fundamentals on engineering thermodynamics pdf

This low steam turbine entry temperature (compared to a gas turbine) is why the Rankine (steam) cycle is often used as a bottoming cycle to recover otherwise rejected heat in combined-cycle gas turbine power stations. This gives a theoretical maximum Carnot efficiency for the turbine alone of about 63.8% compared with an actual overall thermal efficiency of less than 50% for typical power stations.

Unless the pressure and temperature reach super critical levels in the boiler, the temperature range that the cycle can operate over is quite small: Steam turbine entry temperatures are typically around 565 ☌ and condenser temperatures are around 30 ☌. The efficiency of the Rankine cycle is limited by the high heat of vaporization of the working fluid. The greater the differential, the more mechanical power can be efficiently extracted out of heat energy, as per Carnot's theorem. The ability of a Rankine engine to harness energy depends on the relative temperature difference between the heat source and heat sink. Common heat sinks include ambient air above or around a facility and bodies of water such as rivers, ponds, and oceans. Possible heat sources include combustion of fossil fuels such as coal, natural gas, and oil, use of mined resources for nuclear fission, renewable fuels like biomass and ethanol, or energy capture of natural sources such as concentrated solar power and geothermal energy.

The Rankine cycle closely describes the process by which steam engines commonly found in thermal power generation plants harness the thermal energy of a fuel or other heat source to generate electricity.

6 Variations of the basic Rankine cycle.

2 The four processes in the Rankine cycle.

Fundamentals on engineering thermodynamics pdf