Isothermal Temperature Distribution Research Articles

In situ tensile behavior of hybrid carbon and glass fibers reinforced PEEK laminates: Isothermal or fire testing conditions

This work aims at investigating the thermo-mechanical coupling under critical temperature conditions in hybrid carbon/glass fibers reinforced Poly Ether Ether Ketone (PEEK) laminates. Two testing conditions have been considered: (i) isothermal and (ii) fire condition. A tensile loading was applied in homogeneous and isothermal temperature distribution (Room temperature – 350 and 500 °C) by means of a high-temperature furnace to quantify the influence of temperature on the mechanical response and properties. Regarding the fire conditions, a one-of-a-kind bench-scale fire test combining an in situ tensile mechanical loading and a kerosene burner (a flame temperature of 1100 °C ± 80 °C and a heat flux of 116 kW/m2 ± 10 kW/m2) has been designed and instrumented to induce anisothermal temperature conditions. This prototype allows the evolution of various physical quantities to be tracked as a function of the flame exposure time (5-10-15 min). These include temperature, loss of mass, deformation, stress, which are fundamental for understanding the mechanisms brought into play. The decrease of the tensile properties under isothermal conditions is −38% ± 0.6% (axial stiffness) and −54% ± 0.3% (axial strength) with respect to the values obtained at room temperature. The tensile response under fire is similar to the one obtained in isothermal conditions at 500 °C. The creep behavior of CG/PEEK laminates was also investigated with different boundary conditions (with or without a protective shield reducing the delirious effect of flame in terms of damages within the laminates). Compared to virgin specimens, the residual tensile mechanical properties significantly decrease as a function of the flame exposure time (5-10-15 min): 30% ± 1.1% and −55% ± 1.6% in axial stiffness and strength, respectively.

Numerical Investigations of a Counter-Current Moving Bed Reactor for Thermochemical Energy Storage at High Temperatures

High temperature storage is a key factor for compensating the fluctuating energy supply of solar thermal power plants, and thus enables renewable base load power. In thermochemical energy storage, the thermal energy is stored as the reaction enthalpy of a chemically reversible gas-solid reaction. Metal oxides are suitable candidates for thermochemical energy storage for solar thermal power plants, due to their high reaction temperatures and use of oxygen as a gaseous reaction partner. However, it is crucial to extract both sensible and thermochemical energy at these elevated temperatures to boost the overall system efficiency. Therefore, this study focuses on the combined extraction of thermochemical and sensible energy from a metal oxide and its effects on thermal power and energy density during discharging. A counter-current moving bed, based on manganese-iron-oxide, was investigated with a transient, one-dimensional model using the finite element method. A nearly isothermal temperature distribution along the bed height was formed, as long as the gas flow did not exceed a tipping point. A maximal energy density of 933 kJ/kg was achieved, when ( Mn , Fe ) 3 O 4 was oxidized and cooled from 1050 ° C to 300 ° C . However, reaction kinetics can limit the thermal power and energy density. To avoid this drawback, a moving bed reactor based on the investigated manganese-iron oxide should combine direct and indirect heat transfer to overcome kinetic limitations.

On the ability of the spectroscopic Sunyaev-Zeldovich effect measurements to determine the temperature structure of galaxy clusters

(abridged) We explore in this paper the ability of spatially resolved spectroscopic measurements of the SZ effect (SZE) to determine the temperature profile of galaxy clusters. We derive a general formalism for the thermal SZE in galaxy clusters with a non-uniform temperature profile that can be applied to both cool-core clusters and non-cool core cluster with an isothermal or non-isothermal temperature structure. We derive an inversion technique through which the electron distribution function can be extracted from spectroscopic SZE observations over a wide frequency range. We study the fitting procedure to extract the cluster temperature from a set of simulated spatially resolved spectroscopic SZE observations in different bands of the spectrum, from 100 to 450 GHz. The results of our analysis for three different cluster prototypes (A2199 with a low-temperature cool core, Perseus with a relatively high-temperature cool core, Ophiuchus with an isothermal temperature distribution) provide both the required precision of the SZE observations and the optimal frequency bands for a determination of the cluster temperature similar or better than that obtainable from X-ray observations. The precision of SZE-derived temperature is also discussed for the outer regions of clusters. We also study the possibility to extract, from our method, the parameters characterizing the non-thermal SZE spectrum of the relativistic plasma contained in the lobes of radio galaxies as well as the spectrum of relativistic electrons co-spatially distributed with the thermal plasma in clusters with non-thermal phenomena. We find that the next generation SZE experiments with spectroscopic capabilities can provide precise temperature distribution measurements (...)

Evolution of galaxy cluster scaling from XMM-Newton observation of the galaxy clusters at z ⩾ 0.4

We present here new XMM-Newton observations of 3 relatively cool clusters at z ≈ 0.4, complemented by archival observations of 3 other clusters at similar redshift. We derived the M– T and R– T relations from the hydrostatic equation using an isothermal temperature distribution.

