Steam Rankine cycle instead of organic Rankine cycle for distributed high temperature waste heat recovery – pros and cons

The Rankine Cycle for Waste Heat Recovery (WHR) can be operated with various working fluids, all of which have different advantages and disadvantages. This paper compares the pros and cons of a Steam Rankine Cycle (SRC) using water as working fluid to an Organic Rankine Cycle (ORC) using an organic fluid as working fluid for distributed, high-temperature WHR of a stationary Internal Combustion Engine (ICE) in the lower power range. The comparison in this paper is made on the basis of thermodynamic, safety, plant engineering and operational aspects. While organic liquids have disadvantages in the areas of occupational safety, environmental protection and thermal stability, water in Rankine Cycle systems only reaches a comparable efficiency at higher heat source temperatures, and thus at higher live steam temperatures. Additionally, water poses apparatus-technical challenges in the steam generator and the turbine due to the comparatively high evaporation enthalpy and the volume change during phase transition. The thermodynamic parameters within the SRC, the internal consumption and the effects of the integration of an Internal Heat Exchanger (IHX) are compared with ORC plants, depending on the heat source temperature. Differences in the operation of these cycles as well as influences of the fluids on the plant design and costs are described. Finally, industrial applications are discussed in which the SRC could be preferred to the ORC taking into account all relevant aspects. To support these analyses, the thermodynamic design parameters, measurements, experience in apparatus design, as well as operating experience from the SRC pilot plant "MicroRankine" of the TH Nürnberg are applied     «

The Rankine Cycle for Waste Heat Recovery (WHR) can be operated with various working fluids, all of which have different advantages and disadvantages. This paper compares the pros and cons of a Steam Rankine Cycle (SRC) using water as working fluid to an Organic Rankine Cycle (ORC) using an organic fluid as working fluid for distributed, high-temperature WHR of a stationary Internal Combustion Engine (ICE) in the lower power range. The comparison in this paper is made on the basis of thermodynam...     »