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Shock/shock interactions (SSIs) often lead to high thermal loads. To understand the influences of thermochemical non-equilibrium effects on the Type III SSI, four gas models based on the assumption of thermal perfect gas (TPG), thermal equilibrium chemical non-equilibrium gas (TECNG), thermal non-equilibrium chemical frozen gas (TNCFG), and thermochemical non-equilibrium gas (TCNEG) are employed to simulate the Type III SSI at Mach 10. The intersection of incident shock and bow shock is determined by dimensionless intercept of 0.05 and 0.1. It is found that the chemical non-equilibrium effects significantly lift up the impingement position of shear layer by reducing the standoff distance of bow shock. As a result, the peaks of wall pressure and heat flux calculated by TECNG and TCNEG model are higher than TPG and TNCFG model, respectively. Type IIIa SSI occur in the flows calculated by the TECNG and TCNEG model for the case with a dimensionless intercept of 0.1. The peaks of wall pressure and heat flux calculated by TECNG model are both over four times higher than those of TPG model. The thermal non-equilibrium effects slightly increase the standoff distance of bow shock and lower the impingement position of shear layer. In addition, the thermal non-equilibrium reduces the angle to the horizontal direction of shear layer by increasing the specific heat ratio. • Type III shock/shock interaction at Mach 10 are simulated by four gas models. • The influences of non-equilibrium effects on flow fields are analyzed. • The chemical non-equilibrium effects significantly increase the peak values of heat flux and pressure. • The mechanisms of non-equilibrium effects on peak heat flux and pressure are revealed. [ABSTRACT FROM AUTHOR]

The porous ribs and solid ribs paved with porous layer (combining ribs for short) on sidewalls are set respectively in upper and lower channels in double-layered microchannel heat sink (MCHS) with microencapsulated phase change material (MPCM) slurry as coolant to obtain better thermal performance. In the cases, more heat transfer occurs between coolant and solid ribs with MPCM slurry as coolant due to phase change in microencapsulate, and larger specific area in porous layer. The local thermal equilibrium is considered to be in porous layer, and the Forchheimer-Brinkman-Darcy relations were used to describe the flow inside porous ribs. The effects of porous layer, its thickness in combining ribs, channel-to-pitch width ratio and channel aspect ratio on heat transfer and hydraulic properties in channel with MPCM slurry as coolant are investigated. Besides, the heat flux from heating surface released through the upper channel or lower channel to the outside can be allocated with the channel-to-pitch width ratio, width ratio of porous layer to pitch in the lower channel, and channel aspect ratio in double-layered microchannel. The parameter of figure of merit (FOM) is defined to evaluate thermo-hydraulic performance. Compared to the case with copper solid ribs in lower and upper channels as benchmark (i.e. FOM = 1), the 14% and 124.56% higher FOM value occur in the cases respectively of solid and porous ribs, and combining and porous ribs in lower and upper channels, as well as the 18.93% and 65.96% decreases respectively in thermal resistance and pumping power in case of MPCM slurry as coolant with combining and porous ribs in lower and upper channels. The appropriate width ratio of porous layer to pitch and porosity in porous layer will benefit thermal behavior. [ABSTRACT FROM AUTHOR]

Turbulent mixing effect is crucial for coolant subchannels in a nuclear reactor, as it directly influences flow distribution and cooling capacity. The enthalpy in the hottest channel is reduced in this way, thus improving the location of critical heat flux (CHF) to some extent. In order to predict CHF accurately, the inter-channel mixing model is incorporated into the subchannel analysis code to simulate thermal-hydraulic phenomena during a reactor operation. In this paper, a novel inter-channel mixing model has been developed through extensive investigation of experimental research. In addition, the power-law profile is considered for predicting the void distribution resulting from the void drift effect. Finally, the developed mixing model is embedded in a subchannel analysis code, and pressurized water reactor sub-channel and bundle tests (PSBT) data are selected as a benchmark for the model validation. The simulation results show that the current mixing model can accurately predict void fraction and thermal equilibrium quality at specific axial locations with absolute errors of 0.1 and 0.04, respectively. • A novel inter-channel mixing model that combines turbulent mixing and void drift effect has been proposed. • The influence of channel geometry has been taken into account in the current model. • The power-law method was used for characterizing void distribution resulting from void drift effect. • Current model accurately captures the axial development of parameters in different subchannel types. [ABSTRACT FROM AUTHOR]

