Chapter 8

[Pages:41]5/7/2012 8:47 AM

Chapter 8

Vapor Power

Systems

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Dr. Mohammad Abuhaiba, PE

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chapter objective

Study vapor power plants in which the working fluid is alternately vaporized and condensed.

Dr. Mohammad Abuhaiba, PE

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Modeling Vapor Power Systems

To facilitate thermodynamic analysis, overall plant can be broken down into four major subsystems identified by letters A through D on the diagram.

The focus in this chapter is subsystem A, where important energy conversion from heat to work occurs.

Dr. Mohammad Abuhaiba, PE

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Modeling Vapor Power Systems

Dr. Mohammad Abuhaiba, PE

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5/7/2012 8:47 AM

Modeling Vapor Power Systems

Subsystem B supplies energy required to vaporize water passing through boiler. In fossil-fuel plants, this is accomplished by heat transfer to working fluid passing through tubes and drums in boiler from hot gases produced by combustion of a fossil fuel.

Regardless of energy source, vapor produced in boiler passes through a turbine, where it expands to a lower pressure.

The shaft of turbine is connected to an electric generator (subsystem D).

Vapor leaving turbine passes through condenser, where it condenses on outside of tubes carrying cooling water.

Cooling water circuit comprises subsystem C. Cooling water is sent to a cooling tower, where energy taken up in condenser is rejected to atmosphere. Cooling water is then recirculated through the condenser.

Dr. Mohammad Abuhaiba, PE

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Analyzing Vapor Power

Systems - Rankine Cycle

Evaluating Principal Work and Heat Transfers

Rankine cycle is a thermodynamic cycle that models subsystem A on Fig. 8.1

Dr. Mohammad Abuhaiba, PE

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Analyzing Vapor Power

Systems - Rankine Cycle

Evaluating Principal Work and Heat Transfers

TURBINE

CONDENSER

Dr. Mohammad Abuhaiba, PE

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Analyzing Vapor Power

Systems - Rankine Cycle

Evaluating Principal Work and Heat Transfers

Pump

Boiler Thermal Efficiency

Dr. Mohammad Abuhaiba, PE

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