Relevant bibliographies by topics / Temperature jump length

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Temperature jump length'

Author: Grafiati
Published: 4 June 2021
Last updated: 9 February 2022

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Journal articles on the topic "Temperature jump length"

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Davis, J. S., and M. E. Rodgers. "Force generation and temperature-jump and length-jump tension transients in muscle fibers." Biophysical Journal 68, no. 5 (May 1995): 2032–40. http://dx.doi.org/10.1016/s0006-3495(95)80380-2.

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Reiser, P. J., and B. D. Lindley. "Activation in frog atrial trabeculae: dependence on temperature and length." American Journal of Physiology-Heart and Circulatory Physiology 258, no. 4 (April 1, 1990): H1087—H1096. http://dx.doi.org/10.1152/ajpheart.1990.258.4.h1087.

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Isolated frog atrial trabeculae were activated using the method of Na+ withdrawal to induce contractures of relatively steady tension. External Na+ concentration [( Na+]o) during contractures was varied between 0.25 and 45 mM. Isometric contracture tension was measured at cold (4 degrees C) and warm (20 degrees C) temperatures. In addition, rapid temperature jumps (complete in approximately 400 ms) were imposed during cold contractures, resulting in tension transients that consisted of an initial increase in tension followed by a decrease, the latter phase being greater at small and moderate reductions in [Na+]o. Peak contracture tension varied with relative muscle length. The trabeculae became more sensitive with stretch to Na+ withdrawal at 20 degrees C and generated relatively greater tensions at a given [Na+]o. The initial tension increase after a temperature jump was directly proportional to the peak contracture tension immediately preceding the increase in temperature and was therefore interpreted as reflecting an effect of the higher temperature on the attached force-generating cross bridges. The effects of cold and warm steady temperatures and temperature jumps during isometric twitches were also studied. Peak twitch tension varied inversely with temperature (stimulus frequency = 0.2 Hz). In contrast, temperature jumps imposed during the rising phase of twitches at a steady cold temperature (approximately 4 degrees C) resulted in a large initial increase in tension followed by relaxation at a rate that was characteristic of the elevated temperature. The results suggest that, at the warmer temperature (approximately 20 degrees C), activation (i.e., number of attached cross bridges) of the myocardium is significantly less than maximal during the twitch response. The dependence of the tension vs. [Na+]o curves and the tension transients resulting from the temperature jumps on relative muscle length provide evidence for a length dependency of contractile activation in intact atrial trabeculae under conditions of steady-state tension development.
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Greetham, Gregory M., Ian P. Clark, Benjamin Young, Robby Fritsch, Lucy Minnes, Neil T. Hunt, and Mike Towrie. "Time-Resolved Temperature-Jump Infrared Spectroscopy at a High Repetition Rate." Applied Spectroscopy 74, no. 6 (March 30, 2020): 720–27. http://dx.doi.org/10.1177/0003702820913636.

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Time-resolved temperature-jump infrared absorption spectroscopy at a 0.5 to 1 kHz repetition rate is presented. A 1 kHz neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping an optical parametric oscillator provided >70 µJ, 3.75 µm pump pulses, which delivered a temperature jump via excitation of the O–D stretch of a D2O solution. A 10 kHz train of mid-infrared probe pulses was used to monitor spectral changes following the temperature jump. Calibration with trifluoroacetic acid solution showed that a temperature jump of 10 K lasting for tens of microseconds was achieved, sufficient to observe fast processes in functionally relevant biomolecular mechanisms. Modeling of heating profiles across ≤10 µm path length cells and subsequent cooling dynamics are used to describe the initial <100 ns cooling at the window surface and subsequent, >10 µs cooling dynamics of the bulk solution.
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Abdollahzadeh, Jamalabadia, Hyun Park, and Chang Lee. "Thermal radiation effects on the onset of unsteadiness of fluid flow in vertical microchannel filled with highly absorbing medium." Thermal Science 20, no. 5 (2016): 1585–96. http://dx.doi.org/10.2298/tsci140418124a.