• We established a finite element model of HTHP diamond synthesis cavity stacked with sheet alloy catalyst and graphite. • The distribution of temperature fields and heat fluxes inside the cavity were analyzed In different power distribution. • The growth wasteland was explored through simulation analysis. In this study , the thermodynamics and heat conduction of the diamond synthesis cavity of flake catalyst were theoretically analyzed and mathematically deduced to discuss the temperature field and the distribution of pyrophyllite synthesis cavity in flake catalyst-graphite's high-pressure and high-temperature (HTHP) synthesis. The thermal flux and temperature distribution of the pyrophyllite synthesis cavity and the temperature field of the flake catalyst-graphite synthesis rod were simulated and calculated. The calculations revealed that the synthetic rod's temperature rapidly increased in the initial 100 s of heating; When the heating time increased from 100 s to 150 s, the heating rate of the synthetic rod started to slow down. The temperature of the synthetic rod was stable after 170 s of heating, and the whole synthetic rod system reached the thermal equilibrium state; the temperature field of the synthetic rod was also stable. In a steady state, the maximum radial temperature gradient of the sheet catalyst graphite synthetic rod is 0.54 °C/mm, and the axial temperature gradient is about 2.93 °C/mm. The axial temperature gradient inside the synthetic rod was significantly higher than the radial temperature gradient. Further calculations showed that the heat flux of the pyrophyllite synthetic block on the inner wall of the pyrophyllite synthetic cavity was 2734 W in the heating direction, which was greater than that in the non-heating direction around 1312 W. The heat flux of the conductive steel cap in the heating direction was 2436 W, accounting for 60.1% of the total heat flux; This is the main reason for the large axial temperature gradient of the lamellar catalyst-graphite synthesis rod in the pyrophyllite cavity. A comparison of the temperature field of the cavity under different powers revealed that the temperature inside the cavity produces excessive diamond growth wasteland when the power is too high or too low. [ABSTRACT FROM AUTHOR]

In this study a 2D two-temperature chemical non-equilibrium model is established to investigate the flow characteristics and chemical reactions processes around hypersonic inflatable reentry vehicle at different flight altitudes and reentry velocities. This chemical kinetic model is based on the Gupta model and modified by comparing the species mole fractions at thermal equilibrium condition with the results obtained by Saha equation. In order to validate the model, the calculations are performed for a blunt cone ELECTRE and a cylinder, the predicted heat flux and pressure are compared with experimentally measured data and the maximum differences on heat flux and wall pressure are less than 20% and 5%, respectively. Then the flow characteristics behind the shock wave and wall heat flux are discussed in detail for Titans vehicle. It is found that the pressure declines with the increase of altitude and reentry velocity, this variation trend is opposite to the wall heat flux, whose maximum value increases from 58 kw/m2 to 107 kw/m2 with the rise of flight altitude from 79 to 88 km due to the large temperature and component gradients. This indicates that the aerodynamic force and heat flux should be taken into account simultaneously for the design of inflatable reentry vehicle. By analyzing the chemical reactions processes behind the strong shock wave, it is seen that not only the dissociation reactions of N 2 and O 2 molecules play an important role, but also the neutral species exchange reactions contribute to the density change of species. The dominant ionization reactions are N+O→NO++e and NO+M → 4 NO++e+M 4 , while the ionization processes are weak, and the maximum ionization degree is smaller than 1%. The analysis of dominant chemical reactions can provide a reference for the numerical modeling study of hypersonic reentry vehicle. [ABSTRACT FROM AUTHOR]

The presence of diamonds of Archaean age within the cratonic lithosphere is surprising because their formation implies a cool early mantle lithosphere despite the early Earth's hotter state. There remains a widely (albeit not exclusively) held concept that the prevailing geothermal gradient within Archaean cratons was not much different from today. This 'Archaean paradox' is supported by pressure and/or temperature (PT) estimates of potentially ancient diamond inclusion (DI) falling close to modern cratonic geotherms. Solutions to the paradox include more effective Archaean heat loss mechanisms (e.g. heat pipes), deeper lithospheric mantle roots or the early lithosphere forming in a disequilibrium state. Here we demonstrate the effects of a thermally evolving Earth on equilibrium geotherms within the Kaapvaal craton of South Africa. We modelled geotherms from the present-day conditions backward in time to 3.0 Ga at thermal equilibrium in the lithosphere by adjusting three dominant variables: (i) time-corrected crustal heat production; (ii) a secularly cooling mantle potential temperature (T p) in the underlying convecting mantle; and, for illustrative purposes, (iii) variable depth of the lithosphere-asthenosphere boundary (LAB) or variable heat flow at the LAB. Computed model geotherms were compared to DI PT data from the Kaapvaal craton, as well as PT conditions recorded in mantle xenoliths of variable age. It is demonstrated that equilibrium geotherms in the lithosphere cannot be reconciled with PT conditions recorded in Kaapvaal craton DI nor with those recorded in Proterozoic xenoliths if either the lithosphere has remained of constant thickness or held a constant basal heat flux since 3.0 Ga. Rather, provided that PT conditions recorded by DI from the Kaapvaal craton reflect equilibration along fossil ancient equilibrium geotherms, it is required that the early lithosphere was substantially thicker than what is preserved today. The inferred former thickness of Kaapvaal craton could have reached up to ∼350 km if the prevailing mantle T p at the time of diamond encapsulation was high and they are of Archaean age. If, however, the Archaean asthenosphere T p was more modest or if the diamonds formed later than the Archaean the inferred LAB depths are shallower (∼250-275 km), but still substantially deeper than at the present day. Although only the Kaapvaal craton has the necessary DI PT constraints for this exercise, the fundamental nature of radioactive heat production rate and mantle cooling mean that our findings could imply that Earth's continental lithosphere in general attained its maximal vertical extent early in the Archaean and that cratons have been variably eroded and weakened since that time. • It is not valid to project temperature estimates from diamonds onto present-day geotherm families. • The early Kaapvaal lithosphere was substantially thicker than today. • Depending on prevailing T p the root could have reached up to ∼350 km in depth. [ABSTRACT FROM AUTHOR]

