Fluorinert Liquid Research Articles

3D printed cartridge for high-speed capillary electrophoresis with sheath liquid thermostatting and contactless conductivity detection

The high-speed capillary electrophoresis (HSCE) method is a technique that utilizes a high electric field strength applied through a short capillary to reduce the time required for sample separation. However, the increased electric field strength may result in pronounced Joule heating effects. To address this, we describe a 3D-printed cartridge with integrated contactless conductivity detection (C4D) head and a sheath liquid channel. The C4D electrodes and Faraday shield layers are fabricated by casting Wood's metal in chambers inside the cartridge. Effective thermostatting of the short capillary is achieved by flowing Fluorinert liquid, which provides better heat dissipation compared to airflow. A HSCE device is created by using the cartridge and a modified slotted-vial array sample-introduction approach. Analytes are introduced through electrokinetic injection. With the help of sheath liquid thermostatting, background electrolyte concentration can be increased to several hundred mM, resulting in improved sample stacking and peak resolutions. Additionally, the baseline signal is flattened. Typical cations such as NH4+, K+, Na+, Mg2+, Li+, and Ca2+ can be separated within 22 s with an applied field strength of 1200 V/cm. The limit of detection ranges from 2.5 to 4.6 μM with a relative standard deviation of migration times of 1.1–1.2% (n = 17). The method has been applied to detect cations in drinking water and black tea leaching for drink safety testing, and to identify explosive anions in paper swabs. Samples can be directly injected without the need for dilution.

A 1.35-kV/500-kHz Sub-Nanosecond Pulser With High Time Base Stability

In many fields, e.g., ground-penetrating radar and ultra-wideband radiation, a high-pulse-repetition-frequency (PRF) and high-time-base-stability sub-nanosecond pulser is required, and its output waveform should be close to a gaussian pulse. In this article, the transistorized pulser is studied and optimized to improve its output parameters. The printed circuit board circuit parameters of the pulser are first optimized, which is beneficial for the amplitude and the rise time. To improve the time base stability, the collector voltage ramp triggering mode is adopted to replace the conventional base triggering mode for the pulser. For higher PRF, the pulser with the capacitance–transistor parallel structure is immersed in the fluorinert liquid. Moreover, the deficit-charge method is adopted, and small charging capacitances are used in the last few stages to weaken the oscillation in the pulse falling edge. From experimental results, the amplitude of the optimized pulser is 1.35 kV, its rise time is reduced from about 200 to 135 ps, the maximum PRF is improved from 250 to 500 kHz, the pulse jitter is reduced to 22 ps, and the pulse drift is reduced from hundreds of ps/min to 47 ps/min. Meanwhile, the oscillation in its falling edge is greatly suppressed.

Dynamic Pool Boiling Heat Transfer Due to Exponentially Increasing Heat Input-A Review

The boiling heat transfer, specifically transient or unsteady heat transfer has found much practical importance in the engineering applications. Since, explosive boiling occurs during enormous power excursion in the liquid cooled reactor, the safety evaluation of a nuclear reactor is of vital importance. This paper reviews the transient boiling heat transfer which is the study of transition mechanism from natural convection or nucleate boiling to film boiling and critical point of heat flux using the various wetting fluid as working medium (Distilled water, ethanol, fluorinert liquid, etc.) caused by exponentially increasing heat input at various periods. The survey is also extended to study the heating element (wire, rod, film) usually made of aluminum or platinum under a subcooled or saturated condition of working fluid at atmospheric or higher system pressure. During the quasi-steady or rapid transient, an aspect of dynamic boiling like the onset of boiling, delay period, temperature overshoot, homogenous nucleation, heterogeneous nucleation, transient CHF, bubble growth, vapor coalescence and vapor collapse has been analyzed. Moreover, a visualization study of differently oriented test piece at a different heating rate and different phase of boiling has been qualitatively discussed.

