Periodic Reporting for period 2 - PANTTHER (exPerimental And Numerical mulTiscale mulTiphasic Heat ExchangeR) Reporting period: 2022-03-01 to 2023-08-31 Summary of the context and overall objectives of the project Heat exchangers have a fundamental role in aviation engineering. Continuous efforts are made to achieve even greater compactness, less weight, and higher performance. Heat exchanger's operation relies on the use of refrigerant fluids with high global warming potential. Although the F-gas II regulation does not yet apply to the aeronautical field, actions are being taken by the entire industry to reduce the environmental footprint of air traffic and investigate the use of low GWP refrigerants. Currently, multiphasic heat exchanger headers have mainly been designed and optimized with an empirical approach and an experimental validation. And the multiphasic heat exchanger core is up-to-now designed with experimental-based correlations, all obtained with the high GWP fluids.The EU-funded PANTTHER project aims to optimize the performance of multiphase heat exchangers with low GWP fluids using both experimental and numerical strategies. Experimentally, the objectives are to develop innovative diphasic measurement techniques as well as assess the effect of a large series of parameters on the flow maldistribution in the heat exchanger header, which is the cause of up to 30% loss of performances. Numerically, the objectives were to develop an innovative 3D CFD porous media model that takes phase change phenomena and fin structures into account, coupled with a two-phase flow model of the header, that allows to model the complete heat exchanger, but also to investigate how to optimize the performances, considering the flow is diphasic inside the heat exchanger.Experimentally, two experimental facilities were designed and built. An innovative inline measurement technique for diphasic mass flow rate was developed, as well as assess the effect of many parameters on the flow distribution through a Design of Experiment methodology. A vapor cycle system was designed and built, using R1234ze as fluid (GWP of 7), that allowed first to build and experimental database on heat transfer coefficient and pressure losses for R1234ze in a 10mm horizontal pipe, but also allowed to confirm the conclusions drawn from the adiabatic test setup on the flow distribution, but this time applied on an actual evaporator prototype. Numerically, the phase change in 3D CFD porous media model was developed, using as a database for the source term of phase change, VOF simulations on a simplified finned channel. In terms of optimization, two approaches were developed. First, a topological optimization framework was developed for 3D, thermal, hydraulic, and diphasic optimization, but only in laminar conditions. Second, the same Design of Experiment methodology was applied to numerical simulations, to identify the cases with the worst flow distribution, that would be then the starting point for an optimization based on the presence of a perforated plate. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far The key experimental results were:_ Innovative two-phase flow metering technique based on a venturi flowmeter solely_ Design of experiment based on a simplified evaporator header with air/water in flow similarity with refrigerant. The outcome of these tests showed that the main effect of the flow distribution in the channels is the header orientation, followed by the inlet pipe position, diameter, the presence of protrusions in the header, and finally the presence of the splashing grid _ experimental database for non-isobaric evaporation of R1234ze in 10mm horizontal channel_ Design of experiment based on an actual evaporator prototype, working with R123ze. The whole test matrix could not be finalized but the 10 tests performed showed that similarly to the simplified air/water header, the header orientation was the predominant parameter affecting the flow distribution (assessed in these experiments using IR images of the refrigerant channel wall)The key numerical results were:_ Innovative 3D porous model with phase change, developed both for R134a and R1234ze, and for horizontal and vertical channels_ CFD simulations of the complete evaporator prototype (header,core, and air side)_ Use of Design of Experiment to identify the starting point of an optimization_ Topological optimization framework for 3D, thermal, hydraulic and thermal problems, in laminar conditionsA total of 21 technical contributons,16 dissemination activities, and 24 communication activities were made in the framework of the PANTTHER project Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) Thermal management is one of the key challenges of turbofan engine fuel consumption efficiency. High temperatures can lead to a faster deterioration of electronic components, reduce the lubricating properties of oil and therefore result in more frequent maintenance operations. With the aim of studying the impact of the fluid flow distribution in multiphasic heat exchanger to design tailor-made but also lighter systems (-30%), the PANTTHER project will allow to limit aircraft fuel consumption and reduce maintenance operations thereby contributing to minimize the environmental impact of the aerospace industry.The combination of Computational Fluid Dynamics, enhance knowledge on the flow distribution in evaporator headers, and simple optimization equipment like perforated plate, will lead to reinforce the European industrial leadership in compact heat exchanger domain.The PANTTHER project will have an impact in the next 20 years considering that the worldwide civil fleet will double. The possibility to create and realize very complex optimized and customized design will improve the performances of all types of parts (exchangers, burners. . . ) until now inaccessible with traditional technologies. PANTTHER is expected to contribute to the emergence of new jobs in the field of manufacturing as well as engineering, with new profiles of engineers manufacturing and multiphysics simulation.In PANTTHER, the associated numerical and analytical studies will be furnished by PANTTHER partners with their related capabilities and capacities to conduct the simulation and heat exchanger optimizations work. Thanks to this approach, the inherent uncertainties and risks of new technologies will be most effectively and efficiently understood, technically managed and removed. The test facilities developed during the project would be used to open new perspectives to European industrials and academic institutions in order to transpose the developments to other multiphasic heat exchangers (heat pump, or Oil and Gas market). PANTTHER logo
