Details
- ERC sector
- PE8 - Products and Processes Engineering
- ERC subsector
- PE8_6 - Energy processes engineering
- Project start date
- CUP
- D53D23004040006
- Financial support received
- €55.386,00
Description and purpose
The present research project — which involves the University of Parma (UNIPR) as national coordinator, together with the University of Padova (UNIPD), Politecnico di Milano (POLIMI), and the University of Salento (UNISALENTO)— is focused on innovative solution for to be employed in heat exchanger manufacturing with optimized performances in terms of heat transfer capabilities and high-quality surface finishing to mitigate fouling phenomena, while minimizing pressure drop, volume, manufacturing and operating costs.
A strategy that has been successfully explored in the literature to achieve these objectives is the use of emerging manufacturing technologies, which enable the production of surfaces with optimized geometries.
This project aims to strengthen the national research network and to create the multidisciplinary connections required for further developments in this field of study. Based on the cooperation of highly qualified researchers with specialized expertise in various experimental and numerical techniques — also within a complementary and interdisciplinary approach — the project represents a significant opportunity for the entire national research community.
The four research units address different problems and applications, encompassing both single-phase and two-phase heat transfer. Various passive heat transfer enhancement techniques will be analyzed and optimized, e.g.
- Insert devices and ribs of innovative and optimized shape to be adopted in channels during single-phase convection (UNIPR and POLIMI).
- Innovative solutions and emerging technologies for two-phase convection (UNIPD), such as novel enhanced surfaces to trigger surface tension effects for filmwise condensation.
The design and manufacturing of these innovative surfaces have been developed with the key contribution of UNISALENTO, that can guarantee the necessary experience for the smart design and manufacturing of these highly innovative components/surfaces, accounting for the constraints of each specific application. This research has been developed under a strict coordination between the four research units, in particular with regard to:
- the optimization activity, that requires the identification/discussion of the key objective parameters and the sharing of experience on both data processing and simulation approaches;
- the experimental activity that will be implemented and tuned for assessing the overall and local thermal performances of the different techniques/devices investigated.
Website: https://www.mood4hex.unipr.it/
Purpose
The ultimate aim of the present research project — coordinated by the University of Parma, in collaboration with the University of Padova, Politecnico di Milano, and the University of Salento — is to stimulate technological progress and innovation in a sector of great relevance for the national industry, namely heat exchanger manufacturing.
The challenges that companies in this field must face to remain competitive in the global market are driven by the demand for devices that are thermally more efficient, while at the same time characterized by reduced pressure drop, volume, manufacturing and operating costs, and by high-quality surface finishing to mitigate fouling phenomena.
The main objective of the project is to establish a framework for designing the next generation of enhanced heat transfer devices, through scientifically validated procedures and with verified potential benefits.
In addition, the project aims to strengthen the national research network of heat transfer specialists and to foster the multidisciplinary collaborations required for further advancements in this field.
To this end, the consortium brings together three research units with consolidated expertise in heat transfer mechanisms, both theoretical and experimental, and one unit specialized in functional and topological optimization as well as advanced manufacturing techniques.
The project has focused on two potentially disruptive technologies that have emerged over the past decade. On the one hand, topology optimization has been increasingly applied to design components aimed at achieving optimal performance; on the other hand, additive manufacturing (AM) techniques have provided unprecedented geometrical freedom, enabling the realization of components with highly innovative shapes.
Those techniques can work synergically, and the field of enhanced heat transfer, which has reached an evolutionary plateau, has now the opportunity to evolve.
Expected results
To reach the main objective of the project, the following sub-goals were defined:
-The design of a set of at least three geometries with optimized morphology for heat transfer enhancement in pipes and three in narrow channels.
-The design of a set of at least two morphologically enhanced geometries for heat transfer enhancement during condensation
-The experimental test of such geometries, in particular in terms of overall heat transfer enhancement, pressure drop, and other local quantities (e.g. local heat transfer enhancement, liquid film thickness), that highlight the physical mechanisms of thermal performance enhancement.
-The dissemination activity, which includes scientific publications, social network activity, and symposia with companies with potential interest in the technology.
The main expected result of this project was the establishment of an experimentally validated framework for the design of the next generation of heat exchangers within the Italian scientific community, for integrating the recent advancements on shape optimization procedures, manufacturing techniques, materials and the deep heritage on traditional systems and measurement tools.
This goal was pursued through a series of intermediate steps:
-The application of TO and advanced morphological analyses on the following enhanced-heat transfer problems (single-phase convection enhancement in pipe flow with insert devices and in narrow ribbed channels and enhancement of filmwise condensation in pipe flow), which have been deeply studied by the Consortium members.
-The design and fabrication of optimized geometries by means of AM.
