The project is structured in eight work packages, and it runs for 3 years from 2025 to 2028.
WP 0 Project Management
This work package comprises the entire project management and administration.
WP 1 Conceptualization
Establishes the foundation for designing and developing the project’s prototype and pilot demonstration unit. This involves defining specific applications for three use cases, cycle design, and the selection of the appropriate zeotropic refrigerant mixtures, using numerical modelling to assess their theoretical potential in heat pump applications.
The work package includes the following:
- Literature review:
Analyze current knowledge on heat pumps with zeotropic mixtures, compressors for hydrocarbon refrigerants, heat exchange phenomena for boiling and condensing mixtures, measurement methods for concentration measurements of mixtures, and refrigerant charge minimization. - Use case definition:
Identify three promising use cases for zeotropic mixtures, selected through literature review and a screening based on numerical modelling. - Model development:
Develop and adapt steady-state numerical models to assess system performance and refrigerant charge distribution in heat pumps under varying conditions. Special focus is placed on selecting void fraction models for zeotropic mixtures in plate heat exchangers and on modelling the refrigerant charge contents dissolved in the oil lubricating the compressor. - Performance Analysis:
Assess theoretical COP improvements for both design and off-design (year-round) operation. - Charge Reduction Analysis:
Quantify the potential for refrigerant charge reduction in heat pumps using flammable zeotropic mixtures. - In-situ Composition Measurement:
Investigate methods for measuring the circulating composition of zeotropic mixtures, including the effect of oil, and design an experimental setup at DTU based on established infrared spectroscopy techniques.
WP 2 Technology Validation and Prototyping
Aims to validate the conceptual designs from WP1 by developing and evaluating a small-scale prototype heat pump.
The work package includes the following:
- Cycle Design and Development of PI-Diagram:
A prototype will be designed based on screw compressor technology and hydrocarbon refrigerant mixtures, using commercially available components. The aim is the simplest possible cycle design, most likely a simple one stage cycle with an internal heat exchanger, allowing efficient use of mixture refrigerants. The prototype will be suitable for compressor, heat exchanger, and control strategy testing. ATEX safety standards will be observed. - Dimensioning of Main Components, i.e. compressor, heat exchangers, and valves:
The prototype will have a heating capacity of 10-20 kW, with a suitable screw compressor and brazed plate heat exchangers. Control valves will be selected to enable “no superheat” operation at the evaporator outlet. Sight glasses will be installed throughout the system. - Measurement and Data Acquisition:
Comprehensive instrumentation will be integrated for detailed monitoring of refrigerant states and energy consumption. The system will include in-situ measurement of circulating refrigerant composition. Data acquisition will be designed to ensure accessibility for all relevant project partners. - Prototype Construction:
The prototype will be constructed at DTI and integrated with the existing water loop infrastructure in the laboratory. - Performance Evaluation Program:
The prototype heat pump will be evaluated under boundary conditions representing the three use cases identified in WP1. Performance maps will be created for relevant design and off-design conditions for each of the use cases for different compositions of the mixture refrigerants. - Analysis and Improvement Identification:
Experimental results will be compared with theoretical targets. Improvement opportunities will be identified and related to specific heat pump components.
WP 3 Technology Development – Compressors
Aims to assess how compressors designed for pure refrigerants perform when used with hydrocarbon-based zeotropic mixtures.
The work package includes the following:
- Review of Compressor Technologies:
Examine existing compressor solutions for heat pumps using hydrocarbons. Analyze performance maps and efficiencies for relevant compressors operating with pure refrigerants. - Numerical Model Development:
Develop a generic screw compressor model for zeotropic mixtures, capturing main gas compression phenomena, oil/gas phases, and refrigerant/oil solubility. - Theoretical Performance Evaluation:
Use the model to analyze isentropic and volumetric efficiencies, as well as refrigerant charge, for compressors operating with zeotropic mixtures under various conditions. - Experimental Performance Analysis:
Test the prototype heat pump’s compressor with different mixtures to map performance, validate the model, and identify improvement opportunities for compressors used with zeotropic blends.
WP 4 Technology Development – Heat Exchangers
Aims to develop and optimize plate heat exchangers that maximize the benefits of zeotropic temperature glide while minimizing refrigerant charge and material use.
The work package includes the following:
- Test Setup Design:
Develop and integrate a test setup for plate heat exchangers using zeotropic refrigerants within the prototype heat pump. The setup will allow refrigerant charge measurement and enable flow and temperature analysis using transparent end plates and infrared thermography. - Heat Transfer Analysis:
Experimentally evaluate heat transfer coefficients and capacities for zeotropic mixtures compared to pure fluids. Analyze flow patterns to identify design improvement opportunities and use results to validate numerical models. - Refrigerant Charge Analysis:
Assess refrigerant charge in both evaporator and condenser under various conditions and mixtures. Use findings to identify charge minimization parameters and validate existing charge prediction models, with focus on void fraction methods. - New Heat Exchanger Design:
Develop and validate a new plate heat exchanger optimized for zeotropic mixtures. Evaluate its performance using the prototype heat pump.
WP 5 Technology Development – Controls
Aims to develop and validate a control algorithm that enables a zero-superheat condition at the evaporator outlet for optimal glide matching and an efficient and safe compressor operation. Additionally, WP5 aims to create a simple in-situ method for monitoring circulating concentration.
The work package includes the following:
- Dynamic Heat Pump Model:
A dynamic heat pump model will be created in Dymola by upgrading existing steady-state models. The new model will include energy balances, thermal masses, and control algorithms. The model will be applied to investigate the possibility for controlling the evaporator outlet condition based on temperature and pressure measurements together with knowledge on the relation between pressure and temperature in the two-phase area of the relevant zeotropic mixture. - Evaluation of Superheat Control Methods:
Performance characterization of different superheat-control methods. The prototype heat pump will be fitted with different solutions for controlling the evaporator outlet, including an electronic expansion valve, a vapor quality sensor, and a heated sensor. We will compare how well each method controls the system, focusing on stability and overall performance. - Control Algorithm Development and Testing:
A new control algorithm for zero-superheat as well as a prototype controller will be developed. The developed control algorithm will be implemented in the prototype controller, which will be evaluated using the prototype heat pump setup. The performance evaluation will include visualization of the evaporator outlet flow conditions for qualitative assessment of non-equilibrium effects.
WP 6 Pilot Demonstration
Aims to build, test, and demonstrate a 500 kW heat pump system. The system will be designed, constructed, tested in real-world conditions, and its improved performance will be showcased to stakeholders and end-users.
The work package includes the following:
- System Design and Construction:
Design, dimensioning, and construction of a 500 kW system. The system design will incorporate all necessary improvements and innovations identified during the project and will be designed such that it is optimized for one of the use-cases, but may also be operated at the conditions representing the two other use cases - Performance Testing for Different Use Cases:
The full-scale demonstration system will be evaluated under boundary conditions simulating the three use cases defined in WP1 to investigate its performance across different real-world scenarios. Refrigerant mixtures will be adjusted for each case, while system components will stay unchanged while examining the performance for different use scenarios. A comprehensive performance assessment will be performed to verify that the system meets or exceeds the expected benchmarks both at design and off-design conditions. - Testing with Different Mixture Compositions:
Performance evaluation of the pilot demonstration at varying mixture compositions. This investigation will reveal the sensitivity of the heat pump performance to changes in mixture compositions, that may occur over the lifetime of the system. - End-User Demonstration:
Demonstration of the heat pump at Innargy’s facilities, where the heat pump will be integrated to supplement their existing installations producing district heating using geothermal heat as heat source.
WP 7 Dissemination, Exploitation, and Communication
Aims to share project results with relevant stakeholders.
- Dissemination: A comprehensive dissemination plan will ensure that project results are shared with the scientific community, industry stakeholders, and the public. This includes publishing in scientific journals and presenting at key conferences and industry events.
- Exploitation: Identification and development of strategies for exploiting the project results, including commercialization of the final ‘high performance heat pump’. Focus will be on collaboration with end-users and stakeholders to translate the project’s innovations into a market-ready product.
- Communication: We will develop clear and engaging materials such as a website, LinkedIn updates, and workshops to inform a broad audience about the project. Students will also be involved through presentations and student projects.
- Networking: We will participate in professional networks and industry groups, both internationally and in Denmark, to foster collaboration and knowledge exchange.