Based on a nonequilibrium heat transfer model in the living tissue obtained by performing volume average to the local instantaneous energy equations for blood and tissues, the dual-phase lag bioheat ...equations with blood or tissue temperature as sole unknown temperature are obtained by eliminating the tissue or blood temperature from the nonequilibrium model. The present dual-phase model successfully overcame the drawbacks of the existing dual-phase lag bioheat equation obtained by simply modifying the classical Pennes bioheat equation. Under the dual-phase model developed in this work, the phase lag times are expressed in terms of the properties of blood and tissue and the interphase convective heat transfer coefficient and blood perfusion rate. The phase lag times for heat flux and temperature gradient for the living tissue are estimated using the available properties from the literature. It is found that the phase lag times for heat flux and temperature gradient for the living tissue are very close to each other.
Pulsating (or oscillating) heat pipes (PHP or OHP) are new two-phase heat transfer devices that rely on the oscillatory flow of liquid slug and vapor plug in a long miniature tube bent into many ...turns. The unique feature of PHPs, compared with conventional heat pipes, is that there is no wick structure to return the condensate to the heating section; thus, there is no countercurrent flow between the liquid and vapor. Significant experimental and theoretical efforts have been made related to PHPs in the last decade. While experimental studies have focused on either visualizing the flow pattern in PHPs or characterizing the heat transfer capability of PHPs, theoretical examinations attempt to analytically and numerically model the fluid dynamics and/or heat transfer associated with the oscillating two-phase flow. The existing experimental and theoretical research, including important features and parameters, is summarized in tabular form. Progresses in flow visualization, heat transfer characteristics, and theoretical modeling are thoroughly reviewed. Finally, unresolved issues on the mechanism of PHP operation, modeling, and application are discussed.
Three dimensional transient thermal analysis of an air-cooled module that contains prismatic Li-ion cells next to a special kind of aluminum pin fin heat sink whose heights of pin fins increase ...linearly through the width of the channel in air flow direction was studied for thermal management of Lithium-ion battery pack. The effects of pin fins arrangements, discharge rates, inlet air flow velocities, and inlet air temperatures on the battery were investigated. The results showed that despite of heat sinks with uniform pin fin heights that increase the standard deviation of the temperature field, using this kind of pin fin heat sink compare to the heat sink without pin fins not only decreases the bulk temperature inside the battery, but also decreases the standard deviation of the temperature field inside the battery as well. Increasing the inlet air temperature leads to decreasing the standard deviation of the temperature field while increases the maximum temperature of the battery. Furthermore, increasing the inlet air velocity first increases the standard deviation of the temperature field till reaches to the maximum point, and after that decreases. Also, increasing the inlet air velocity leads to decrease in the maximum temperature of the battery.
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► Properties of water are evaluated with reverse non-equilibrium molecular dynamics. ► The five-site models predict thermal conductivity and viscosity more accurately. ► Three-site ...models have better performance in calculating specific heats.
The thermal conductivity and shear viscosity of water are evaluated for eight rigid water models with reverse non-equilibrium molecular dynamics (RNEMD). Specific heats under constant volume and constant pressure are calculated within NVT and NPT ensembles. The five-site models (TIP5P and TIP5P-Ew) can predict thermal conductivity more accurately than other rigid water models. It appears that TIP5P-Ew is the best potential to predict the trend of the thermal conductivity. Both five-site models can accurately predict shear viscosity values as well as its trends along with temperature. Three-site model (TIP3P) has better performance in calculating specific heats.
Au fil du développement de la crise sanitaire liée à la COVID-19, de plus en plus de pays ont adopté le dispositif de type « pass sanitaire » pour tenter d’endiguer la propagation du virus. Cet ...article prend le « pass sanitaire » français comme objet de recherche, en le comparant avec le QR code de santé chinois. Il affirme que, premièrement, la conception et l’usage du « pass sanitaire » favorise l’indépendance technologique et la gouvernance numérique en France. Deuxièmement, bien que l’usage technique du QR code soit différent, de StopCovid au « pass sanitaire », il construit tout de même une surveillance du grand public à travers un dispositif numérique en France comme en Chine. Enfin, cette QR code-isation sociale renforce une potentielle classification des individus reposant sur la collecte des données personnelles.
As the COVID-19 pandemic has spread, causing a health crisis in countries across the world, more and more countries have adopted a « health pass » as solution in an attempt to control the spread of the virus. This article considers France’s « health pass » and compares it with the Chinese health QR code. It is shown that, the design and use of the « health pass » promotes technical independence and digital gouvernance in France. Second, although the technical elements of China’s health QR code differ to France’s « health pass », it still builds a surveillance of the general public through a digital device in France as in China. Finally, the social QR code-ization is reinforcing a potential classification of individuals based on the collection of personal data.
Molecular dynamics simulation is carried out to study the rapid boiling of liquid water film heated by a hot copper plate in a confined space. 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. The results show that liquid water molecules close to the plate are instantly overheated and undergo a rapid phase transition. A non-vaporization molecular layer, with a constant density of 0.2 g/cm3, tightly attached to the surface of the plate is observed. Temperatures at three corresponding regions, which are vapor, liquid, and vapor from the top plate surface, are also computed and analyzed along with the piston-like motion of the bulk liquid film.