-The experimental tests on the new configurations and the assessment of the improvements and limitations given by new methodology.
Specifically, the project planned to test at least three innovative geometries for each single-phase application and at least two enhanced surfaces for condensation.
Such research will support the introduction of new solutions and innovative products to the market of heat exchangers. In fact, all the members of the Consortium have developed strong bonds with the industrial world, and in particular with companies where thermal management is a key factor.
Finally, one desired outcome of the project was the training of young scientists on high and innovative technologies. With this aim, 3 post-doc positions have been opened to insert early stage researchers in a scientific project characterized by a strong multidisciplinary approach, to hone their technical awareness and collaborative skills.
Achieved results
Single-phase heat transfer: Passive butterfly-shaped inserts have been designed and fabricated by additive manufacturing under the coordination of the UNISALENTO Unit, with material properties tailored to the experimental requirements. Different shapes have been considered and experimentally tested by UNIPR Unit by monitoring both the fluid/wall temperatures and the pressure losses in steady-state conditions. Such novel inserts have been characterized in terms of thermofluidic characteristics, such as local pressure loss coefficient and local/average Nusselt number. The best geometrical configuration, i.e., the one providing highest Nusselt number in relation to the resulting pressure drops, has been identified. Additional core outcomes have been reached during the study of interrupted helical fins for triple-tube heat exchangers treating non-Newtonian, highly viscous fluids. The novel geometry has been numerically studied and experimentally tested in an industrial plant to understand its beneficial effects in terms of fluid thermalization. The optimal displacement of finned sections has been identified for different fluids and working conditions.
Innovative turbulator geometries were developed by POLIMI Unit using the ToffeeX software, which can design complex organic surfaces using an "additive" procedure and targeting the maximization or minimization of a thermal and/or fluid dynamics objective function. It was firstly used constraining the channel fraction to be occupied by the optimized structures, and the optimum filling ratio and morphology in this case was selected, returning a first optimized configuration for the turbulators’ distribution in the channel. Then, the volume constraint was removed, and a second configuration was obtained. Finally, the aim of reaching a patterned geometry was considered, identifying the most promising obstacles generated by ToffeeX in the unconstrained optimization and creating a periodical series of turbulators from each of them.
All the geometries were analysed by RANS CFD simulations with OpenFOAM, to evaluate the thermal-fluid dynamics fields and the thermal performance. The most promising patterned geometry was then 3D printed in resin and experimentally tested. The setup for the tests was improved with respect to the pre-project version and also used to test conventional ribs, among which the V-Down shape confirmed to be the most performant.
In-depth analysis of the experimental results and comparison with the numerical ones is currently ongoing.
Topology optimization was carried out by the UniSalento using OptiStruct and the Darcy flow method, in order to improve fluid distribution within the channel. The procedure led to the identification of optimized topologies enhancing flow efficiency. These results represent a starting point for further comparisons with the geometries generated by other optimization approaches.
Two-phase heat transfer: An innovative test section with a 2.76 mm inner-diameter channel was fabricated by UNIPD Unit in AlSi10Mg using Laser Powder Bed Fusion (LPBF) to enable accurate local heat transfer measurements with refrigerants. Its geometry was optimized through detailed CFD simulations in ANSYS Fluent, designed to improve temperature measurement accuracy on both secondary fluid (water) and wall sides. Condensation experiments with R1234ze(E) and R1233zd(E) were performed to determine local heat transfer coefficients, visualize flow patterns under different operating conditions and validate the existing predicting models.
A second test section was developed to investigate condensation inside a wick heat pipe, with the aim of enabling non-invasive measurements of liquid film thickness on enhanced surfaces. The fin geometry was studied through Volume-of-Fluid (VOF) simulations in ANSYS Fluent with different refrigerants (R134a, R245fa, R290, R717). The test section, produced in AlSi10Mg by Additive Manufacturing, is now being instrumented and is being prepared for upcoming measurements of heat transfer coefficients and liquid film thickness through a chromatic confocal sensor.
UNISALENTO contributed to the preliminary study for the 3D printing of the test section.
A Special Session on “Morphology Optimized Design for Heat Exchangers” was organized to disseminate the project results within the framework of the International Conference EUROTHERM 2024 (10–13 June 2024, Bled, Slovenia).
Chair: Prof. Sara Rainieri, University of Parma, Italy
Co-chair: Prof. Marcelo Colaço, Universidade Federal do Rio de Janeiro, Brazil
https://www.eurotherm2024.si/.
The Special Session represented a valuable opportunity to share and discuss the main outcomes of the project with the international scientific community, to stimulate interdisciplinary debate, and to promote further collaborations. It also contributed to enhancing the dissemination and impact of the research, complementing the experimental and numerical activities carried out within the project.
Scientific director
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