnergy rejected in the condenser, q 2 =h 4 – h 1 Work done on the pump per kg of water: W P= h 2 – h 1Įnergy added in steam generator: q 1= h 3 – h 2 However, because of the low volume of liquids, the pump work is relatively small and often neglected in thermodynamic calculations. The pressure of the condensate is raised in the feed pump. In well-designed and maintained condensers, the pressure of the vapour is well below atmospheric pressure, approaching the saturation pressure of the operating fluid at the cooling water temperature. The vapour-liquid mixture leaving the turbine (3-4) is condensed at low pressure, usually in a surface condenser using cooling water. Therefore, exit vapour qualities should be greater than 90% to avoid blade erosion. However, in practice, the expansion is limited by the cooling medium's temperature and by the turbine blades' erosion by liquid entrainment in the vapour stream as the process moves further into the two-phase region. The vapour is expanded in the turbine, thus producing work that may be converted to electricity. Further addition of energy causes evaporation of the liquid until it is fully converted to saturated steam (3). High-pressure liquid enters the boiler from the feed pump (1-2) and is heated to the saturation temperature (2). WP amount of work input is required to run the pump. Q s amount of heat is supplied to the boiler then water converted into steam, this high thermal energy steam passes through nozzle then this high-velocity stream impinging the turbine blade so that turbine produces WT amount of work then it passes through the condenser, QR amount of heat rejected from the steam so that steam is converted into water then this water pumped into the boiler by using a hydraulic pump. First, heat is supplied to the working substance so that it can produce some amount of work. The Rankine cycle analyses the changes in working substances in steam turbine power plants.
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