Power Plant Design

SHOW ALL YOUR WORK and VALUES!

USCS UNITS ONLY!

THIS ASSIGNMENT ASSUMES THAT YOU HAVE GOOD COMPRESSED LIQUID TABLES SUCH AS OUR TEXT BOOK HAS IN TABLE A-3 (EL Wakil).

The figure shows a regenerative reheat Rankine cycle power plant. The boiler feed pump is 80% efficient, the condensate pump is 60% efficient, and each of the three turbine sections is 85% efficient. The feedwater system consists of a condensate pump, a closed feedwater heater (No. 1), an open feedwater heater (No. 2), a boiler feed pump, & another closed feedwater heater (No. 3). The closed heaters are not ideal. The closed heaters are both desuperheating plus condensing type; they condense the extraction steam to be a saturated liquid. No. 3 heater has a TTD (Terminal Temperature Difference) of -5.4 degrees F, No. 1 heater has a TTD of +12.04 F.

The No. 1 heater drains cascade backward to the condenser. The No. 3 heater drains cascade backward to the open heater (No. 2). The drain flows are regulated by control valves (assume these valves throttle the flows so the valve exit enthalpy is the same as the inlet enthalpy – see Cengel & Boles, Ch. 5) and assume that the valve reduces the fluid pressure to the pressure of the next lower pressure component (open heater or condenser).

Assume that the pressure drop associated with each closed heater and the associated piping is negligible, except for the throttling action of the heater level control valves in the drain piping of the two closed heaters. There are no pressure drops through the boiler or reheater.

Determine the feedwater temperature and enthalpy at the exit of each heater and the extraction steam flow rate (8x, 10x, 11x) to each of the three feedwater heaters.

Find the steam flow rate through each turbine section (m’7, m’9, m’11y).

Also find the power developed by each of the three turbines in Btu/hr. Turbine work in Btu/lbm is not a suitable answer.

Find the cycle efficiency.

Determine the energy which the condenser must reject to the circulating water (Btu/hr.)