Showing papers on "Boiling published in 2014"
Book•
19 Aug 2014
TL;DR: In Al Gore's documentary film on climate change, An Inconvient Truth, he employs a short cartoon to illustrate the different ways in which animals react to gradual vs. sudden change.
Abstract: In Al Gore's documentary film on climate change, An Inconvient Truth, he employs a short cartoon to illustrate the different ways in which animals react to gradual vs. sudden change. In one frame of the cartoon a frog is dumped into a pot of boiling water at which instant it jumps right out. In a second frame the frog is placed into a pot of cold water which is then gradually heated to boiling to which the frog does not react. What Gore was attempting to illustrate about animal behavior is so fundamental that little time is spent in discussion. It's relevance to climate change is similarly too obvious, supposedly, to need much explanation climate change is so gradual that it does not trigger rapid response.
370 citations
TL;DR: In this article, the effects of structure size on bubble nucleation and departure characteristics as well as the heat transfer coefficient are discussed on horizontal heated surfaces with micro- and nano-sized structures.
294 citations
TL;DR: In this paper, the authors present a review of methods for predicting heat transfer in condensing and boiling mini/micro-channel flows, and show that despite the success of previous predictive methods for specific fluids and narrow databases, these methods are incapable of providing accurate predictions against entire consolidated databases.
236 citations
TL;DR: In this article, the ability of a boiling process to thermally condition (homogenization and cooling) batteries is investigated and the influence of pressure variation on the boiling process is investigated.
217 citations
TL;DR: In this paper, a technique to simultaneously measure the liquid-vapor phase boundary, temperature distribution, and heat transfer distribution at a boiling surface is described, and the technique is fully synchronized in time and spatially resolved, and is applied to explore single-bubble nucleate boiling phenomena in a pool of water subcooled by 3°C under atmospheric pressure.
207 citations
TL;DR: In this article, the physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation, and it was shown that controlling micro-explosion and puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed.
Abstract: The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.
203 citations
TL;DR: In this paper, the effect of microchannel geometry on heat transfer performance for water boiling at atmospheric pressure on 10mm×10mm copper chips was investigated by electrodepositing microporous coatings on the fin tops of microchannels.
190 citations
TL;DR: In this article, molecular dynamics simulations have been conducted to understand the mechanism for bubble formation on a platinum substrate with particular emphasis on the surface texture, and the nano-sized bubbles are formed under different degree of superheat and surface conditions.
168 citations
TL;DR: In this article, heat transfer characteristics of isolated bubble saturated pool boiling of water were investigated by local wall temperature measurement using an original micro-electro-mechanical systems (MEMS) sensor and a wall heat transfer evaluation.
162 citations
TL;DR: The present study addresses this limitation by discussing the development of two consolidated mini/micro-channel databases, used to assess the accuracy of previous models and correlations as well as to develop ‘universal’ correlations that are applicable to a large number of fluids and very broad ranges of operating conditions.
153 citations
TL;DR: In this article, a single annular flow boiling with deionized water in silicon microchannels was shown to significantly enhance the heat transfer coefficient (HTC) and critical heat flux (CHF) in the self-stabilized and single flow boiling regime.
TL;DR: In this article, the effects of carbon nanotubes structures and different functional groups were studied on the pool boiling heat transfer coefficients (HTC) and critical heat fluxes (CHF).
TL;DR: In this paper, a two-step electrodeposition technique involving application of high current density for a short time, followed by a lower currentdensity for a longer time was investigated, which allowed a close control of the pore size and porous layer thickness.
TL;DR: In this article, a modified level-set method was used to simulate the laser drilling process on aluminum slab with millisecond pulsed laser and a 2D model was developed to trace the liquid-gas interface as well as consider mass loss during evaporation and boiling.
TL;DR: Boiling of tap water can be regarded as a "detoxification" process and may reduce human exposure to halogenated DBPs through tap water ingestion.