In this study, a fully coupled analytical model is developed for thermal energy transfer in a single fracture-rock matrix system where the coupling implies that the governing equations of thermal transfer in the fracture and rock matrix are supplemented with the continuity conditions of temperature and thermal flux at the interfaces of the fracture-rock matrix. The proposed model accounts for thermal convection, longitudinal thermal conduction and thermal dispersion in the fracture, and transverse thermal conduction in the rock matrix. The fully coupled two-dimensional model is established to investigate the thermal energy transfer processes, assess the spatiotemporal temperature distribution in the fracture and rock matrix system and investigate the role of the rock matrix. The solutions are verified with the existing studies and proven to be accurate and robust. The present study demonstrates that: 1) thermal dispersion in the fracture plays an important role in the temperature distribution in the fracture and rock matrix domains, and longitudinal thermal conduction in the fracture has minor effects on the temperature distribution in the system; 2) transverse thermal conduction in the rock matrix is a critical parameter that determines the spatiotemporal temperature distribution in both the fracture and the rock matrix domains. Ignoring thermal conduction in the rock matrix will lead to a significant overestimation of temperature in the short and long terms; 3) the sensitivity analysis implies that thermal energy transfer in the system is sensitive to the fluid velocity in the fracture, thermal dispersivity in the fracture and thermal conductivity in the rock matrix, and less sensitive to thermal conductivity in the fracture. • A model for heat transfer in the fracture-rock matrix system is proposed with thermal convection, conduction and dispersion • Thermal dispersion in the fracture is important to the temperature distribution in the system • Transverse thermal conduction in the rock matrix is a critical parameter for heat transfer in the fracture [ABSTRACT FROM AUTHOR]

Abstract: Heat transfer is one of the fundamental and veiled energy transfer processes. The complex characteristics of heat transfer in a thermal process are far from being understood entirely. We here propose a statistical thermodynamic transport theory which is applicable to the heat transfer mechanisms for non-equilibrium, quasi-equilibrium, and equilibrium to overcome limits on the heat diffusion equation. The heat transfer theory adopts a postulate that temperature, time, and displacement are independent and orthogonal variables in extended phase spaces. The solutions of the heat transfer theory are obtained for thermal non-equilibrium, quasi-equilibrium, and equilibrium and the heat fluxes are expressed as the functions of temperature, time, and displacement. The heat transfer theory demonstrates that there are heat flux gaps and broken discrete symmetries at the activation temperature, time, and displacement. The theory is consistent with statistical thermodynamics. The kinetic theory is the unification of conduction and internal convection heat transfer, a non-equilibrium generalization beyond quasi-equilibrium theories for isothermal and isentropic processes, and the integration of internal equilibrium and internal non-equilibrium. [Copyright &y& Elsevier]