Pool boiling heat transfer driven by an acoustic standing wave in terrestrial gravity and microgravity

Terrestrial and microgravity pool boiling generated from a platinum wire heater in the presence of an acoustic standing wave were performed using degassed FC-72 Fluorinert liquid. The sound wave was created by driving a half wavelength resonator at a frequency of 10.15kHz. Microgravity conditions were created using the 2.1 second drop tower on the campus of Washington State University. Burnout of the heater wire, often encountered with heat flux controlled systems, was avoided by using a constant temperature controller to regulate the heater wire temperature. The amplitude of the acoustic standing wave was increased from 28kPa to over 70kPa and these pressure measurements were made using a hydrophone fabricated with a small piezoelectric ceramic. Cavitation incurred during experiments at higher acoustic amplitudes contributed to the vapor bubble dynamics and heat transfer. The heater wire was positioned at three different locations within the acoustic field: the acoustic node, antinode, and halfway between these locations. Complete boiling curves are presented to show how the applied acoustic field enhanced boiling heat transfer and increased critical heat flux in the terrestrial environment, while in microgravity the acoustic field was found to be capable of filling the role of terrestrial gravity in maintaining nucleate boiling. Video images provide information on the interaction between the vapor bubbles and the acoustic field.

Local measurement of flow boiling heat transfer in an array of non-uniformly heated microchannels

As electronics packages become increasingly thinner and more compact due to size, weight, and performance demands, the use of large intermediate heat spreaders to mitigate heat generation non-uniformities are no longer a viable option. Instead, non-uniform heat flux profiles produced from chip-scale variations or from multiple discrete devices are experienced directly by the ultimate heat sink. In order to address these thermal packaging trends, a better understanding of the impacts of non-uniform heating on two-phase flow characteristics and thermal performance limits for microchannel heat sinks is needed. An experimental investigation is performed to explore flow boiling phenomena in a microchannel heat sink with hotspots, as well as non-uniform streamwise and transverse peak-heating conditions spanning across the entire heat sink area. The investigation is conducted using a silicon microchannel heat sink with a 5×5 array of individually controllable heaters attached to a 12.7mm×12.7mm square base. The channels are 240μm wide, 370μm deep, and separated by 110μm wide fins. The working fluid is the dielectric fluorinert liquid FC-77, flowing at a mass flux of approximately 890kg/m2s. High-speed visualizations of the flow are recorded to observe the local flow regimes. Despite the substrate beneath the microchannels being very thin (200μm), significant lateral conduction occurs and must be accounted for in the calculation of the local heat flux imposed. For non-uniform heat input profiles, with peak heat fluxes along the streamwise and transverse directions, it is found that the local flow regimes, heat transfer coefficients, and wall temperatures deviate significantly from a uniformly heated case. These trends are assessed as a function of an increase in the relative magnitude of the nonuniformity between the peak and background heat fluxes.

Pool boiling heat transfer of tandem tubes provided with the novel microstructures

The paper presents experimental data on pool boiling heat transfer of tandem tubes, arranged one above the other in the same vertical plane. The outer surface of the tubes is provided with the novel microstructures. The structure elements are micropins created by electrolytic deposition of copper upon the tube, using a specially treated polycarbonate foil. By this technique the pins diameter can be varied from 0.1 μm up to 25 μm, the pins height goes up to 100 μm at densities up to 1 × 10 9 pins/cm 2 and pins inclination almost up to 180° regarding the base surface. Micropins with several different inclinations can be created simultaneously on the same surface. Experiments were conducted with two different microstructures using the refrigerant R134a and the highly wetting Fluorinert liquid FC-3284 at pressures of 5–9 bar and 0.5–1.5 bar, respectively. The advantages of the novel microstructure regarding the boiling heat transfer for tandem tubes turned out to be practically the same as for a single tube arrangement. Microstructured tubes have the superheat independent on the heat flux, they show a very low boiling inception superheats (below 2 K), are highly effective in comparison with a technically smooth tubes, and operate stable over the long periods of time.

Rewetting velocity in quenching at reduced gravity

The results of quenching tests in tubes at microgravity and normal gravity conditions are presented. The aim of the experimental campaign was to gather both quantitative data and direct observations regarding phenomena involved in the rewetting of tubes. The rewetting velocity at different refrigerant flow-rate and subcooling conditions is obtained from experimental data. Test sections are made of Pyrex tubes with three different inner diameters: 2.0 mm, 4.0 mm and 6.0 mm. They are coated with Indium-Tin-Oxide (ITO), which is transparent but allowing the direct heating of the Pyrex tube. Tests are performed with vertical test section and downward liquid flow. The working fluid is FC-72, a fluorinert liquid. Measurements included wall temperatures along the flow channel, inlet and outlet temperatures, pressures and mass flow-rate. The 6.0 and 2.0 mm tubes show a significant decrease in the quenching velocity at reduced gravity and a dependence on the coolant mass flow-rate, especially for ground experiments. The results of the 4.0 mm tube show a contradictory behaviour in micro/normal gravity comparison.