Abstract: Tap water typically contains numerous halogenated disinfection byproducts (DBPs) as a result of disinfection, especially of chlorination. Among halogenated DBPs, brominated ones are generally significantly more toxic than their chlorinated analogues. In this study, with the aid of ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry by setting precursor ion scans of m/z 79/81, whole spectra of polar brominated DBPs in simulated tap water samples without and with boiling were revealed. Most polar brominated DBPs were thermally unstable and their levels were substantially reduced after boiling via decarboxylation or hydrolysis; the levels of a few aromatic brominated DBPs increased after boiling through decarboxylation of their precursors. A novel adsorption unit for volatile total organic halogen was designed, which enabled the evaluation of halogen speciation and mass balances in the simulated tap water samples during boiling. After boiling for 5 min, the ove...
TL;DR: A review of different manufacturing techniques employed to manufacture porous surfaces in pool boiling application can be found in this article, where different types of surfaces developed using these techniques are reviewed and their pool boiling performance is discussed.
Abstract: Continuous development of high-performance microelectronic chips requires efficient cooling systems to dissipate large amount of heat produced over a small footprint. Pool boiling is capable of dissipating large heat fluxes while maintaining low wall superheat and is receiving renewed interest. Porous surfaces have been investigated extensively for pool boiling enhancement. This paper presents a review of different manufacturing techniques employed to manufacture porous surfaces in pool boiling application. Different types of surfaces developed using these techniques are reviewed and their pool boiling performance is discussed.
TL;DR: In this article, a novel method of optic cavitation that uses low power CW lasers incident in highly absorbing liquids is described, which is called thermocavitation, where light absorbed heats up the liquid beyond its boiling temperature (spinodal limit) in a time span of microseconds to milliseconds (depending on the optical intensity).
Abstract: The most common method to generate optic cavitation involves the focusing of short-pulsed lasers in a transparent liquid media. In this work, we review a novel method of optic cavitation that uses low power CW lasers incident in highly absorbing liquids. This novel method of cavitation is called thermocavitation. Light absorbed heats up the liquid beyond its boiling temperature (spinodal limit) in a time span of microseconds to milliseconds (depending on the optical intensity). Once the liquid is heated up to its spinodal limit (∼300 °C for pure water), the superheated water becomes unstable to random density fluctuations and an explosive phase transition to vapor takes place producing a fast-expanding vapor bubble. Eventually, the bubble collapses emitting a strong shock-wave. The bubble is always attached to the surface taking a semi-spherical shape, in contrast to that produced by pulsed lasers in transparent liquids, where the bubble is produced at the focal point. Using high speed video (105 frames/s), we study the bubble’s dynamic behavior. Finally, we show that heat diffusion determines the water superheated volume and, therefore, the amplitude of the shock wave. A full experimental characterization of thermocavitation is described.
TL;DR: In this article, a more physically sound thermostat is applied to control the temperature of the metal plate and then to heat water molecules that are placed in the elastic wall confined simulation domain.
TL;DR: In this paper, the authors used a heating surface composed of a hydrophilic substrate with hydrophobic dots to characterize the effect of spatially-different surface characteristics on critical heat flux (CHF) and nucleate boiling.
TL;DR: In this article, a review focusing mainly on those works from the literature that analyzed the main issues of falling film evaporation of refrigerants, to better understand heat transfer and fluid dynamics in such evaporators.
TL;DR: A survey of the most recent work aimed at physically characterizing local heat transfer in flow boiling in microchannels is presented in this article, which includes recent experimental work, new flow boiling prediction methods, and numerical simulations of microchannel slug flows with evaporation.
TL;DR: The Kutateladze correlation for CHF was obtained on basis of dimensions analysis as discussed by the authors, which is a well-known correlation for pool boiling crisis, and it has been shown that at moderate and high reduced pressures the equation of the hydrodynamic model agrees satisfactorily with the data.
3 Nov 2014
TL;DR: In this paper, a new battery temperature control system called Boiling Liquid Battery Cooling (BLBC) is developed for the electric vehicle application, where the battery cells are immersed in hydrofluoroether liquid; it has high electric resistance, non-inflammability and environmental friendliness and also the boiling temperature is close to the battery operating temperature.
