What does the term temperature limits refer to? The maximum and minimum temperatures attained by the working fluid during the cycle. Hence, to determine the maximum efficiency of the power plant, you have to replace your entire Rankine cycle set-up with a Carnot cycle working between the same two temperature limits. Net work output, as stated already, is given by the gross turbine output minus the pump work.įinally, the Carnot's Theorem states that 'll heat engines between two heat reservoirs are less efficient than a Carnot heat engine operating between the same reservoirs.'. Hence, for the power-plant, this efficiency is given by the ratio of the net turbine work output to the heat added. Then, efficiency is defined as the ratio of the desired output to the given input. Hence, your change in enthalpy is taken care off in the heat additions as given. How is the enthalpy increased? It is done by adding heat to the system. Next, what is enthalpy? It is the heat content of the system. Multiplying this by the mass flow rate of steam gives us the power output in terms of kW. In fact, the units used by you are wrong.
Hence, you need not be bothered about the mass anywhere here. What you have calculated in the above equation is the turbine output per unit mass flow rate. Next, to calculate gross turbine power output, you have to use the principle of conservation of energy. Hence the net power generated by the turbine is equal to the gross power output ($W_$) minus the pump work input. Hence, the part of the power produced by the turbine is used to run the pump. Now it doesn't make sense to have a separate power source for the compressor when you have a power-producing turbine a few metres away from it. The pump consumes power while the turbine generates power. In a steam power plant, you have a pump, turbine, boiler and condenser. Let me answer your second question first.
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