Distributed electrical generation used in conjunction with energy recovery is a topic of great interest by the U. S. Department of Energy. One of the major manufacturers of large gas-turbine based generating systems is Solar Turbines, a subsidiary of Caterpillar Corporation. Solar offers a wide array of systems with electrical outputs ranging from 1 MWe to 15 MWe. The Mars 90 Solar turbine has a nominal output of 10 MWe. This project involves the preliminary design of a heat exchanger to use reject heat from a Mars 90 turbine exhaust to heat water for process energy use. Some idea of the size and operating conditions of the Mars 90 can be gained from the attached Solar Turbines advertisement in Figure 1.
At standard conditions and full load, the Mars 90 turbine exhaust has a flow rate of 318,760 lb/hr at a temperature of 8700F and 1.3 atmospheres pressure.
The requirement is to design a heat exchanger that will use the exhaust gas stream to heat process hot water from 700F to 2000F. The air-inlet free-flow area is to be such that the Reynolds number of the exhaust gas flow inside the core is to be near 2000. To prevent issues with condensation, the exit temperature of the gas from the heat exchanger can be no lower than 3000F. The tube-side flow will be manifolded to maintain at least a 2 ft/sec flow through the tubes.
(a) Specify the dimensions (L1, L2, and L3, Figure 2) of a heat exchanger that will meet the specification outlined in the previous paragraphs. The heat exchanger dimensions L1 and L3