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This study presents the effect of thermal radiation on the steady flow in a vertical micro channel filled with highly absorbing medium. The governing equations (mass, momentum and energy equation with Rosseland approximation and slip boundary condition) are solved analytically. The effects of thermal radiation parameter, the temperature parameter, Reynolds number, Grashof number, velocity slip length, and temperature jump on the velocity and temperature profiles, Nusselt number, and skin friction coefficient are investigated. Results show that the skin friction and the Nusselt number are increased with increase in Grashof number, velocity slip, and pressure gradient while temperature jump and Reynolds number have an adverse effect on them. Furthermore, a criterion for the flow unsteadiness based on the temperature parameter, thermal radiation parameter, and the temperature jump is presented.
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Menssen, Ryan J., and Andrei Tokmakoff. "Length-Dependent Melting Kinetics of Short DNA Oligonucleotides Using Temperature-Jump IR Spectroscopy." Journal of Physical Chemistry B 123, no. 4 (January 7, 2019): 756–67. http://dx.doi.org/10.1021/acs.jpcb.8b09487.

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TAWFIK, A., M. Z. SAID, and O. M. HEMEDA. "THE EFFECT OF AMOUNT TANTALUM DOPING ON THE PROPERTIES OF MgCuZn FERRITES." International Journal of Modern Physics B 25, no. 19 (July 30, 2011): 2583–91. http://dx.doi.org/10.1142/s0217979211100722.

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The systems MgCuZn Fe 2 O 4 doped (0–0.6 wt% Ta) are prepared by the general ceramic method using the sintering temperature at 1200°C. The variations of the sintered density, lattice parameter, jump length of electrons, and initial permeability were studied. A maximum density was obtained at 1200°C during the preparation process. The electrical resistivity decreases with increasing tantalum ( Ta ) content upto 0.1 wt% and then increases for higher concentrations. The initial permeability and the change carries mobility increase upto 0.1 Ta and then decreases. The jump length decreases with enhancing Ta ions because the substitution of Ta ion with small size instead of Fe 3+ at the A sites increase the concentration of iron ions at the B sites. The increase of the iron content causes the decrease of the jump length of electrons between Fe 3+ and Fe 2+. These improvements of the magnetic properties give some light about the importance of these compositions to be used in technology.
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Beikircher, T., N. Benz, and W. Spirkl. "A Modified Temperature-Jump Method for the Transition and Low-Pressure Regime." Journal of Heat Transfer 120, no. 4 (November 1, 1998): 965–70. http://dx.doi.org/10.1115/1.2825916.

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For modeling the gas heat conduction at arbitrary Knudsen numbers and for a broad range of geometries, we propose a modified temperature-jump method. Within the modified approach, we make a distinction between an inner convex surface and an outer concave surface enclosing the inner surface. For problems, where only a single geometric length is involved, i.e., for large parallel plates, long concentric cylinders and concentric spheres, the new method coincides at any Knudsen number with the interpolation formula according to Sherman, and therefore also with the known solutions of the Boltzmann equation obtained by the four momenta method. For the general case, where more than one geometric length is involved, the modified temperature method is trivially correct in the limit of high pressure and identical with Knudsen’s formula in the limit of low pressure. For intermediate pressure, where there is a lack of known solutions of the Boltzmann equation for general geometries, we present experimental data for the special two-dimensional plate-in-tube configuration and compare it with results of the modified temperature-jump method stating good agreement. The results match slightly better compared to the standard temperature method and significantly better compared to the interpolation formula according to Sherman. For arbitrary geometries and Knudsen numbers, the modified temperature method shows no principal restrictions and may be a simple approximative alternative to the solution of the Boltzmann equation, which is rather cumbersome.
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Menssen, Ryan J., and Andrei Tokmakoff. "Correction to “Length-Dependent Melting Kinetics of Short DNA Oligonucleotides Using Temperature-Jump IR Spectroscopy”." Journal of Physical Chemistry B 123, no. 10 (February 28, 2019): 2467. http://dx.doi.org/10.1021/acs.jpcb.9b01693.

