Question

A fired boiler is used to produce thirty thousand lbm/hr of saturated (vapor) steam at 200 psia, from liquid water which enters at 70 degrees F. Natural gas (assume pure methane) is used for fuel with 10% excess air. Assuming complete combustion, with exhaust flue gas leaving at 500 degrees F, and constant Cp values (evaluated at room temperature), determine:

a) the new power that can be produced in a Rankine cycle given the following conditions:

* Turbine and pump efficiencies are 90% compared to isentropic

* Cooling water is available at 70 degrees F and limited to 20 degrees F temperature rise

* Minimum driving force for heat transfer is 10 degrees F

* Turbine outlet must have no more than 5% moisture (x>95%)

Answer 1

J