The Rankine cycle is the basic cycle used in most coal-fired power stations, as well as in most concentrating solar thermal (CST) power plants. These cycles can currently be modelled in ASCEND through the use of the external-library freesteam routines (and, more recently, FPROPS) for steam property calculations.
A sequence of models of increasing order of complexity are given in the file models/johnpye/rankine.a4c. The models include test cases that reproduce values calculated in the textbook by Moran & Shapiro
You can load these models and solve them, and then play around with operating parameters and limits.
A sample plot generated using the Rankine cycle models as a base, plotted from within ASCEND (node labels added later), is shown at right.
The model file models/johnpye/rankine.a4c contains models of
- pump with isentropic efficiency
- turbine with isentropic efficiency
- condenser with outlet steam quality specified
- boiler with outlet temperature specified
- steam trap with inlet steam quality specified
- bleed point
- open feedwater heater
- closed feedwater heater (with temperatures on one side known; not LMTD etc calculation here)
We also have full-blown heat exchanger models that we are in the process of validating currently (by Jose Zapata)
Currently these models are all hard-wired to use steam as their working fluid; we'd like to change that.
The models in the models/johnpye/rankine.a4c file are
- rankine - the simplest possible Rankine cycle
- rankine_reheat - Rankine cycle with an additional boiler stage
- rankine_regen - regenerative Rankine cycle (one bleed, with open feedwater heater)
- rankine_reheat_regen reheat-regenerative Rankine cycle, with two turbines, two bleeds, one open feedwater heater and one closed feedwater heater.
Some of these models require certain solver parameters to be set before they are solved; check the instructions in the code file.
- ↑ Moran & Shapiro, Fundamentals of Engineering Thermodynamics, Wiley, 4th Ed.