Question

Consider a steam power plant that operates on a reheat Rankine cycle and has a net power output of 80 MW. Steam enters the high pressure turbine at 10 MPa and 500oC and the low pressure turbine at 1 MPa and 500oC. Steam leaves the condenser as a saturated liquid at a pressure of 10 kPa. The isentropic efficiency of the turbine is 80% , and that of the pump is 95% .Show the cycle on a T-s diagram with respect to saturation lines, and determinea) Quality (or temperature, if superheated) of the steam at the turbine exit,b) The thermal efficiency of the cycle,c) The mass flow rate of the steam.

Answer 1

The reheat Rankine cycle is commonly used in steam power plants. By analyzing the given values, we can determine the quality of the steam at the turbine exit, the thermal efficiency of the cycle, and the mass flow rate of the steam.

Step-by-step explanation:

The reheat Rankine cycle is a thermodynamic cycle commonly used in steam power plants. In this cycle, steam enters the high-pressure turbine at a temperature of 500°C and a pressure of 10 MPa. The isentropic efficiency of the turbine is given as 80%. The steam then enters the low-pressure turbine at a pressure of 1 MPa and the same temperature of 500°C.

The cycle is completed by condensing the steam in the condenser, where it becomes a saturated liquid at a pressure of 10 kPa. Using these values, we can now determine the quality (or temperature if superheated) of the steam at the turbine exit, the thermal efficiency of the cycle, and the mass flow rate of the steam.

Answer 2

To show the cycle on a T-s diagram, we need to consider the different processes involved in the cycle, including the isentropic efficiency of the turbine. The quality or temperature of the steam at the turbine exit can be determined using the known values of the inlet state. The thermal efficiency of the cycle and the mass flow rate of the steam can also be calculated.

Step-by-step explanation:

To show the cycle on a T-s diagram, we need to consider the different processes involved in the cycle:

• Process 1-2: Steam enters the high-pressure turbine at 10 MPa and 500°C. The steam expands isentropically (with an isentropic efficiency of 80%) to a lower pressure and temperature.
• Process 2-3: The steam is reheated at constant pressure to 500°C.
• Process 3-4: The steam expands isentropically (with an isentropic efficiency of 80%) in the low-pressure turbine to a final pressure of 10 kPa. This process ends at the saturated liquid line.
• Process 4-1: The steam is condensed at constant pressure to a saturated liquid state.

To determine the quality (or temperature if superheated) of the steam at the turbine exit (point 4), we can use the isentropic efficiency of the turbine and the known values of the inlet state. Similarly, we can calculate the thermal efficiency of the cycle using the given net power output and the mass flow rate of the steam. Lastly, the mass flow rate of the steam can be determined by applying the mass and energy conservation principles in the cycle.