[home] [Personal Program] [Help]

---

Session: Parallel Session: Working fluids
Session starts: Friday 23 September, 14:00
Presentation starts: 14:40
Room: Senaatszaal

---

Andreas Grill (Orcan Energy GmbH)
Richard Aumann (Orcan Energy GmbH)
Andreas Schuster (Orcan Energy GmbH)
Jens-Patrick Springer (Orcan Energy GmbH)

Abstract:
ORC Application for CHP can be considered as state of the art for large biomass boilers. The organic Fluid is therefore evaporated by means of a heat carrier. In a heating condenser the remaining heat from the ORC-system is transferred to a heating system. In smaller block heat and power systems a use of an ORC is also possible. In this study different fluids are compared for different heat carrier and return flow temperatures of an ORC system. In order to evaluate the system in a practical way, a two-step approach for the benchmarking of the suitability of different fluids is done. In a first step, the thermodynamic potential is compared. For each combination of temperatures, isentropic efficiencies for the expansion machine as well as the feed pump are set to a fixed value. Afterwards specific boundary conditions in terms of return flow temperature in the heating condenser and heat carrier temperature in the evaporator inlet are set and optimal operation pressures and temperatures are calculated for each fluid. As optimized parameter the net power output of the system is used. The result gives an overview over which fluid is thermodynamically best for selected applications. In a second step, constructive aspects coming along with different fluids are rated. For a fast assessment of the constructive effort and therefore the cost of the system, specific parameters as heat exchanger surface and volume flow rate are compared. A power-independent comparison is obtained by calculating relative deviations of the constructive parameters from the optimal system of the first step optimization. Furthermore the improvements of the systems by means of the use of a recuperator are investigated. Although theoretically improvements in efficiency and net power output can be achieved, real effects as pressure drop across the component needs to be considered in detailed planning as it decreases the technical power of the expansion machine. Moreover the cost of an extra component coming along with increasing efforts for piping and casing does not necessarily lead to cheaper power related specific costs. By means of this two-step approach a fast evaluation of an ORC system is possible. Not only thermodynamic aspects, but also cost-related aspects can be rated and taken into account for next steps towards the realization of such a system. The same approach for the rating of an ORC system is done in another investigation presented at the conference [1]. REFERENCES [1] D. Gewald, et al, Two Step Optimization approach for increase of engine-ORC efficiency, ORC 2011 TU Delft, NL