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Cowley, Adam, Daniel Maynes, and Julie Crockett. "Effective temperature jump length and influence of axial conduction for thermal transport in superhydrophobic channels." International Journal of Heat and Mass Transfer 79 (December 2014): 573–83. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.08.033.

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Lutz, G. J., and L. C. Rome. "Muscle function during jumping in frogs. I. Sarcomere length change, EMG pattern, and jumping performance." American Journal of Physiology-Cell Physiology 271, no. 2 (August 1, 1996): C563—C570. http://dx.doi.org/10.1152/ajpcell.1996.271.2.c563.

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We determined the influence of temperature on muscle function during jumping to better understand how the frog muscular system is designed to generate a high level of mechanical power. Maximal jumping performance and the in vivo operating conditions of the semimembranosus muscle (SM), a hip extensor, were measured and related to the mechanical properties of the isolated SM in the accompanying paper [Muscle function during jumping in frogs. II. Mechanical properties of muscle: implication for system design. Am. J. Physiol. 271 (Cell Physiol. 40): C571-C578, 1996]. Reducing temperature from 25 to 15 degrees C caused a 1.75-fold decline in peak mechanical power generation and a proportional decline in aerial jump distance. The hip and knee joint excursions were nearly the same at both temperatures. Accordingly, sarcomeres shortened over the same range (2.4 to 1.9 microns) at both temperatures, corresponding to myofilament overlap at least 90% of maximal. At the low temperature, however, movements were made more slowly. Angular velocities were 1.2- to 1.4-fold lower, and ground contact time was increased by 1.33-fold at 15 degrees C. Average shortening velocity of the SM was only 1.2-fold lower at 15 degrees C than at 25 degrees C. The low Q10 of velocity is in agreement with that predicted for muscles shortening against an inertial load.
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Dissertations / Theses on the topic "Temperature jump length"

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Cowley, Adam M. "Hydrodynamic and Thermal Effects of Sub-critical Heating on Superhydrophobic Surfaces and Microchannels." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6572.

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This dissertation focuses on the effects of heating on superhydrophobic (SHPo) surfaces. The work is divided into two main categories: heat transfer without mass transfer and heat transfer in conjunction with mass transfer. Numerical methods are used to explore the prior while experimental methods are utilized for the latter. The numerical work explores convective heat transfer in SHPo parallel plate microchannels and is separated into two stand-alone chapters that have been published archivally. The first considers surfaces with a rib/cavity structure and the second considers surfaces patterned with a square lattice of square posts. Laminar, fully developed, steady flow with constant fluid properties is considered where the tops of the ribs and posts are maintained at a constant heat flux boundary condition and the gas/liquid interfaces are assumed to be adiabatic. For both surface configurations the overall convective heat transfer is reduced. Results are presented in the form of average Nusselt number as well as apparent temperature jump length (thermal slip length). The heat transfer reduction is magnified by increasing cavity fraction, decreasing Peclet number, and decreasing channel size relative to the micro-structure spacing. Axial fluid conduction is found to be substantial at high Peclet numbers where it is classically neglected. The parameter regimes where prior analytical works found in the literature are valid are delineated. The experimental work is divided into two stand-alone chapters with one considering channel flow and the other a pool scenario. The channel work considers high aspect ratio microchannels with one heated SHPo wall. If water saturated with dissolved air is used, the air-filled cavities of SHPo surfaces act as nucleation sites for mass transfer. As the water heats it becomes supersaturated and air can effervesce onto the SHPo surface forming bubbles that align to the underlying micro-structure if the cavities are comprised of closed cells. The large bubbles increase drag in the channel and reduce heat transfer. Once the bubbles grow large enough, they are expelled from the channel and the nucleation and growth cycle begins again. The pool work considers submerged, heated SHPo surfaces such that the nucleation behavior can be explored in the absence of forced fluid flow. The surface is maintained at a constant temperature and a range of temperatures (40 - 90 °C) are explored. Similar nucleation behavior to that of the microchannels is observed, however, the bubbles are not expelled. Natural convection coefficients are computed. The surfaces with the greatest amount of nucleation show a significant reduction in convection coefficient, relative to a smooth hydrophilic surface, due to the insulating bubble layer.
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Beny, Cedric. "Monte Carlo Study of the Magnetic Flux Lattice Fluctuations in High-Tc Superconductors." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1222.

