Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.

Pump-enhanced, immersion-cooling of electronic component(s)

Abstract: Cooling apparatuses and methods of fabricating thereof are provided which facilitate pumped immersion-cooling of an electronic component(s). The cooling apparatus includes an enclosure having a compartment accommodating the electronic component(s), and dielectric fluid within the compartment at least partially immersing the electronic component(s). A liquid-cooled heat sink is associated with the enclosure to cool at least one cooling surface associated with the compartment, and facilitate heat transfer to the heat sink from the electronic component(s) via the dielectric fluid. A pump is disposed external to the compartment and in fluid communication therewith to facilitate pumped dielectric fluid flow through the compartment. The pumped dielectric fluid flow through the compartment enhances heat transfer from the electronic component(s) to the liquid-cooled heat sink via the cooling surface(s). In one implementation, the pumped dielectric fluid flow provides two-phase cooling to the electronic component(s) via flow boiling.

Computation and analysis of dielectric losses in MV power electronic converter insulation

Abstract: The newly available Medium Voltage (MV) Silicon-Carbide (SiC) devices enable a great extension of the design space of MV inverters. This includes the utilization of unprecedented blocking voltages, higher switching frequencies, higher commutation speeds, and high temperature operation. However, all these factors considerably increase the insulation stress. This paper details the computation of dielectric losses, which are directly related to the insulation stress and can be used for the insulation design and diagnostic. After a review of the method used to compute dielectric losses, scalable analytical expressions are derived for the losses produced by PWM waveforms of DC-DC, DC-AC, and multilevel DC-AC inverters. Finally, a Medium-Frequency (MF) transformer is analyzed and the impacts of the insulation material and the operating temperature on the dielectric losses are discussed. It is found that the insulation losses can represent a significant share (17%) of the total transformer losses.

Direct Comparison of Immersion and Cold-Plate Based Cooling for Automotive Li-Ion Battery Modules

Abstract: The current paper evaluates the thermal performance of immersion cooling for an Electric Vehicle (EV) battery module comprised of NCA-chemistry based cylindrical 21700 format Lithium-ion cells. Efficacy of immersion cooling in improving maximum cell temperature, cell’s temperature gradient, cell-to-cell temperature differential, and pressure drop in the module are investigated by direct comparison with a cold-plate-cooled battery module. Parametric analyses are performed at different module discharge C-rates and coolant flow rates to understand the sensitivity of each cooling strategy to important system performance parameters. The entire numerical analysis is performed using a validated 3D time-accurate Computational Fluid Dynamics (CFD) methodology in STAR-CCM+. Results demonstrate that immersion cooling due its higher thermal conductance leads to a lower maximum cell temperature and lower temperature gradients within the cells at high discharge rates. However, a higher rate of heat rejection and poor thermal properties of the dielectric liquid results in a much higher temperature non-uniformity across the module. At lower discharge rates, the two cooling methods show similar thermal performance. Additionally, owing to the lower viscosity and density of the considered dielectric liquid, an immersion-cooled battery module performs significantly better than the cold-plate-cooled module in terms of both coolant pressure drop.

Electrohydrodynamic instabilities at interfaces subjected to alternating electric field

Abstract: Instabilities at the interface of two immiscible fluids, either perfect or leaky dielectrics, subjected to alternating electric fields, is studied using a linear stability analysis in the limit of the electrode spacing being large compared to the wavelength of the perturbation. The Floquet analysis of the stability of this system indicates a significant effect of the frequency on the value of smax, the growth rate of the fastest growing instabilities and ETaylor, the minimum field required to excite an instability. It is seen that alternating fields act to damp the system instabilities compared to the direct current (dc) case. Moreover, the growth rate of the instabilities can be tuned from that of leaky dielectric fluids subjected to dc fields, in the low frequency limit, to that of perfect dielectrics in the high frequency limit. It is also observed that for a leaky dielectric-leaky dielectric interface, the alternating current (ac) fields can induce instabilities in a system which is stable at zero fre...