ORC Design – AxCYCLE™

Allied with the AxSTREAM® platform AxCYCLE™ allows designers to perform a very significant part of Organic Rankine Cycles (ORC) design, analysis and optimization.

AxCYCLE allows users to quickly and easily ORC design, analyze and optimize various thermodynamic cycles (thermodynamic simulation and heat balance calculations), including Waste Heat Recovery/Organic Rankine Cycles in a user-friendly and flexible environment, from a restricted amount of known data, all the way to techno-economic calculations and optimizations with the AxCYCLE Economics tool.

The tasks user can solve with AxCYCLE include:

  • Design new organic Rankine cycles from scratch
  • Analyze existing ORC and their performance at design and off-design conditions
  • Redesign, optimize, rerate and upgrade existing ORC systems/components
  • Troubleshoot and correct efficiency/reliability issues in existing hardware
  • Investigate upgrades/overhauls and deteriorations.

For reliable results fluid properties available from different sources including the NIST Refprop database (third-party application) and the CoolProp library (free). Examples of available fluids include R245fa, R245ca, R134a, R11, Ethanol, Isopentane, Ammonia, etc. and mixtures are also possible.


AxCYCLE can be used to design, analyze and optimize cycles for power generation, heat generation (including space heating) and – CHP - combined heat-power (cogeneration/tri-generation). The ORC system conditions of operation can be subcritical, transcritical or supercritical to calculate performance of any heat source, including in the context of waste heat recovery from solar, geothermal, steam cycle, gas turbine, ICE (internal combustion engines from the embedded library), biomass, etc.

Some of the different components of organic Rankine cycles that can be used in AxCYCLE include turbines, pumps, compressors, extractions/injections components, boilers and heat exchangers (including condensers, recuperators, reheats and coolers/chillers), liquid separators, seals, expansion valves, generators, bearings, gear boxes, and so on.

Cycle Creation Process

In AxCYCLE, thermodynamic systems are created by first selecting the desired components in corresponding libraries. Then these can be assembled (connected) in any desired way to create an infinite number of different cycles. Boundary conditions can then be selected among the available parameters to allow for enhanced flexibility of calculation task (compute vs input electrical power production, for example). Once these steps are performed computations can be run for any design or off-design condition as well as for optimization tasks.

Scope of Analysis

Throughout its multiple tools AxCYCLE allows running single operating point calculations as well as off-design computations and optimizations.

For parametric studies the MAP and QUEST tools can be used. The former allows users to study the influence of operational parameters on cycle performance and calculate cycle performance curves while accounting for off-design characteristics of the different cycle components. The latter uses a quasi-random sequence generator to pick a certain number of values within a given range for any number of parameters. Its results are presented on a design space.

For optimization tasks the PLAN tool is typically used. It uses a Design of Experiment (DoE) approach to reduce calculation times and reach better performance results compared to traditional optimization methods.

Finally, discrete cycle load points can be calculated with the CASE tool to determine, for example, what the net power production is based on the heat source fluctuating conditions or what happens when a valve is opened or closed.

AxSTREAM-AxCYCLE Interactions

The AxSTREAM® platform of multidisciplinary turbomachinery design, analysis and optimization software tools provides a fully integrated and streamlined solution for the complete flow path design, analysis and optimization process of turbomachines, including ORC turbines, ORC pumps and ORC compressors. Its scope ranges from preliminary design to meanline/streamline calculations, 3D blade design, 3D FEA, 3D CFD, secondary flows, rotor design, bearing analysis and rotor dynamics.

The boundary conditions of turbomachines within the thermodynamic cycle can be exported to the AxSTREAM® platform to perform their preliminary and detailed design.

Once a turbomachine has been calculated in AxSTREAM at the 1D, 2D or 3D level its characteristics at design and off-design conditions can be exported for use in AxCYCLE to study the full system’s behavior at different operating points.