Designed Experiments: Statistical Approach to Energy- and Exergy-Based Optimization

We extend the energy and exergy-based methodology presented in previous work 1,2 from analysis to preliminary design. Therein, a three-component system was modeled in which heat transfer from the energy source was allowed, while the other devices were considered to be reversible. Those single-parameter studies yielded many results which were physically impossible, clearly suggesting that the analysis/design paradigm be changed from energybased to exergy-based. Here, we extend the analysis to preliminary design applications. A steam turbine with fixed inlet conditions was modeled thermodynamically and simulated in MATLAB using three design variables: turbine exit quality, turbine exit pressure, and turbine heat transfer. A statistically generated test matrix was developed using Design of Experiments (DOE) for three test cases. For the first test case, only the quality was varied while exit pressure and heat transfer remained constant. For the second test case, both quality and exit pressure were varied while heat transfer remained constant. The last case allowed all three design variables to vary simultaneously. The test matrix was analyzed using a 1 st Law as well as combined 1 st and 2 nd Law methodology to determine turbine specific work and exergy destruction for the system. Results from the test cases were analyzed to generate surrogate models used for turbine optimization.