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By allowing to measure the magnetic field distribution inside a material, muon spin rotation experiments have the potential to provide valuable information about microscopic properties of high-temperature superconductors. Nevertheless, information about the intrinsic superconducting properties of the material is masked by random thermal and static fluctuations of the magnetic field which penetrates the material in the form of vortices of quantized magnetic flux. A good understanding of the fluctuations of those vortices is needed for the correct determination of intrinsic properties, notably the coherence length ξ, and the field penetration depth λ. We develop a simulation based on the Metropolis algorithm in order to understand the effect, on the magnetic field distribution, of disorder- and thermally-induced fluctuations of the vortex lattice inside a layered superconductor.

Our model correctly predicts the melting temperatures of the YBa2Cu3O6. 95 (YBCO) superconductor but largely underestimates the observed entropy jump. Also we failed to simulate the high field disordered phase, possibly because of a finite size limitation. In addition, we found our model unable to describe the first-order transition observed in the highly anisotropic Bi2Sr2CaCu2O8+y.

Our model predicts that for YBCO, the effect of thermal fluctuations on the field distribution is indistinguishable from a change in ξ. It also confirms the usual assumption that the effect of static fluctuations at low temperature can be efficiently modeled by convolution of the field distribution with a Gaussian function. However the extraction of ξ at low fields requires a very high resolution of the field distribution because of the low vortex density.
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Book chapters on the topic "Temperature jump length"

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Davis, Julien S., and William F. Harrington. "Kinetic and Physical Characterization of Force Generation in Muscle: A Laser Temperature-Jump and Length-Jump Study on Activated and Contracting Rigor Fibers." In Mechanism of Myofilament Sliding in Muscle Contraction, 513–26. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2872-2_47.

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Conference papers on the topic "Temperature jump length"

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Xiao, Xiu, Chunji Yan, and Yulong Ji. "Mechanisms of Heat and Mass Transfer for Thin-Film Evaporation With Velocity Slip and Temperature Jump." In ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/mnhmt2019-4213.

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Abstract Velocity slip and temperature jump at the solid-liquid interface are important phenomena in microchannel heat transfer. A comprehensive mathematical model considering both velocity slip condition and temperature jump at the solid-liquid interface is developed to understand the mechanisms of heat and mass transfer during thin-film evaporation in this paper. The model structure is established based on the lubrication theory, Clausius-Clapeyron equation and Young-Laplace equation. To better formulate the film evaporation process, three dimensionless parameters representing the effects of slip length coefficient, temperature jump and wall superheat degree respectively, are introduced in the present model. The analytical solution provides insight of film thickness and heat transfer characteristics for the evaporating thin film. It shows that as the slip length and temperature jump coefficient decrease, the length of evaporating thin film region is shortened and the location of maximum heat flux moves closer to the initial evaporating point. The effect of slip condition on heat flux is small, but the increase of temperature jump can reduce the peak heat flux significantly. Furthermore, the analysis on the three thermal resistances which are caused by temperature jump, conduction through liquid film and evaporation on liquid-vapor interface result in a better understanding for effective heat transfer during thin-film evaporation.
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Cowley, A., D. Maynes, J. Crockett, and B. W. Webb. "Effective Temperature Jump Length and Influence of Axial Conduction for Thermal Transport Through Channels With Superhydrophobic Walls." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63858.

