Session: 30-07 Heat Pumps

Submission Number: 177385

Computational and Experimental Assessment of a Turbine in a Transcritical CO2 Heat Pump Operating in Liquid and Two-Phase Conditions 

Historically dependent on fossil fuel combustion, the district heating sector is undergoing a critical transformation toward cleaner, more sustainable technologies in response to global decarbonisation goals. Among the emerging solutions, large-scale transcritical carbon dioxide (CO₂) heat pumps powered by renewable energy sources stand out as a promising pathway for low-carbon thermal energy production.

A central factor in optimizing the cycle’s coefficient of performance (COP) is the integration of a turbine for work recovery during the expansion process. Ideally, this turbine should be capable of operating in the two-phase regime to maximize energy extraction.

This study presents a detailed evaluation of a radial turbine integrated into an industrial-scale transcritical CO₂ heat pump system. Using Computational Fluid Dynamics (CFD) simulations, the turbine’s performance is analyzed across a range of operating conditions, including the critical transition from liquid to two-phase flow. These simulations inform the development of a comprehensive turbine performance model.

To validate the model, experimental data from a full-scale demonstration heat pump system—capable of delivering up to 35 MW of thermal energy—are compared with the CFD results.

The findings confirm the radial turbine’s effectiveness in both liquid and two-phase conditions, highlighting its potential to enhance the overall efficiency and sustainability of industrial heat pump systems. This contributes to the advancement of energy-efficient and environmentally friendly heating and cooling technologies.

Presenting Author: Sebastiano Mauri Everllence Switzerland Ltd.

Presenting Author Biography: S.M. is a Senior R&D Engineer at Everllence, where he leads initiatives in the development of advanced compressor stages and turbines. His work also encompasses tool development and the integration of cutting-edge design technologies within the aerodynamics department.
Prior to joining Everllence. worked at the Swiss National Supercomputing Centre, where he was responsible for porting and optimizing scientific simulation software in meteorology and chemistry for vector supercomputers.
Earlier in his career, he contributed to the development of design tools for hydraulic turbines at Sulzer Hydro (now ANDRITZ Hydropower).
S.M. holds a Master’s degree in Mechanical Engineering from ETH Zurich and earned his PhD from EPFL, where he conducted research on fluid instabilities in hydraulic turbines.

Authors:

Sebastiano Mauri Everllence Switzerland Ltd.
George Kleynhans Everllence Switzerland Ltd.
Bob Mischo Everllence Switzerland Ltd.
Philipp Jenny Everllence Switzerland Ltd.