responsible for a thermal machine. The machine operates according to the cycle below, functioning as a Rankine cycle. Figure 1. T-S diagram of the Rankine cycle. As a good engineer, you already know that, in order to know how a machine works, it is necessary to know its operating conditions. The boiler operates at a
Imagine that today is your first day on the job, and that from now on you will be the engineer responsible for a thermal machine. The machine operates according to the cycle below, functioning as a Rankine cycle. Figure 1. T-S diagram of the Rankine cycle.
As a good engineer, you already know that, in order to know how a machine works, it is necessary to know its operating conditions. The boiler operates at a constant pressure equal to 8600 kPa and generates water vapor whose temperature is 400 °C. When passing through the turbine, the steam is expanded isetropically and enters the condenser as a two-phase mixture with a title equal to 0.80. The fluid is condensed at a constant pressure of 10 kPa, and then compressed isentropically, so that the fluid enters the boiler as a subcooled liquid. According to the information given above, determine:
a) The change in internal energy (ΔU) and the change in entropy (ΔS) of the cycle.
b) The net work recognized by the cycle (WNet).
c) The thermal efficiency of the Rankine cycle operating under normal conditions.
The potential and kinetic energy variations in the cycle are negligible. Enthalpy without superheated steam at 8600 kPa and 400 ºC = 3129.4 kJ / kg Enthalpy of saturated steam at 10 kPa = 2584.8 kJ / kg Enthalpy of saturated liquid at 10 kPa = 191.8 kJ / kg Liquid enthalpy at boiler inlet = 200.5 kJ / kg
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