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This paper presents a numerical investigation of thermal transport in a parallel-plate channel comprised of superhydrophobic walls. The scenario analyzed in this paper is laminar, fully developed, steady flow with constant properties. The superhydrophobic walls considered here have alternating micro-ribs and cavities aligned perpendicular to the flow direction. The cavities are assumed to be non-wetting and contain air. The thermal transport through the ribs is considered to have a constant heat flux while the thermal transport through the air/fluid interface over the cavity is considered to be negligible. Numerical results have been obtained over a range a Peclet numbers, cavity fractions, and relative rib/cavity widths. Results were also obtained where axial conduction was neglected and these results are compared to previous analytical work with excellent agreement. When the influence of axial conduction is not neglected, however, the results for local wall temperatures and Nusselt numbers show departure from the previous analytical results. The departure is more pronounced at low Peclet numbers and at large relative channel diameters. This paper provides a comparison over a wide range of parameters that characterize the overall influence of axial conduction. In general, the results show that the relative size of the cavity compared to the total rib/cavity module width (cavity fraction) and the flow Peclet number have a significant impact on the total thermal transport properties. Also, the rib/cavity module width compared to the hydraulic diameter affects the overall thermal transport behavior. Lastly, this paper explores the concept of a temperature jump length which is analogous to the hydrodynamic slip length. The ratio of temperature jump length to hydrodynamic slip length is presented in terms of cavity fraction, Peclet number, and relative size of the rib cavity module.
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Mishra, Vivek, Aydin Nabovati, Daniel P. Sellan, and Cristina H. Amon. "A Transient Modified Fourier-Based Approach for Thermal Transport Modelling in Sub-Continuum Regime." In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58347.

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The presence of sub-continuum effects in nano-scale systems, including size and boundary effects, causes the continuum-level relations (e.g., Fourier heat equation) to break down at such scales. The thermal sub-continuum effects are manifested as a temperature jump at the system boundaries and a reduced heat flux across the system. In this work, we reproduce transient and steady-state results of Gray lattice Boltzmann simulations by developing a one-dimensional, transient, modified Fourier-based approach. The proposed methodology introduces the following two modifications into the Fourier heat equation: (i) an increase in the sample length by a fixed length at the two ends, in order to capture the steady-state temperature jumps at the system boundaries, and (ii) a size-dependent effective thermal diffusivity, to recover the transient temperature profiles and heat flux values. The predicted temperature and heat flux values from the proposed modified Fourier approach are in good agreement with those predicted by the Gray lattice Boltzmann simulations.
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Barisik, Murat, Ziyuan Shi, and Ali Beskok. "Heat Conduction and Interface Thermal Resistance in Liquid Argon Filled Silver and Graphite Nanochannels." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75231.

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Heat conduction between two parallel solid walls separated by liquid argon is investigated using three-dimensional molecular dynamics (MD) simulations. Liquid argon molecules confined in silver and graphite nano-channels are examined separately. Heat flux and temperature distribution within the nano-channels are calculated by maintaining a fixed temperature difference between the two solid surfaces. Temperature profiles are linear sufficiently away from the walls, and heat transfer in liquid argon obeys the Fourier law. Temperature jump due to the interface thermal resistance (i.e., Kapitza length) is characterized as a function of the wall temperature. MD results enabled development of a phenomenological model for the Kapitza length, which is utilized as the coefficient of a Navier-type temperature jump boundary condition using continuum heat conduction equation. Analytical solution of this model results in successful predictions of temperature distribution in liquid-argon confined in silver and graphite nano-channels as thin as 7 nm and 3.57 nm, respectively.
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Kim, BoHung, Ali Beskok, and Tahir Cagin. "Molecular Dynamics Simulations of Thermal Interactions in Nanoscale Liquid Channels." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67448.

