Non-linear dynamical analyses of transient surface temperature fluctuations during subcooled pool boiling on a horizontal disk

Sathyamurthi, Vijaykumar; Banerjee, Debjyoti

doi:10.1016/j.ijheatmasstransfer.2009.06.023

Cited by 7 publications

(3 citation statements)

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“…Convective heat transfer values were derived from the experiments by using the wall temperature gradient measurements that were obtained in these experiments. [38][39][40][61][62][63] In these studies, the nanoparticle material, concentration of the nanoparticles, duration of experimentation, flow rates and surface temperature were reported to affect the thermal performance of the nanofluids. …”

Section: Yu Et Almentioning

confidence: 99%

Numerical Investigation of the Effect of Chirality of Carbon Nanotube on the Interfacial Thermal Resistance

Hu¹

2013

J Nanofluids

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Concentrated Solar Power (CSP) systems are used widely as a stable and reliable renewable source of energy. However, intermittency of this power source and the variability in demand for electrical power creates challenges that necessitate the integration with energy storage for reliable dispatch of power. Thermal Energy Storage (TES) systems provide a cheap, cost-effective and reliable option for energy storage in renewable power delivery systems. Due to their low vapor pressures at elevated temperatures, molten salts and their eutectics are used in conventional high temperature thermal energy storage (TES) systems and also as coolants for energy conversion, such as in power tower configurations that are typically used in CSP applications. A major drawback of the molten salts is their relatively poor thermo-physical properties, which may lead to lower systemic efficiencies in CSP/TES. Recent reports in the literature have shown that doping molten salts with nanoparticles at minute concentrations (typically less than 5% mass fraction and ideally at less than 1-2% mass fraction) can significantly enhance the thermo-physical properties of these nanomaterial (also termed as "nanocomposites" in solid state and "nanofluids" in liquid state). The dominant factor that controls the resultant thermo-physical properties of these nanomaterials is the interfacial thermal resistance (or Kapitza Resistance "R k ") that impedes the heat transfer between the nanoparticle surface and the bulk solvent molecules.ii In this study, the interfacial thermal resistance between a carbon nanotube (CNT) and carbonate molten salt eutectics were calculated by using numerical models that were then implemented in Molecular Dynamics (MD) simulations. The estimates for "R k " obtained from these simulations enabled the prediction of the optimum dimensions of the nanoparticles for maximizing the thermo-physical properties of the mixture, i.e. thermal conductivity and specific heat capacity values of these nanomaterial. The simulations were restricted to the carbonate salt eutectic, which is composed of a molar ratio of 62:38 for lithium carbonate (Li 2 CO 3 ) and potassium carbonate (K 2 CO 3 ). In this study, parametric simulations were performed to estimate the values of "R k " by varying the chirality of a single walled CNT (i.e, for armchair, chiral, and zig-zag CNT). The results show that the Kapitza resistance of the CNT is significantly affected by the change in the chirality of the CNT.

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Section: Yu Et Almentioning

confidence: 99%

Numerical Investigation of the Effect of Chirality of Carbon Nanotube on the Interfacial Thermal Resistance

Hu¹

2013

J Nanofluids

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“…The complexity of boiling dynamics in the nucleate boiling regime discussed in section 4 is highest for which the reconstructed attractors have very complicated trajectories as shown in Figure . The nucleate boiling regime has been established to be significantly more complex so that higher embedding dimensions are required to unfold the attractor and a higher-order model is required to predict its dynamics compared to transition boiling and film boiling regime. , Onset of nucleate boiling (ONB) has a fractal dimension higher than that of fully developed boiling. A better reconstruction obtained at lower Δ T sub = 30 °C can be explained by the fact that the nucleate boiling develops to be much better as a result of bubble merger facilitated along axial and radial direction of the heated section.…”

Section: Nonlinear Analysis Of Experimental Time Seriesmentioning

confidence: 99%

Nonlinear Analysis of Chaotic Time Series in a Natural Circulation Boiling Loop

Karmakar

Paruya

2012

Ind. Eng. Chem. Res.

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The present study reports chaotic flow oscillations observed in a natural circulation boiling loop. The periodic oscillations of wall temperature (thermal oscillations) initiate at a certain condition of heat flux and inlet subcooling in addition to geysering instability and pressure-drop oscillations. We observed that boiling regime changes from nucleate boiling to transition boiling as a result of decrease in inlet subcooling and increase in heat flux. The thermal oscillations are strongly coupled with pressure-drop oscillations. Nonlinear analysis of the time series of loop flow rate at various heater power and inlet subcooling have been carried out using statistical analysis, fast Fourier transform (FFT), time delay embedding for attractor reconstruction, autocorrelation, and correlation dimension. The analysis confirms that the oscillations are more chaotic at relatively low heater power and high inlet subcooling. The complexity of the oscillations strongly depends on boiling heat transfer regime. Our observations and analysis have been supported by other relevant experiments.

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“…Transient wall temperature measurements using microheater arrays [8][9][10][11][12][13][14], infrared cameras [15][16][17][18][19][20][21], and microsensor arrays [22][23][24][25][26][27][28][29] have been used to reveal the intricate physics that dictate bubble nucleation and departure. More recently, researchers have also made inroads in exploring transient dynamics in flow boiling [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporally resolved heat transfer measurements for flow boiling in microchannels

Rao

Peles

2015

International Journal of Heat and Mass Transfer

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a b s t r a c tSpatiotemporally resolved wall heat transfer measurements can provide valuable insight into the fundamental mechanisms affecting flow boiling in microchannels. Operating at the microscale, necessitates resolving changes in local and instantaneous heat transfer characteristics on the order of 100 lm and 1 kHz, respectively. Straightforward interpretation of transient temperature measurements is often challenging due to the conjugate conduction effects in the substrate, which can dampen the measured and inferred heat transfer quantities. These damping effects are described using a slip coefficient (S), which represents the fraction of the change in the local heat transfer that is registered by a sensor (negligible thermal mass) located on a given substrate. Using S, arguments are presented that the conduction patterns in the substrate are predominantly 1-D (i.e. into the substrate) at suitable spatiotemporal-scales. Building on these fundamental considerations, a numerical procedure is adopted to allow a time varying estimate of the local convective heat flux and heat transfer coefficient from transient temperature measurements. Examples of this framework are showcased with experimental results and discussions for interactions observed during flow boiling of HFE 7000 in a single microchannel (hydraulic diameter = 370 lm). At the relatively low mass flux of 200 kg/m 2 s reported in this work, liquid evaporation was found to dictate the local heat transfer trends. High rates of heat transfer were observed to accompany the growth of bubbles and evaporation of the liquid film under vapor slugs. Local dryout was routinely observed in the bubbly and slug flow regime and found to initially enhance heat transfer (i.e. at the creation and subsequent propagation of the three-phase contact line) and present near-zero heat transfer rates in the dried-out domain.

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Non-linear dynamical analyses of transient surface temperature fluctuations during subcooled pool boiling on a horizontal disk

Cited by 7 publications

References 35 publications

Numerical Investigation of the Effect of Chirality of Carbon Nanotube on the Interfacial Thermal Resistance

Numerical Investigation of the Effect of Chirality of Carbon Nanotube on the Interfacial Thermal Resistance

Nonlinear Analysis of Chaotic Time Series in a Natural Circulation Boiling Loop

Spatiotemporally resolved heat transfer measurements for flow boiling in microchannels

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