Thermodynamics 2 - ME133-2

• M1: Identify properties of H2O as a working substance and calculate property change, the heat and work produced, when it undergoes thermodynamic processes or used in the Rankine Cycle.
• M2: Enumerate ways to increase the thermal efficiency of the Rankine cycle and calculate for incremental increase from being a simple to modified Rankine Cycle; modification that will make use of added equipment such as the superheaters, reheaters, regenerators and economizers.
• M3: Apply further methods of increasing the thermal efficiency though use of combined heat exchangers in the steam power plant and combining the basic Rankine cycle with industrial process heat requirements (Cogeneration), or with another thermodynamic cycle (Brayton cycle).
• Objectives

  • Analyze vapor power cycles in which the working fluid is alternately vaporized and condensed.
  • Analyze power generation coupled with process heating called cogeneration.
  • Investigate ways to modify the basic Rankine vapor power cycle to increase the cycle thermal efficiency.
  • Analyze the reheat and regenerative vapor power cycles.
  • Analyze power cycles that consist of two separate cycles known as combined cycles and binary cycles.
• Laws of Thermodynamics (Review)

  1st law - energy can be neither created nor destroyed during a process; it can only change forms.

  Closed System: ^E = Qin - Wout

  Open System: Qin = ^H + ^PE + ^KE + Wout
• 2nd Law of Thermodynamics:

  • Kelvin-Planck Statement: It is impossible for any device operating on a cycle to receive heat from a single reservoir and produce a net amount of work
  • Clausius Statement: It is impossible to construct a device that operates in a cycle and produces no effort other than the transfer of heat from a lower-temperature body to a higher-temperature body
• The equation Wnet = Qin - Qout represents the 2nd law of thermodynamics
• According to the Clausius statement, it is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow
• Heat can flow spontaneously from a hot object to a cold object, but it will not flow spontaneously from a cold object to a hot object
• Laws of Thermodynamics (Review)

  3rd law:

  This law of thermodynamics provides an absolute reference point for the determination of entropy. The law states that the entropy of a pure crystalline substance at absolute zero ( 0 deg K) temperature is zero since there is no uncertainty about the state of the molecules at that instant.
• Laws of Thermodynamics (Review)

  Zeroth law of thermodynamics states that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. By replacing the third body with a thermometer, the zeroth law can be restated as two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact.