Firstly thank you for this great site with infinite knowledge. I hope to learn and share more on this website.
I'm a ChemE student working on our design project. For the project, we are exploring a novel modification to
an existing Organic Rankine Cycle (ORC) technology. In short, this Rankine cycle uses a caisson (basically a well drilled a few meters deep) to generate head instead of a pump. I’ve included the draft PFD of our system.
PFD: PFD.pdf 10.52KB 28 downloads
As in our system, the heat source (geo-water) is coming into evaporator at 50000 m3/d (140ºC and 1400kPa). Heat transfers to and vaporizes our working fluid (Propane) which eventually rises and spins our gas expander to generate work. The expander outlet will then go through a condenser which cools working fluid to saturated liquid. Then it goes through a surge tank to the caisson again. This cycle repeats to generate work from low temperature heat source.
The objective of our project is to maximize the efficiency of the modified ORC system and compare it to a pump dependent system.
It was quite confusing where to start in this cycle as every point depends on the previous unit/state.Any suggestions on how/where to start our equipment sizing calculations will be appreciated.
Also how can we find optimal mass flow rate of the working fluid for our system? Do we assume some value for this? If yes, then what could be the appropriate value?
In this process, we introduced the surge tank mainly for maintenance (refill, flow control, etc.) and safety purpose. How can we determine the best type of tank for this purpose (eg. Floating roof tank, Fixed Roof Tanks,…). Also how can we determine the height to diameter ratio? (eg. Max for floating roof tank was given as 2:1 for height:dia)
Expander type: some ORC specific type expanders were looked at. For example scroll type and screw type etc. Our scope was not to focus on the mechanical detailing of these but solely the performance of these. Is there any specific advantages/disadvantages on these expander? And what should I be concentrating on when performing design calculations on gas expanders?
We value your advice and suggestions.
Thank you for guiding us.
Vig from (Team WORC)