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Molecular Dynamics (MD) simulations of nano-scale flows typically utilize fixed lattice crystal interactions between the fluid and stationary wall molecules. This approach cannot properly model thermal exchange at the wall-fluid interface. Therefore, we use an interactive thermal wall model that can properly simulate the flow and heat transfer in nano-scale channels. Using the interactive thermal wall, Fourier law of heat conduction is verified for the 3.24 nm channel, while the thermal conductivity obtained from Fourier law is verified using the predictions of Green-Kubo theory. Moreover, temperature jumps at the liquid/solid interface, corresponding to the well known Kapitza resistance, are observed. Using systematic studies thermal resistance length at the interface is characterized as a function of the surface wettability, thermal oscillation frequency, wall temperature and thermal gradient. An empirical model for the thermal resistance length, which could be used as the jump-coefficient of a Navier boundary condition, is developed.
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Morshed, A. K. M. M., T. C. Paul, and Jamil A. Khan. "Nanostructures Length Effect on Phase Transition Phenomena of Ultra-Thin Liquid Film From a Nanostructured Surface: A Molecular Dynamics Study." In ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2011. http://dx.doi.org/10.1115/icnmm2011-58099.

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A molecular dynamics simulation has been employed to investigate the boiling phenomena of few molecular-layer thin liquid-film adsorbed on a nanoscale roughened solid surface. The molecular system comprises of three phase system: solid platinum wall, liquid argon and argon vapor. A few layer of liquid argon has been placed on the nanoposts decorated solid surface where nanoposts ensemble surface roughness. Nanoposts height has been varied keeping liquid film thickness constant to capture three scenario: (i) Liquid-film thickness is higher than the height of the nanoposts (ii) Liquid-film and nanoposts are of same height (iii) Liquid-film thickness is less than the height of the nanoposts. Rest of the simulation box space has been filled with argon vapor. The simulation starts from the equilibrium three phase system and then suddenly the wall is heated to a higher temperature which resembles an ultra fast laser heating. Two different jump temperatures has been selected: one is a few degrees above the boiling point to initiate normal evaporation and the other one is far above the critical point temperature to initiate explosive boiling. Simulation results indicate nanostructures play significant role in both the cases. Argon responds very quickly in the nanoposts decorated surface and evaporation rate increases with the nanoposts height. Different boiling behavior has been observed for the nanoposts decorated surface.
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Hong, Chungpyo, Yutaka Asako, and Koichi Suzuki. "Convection Heat Transfer in Concentric Micro Annular Tubes With Constant Wall Temperature." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88171.

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Heat transfer characteristics of gaseous flows in concentric micro annular tubes with constant wall temperature whose temperature is lower or higher than the inlet temperature were numerically investigated. The slip velocity, temperature jump and shear stress work were considered on the slip boundary. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for two thermal cases. This is, the wall temperature was constant at the outer wall and inner wall was adiabatic (Case i) and the wall temperature was constant at the inner wall and the outer wall was adiabatic (Case ii). The stagnation temperature was fixed at 300 K and the computations were done for the wall temperature which ranges from 250 K to 350 K. The outer tube radius ranged from 20 to 150 μm with the radius ratio 0.02, 0.05, 0.1, 0.25 and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 0.8. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro annular tubes were obtained. The bulk temperature and the total temperature are compared with those of both cooled and heated cases and also compared with those of the simultaneously developing incompressible flow obtained by SIMPLE algorithm. The results show that the compressible slip flow static bulk temperature along the length is different from that of incompressible flow. Therefore heat transfer characteristics of the gaseous flow are different from those of the liquid flow and also have different trends whether the wall temperature is lower or higher than the inlet temperature. A correlation for the prediction of the heat transfer rate of gas slip flow in concentric micro annular tubes is proposed.
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Niazmand, Hamid, and Behnam Rahimi. "High Order Slip and Thermal Creep Effects in Micro Channel Natural Convection." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30688.