Quenching experiments inside 6.0 mm tube at reduced gravity

This paper addresses the experimental results of quenching in tubes under microgravity conditions. The objective of the experiment is to obtain quantitative data and observations of the rewetting phenomenon under low gravity level and compare results with the equivalent terrestrial gravity ones. Test tube is made of Pyrex with 6.0 mm in diameter. Tests are performed with FC-72, a fluorinert liquid, flowing inside a vertical test section and upward liquid flow. Measurements included outer wall temperatures along the flow channel, inlet and outlet fluid temperatures, pressure and mass flow-rate. The results show a significant decrease in the quenching velocity at reduced gravity, while the rewetting temperature does not look to be affected by gravity level. The observed flow patterns are inverted annular flow and bubbly flow. The analyses are completed with a detailed high speed video images at normal gravity. These tests reveal the influence of mass flow-rate on the structure of vapour–liquid configuration during the inverted annular flow.

Silicon Dioxide-Encapsulated High-Voltage AlGaN/GaN HFETs for Power-Switching Applications

In this letter, new approach in achieving high breakdown voltages in AlGaN/GaN heterostructure field-effect transistors (HFETs) by suppressing surface flashover using solid encapsulation material is presented. Surface flashover in III-Nitride-based HFETs limits the operating voltages at levels well below breakdown voltages of GaN. This premature gate-drain breakdown can be suppressed by immersing devices in high-dielectric-strength liquids (e.g., Fluorinert); however, such a technique is not practical. In this letter, AlGaN/GaN HFETs encapsulated with PECVD-deposited SiO2 films demonstrated breakdown voltage of 900 V, very similar to that of devices immersed in Fluorinert liquid. Simultaneously, low dynamic ON-resistance of 2.43 mOmega ldr cm2 has been achieved, making the developed AlGaN/GaN HFETs practical high-voltage high-power switches for power-electronics applications.

Experimental investigation on thermocapillary drop migration at large Marangoni number in reduced gravity

Results from a space experiment on thermocapillary drop migration conducted on board the Chinese spacecraft ShenZhou-4 are presented in this paper. In the experiment, isolated drops of Fluorinert liquid moved in a matrix liquid of 5cst silicone oil at values of the Marangoni numbers (Ma) ranging up to 5500 and the interferometry images showed the temperature distribution inside the test cell. The drop migration velocity was measured. The experimental results show that the scaled drop migration velocity V / V YGB obviously decreases with Ma increasing the values up to 5500. The space experimental results are also compared with those from our early experiments, other space experiments, and some theoretical predictions.

Experimental study on CPU cooling system of closed-loop two-phase thermosyphon

This paper reports on an indirect cooling method of high-power CPU of notebook computers using a closed-loop two-phase thermosyphon with Fluorinert (FC-72) as the working fluid. The experimental setup consists of an evaporator with an electric heater, a condenser, and flexible tube connecting them. The heater and condenser act as a high-power CPU and a cooling plate located behind the display of a notebook computer, respectively. The evaporator and the condenser have the outer dimensions of 50mm × 50mm × 20mm and 150mm × 200mm × 20mm, respectively. Four possible boiling surfaces of an evaporator were examined, i.e., a smooth surface (Type A), rough one, ones with smooth plate fins and rough plate fins (Type D). Type D evaporator shows the highest performance, i.e., it reduces the temperature at the evaporator/heater interface by about 18% in comparison with that of the smooth surface evaporator (Type A). Type D evaporator keeps the temperature difference between the evaporator/heater interface and the ambient to be around 55 K at the highest heat input Q = 30W. The effects of the heat input Q, the volumetric amount of Fluorinert liquid F in the thermosyphon, and the evaporator type on the heat transfer characteristics of the cooling system were examined experimentally. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(3): 147–159, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20057

Prandtl-number effects and generalized correlations for confined and submerged jet impingement

The influence of fluid thermophysical properties on the heat transfer from confined and submerged impinging jets is experimentally investigated. Results from previous studies at low and high Prandtl numbers (using air and Fluorinert liquid FC-77, respectively) are supplemented by new experiments for an intermediate Prandtl number (using water). Local heat transfer coefficients are obtained from a discrete heat source under axisymmetric confined and submerged jets. The parameter ranges studied include: orifice diameters of 1.59–12.7 mm, turbulent-flow Reynolds numbers of 4000–23 000, and orifice to heat-source spacings of 1–5 jet diameters. Generalized correlations for heat transfer rates are proposed based on these results, and are valid over the range of coolant Prandtl numbers from 0.7 to 25.2.

