Modeling an Organic Rankine Cycle 1

[rewenila]

Hi! I am evaluating the energy efficiency of a combined gas-turbine cycle with a Rankine bottoming cycle. As for the Rankine cycle, I need to determine a range of values for the turbine inlet temperature and pressure, preferably relative to its critical values. I also need to determine a value for the turbine outlet pressure. I know that before entering the turbine the steam is in the state of overheated steam. I will need to vary this temperature and this pressure to find the configurations for the best cycle efficiency. The working fluids I'm using are propane, R134a and R22. Can someone help me?

 

[davefitz]

first of all, in your referenced figure, the symbols for turbines are reversed- the high pressure fluid enters the small end of the turbine. That shape is supposed to reflect the smaller dimensions of the hp turbine inlet blades compared to the large diameter LP exhaust blades.

secondly you need to reference the known temperatures. The heat sink is likely ambinet air at 20 C, and a 10C pinch is typical at a condenser , so the condenser operating fluid temp is 30 C. The condenser pressure ( organic turbine exhaust P ) is the saturation P at 30C temp.

commercial power gas turbines are roughly divided into 2 groups; aeroderivative ( small) with an exhaust temp of about 425C and large frame turbines with exhaust temp of about 635 C ( inlet T=TiT= 1425 C). The organic vapor entering the organic HP turbine will be about 50C cooler than the regenerators exhuast temp.



"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick