Deliverables
D1.1 – Project handbook
This document is the exFan Project Handbook and contains all relevant information regarding management, administration, and coordination of the project. It provides a short and comprehensive description of the management procedures, administrative aspects of the project, quality assurance procedures, the risk management approach, the progress monitoring procedures and any issue concerning confidentiality. Additional advice and support can be sought from the coordinator.
D2.1 - Dissemination and Communication Plan and activities report
This deliverable outlines a strategic plan for Dissemination & Communication activities within the exFan project, emphasizing audience engagement and impact optimization. Through a structured five-step approach, target audiences are identified, and key messages aligned with project objectives. A series of activities are then proposed to effectively convey these messages, with ongoing monitoring and evaluation facilitated by digital analytics tools. Furthermore, the introduction of the "exFan e-Approval Tool" highlights the project's commitment to safeguarding intellectual property rights and ensuring publication integrity.
D2.2 – Update Dissemination and Communication Plan and activities report
This deliverable is an extension to D2.1 by providing a detailed update of all the Dissemination and Communication (D&C) activities conducted in the first eighteen months (M01-M18) of the project. These activities aim to promote the project in general and bring to the spotlight the most significant achievements reached so far. Finally, D2.2 provides an evaluation of the above-mentioned D&C activities through the website and social media analytics along with a summary of all the scientific and non-scientific endeavours of the consortium as they are reflected through the approval process.
D2.4 – Preliminary Exploitation Plan
This deliverable describes the strategies and methods that will be applied during the exFan project to facilitate identification, assessment, protection and exploitation of project results. It contains a managements strategy for knowledge & IPR, initial exploitable results, results of a barrier analysis regarding patents and standardization and describes in detail how the individual business models for key exploitable results need to be created. Finally, the method for an assessment of the economic impact of project KERs is shown and a timetable for upcoming exploitation activities is given. This deliverable defines all strategies and methods that will be applied to achieve the updated Exploitation Plan (D2.5/M36) and final Exploitation Plan (D2.6/M48).
D3.1 – Boundary Conditions Report
This work focuses on identifying aircraft integration options and operating conditions that are most advantageous for advanced thermal management, heat recuperation, and fuel cell–based electric propulsion systems. The objective is to understand how thesesubsystems can be combined in a synergistic way to improve overall efficiency, while remaining compatible with conventional aircraft configurations.
A holistic investigation was carried out to determine the boundary conditions under which thermal management and heat recuperation perform most effectively when coupled with a fuel cell geared electric propulsion system.
In parallel, concepts for optimal integrating of the heat propulsion system at different aircraft locations were assessed, including nacelle-mounted and rear-fuselage-mounted installations. Although the development of new aircraft configurations was not within the scope of this task, the study acknowledges that propulsion system location has a significant influence on system design and therefore must be considered early in the process.
The report describes the newly developed environment model and summarizes the outcomes of the conducted parameter studies. These investigations were conducted to explore how operating conditions affect system efficiency and component geometry. These studies help clarify the trade-offs between performance, thermal loads, and design constraints across different phases of a representative mission profile.
In addition, propulsion system requirements were evaluated with respect to the number of propulsion units and their operational roles over the mission. This analysis supports informed decision-making on system sizing and integration strategies. The report also introduces eight preliminary heat–propulsor integration concepts, selected for further investigation.
D3.2 – Propulsion System Layout and sizing tool
This deliverable addresses the definition, assessment, and system-level integration of fuel cell–based electric propulsion technologies for aviation applications. Its overall objective is to establish a consistent understanding of thermal, electrical, and architectural boundary conditions, and to translate these into validated system requirements and models that support subsequent aircraft and propulsion system design activities.
A first major focus is the investigation of aviation-relevant fuel cell and battery technologies. Different fuel cell types are reviewed and compared with respect to their suitability for the exFan project, including current maturity, expected performance, and future development perspectives. Special attention is given to the boundary conditions of heat generation and temperature levels, which are critical for thermal management and system integration. The trade-off between fuel cell power load and electrical efficiency is analysed, as this directly influences heat production, overall efficiency, and component sizing. In addition, requirements for auxiliary systems such as air compressors, humidification systems upstream of the fuel cell stack, as well as de-humidification and power recovery of unused air downstream of the stack, are assessed.
Building on these findings, a comprehensive calculation and modelling environment is developed to represent the aircraft, its operating environment, and the relevant propulsion system components. Inputs from the fuel cell studies and from previously defined operating conditions are used to evaluate key system interactions. The model enables estimation of the air mass flow required through heat exchangers to dissipate the heat generated by the propulsion system and supports the dimensioning of flow paths and propulsion components. Furthermore, the tool allows first estimations of additional thrust contributions from heat propulsor concepts under representative operating conditions.
Using sensitivity analyses, the modelling framework supports the definition of an overall system topology and the specification of interfaces for mass, energy, and signal flows between individual components. This interface definition represents a key foundation for future work packages and for the consistent development of subsystem models by the project partners. In addition, the outcomes of an initial propulsion system sizing study are presented, providing a first integrated view of system mass and performance. The work concludes with the definition of a baseline aircraft configuration, including key data on mass and power demand, which will serve as a reference point for the subsequent aircraft design activities in the next project phase.
D3.3 – exFan Requirements Report
A process for developing requirements specifications in exFan is demonstrated in this deliverable. The process applies Stakeholder Expectations as the input for the system requirements. In the case of the exFan project, these Stakeholder Expectations are based on the Grant Agreement Objectives & Ambitions, on the results of a requirements workshop with industry members of the Technical Advisory Board and results of WP3. The rationale of these expectations has been extracted, documented and summarized from the Grant Agreement, D3.1 and D3.2. Figures or merit and strategies/concepts of operations have been defined as a source for technical requirements. Based on the rationale, requirements were derived for the main system components of the system architecture down to the propulsion system and exFan components (D3.2). The technical requirements were validated through a requirements matrix in which the individual dependencies are visible. The technical requirements are summarized in this document build the baseline as of WP3 and will continue to be detailed during WP4 and the further course of the project.
D4.1 – exFan Concept
The deliverable 4.1 documents the methodology, process and results of the conceptual design of the exFan, with focus on the electric machine, inverter, gearbox, fan, energy system and thermal management system. In the first step, a general sensitivity analysis of key performance parameters of the components of the exFan is conducted. Based on the knowledge gained by this analysis, the conceptual design of individual components within a multidisciplinary approach is documented. Mass, build volume and efficiencies over a design mission as well as low-detail 3D-representations are given for all components. Finally, a 3D-exFan system concept is created to demonstrate component assembly and envisioned aircraft integration on a low level of detail. The designed exFan concept is capable for use in the Baseline Aircraft described in D3.2 and can overcome harsh environmental conditions like hot-day take-off through smart combination of TMS and energy system features.
D4.2 – Heat Propulsor Concept & requirements
The objective of the tasks in this deliverable is to define the system architecture and derive key design requirements that enable efficient integration with advanced electric and fuel cell–based propulsion systems.
The heat propulsor concept builds on the outcomes of earlier project activities, in particular the system analyses performed in Work Package 3. Based on these results, internal flow system data are provided for a wide range of representative operating conditions, including different flight altitudes, Mach numbers, and environmental conditions. These data describe the airflow behaviour through ducts and heat exchangers and form the basis for detailed investigations of the Heat Propulsor components.
The study examines the relevant heat transfer processes, geometries, and flow arrangements within the system. Key components include intake, diffuser, heat exchanger, and variable area nozzle. The intake and diffuser are analysed to ensure effective airflow deceleration and pressure recovery, which are essential for the efficient operation of downstream elements such as the fan and heat exchanger. The heat exchanger is investigated with respect to thermal transfer efficiency and pressure losses, as both strongly influence overall propulsion performance.
A particular focus is placed on geometric design aspects of the heat exchanger, considering both conventional manufacturing approaches and additively manufactured solutions. This allows the evaluation of innovative geometries that may enhance heat transfer while limiting weight and pressure losses. Furthermore, the implementation of a variable area nozzle is assessed to enable adaptive control of the exhaust flow across different flight regimes, supporting improved thrust generation and effective heat dissipation under varying operating conditions.
Parametric studies are performed to quantify the influence of geometric and thermodynamic parameters on the global performance of the Heat Propulsor system.
D5.1 – Heat Propulsor interfaces report
This deliverable presents the development and application of an analytical framework for the evaluation and comparison of compact heat exchanger geometries. An analytical tool was implemented using the ε-NTU approach to assess thermal effectiveness and pressure losses under different operating conditions.
The methodology enables a comparison of different heat exchanger configurations by combining dimensional performance indicators, such as heat transfer rate and pressure drop, with non-dimensional parameters including Reynolds number, Nusselt number, Colburn factor, and Fanning friction factor. Reference correlations and experimental data from the open literature are used to choose the compact heat exchanger geometries.
The tool supports both rating and sizing analyses. In the rating mode, the thermal and hydraulic behaviour of already sized heat exchangers is evaluated under varying inlet conditions. In the sizing mode, the required heat exchanger dimensions are determined to meet a specified heat transfer demand. The analysis finally shows how different heat exchanger geometries influence overall heat propulsor performance, in terms of both heat transfer capability and jet efficiency.
Overall, this deliverable provides a robust and transparent framework for the preliminary assessment and comparison of compact heat exchanger solutions based on literature configurations. The results establish a common baseline for future design activities and optimization studies.
D6.1 – Surface finishing method
This deliverable reports on the development and optimisation of surface treatments for Additive Manufacturing (AM)-produced Heat Exchangers (HX) within the exFan project. The AM process enables the creation of HXs with optimized geometries that enhance heat transfer efficiency and minimize pressure losses. However, the surface roughness and defects inherent to AM components require effective surface treatment interventions. This study focuses on the application of chemical polishing and electroless nickel-phosphorus (NiP) coatings to reduce surface roughness, mitigate fouling, and improve the performance of AM HXs. Additionally, an "out-of-bath" system was implemented to treat complex internal geometries, ensuring uniform coating distribution in challenging structures such as Triply Periodic Minimal Surfaces (TPMS).
The findings demonstrate that chemical polishing significantly enhances surface quality, while NiP coatings improve wear and corrosion resistance. Particular attention was given to optimising coating uniformity in complex geometries, where the "out-of-bath" system proved effective in achieving consistent coating distribution, even in internal channels. These results are essential for the upcoming phases of the project, providing key insights for the design and optimisation of HX geometries and surface treatments.
D6.2 – Heat exchanger design
This deliverable reports on the design and optimization of Heat Exchanger (HX) geometries for the exFan project, addressing both downscaled and full-scale configurations. The task encompasses two complementary approaches: the development of downscaled HX geometries for experimental surface finishing validation (T6.2a), and the simulation-based optimization of full-scale HX geometries for thermal-hydraulic performance enhancement (T6.2b).
For the downscaled approach, HX geometries were adapted to fit surface finishing test setups at CIDETEC while maintaining representative features. Various models were developed to distinguish between surface-related and geometry-related effects at smaller scales, ensuring all samples conform to standardized volume dimensions for testing. For the full-scale investigation, computational fluid dynamics (CFD) simulations were employed to evaluate different HX geometries under cruise boundary conditions, analyzing heat transfer efficiency and pressure loss characteristics. Shape optimization techniques were applied to the most promising geometries to further enhance performance.
The results provide a comprehensive comparison of HX geometry performance characteristics and establish the foundation for test article fabrication. The downscaled geometries enable meaningful experimental validation of surface treatments, while the optimized full-scale designs inform the specifications for the heat propulsor system and subsequent testing phases.
D6.3 – Heat exchanger test articles
This deliverable documents the fabrication and surface treatment of Heat Exchanger (HX) test articles for experimental validation within the exFan project. Building upon the optimized designs from Task 6.2, this task encompasses the additive manufacturing of test specimens (T6.3a), their subsequent surface treatment (T6.3b), and the development of an enhanced out-of-bath coating system (T6.3c).
A total of at least 17 HX test articles were fabricated using Additive Manufacturing techniques, incorporating both downscaled and optimized full-scale geometries. These specimens were then subjected to the surface treatments developed in Task 6.1, including chemical polishing and electroless nickel-phosphorus (NiP) coatings. To address the challenges of treating large-scale HXs with complex internal geometries, the out-of-bath device was significantly upgraded with enhanced peripheral and control systems, enabling uniform coating distribution across components of varying sizes and geometries.
The manufactured and surface-treated HX test articles provide the experimental foundation for comprehensive performance testing in Task 6.4. The upgraded out-of-bath system represents a scalable solution for surface treatment of complex AM HX structures, bridging the gap between laboratory-scale development and industrial application.
D6.4 – Experimental verification report
This deliverable presents the comprehensive experimental characterization of Heat Exchanger (HX) performance and fouling behavior, evaluating the effectiveness of surface treatments developed within the exFan project. The task encompasses the design and construction of specialized test rigs (T6.4a, T6.4c, T6.4d), experimental characterization of thermal-hydraulic and fouling properties (T6.4b, T6.4e), and comparative analysis of results (T6.4f).
Two dedicated test facilities were developed: a wind tunnel setup at TUW for characterizing pressure losses and heat transfer properties, and a fouling test stand designed to replicate representative environmental conditions using dust collected from Vienna International Airport. The thermal-hydraulic characterization assessed both untreated and surface-treated HX specimens under cruise, take-off, and landing boundary conditions, enabling direct comparison with CFD simulations. The fouling experiments evaluated particle accumulation rates and mechanisms under accelerated yet representative conditions, providing insights into the anti-fouling effectiveness of the developed surface treatments.
The findings demonstrate the combined effects of geometry optimization and surface finishing on HX performance, including quantifiable improvements in heat transfer efficiency, pressure loss reduction, and fouling resistance. These results validate the integrated design and surface treatment approach, providing critical data for scaling up to full-scale heat propulsor applications and informing future maintenance strategies for AM HX systems in aerospace environments.
