How the DUOHEAT heat pump works
From an oil-free centrifugal compressor to a life-cycle assessment of the finished system — the engineering behind a heat pump built for industrial temperatures.
Matching exchangers to a demanding cycle
Heat exchangers are essential to the DUOHEAT system because they transfer thermal energy between the waste-heat source, the working fluid and the final industrial heat user. Their design must remain efficient under demanding conditions, including elevated pressure, phase change and temperatures approaching 200 °C.
Designing for non-standard operating conditions
The first stage of the work focuses on mathematical modelling of the heat exchangers required by the two-stage heat-pump cycle. One-dimensional models developed in MATLAB will be used to estimate the most important design parameters, including heat-transfer area, pressure losses and expected thermal effectiveness.
These calculations will support the selection of commercially available exchangers wherever suitable products exist. However, one of the main system components will operate under particularly challenging conditions close to the critical temperature of the working fluid and at condensation temperatures of approximately 200 °C.
Because standard market solutions are not optimised for such operating conditions, a dedicated prototype high-temperature heat exchanger will be developed.
From CFD model to laboratory prototype
The new exchanger geometry will be analysed using three-dimensional numerical models. ANSYS SpaceClaim will be used to create the geometry, Fluent Meshing to generate the computational grid and ANSYS Fluent to simulate heat transfer and fluid flow.
The CFD analysis will make it possible to investigate:
- temperature and velocity distributions,
- local heat-transfer coefficients,
- pressure losses,
- flow maldistribution,
- thermal stresses,
- and the influence of geometric modifications on overall performance.
At the same time, a dedicated laboratory test rig will be constructed. The measured data will be used to validate the numerical model and verify that the predicted heat-transfer and pressure-loss characteristics are representative of real operation.
Optimisation and prototype development
After validation, the numerical model will be used in a broad design and optimisation study. The optiSLang environment will support the search for geometries that maximise thermal performance while respecting constraints related to pressure drop, manufacturability, strength and nominal operating conditions.
The selected design will be used to manufacture a prototype exchanger capable of operating at condensation temperatures close to 200 °C. The development process will include material selection, mechanical design, component integration and preparation for testing within the complete DUOHEAT demonstrator.
The prototype will then be delivered for system-level testing, where its effectiveness and operational stability will be assessed under realistic heat-pump conditions.
A family of exchangers for future applications
The final stage of the project will extend the work from a single prototype to a family of heat exchangers with different nominal capacities. This will make the technology more adaptable to a broader range of industrial applications.
Because testing every geometric variant using full CFD would require substantial computational effort, reduced-order surrogate models will be developed. These metamodelling tools will be based on CFD data and may include artificial-intelligence methods such as radial basis function networks.
The surrogate models will predict exchanger performance for many combinations of geometry and operating conditions without requiring a new high-fidelity simulation each time. They will then be coupled with optimisation algorithms, including genetic algorithms, to identify efficient exchanger designs for different power levels.
This approach will significantly shorten the design process and support the development of scalable, high-performance heat exchangers tailored to future high-temperature heat-pump systems.