SIMPLE STEAM POWER CYCLE AND ITS PROCESS

 A power cycle continuously converts heat (energy released by burning of fuel) into work (shaft work), in   which a working fluid repeatedly performs a succession of  processes. The components of a simple   vapor plant. In the vapor power cycle the working fluid, which is the water, undergoes a change of phase. 

 In the vapor power cycle the working fluid , which is water, undergoes a change of phase. Heat is   transferred to water in the boiler from an external source ( furnace, where fuel is continuously burnt ) to   raise steam, the high pressure, high temperature steam leaving the boiler expands in the turbine to   produce shaft work, the steam leaving the turbine condenses into the water in the condenser , rejecting   heat, and then the water is pumped back into the boiler. Unit mass of the working fluid, sometimes in the liquid phase and sometimes in the vapor phase, undergoes various external heat and work interactions in executing a power cycle. Since the fluid is undergoing a cyclic process, there will be no net change in its internal energy over the cycle, and consequently the net energy transferred to unit mass of the fluid as heat during the cycle must equal the net energy transfer as the work from the fluid. The cyclic heat engine operating on a vapour power cycle, where the working substance water, follows along the B-T-C-P ( Boiler - Turbine - Condenser - Pump ) path, interacting externally and converting net heat input to net work output continuously. By the first law, 

Qnet = Wnet 

or 

Q1 - Q2 = Wt - Wp 

where Q1 = heat transferred to working fluid (kJ / kg) 

          Q2 = heat rejected form the working fluid (kJ / kg)

          Wt = work transferred from the working fluid (kJ / kg)

          Wp = work transferred into the working fluid (kJ / kg) 

The efficiency (N) of  the vapor power cycle would be given by 

N(cycle) = Wnet / Q1 = (Wt-Wp) / Q1 = ( Q1 - Q2 ) / Q1