Liquid dielectric

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

Experimental investigation of saturation boiling of HFE-7000 dielectric liquid on rough copper surfaces

Abstract: Experiments are performed to investigate saturation boiling of the Novec HFE-7000 dielectric liquid on uniformly heated, 10 × 10 mm rough Cu surfaces in the horizontal upward facing orientation. The six surfaces employed have average roughness, Ra = 0.039, 0.134, 0.21, 0.28, 0.33 and 0.58 μm. The critical heat flux (CHF) and nucleate boiling heat transfer coefficient, hNB, and the corresponding surface superheats (ΔTsat), and the surface temperature excursion prior to boiling incipience are correlated in terms of Ra. Recorded still photos and video images of boiling in the different regions helped interpretation of experimental data and observations. For the HFE-7000 liquid, CHF increased ~39%, from 21.6 to 30 W/cm2, and the maximum nucleate boiling heat transfer coefficient (hMNB) increased ~2.32 times, from 0.82 to 1.9 W/cm2 K, and the corresponding surface superheats, ΔTexc, decreased ~38% and 41%, with increased Ra from 0.039 to 0.58 μm, respectively. The value of ΔTexc decreased from ~36.4 K to ~10 K with increased Ra from 0.039 to 0.58 μm. To quantify the effect of liquid properties, the values and correlations of CHF, hMNB, and hNB,sat are compared to those of PF-5060 dielectric liquid, which has different properties and ~64% higher boiling point (Table 1). The values of hNB,sat, hMNB, and CHF are ~11%, ~16–28%, and ~41% higher than for the PF-5060 dielectric liquid, respectively. The heat flux for liquid natural convection prior to boiling incipience is practically independent of Ra, but ~10.5% higher than for PF-5060 liquid. The present correlation of hNB,sat is in general agreement with widely referenced correlations by others.

Electrical Discharge Machining Non-Conductive Ceramics: Combination of Materials

Abstract: One of the promising processing methods for non-conductive structural and functional ceramics based on ZrO2, Al2O3, and Si3N4 systems is electrical discharge machining with the assistance of an auxiliary electrode that can be presented in the form of conductive films with a thickness up to 4–10 µm or nanoparticles - granules, tubes, platelets, multidimensional particles added in the working zone as a free poured powder the proper concentration of which can be provided by ultrasound emission or by dielectric flows or as conductive additives in the structure of nanocomposites. However, the described experimental approaches did not reach the production market and industry. It is related mostly to the chaotic development of the knowledge and non-systematized data in the field when researchers often cannot ground their choice of the material for auxiliary electrodes, assisting powders, or nano additives or they cannot explain the nature of processes that were observed in the working tank during experiments when their results are not correlated to the measured specific electrical conductivity of the electrodes, particles, ceramic workpieces or nanocomposites but depends on something else. The proposed review includes data on the main electrophysical and chemical properties of the components in the presence of heat when the temperature in the interelectrode gap reaches 10,000 °C, and the systematization of data on ceramic pressing methods, including spark plasma sintering, the chemical reactions that occur in the interelectrode gap during sublimation of primary (brass and copper) and auxiliary electrodes made of transition metals Ti, Cr, Co, and carbon, auxiliary electrodes made of metals with low melting point Zn, Ag, Au, Al, assisting powder of oxide ceramics TiO2, CeO2, SnO2, ITO, conductive additives Cu, W, TiC, WC, and components of Al2O3 and Zr2O workpieces in interaction with the dielectric fluid - water and oil/kerosene medium.

Partial discharge measurements in dielectric liquids under impulse voltage

Abstract: Current pulses caused by partial discharges (PDs) are measured using light-emitting diodes (LEDs) and fiber optics under impulse voltage conditions. This system has the advantage of having good isolation from the HV power supply and no effect from electromagnetic noise as compared with ordinary systems. It can detect a PD pulse having a half width of 3 ns, and has the capability of measuring PD pulse charges in the range of 1 to 2000 pC, when the optimum DC bias is applied. PD pulses and light emission or streamer formation in dielectric liquids are measured simultaneously by using an image converter camera. >

Development of Film-on-Foil Ceramic Dielectrics for Embedded Capacitors for Power Inverters in Electric Drive Vehicles

Abstract: Advanced power inverters for electric drive vehicles require capacitors that operate under high voltage at under-hood temperatures and have minimal footprint. This need can be realized by embedding ceramics with high dielectric constant within a printed wire board (PWB). The ‘‘film-onfoil’’ approach, where the high-dielectric-constant ceramic is first deposited on base-metal foil, is a promising method for embedding the capacitors within a PWB. We have deposited lead lanthanum zirconium titanate (PLZT) on nickel foils and characterized the samples in the temperature range between 50 and 250 C. The measured dielectric constants varied with temperature: from 700 at 50 Ct o2200 at 250 C. The dielectric loss remained fairly constant at 0:05{0:08. At 300V bias, a dielectric constant of 110 and dielectric loss of 0:004 were measured. Hysteresis loop analysis showed an energy density of 85J/cm 3 . The fabrication procedures and dielectric properties of the PLZT film-on-foils will be described in this paper. # 2013 The Japan Society of Applied Physics