General Idea

The research project TRI-MAX has as main objective the development, construction and experimental assessment in real environment of a thermal engine based on Trilateral Flash Cycle (TFC), which recovers waste heat and converts it into power. The TFC is consisted by the same components with an Organic Rankine Cycle, with the only difference that the organic working fluid is heated up to the saturation temperature under high pressure rather than vaporized. As the organic fluid expands from the saturation, instantaneously changes phase (flashing process), resulting in a significant reduction of the irreversibilities generation through the avoided intermediate processes.

Figure 1. Biomass combustion system illustration with conventional ORC integration for the exploitation of exhaust gases

The cycle design will take place for low temperatures (up to 130oC), while the cycle power output is estimated around 10-15 kWe. The project goal is the efficiency increase of the thermal energy conversion to electricity, up to 20% in comparison with the traditional ORC technologies, which are mainly in use today and present low efficiency (5-6%) for waste heat recovery from low-temperature heat sources. This goal will be achieved taking advantage of two significant characteristics of the TFC, in order to maximize the cycle efficiency according to the 1st and 2nd Thermodynamic Laws. These two characteristics are:

  • Prevention of the isothermal vaporization.
  • Adjustment of the pinch-point during the fluid heating.

The specific objectives to be achieved for the project successful completion, are:

  • Study and analysis of the two-phase flow during expansion, in order to evaluate how it affects the whole cycle.
  • Analysis of the power cycle processes in order to optimize its efficiency.
  • Development of the simulation and optimization tool for the expansion process and the entire cycle.
  • Detailed design of the TFC for 10-15 kW and test runs.
  • Experimental tests for the cycle operation in laboratory.
  • TFC tests in real field.
  • Technoeconomical assessment of TFC and comparative analysis with competitive technologies.




The specific objectives expected to be achieved are:

  • The qualitative and quantitative evaluation of biomass and its supply chain organization
  • The simulation and optimization of the ORC system in combination with a biomass boiler and the design of the ORC
  • The construction of an ORC unit prototype and laboratory tests
  • The installation of the ORC prototype system in the greenhouse unit and tests in real circumstances
  • The economic and technical evaluation of the overall cogeneration system

Figure 3. Simple ORC layout thermodynamic cycle with isentropic expansion of isothermal and quasi-isothermal expansion (IE-E)

Organic fluid selection

An important research element has been the selection of the appropriate working fluid. According to the European Refrigerant Regulation, also known as the F-gas Regulation, the use of organic fluids with high Global Warming Potential (GWP) has begun to be limited in order to reinforce the use of environmentally friendly fluids. In addition, all fluids should have zero Ozone Depletion Potential (ODP). In this context, and in order to ensure the future use of the Greenco unit without any restriction, the R1224yd (Z) has been chosen, which is one of the most efficient for heat transfer in the range below 120 oC and also has a low GWP.


  • Part of the research on the heat exchangers’ design was presented on the 8th World Congress on Momentum, Heat and Mass Transfer (MHMT’23), which took place in Lisbon, March 26-28. You can read the study at the following link:
  • In the context of the research project, the TRIMAX unit was manufactured and transported from the Psyctotherm premises to the test facilities of the Agricultural University of Athens, in order to investigate experimentally its operation and study the engine’s performance under varying conditions.

  • On December 13th and 14th, another dissemination action of the developing technology based on the Trilateral Flash Cycle (TFC) took place by the scientific teams from the Center for Research and Technology Hellas(CERTH), the Agricultural University of Athens (AUA) and Psyctotherm: Cooling & Air Conditioning in the region of Boltonia (Italy). The scientific teams in collaboration with the University of Bologna (UNIBO) visited two existing livestock units in order to study and evaluate the possibility of installing a unit similar to that of TRI-MAX in the near future. In addition, the CERTH Scientific Team once again presented the initial results obtained during the TFC simulation process, as presented in the first two CERTH reports in Deliverables 1.1 and 1.2.

  • Here is the first brochure of our project TRI-MAX!
  • In the context of the disseminetion and promotion of the developing technology based on the Trilateral Flash Cycle (TFC), the scientific teams from the Center for Research and Technology Hellas(CERTH), the Agricultural University of Athens (AUA) and Psyctotherm: Cooling & Air Conditioning visited the University of Ghent in Belgium and the existing livestock building for the future installation of a similar unit on 21 & 22 October. In addition, an overall presentation and analysis was made by the CERTH scientific team on the results obtained during the initial simulations of the TFC, as presented in the first two CERTH / IDEP reports in Deliverables 1.1 and 1.2.
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