Selection of Rankine Cycles for Various Resources

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# Selection of Rankine Cycles for Various Resources - PowerPoint PPT Presentation

Selection of Rankine Cycles for Various Resources. P M V Subbarao Professor Mechanical Engineering Department. Match the Cycle and Resource …. Improved thermal efficiency, feeding the turbine with ~340 °C (15 MPa) steam instead of ~285 °C   (7MPa) . Thermohydraulic considerations.

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### Selection of Rankine Cycles for Various Resources

P M V Subbarao

Professor

Mechanical Engineering Department

Match the Cycle and Resource …

Improved thermal efficiency, feeding the turbine with ~340 °C (15 MPa) steam instead of ~285 °C   (7MPa)

Thermohydraulic considerations
• A thermal design criterion for a PWR reactor core is the limit of the fuel temperature (melting point of UO2 about 2800 °C), being the design temperatures 2000 °C at rated power and 2350 °C at a maximum linear fuel rating of 54 kW/m.
• According to this criterion, recent PWR cores have an average linear fuel rating of 17.9 kW/m and maximum linear fuel rating of 44 kW/m. For a BWR, the maximum allowable temperature at the center of a fuel rod is 2500 °C in an emergency and 1850 °C during normal operation .
Thermohydraulic considerations
• Following this criterion, a HP-BWR with a thermal power of ~2700 MW, and an electrical power output of ~1000 MW, may have a core with an average linear fuel rating of 13.6 kW/m and a maximum linear fuel rating of 44 kW/m.
• Without any fuel modifications, the temperature at the center of a fuel rod during normal operation is slightly higher and has been estimated to be 1885 °C.
• The maximum temperature of the Zircaloy-2 fuel cladding is around 491 °C, which is lower than the allowed maximum temperature of 550 °C.

### Hardware Modifications for Creation of Better Cycle Conditions

Fossil Fuel Based Systems

Role of SG in Rankine Cycle

Using Natural resources of energy.

Hot Flue

Gas

Thermal Structure

SH

Steam

Rise in Enthalpy of

Steam

Convection HT

Drop in Enthalpy

of Flue Gas

Convection &

Mechanism of Heat Transfer

Thermal Structure

Sink /Demand

Source/Supply

Phenomenological Model

Thot gas,in

Thot gas,out

Tcold steam,out

Tcold steam,in

• Rate of heat transfer from hot gas to cold steam is proportional to:
• Surface area of heat transfer
• Mean Temperature difference between Hot Gas and Cold Steam.

Thot gas,in

Thot gas,out

Tcold steam,out

Tcold steam,in

Thot gas,in

Thot gas,out

Tcold steam,out

Tcold steam,in

Log Mean Temperature Difference
• Rate of Heat Transfer
• U Overall Heat Transfer Coefficient, kW/m2.K