Thermodynamics: The Rankine Cycle

Sirindhorn International Institute of Technology
Thammasat University

CHS242 Thermodynamics I: The Rankine Cycle

Ratchawit Janewithayapun (5722800349)
Punyasiri Panprung (5722792751)

1. Introduction:
Presently, most of our power comes from the chemical energy of fuels and nuclear energy. To produce power from these sources, we rely on large facilities that convert heat energy released by these sources into work. However, because of the second law of Thermodynamics the efficiency of these conversions cannot reach 100%; in fact, the efficiency a majority of steam-power plants are lower than 35%. However, under certain conditions, efficiency higher than 50% can be achieved. A common method of converting heat to work is through

The heating process comprises three sections. First, the subcooled liquid is heated up to its saturation temperature. Second, the saturated liquid is vaporized at a constant temperature and pressure. Finally, the vapor is superheated to a temperature that is much higher than its saturation temperature. It is in this process that we have heat input from the combustion of fuels (or energy from a nuclear reactor). This acts as the high-temperature reservoir, an assumption similar to the low-temperature reservoir, but with the channel being able to provide a steady supply of heat instead. The rate of heat transfer in the boiler is Q ̇_H and is given by the

The Rankine Cycle does have limitation; for example, the Rankine Cycle assumes that the processes are reversible; which they are not. Despite these limitations, the Rankine Cycle is still applicable in real life situations. Some processes such as the transition from states 1 to 2 would not change much even if the process was not reversible. Also modifications to the Rankine Cycle allow the system to be more thermal efficient as well as cost efficient, and it’s these systems which produce much of the electricity we use