Abstract: For the Electric Vehicle application, battery cooling is a crucial issue for safety, battery life and low temperature performance. As a new battery temperature control system, “Boiling Liquid Battery Cooling” is developed. The battery cells are immersed in hydrofluoroether liquid; it has high electric resistance, non-inflammability, and environmental friendliness and also the boiling temperature is close to the battery operating temperature. The result shows the cell temperature is controlled around 35 °C continuously during cyclic charging and discharging, even if it is operated at very high rate discharging and charging (around 20C).
TL;DR: In this article, the thermal stability of boiling-favorable merits of nanowire arrays are discussed for thermal stability in pool boiling environments and local and temporal heat transfer characteristics are evaluated on vertically aligned nanowires arrays using a temperature-array sensor.
TL;DR: In this article, the convective boiling characteristics of dilute dispersions of CuO nanoparticles in water/ethylene glycol as a base fluid were studied at different operating conditions.
Abstract: The convective boiling characteristics of dilute dispersions of CuO nanoparticles in water/ethylene glycol as a base fluid were studied at different operating conditions of (heat fluxes up to 174 kW m−2, mass fluxes range of 353–1,059 kg m−2 s−1 and sub-cooling level of 343, 353 and 363 K) inside the annular duct. The convective boiling heat transfer coefficients of nanofluids in different concentrations (vol%) of nanoparticles (0.5, 1, and 1.5) were also experimentally quantified. Results demonstrated the significant augmentation of heat transfer coefficient inside the region with forced convection dominant mechanism and deterioration of heat transfer coefficient in region with nucleate boiling dominant heat transfer mechanism. Due to the scale formation around the heating section, fouling resistance was also experimentally measured. Experimental data showed that with increasing the heat and mass fluxes, the heat transfer coefficient and fouling resistance dramatically increase and rate of bubble formation clearly increases. Obtained results were then compared to some well-known correlations. Results of these comparisons demonstrated that experimental results represent the good agreement with those of obtained by the correlations. Consequently, Chen correlation is recommended for estimating the convective flow boiling heat transfer coefficient of dilute CuO-water/ethylene glycol based nanofluids.
TL;DR: In this article, the authors review the mechanisms of nanoparticle deposition and the effects induced by deposited nanoparticles on surface roughness, force balance at the triple line, surface wettability, active nucleation site density, receding and advancing contact angles, boiling heat transfer coefficient and critical heat flux.
Abstract: Suspended nanoparticles inside the nanofluids can modify the characteristics of heated surfaces and the physical properties of the base liquids, offering a great opportunity to optimize boiling heat transfer. This paper reviews the mechanisms of nanoparticle deposition and the effects induced by deposited nanoparticles on surface roughness, force balance at the triple line, surface wettability, active nucleation site density, receding and advancing contact angles, boiling heat transfer coefficient and critical heat flux. Both enhancement and deterioration effects on boiling heat transfer coefficient and critical heat flux have been discussed. Most of the existing experimental data confirms the enhancement of critical heat flux using alumina nanofluid, however there is no consistency about its boiling heat transfer coefficient.
TL;DR: The fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions, namely on impact with Weber numbers ≥40 at T ≥ 325 °C are reported.
Abstract: Leidenfrost phenomena on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems utilizing boiling phenomena. They also provide an elegant means to direct droplet motion in a variety of recently emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions, namely on impact with Weber numbers ≥40 at T ≥ 325 °C. The directionality for these droplets is opposite to the direction previously exhibited by macro- and microscale Leidenfrost ratchets where movement against the tilt of the ratchet was observed. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask, with mean pillar diameters of 100 nm and heights of 200–500 nm. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no prefe...
TL;DR: In this paper, the authors investigated the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface.
Abstract: Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations. [DOI: 10.1115/1.4025697]
TL;DR: SiC nanofluid was used for critical heat flux (CHF) enhancement in the case of water pool boiling as discussed by the authors, and two kinds of test sections with different dimensions were used for verifying CHF enhancement trends for SiC nanoftluid.
TL;DR: In this paper, the heat transfer during spray cooling was studied experimentally using deionized water to investigate the spray characteristics and the differences between spray cooling on smooth and enhanced silicon surfaces with micro-structures (characteristic size 25-200μm).