•Molecular dynamics simulation is carried out to study the rapid boiling of liquid water film.•A more physically-sound thermostat is applied to control the temperature of the metal plate.•The liquid water molecules near the plate are instantly overheated and undergo a rapid boiling.•A non-vaporization molecular layer tightly attached to the surface of the plate is observed.•The piston-like motion of the bulk liquid film are computed and analyzed.
•Temperature uniformity of a heated Li-ion battery has been analyzed.•Factors influence on temperature uniformity of a Li-ion battery have been analyzed.•Two heat methods have been compared.
At low ...temperatures, charge–discharge performances of lithium-ion batteries decline rapidly. Preheat is essential for an effective battery thermal management system. Temperature uniformities of lithium-ion battery cells heated by the self-heating lithium-ion battery structure (SHLB) method and the wide-line metal film (WLMF) method are studied by the transient three-dimensional heating finite element models. Under the same condition, the temperature of a lithium-ion battery cell heated by SHLB heating method is three times more uniform than that heated by the WLMF heating method. However, temperature uniformity of a lithium-ion battery cell heated by SHLB method still is poor. Effects of environment temperature, heating time, heating power, thickness of a lithium-ion battery cell and stand time after heating on temperature distribution of a lithium-ion battery cell heated have been analyzed. For the two heating methods, heating power, thickness of a lithium-ion battery cell and stand time after heating have remarkably influences on temperature distribution of a heated lithium-ion battery cell. For SHLB heating method, temperature uniformity of a heated lithium-ion battery cell is acceptable by decreasing heating power and thickness of a lithium-ion battery cell if there is no safety issue on the structure. Meanwhile, for WLMF heating method, temperature uniformity of a heated lithium-ion battery cell is also acceptable by decreasing heating power, thickness of a lithium-ion battery cell or increasing stand time after heating.
Laminar forced convection heat transfer of the Al2O3–water nanofluid in a pipe with a return bend is analyzed by using a finite element method. The results show that the average Nusselt number ...increases with increasing Reynolds number and Prandtl number, and the increment of specific heat in the nanofluid contributes to the heat transfer enhancement. The average Nusselt number in the return bend appears higher than that in the inlet and outlet pipes due to the secondary flows. However, the pressure drop in the pipe largely increases with the increment of nanoparticle volume concentration. The empirical correlations for the average Nusselt numbers are obtained as functions of the Dean number and the Prandtl number.
► Heat transfer of Al2O3–water nanofluid in pipe with return bend is analyzed by FEM. ► Nusselt number increases with Reynolds number and Prandtl number. ► Increment of specific heat contributes to the heat transfer enhancement. ► Nusselt number in return bend is higher than other parts due to secondary flows. ► Pressure drop in pipe largely increases with nanoparticle volume concentration.
The femtosecond laser pulse heating of silver film is investigated by performing quantum mechanics (QM), molecular dynamics (MD), and two-temperature model (TTM) integrated multiscale simulation. The ...laser excitation dependent electron thermophysical parameters (electron heat capacity, electron thermal conductivity, and effective electron–phonon coupling factor) are determined from ab initio QM calculation, and implemented into TTM description of electron thermal excitation, heat conduction, as well as electron–phonon coupled thermal energy transport. The kinetics of atomic motion is modeled by MD simulation. Energy evolution of excited electron subsystem is described by TTM in continuum. The MD and TTM are coupled by utilizing the effective electron–phonon coupling factor. Laser heating with varying laser fluences is systematically studied to determine the thresholds of homogeneous melting and ablation. The thermal ablation induced by rapid expansion of locally and excessively superheated silver is reported. This paper provides a basis for interpreting the phase-change process induced by laser heating, and facilitates the advancement of femtosecond laser pulse processing of material.
•Chaotic flow in a 2D closed loop pulsating heat pipe is investigated.•Volume of Fluid method was applied for two phase flow simulation.•Quantitative approaches were employed to investigate ...chaos.•Chaotic behavior was observed under specific operating conditions.
In the present study, investigation of chaotic flow in a two-dimensional closed-loop pulsating heat pipe has been carried out numerically. Constant temperature boundary conditions have been applied for the heating (evaporator) and the cooling (condenser) sections. The width of the tube was 3 mm and water was used as working fluid. Structured meshing configuration has been used and Volume of Fluid (VOF) method has been employed for two-phase flow simulation. The investigated temperature ranges for the evaporator and the condenser were 100–180 °C and 20–50 °C, respectively. The range of filling ratio was from 30 to 80%. Volume fraction of liquid and vapor in the pulsating heat pipe was investigated for different operating conditions. Time series analysis of the adiabatic wall temperature, correlation dimension, power spectrum density, Lyapunov exponent and autocorrelation function were used to investigate chaos in the pulsating heat pipe. Chaotic behavior was observed under several operating conditions. It was found that the time series has complicated, irregular and aperiodic behavior. Absence of dominating peaks in the power spectrum density curves denoted the existence of chaos in the pulsating heat pipe. It was observed that by increasing the filling ratio and evaporator temperature, the correlation dimension increases. Positive values of Lyapunov exponent were obtained for temperatures between 140 and 180 °C at filling ratio of 30%. At filling ratio of 75%, all of the Lyapunov exponents were positive for the temperature interval between 120 and 180 °C.
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