Design of Thermal Systems

Design Project Description

The Richard Gould Steam Electric Power Plant is under design to provide 700 MW net output additional generating capacity for the Duke Energy system. You are the design team responsible for the condenser in the turbine cycle and the components in the circulating water system that provides cold water to the condenser. The circulating water system components include three pumps in parallel to provide the design flow, and the associated piping and valves to supply the water to the condenser. The water is drawn from a captive lake and is returned to the lake.

The design point for the project is full load (735 MW generator output) when the lake temperature is 85°F. The team responsible for the turbine cycle has already established that the efficiency of the unit, described as turbine cycle gross heat rate and based on the generator output, is 9,000 Btu/kWh with 1 inch tubes & water side fouling at design point. The design circulating water system flow is 273,000 gpm. However, the three pumps have already been purchased and may or may not be able to meet the design flow rate.

(a) Condenser design: analysis of the design options and impact on condenser P.

I. Condenser Design

The "footprint" under the steam turbine requires that the condenser tubes be 50 feet long. The water goes through one tube pass, then makes a u-turn and returns through a second set of tubes. The active volume in the condenser for each set of tubes is 10 feet wide and 15 feet high. Assume the convective heat transfer coefficient, hD avg, for the condensing steam is 7,500 W/m2-K for 7/8- tubing and 7,250 W/m2-K for 1- tubing. Your suppliers can supply you with the following tube options:

Stainless Steel 304 1- OD or 7/8- OD: 22 BWG

(a) Using a rule of thumb that the ligament between tubes (minimum distance between holes in the tubesheet) is one-fourth of the tube outer diameter, find the maximum number of tubes that each tubing option can contain.

(b) Assume that the turbine inlet steam conditions are 1,000 psia and 1,000°F, the steam flow is constant from design conditions above, and that the turbine is isentropic. Lake water temperatures can vary between 50 and 90°F. Create tables (10°F increments) and plots of how the following change with lake temperature:

• the overall heat transfer coefficient, Uo

• the expected condenser pressure, psia

• the expected gross generator output power, MW