Deep geothermal contributions can affect the thermal equilibrium of glacial systems, which can induce changes in their thermal state. These changes can be influenced by glacier dynamics and by the different ice flow velocities experienced over time, which dictate the static and dynamic interactions with glacial trough bedrock. To assess such interactions and to weight the effects of ice mass thermalisations on bedrock, 2D multistage numerical modelling was performed for Priestley Glacier (an outlet glacier) in the East Antarctic glacial system (northern Victoria Land), which has experienced extreme heat flux variations related to rifting and late Cenozoic volcanism. The thermal evolution of Priestley Glacier over the last ~500 ka was modelled considering the mutual contributions of local and deep thermal sources through a parametric variation in the geothermal heat flux. The ice mass velocity was indirectly taken into account by assuming an ice persistence time over the bedrock under timelled considering the mutual contributions of local and deep thermal sources through a parametric variation in the geothermal heat flux. The ice mass velocity was indirectly taken into account by assuming an ice persistence time over the bedrock under time-dependent modelling conditions. Ice thickness and geothermal heat fluxes, varying from 50 to 120 mW/m2, were conditions are strongly linked in determining the thermal state of the glacier base and consequently its impact on basal erosion. According to the adopted ice stationing levels, heat flux conditions not exceeding 70 mW/m2 are needed for preserving a dry-based glacier only assuming velocity conditions equal to or lower than those observed to date along Priestley Glacier. Assuming increased velocity conditions, the glacier sensitivity to heat fluxes decreases, and high to very high heat fluxes are not sufficient to cause glacier base transitions to wet states. • Static and dynamic interactions among ice and bedrock control the glacier bed state. • The thermal evolution of Priestley Glacier (Antarctica) was numerically modelled. • Ice sensitivity to ice velocity, thickness and heat flux was calculated. • A heat flux <70 mW/m2 is required to keep dry-based glaciers beneath a slow ice flow. [ABSTRACT FROM AUTHOR]

Abstract: A vertical porous layer subject to lack of local thermal equilibrium and differentially heated from its sidewalls experiences extremely different conditions when it is heated via a constant heat flux, rather than via a hot temperature imposed on the sidewall. For a start the steady state basic temperatures of the fluid and solid differ, as distinct from the corresponding case of imposed temperature on the sidewall when both fluid and solid temperatures are identical and linear at steady state and the lack of local thermal equilibrium (LaLotheq) can manifest itself at transients or when the basic temperature profiles stated above become unstable. In addition, in the case of heating via a constant heat flux the steady state basic temperatures of the fluid and solid are not only distinct but also nonlinear. The analytical derivation of these nonlinear solutions for the basic natural convection in a vertical porous layer differentially heated from its sidewalls, subject to lack of local thermal equilibrium and heating via a constant heat flux is presented and the results analyzed over a wide range of parameter space. In general it is shown that the lack of local thermal equilibrium destroys the symmetry of the problem via deviatoric terms in the solutions. [Copyright &y& Elsevier]

Sensors simulate the response of human skin in the thermal environment and therefore play a crucial role in the prediction of the skin burn injury for the evaluation of the thermal protective clothing. In this study, a skin simulant is developed by Macor® material to mimic the surface thermal properties of human skin. The developed skin simulant is then used in the test method for radiant protective performance evaluation. A copper sensor is also used as a comparison in the tests. The results showed that the skin simulant better simulated the surface temperature rises of the human skin whereas the temperature responses of the copper sensor were in a linear behavior. The copper sensor fails to simulate the heat resistance process of the human skin, especially for the cooling phase. For the heat exposure phase, the heat flux at the skin surface is higher than that at the copper sensor surface. For the cooling phase, the skin simulant quickly recovered to a thermal equilibrium state, whereas, the copper sensor continues to release heat until the end of the test. Since the copper sensor underestimated the endothermic process and overestimated the exothermic process, it underestimated the potential skin burn risk. [ABSTRACT FROM AUTHOR]

• Finite element formulation allowing temperature discontinuities at liquid-vapor interfaces. • Relaxing the requirement of local liquid-vapor equilibrium conditions. • Continuum-level simulations of nano and micro scale evaporative systems. • Associated resistance to vapor phase flow is mostly controlled by interfaces. • Accurately predict evaporative fluxes in a nano heat pipe. Continuum numerical methods modeling liquid-vapor phase change processes typically assume local thermal equilibrium at the liquid-vapor interface – continuity of temperature at phase interfaces, and a relation between interfacial saturation pressure and temperature based on phase co-existence curves. Several standard macroscopic problems have been solved accurately by adhering to this assumption. However, in micro-scale and certain non-standard macro-scale applications, significant jumps in temperature are observed at liquid-vapor interfaces during phase change, and vapor pressure can be far from equilibrium values. In this paper, we present a locally discontinuous arbitrary Lagrangian Eulerian finite element formulation with temperature discontinuities at interfaces. A penalty-based approach is used to weakly enforce the temperature jump condition. Furthermore, we use kinetic-theory-based Schrage relationship to evaluate the rate of phase change. We apply our methodology to solve the problem of flowing vapor in a planar heat pipe. The flow rates predicted by our continuum simulations are in excellent agreement with recently published molecular dynamics simulation results of the same problem. Interestingly, accounting for temperature discontinuities leads to only a slight improvement in the prediction of mass fluxes as compared to the case when temperature continuity is assumed. This is in contrast to the large improvement in the prediction of temperature profiles and is a consequence of a weak dependence of the evaporation/condensation rates on the vapor temperature. [ABSTRACT FROM AUTHOR]