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Developing natural convection gaseous flows in an open-ended parallel plate vertical microchannel with isothermal wall conditions are numerically investigated to analyze the rarefaction effects on heat transfer and flow characteristics in slip flow regime. The Navier-Stokes and energy equations are solve by a control volume technique subject to higher-order temperature jump and velocity slip conditions including thermal creep effects. The flow and thermal fields in the entrance and fully developed regions along with the axial variations of velocity slip, temperature jump, and heat transfer rates are examined in detail. It is found that rarefaction effects significantly influence the flow and thermal fields such that mass flow and heat transfer rates are increased considerably as compared to the continuum regime. Furthermore, thermal creep contribution to the velocity slip is found to be dominant close to the channel inlet and vanishes in the fully developed region, while velocity slip approaches a finite value there. Both Mass flow rate and thermal entrance length increase with increasing Knudsen number in slip flow regime.
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Maynes, D., J. Vanderhoff, and G. Rosengarten. "Fully-Developed Thermal Transport in Microchannels With Streamwise Grooved Superhydrophobic Walls at Constant Heat Flux." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89441.

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This paper presents an analytical investigation of constant property, steady, fully-developed, laminar thermal transport in a parallel-plate channel comprised of metal superhydrophobic walls. The superhydrophobic walls considered here exhibit micro-ribs and cavities aligned in the streamwise direction. The cavities are assumed to be non-wetting and contain air, such that the Cassie-Baxter state is the interfacial state considered. The scenario considered is that of constant heat flux through the rib surfaces with negligible thermal transport through the air cavity interface. Closed form solutions for the local Nusselt number and local wall temperature are presented and are in the form of infinite series expansions. The analysis show the relative size of the cavity regions compared to the total rib and cavity width (cavity fraction) exercises significant influence on the aggregate thermal transport behavior. Further, the relative size of the rib and cavity module width compared to the channel hydraulic diameter (relative module width) also influences the Nusselt number. The spatially varying Nusselt number and wall temperature are presented as a function of the cavity fraction and the relative module width over the ranges 0–0.99 and 0.01–1.0, respectively. From these results the rib/cavity module averaged Nusselt number was determined as a function of the governing parameters. The results reveal that increases in either the cavity fraction or relative module width lead to decreases in the average Nusselt number and results are presented over a wide range of conditions from which the average Nusselt number can be determined for heat transfer analysis. Further, analogous to the hydrodynamic slip length, a temperature jump length describing the apparent temperature jump at the wall is determined in terms of the cavity fraction. Remarkably, it is nearly identical to the hydrodynamic slip length for the scenario considered here and allows straightforward determination of the average Nusselt number for any cavity fraction and relative rib/cavity module width.
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Manzo, Ernesto T., Rachel Green, Mustafa Hadj Nacer, and Miles Greiner. "Prediction of Cladding Temperatures Within a Used Nuclear Fuel Transfer Cask Filled With Rarefied Helium." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29048.

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During the used nuclear fuel vacuum drying process, helium is evacuated to pressures as low as 70 Pa, to promote water vaporization and removal. At these low pressures the gas is rarefied to the extent that there is a temperature jump thermal resistance between the surface and gas. This occurs when the mean free path of a molecule becomes a comparable to the characteristic length of a system. In order to correctly apply this jump model to a nuclear transfer cask, a two dimensional model of parallel plates and concentric cylinders were created using ANSYS/Fluent package. Heat generation was plotted against a variety of relevant pressures. The results in these simple geometries are compared to kinetic model calculations, performed by other investigators, to determine the appropriate collision diameters to use in rarefied helium gas simulations within complex geometries. A two dimensional mesh of a transfer cask containing 24 pressurized water reactor used fuel assemblies is then constructed, and the rarefied gas model was implemented in the helium-filled regions between the fuel and basket support structures. Steady state simulations with a fuel heat generation rate of 710 W/m/assemble shows that the cladding is measurably hotter when the helium gas pressure is reduced from atmospheric conditions ∼105 Pa to 500 Pa. The heat generation rate that brings the peak cladding temperature to a hydride dissolution temperature of 400°C is as much as 10% lower when the gas is at 500 Pa than under atmospheric conditions.
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