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ItemNumerical Computation of In-cell Parameters for Multiwire Formalism in FDTD(IEEE, 2024)The finite-difference time-domain method is a very suitable tool to analyse the propagation of, among others, lightning and arcing through new high voltage high power distribution networks in aircraft. This paper presents a numerical method for the computation of the in-cell inductance and in-cell capacitance matrices, required to accurately model wire bundles in a finite-difference time-domain grid. The method extends the multiwire formalism proposed by Bérenger, and enables the inclusion of inhomogeneous media, as well as non-cylindrical conductors. Moreover, the method accurately computes the interactions between closely spaced wires that are neglected by the analytical formulation of Bérenger. The presented method is applied to a testcase that can be compared to Bérenger’s results. Finally, results for a testcase that involves dielectric insulation are given.
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ItemThermal-hydrodynamic modeling and design for microchannel cold plates subjected to multiple heat sources(Elsevier, 2025)With advancing electronics, effective thermal management is crucial to maintain optimal performance and prevent overheating. Addressing the challenge of efficient cooling solutions has become a crucial area of research in modern thermal management. This paper applies and validates the Thermal-Hydrodynamic Model to bridge the knowledge gap on how straight, manifold, and serpentine microchannel configurations meet industry standards. The model predicts critical parameters, including electronic package temperatures, temperature differences across packages, thermal resistances, and pressure drops. Findings underscore the effectiveness of the model in accurately estimating thermal resistances and pressure drops within acceptable error margins compared to numerical simulations. Pressure drop estimates for straight channels consistently remain within a 10% error margin. For serpentine microchannels, the error is within 10% when the Dean number is at maximum 40. Manifold configurations, however, do not meet the 10% criterion. For manifold predictions within a 15% error margin, an Inlet Ratio of at most 0.13, a Velocity Ratio of unity, and low Reynolds numbers are necessary. Furthermore, for thermal resistance estimations, a number of grooves of at least 23 is required to maintain 10% validity. Additionally, a case study demonstrates the model’s potential as a practical alternative to simulation-based methods for identifying the optimal cold plate configuration, achieving cooling power requirements at least twice as low as other configurations within the design space.
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ItemTransient Modelling of Pumped Two-Phase Cooling Systems: Comparison between experiment and simulation with R134a( 2017)Two-phase pumped cooling systems are applied when it is required to maintain a very stable temperature in a system, for example in the AMS02, which was launched with a space shuttle (in May 2011) and subsequently mounted on the International Space Station. However, a two-phase pumped cooling system can show complex transient behavior in response to heat load variations. For example, when the heat load is increased, a large volume of vapor is suddenly created, which results in a liquid flow into the accumulator and an increase in the pressure drop. This will result in variations in the temperature in the system, which are undesired. It is necessary to calculate these temperature variations before an application is being built. For this reason, a software tool for transient two-phase systems has been developed by NLR. This tool numerically solves the one-dimensional time-dependent compressible Navier-Stokes equations, and includes the thermal inertia of all the components. In this paper, the numerical results from the model are compared to experimental results obtained with the NLR two-phase test facility with R134a as refrigerant.
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ItemLightweight Two-Phase Pumped Cooling System with aluminium components produced with Additive Manufacturing( 2019)The amount of waste heat that is generated in electronic components in aerospace application is increasing because of higher electrical power demands. As a result, conventional cooling methods are not able to maintain the electronic component below its maximum temperature. For this reason, a two-phase Mechanically Pumped Fluid Loop has been developed for high-power electronic components in a commercial aerospace application. These electronic components generate a waste heat of 1200 W that is divided over several hotspots while the temperature gradient over the component has to be kept to a minimum. The developed cooling system uses R245fa as refrigerant and is made from aluminum components produced with additive manufacturing. The use of this novel production technique results in an unprecedented low system mass (2.5 kg) and small system dimensions. Measurements show that the system has an excellent thermal performance and is able to cool 2400W.
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ItemTesting of high heat flux 3D printed aluminium evaporators( 2018)The amount of waste heat that is generated in electronic components in aerospace application is increasing because of higher electrical power demands. As a result, conventional cooling methods are not able to maintain the electronic component below its maximum temperature. For this reason, a two-phase Mechanically Pumped Fluid Loop is being developed for high-power electronic components in a commercial aerospace application. These electronic components generate a heat load of 722 W on a 3.8 cm x 3.8 cm surface, resulting in a heat flux of 50 W/cm2. Tests with 8 different evaporator samples were carried out to determine the heat transfer coefficients and pressure drop and to select the optimal evaporator sample that is further developed in the detail design phase of the project. The tests show that the 3D printed aluminium evaporators are able to keep the heat source well below its maximum temperature.