00/02159 Study on usage of fluorocarbon for toroidal field coil cooling

In JT-60 machine, usage of fluorocarbon as an alternate coolant to a cooling channel of toroidal field coil (TF coil) in which a crack was detected is investigated. Fluorinert (a registered trademark of 3M) liquid which is one of fluorocarbon was reviewed, and liquid `FC-43` was found as an appropriate one for TF coils cooling because of its physical properties about boiling point and thermal capacity. Fortunately, Fluorinert does not have impact on the greenhouse effect for the earth under the temperature of its boiling point. And thermal analysis shows that the cooling effectiveness obtained with liquid `FC-43` for TF coils is rather well. Moreover, corrosion tests were carried out between liquid `FC-43` and materials used in JT-60 by considering deterioration of TF coils. The test results demonstrate that there is no problem in applying liquid `FC-43` as a coolant to cooling channel of TF coils. Results obtained above conclude that usage of fluorocarbon is one of the effective means to perform further experiments in JT-60. (author)

Measurement of refractive index of PF-5060

For optical studies of boiling heat transfer process, it is essential that the refractive index and its dependence on temperature for the test liquid be known. In this work a simple set-up was built to measure the refractive index of Fluorinert Liquid PF-5060 with temperature compensation and temperature control. The pinhole laser light beam was used for determining the refraction angle. The refractive index data obtained in the temperature range 0–60°C is found to correlate linearly with temperature.

Natural Convection Cooling of Multiple Heat Sources in Parallel Open-Top Cavities Filled With a Fluorinert Liquid

Natural convection immersion cooling of discrete heat sources in a series of parallel interacting open-top cavities filled with a fluorinert liquid (FC–72) has been numerically studied. A series of open-top slots which are confined by conductive vertical walls with two heat sources on one side are considered. One of the slots is modeled and simulated. The effect of the separation between the heat sources on the flow and heat transfer characteristics of the wall and the effect of strength of the lower heat source (which location is upstream of the other one) on the flow and heat transfer of the upper heat source are considered. The wall thermal conductivity considered ranges from adiabatic to alumina-ceramic. The results of bakelite and alumina-ceramic are shown, which are commonly used as wiring boards in electronic equipment. It is found that conduction in the wall is very important and enhances the heat transfer performance.

Experimental study on local heat transfer with liquid impingement flow in two-dimensional micro-channels

Experiments were performed to investigate the heat transfer characteristics of impingement flow of transformer oil and 3M fluorinert liquid FC-72 in two-dimensional micro-channels. Jet impingement technique was used in this research for its high heat transfer rate and large potential in industrial applications. Local heat transfer coefficients were recorded both at stagnation and parallel flow regions in the range of Reynolds number from 70 to 170, and 911 to 4807, for oil and FC-72, respectively. The influences of different parameters, such as liquid velocity, channel size and fluid Prandtl number, on heat transfer behavior were examined. Empirical correlations of local heat transfer were developed for the whole channels. Very significant enhancement of heat transfer was observed and recorded.

Critical Heat Loads in Boiling Heat Transfer from Porous Studs to FLUORINERT Liquid.

The device considered in this paper is a porous stud having a net of microchannels, designed to enhance boiling heat transfer from the electronic component at the stud base to the pool of FC-72. The two-step approach was taken to clarify the effects of geometrical parameters on the critical heat load on the porous stud. In the first step, the attention was focused on the burn-out condition in a confined space, using a pair of thermal chips to simulate the geometry of microchannels. The data were obtained by changing the microchannel gap in a range of 0.1∼5mm; and based on these data, the correlation was derived for the critical heat flux vs. the microchannel size. In the second step, the heat conduction analysis was performed assuming the critical state at the stud base and using the experimentally determined correlations of boiling heat transfer for the rest of the stud zone. Finally, it is shown that there exist optimum sizes of microchannels that maximize the alowable heat load within a certain set of geometrical constraints.

Application of fluorinert liquid in the failure analysis of semiconductor integrated circuits : M. Narayanan and V. Soni. Solid St. Technol. p. 45 (February 1978)

Application of fluorinert liquid in the failure analysis of semiconductor integrated circuits : M. Narayanan and V. Soni. Solid St. Technol. p. 45 (February 1978)