On the energetics of maximum‐entropy temperature profiles

AbstractThe problem of determining a maximum‐entropy state in an atmospheric column has different solutions depending on the constraints imposed. As was first shown by J. W. Gibbs, maximization of entropy in a thermally‐isolated, i.e. energy‐conserving, atmosphere yields an isothermal temperature distribution. It has since been argued that conservation of the mass‐weighted integral of potential temperature, or of the column potential enthalpy, is more appropriate for certain dynamical processes. The solution of the maximization problem satisfying this second constraint is quite different: an adiabatic temperature profile.Here, the comparative energetics of entropy maximization is examined in more detail. The main new result is that some exact statements may be formulated as inequalities. It can be rigorously shown, for example, that maximization of entropy under the conservation of potential enthalpy in an initially stable stratification always requires additional energy, and so cannot be accomplished in an isolated layer. Conversely, a temperature profile satisfying the second condition always possesses less entropy than an isothermal state with the same total energy, and so cannot be in thermodynamic equilibrium. Starting with these fundamental results, this paper discusses basic properties, and specific examples, of dynamical processes transporting heat vertically and generating entropy under various constraints, and demonstrates the importance of their physically‐consistent parametrization in atmospheric models. Copyright © 2008 Royal Meteorological Society

The effect of wind on the snow cover

AbstractResults of wind-tunnel investigations of the propagation of air within snow showed that the process responsible for causing horizontal air flux in the pore space of snow was not necessarily related to specific surface topography. The reasons for this flux formation are: (i) the near-surface wind characteristics, such as the frequency of the pressure variation related to the turbulent character of the near-surface wind; (ii) the structure of the near-surface snow, responsible for the air exchange between the atmosphere and the pore space; and (iii) the temperature difference between the snow and the atmosphere, forming the air-density difference which augments or decreases the air exchange. This paper summarizes the experimentally observed effects that the wind and the air flux generated in the pore space had on snow. These included isothermal temperature distributions throughout the artificial snow cover, snow-density change and snow recrystallization.

B208 カラー画像解析による温度・速度の同時計測

The Visualization technique using micro capsuled thermo-sensing liquid crystals (TLC) suspension method can be obtained to the information both temperature and velocity, simultaneously. It is, however, not so easy to apply its technique to the quantitative measurement. This paper presents a procedure to determine the instantaneous isothermal temperature distributions in a time-varying thermal flow field visualized by the TLC tracer particles. Liquid crystal video images photographed by a 3-CCD camera are digitized into three frames concerning the intensities of red, green and blue light. These three RGB images are filtrated by the weighted averaging method. By using Munsell color system. the relations between colors and temperatures are calibrated. This color image processing technique has been applied to the unsteady thermal flow field, and two dimensional isothermal temperature distributions were successfully measured.

Hydrography of the Argentine continental shelf between 38° and 42°S

The hydrography of the Argentine continental shelf between 38° and 42°S is presented and interpreted from historical data (1957–1980) on a 1/2 ° latitude-longitude grid. The data are grouped into seasons. The study area is divided into two main domains, the coastal or inner shelf and the outer shelf. The coastal waters, delimited by the 40 m isobath, are generally homogeneous. The outer shelf waters undergo strong seasonal variations, they are almost vertically homogeneous in winter, but are stratified in the other seasons. The isothermal temperature distributions suggest a warm water flow towards the southwest along the outer shelf from spring to autumn. A shelf-break front is a permanent feature of the mean distributions. This feature separates shelf waters from the cooler and more saline slope waters of the Malvinas (Falkland) current.

Maximising the performances of flat-plate heat exchangers experiencing free or forced convection

Steady-state free and forced convective cooling of vertical, rectangular, 3 mm thick, 250 mm long fins, uniformly separated and protruding vertically upwards from a 250 mm × 190 mm isothermal horizontal base was investigated. For each combination of specified fin protrusion, horizontal forced air flow-rate in the direction along the fins and fin base temperature, the optimal fin spacing—corresponding to the maximum rate of heat loss—has been deduced. As the fin protrusion of the heat exchanger increases, this optimal value rises significantly in forced convection conditions, but declines slightly in the presence of free convection alone. The temperature distributions over the fins' surfaces were also studied, when the fin base was maintained at constant temperatures of either 40°C, 60°C or 80°C above that of the ambient environment. Large temperature depressions occurred near the leading edges and tips of the fins in forced convection, whereas much nearer isothermal temperature distributions were present under free convection conditions.

Inherent Problems of Detonation Formation in the Cores of 4-8 M Stars

view Abstract Citations (37) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Inherent Problems of Detonation Formation in the Cores of 4-8 M Stars Mazurek, T. J. ; Meier, David L. ; Wheeler, J. Craig Abstract A propagating detonation in a degenerate C/O core of 1.4 M0 may be self-consistent; however, its initiation for plausible configurations in the core is questionable. We argue that a detonation cannot form immediately upon carbon ignition for p > 10 g since the energy of the initial shock/burning front is limited to values well below that associated with a Chapman-Jouguet detonation. A portion of the core may be burned by repeated supersonic flashes which are controlled by the initial temperature structure. We find that while a series of such flashes may consume a core with an isothermal temperature distribution, such cannot be the case for the more realistic configuration with an adiabatic temperature gradient. In the latter case, rapid burning prior to hydrodynamic expansion occurs over no more than 10% of the core. Subject headings: nucleosynthesis - stars: interiors - stars: supernovae Publication: The Astrophysical Journal Pub Date: April 1977 DOI: 10.1086/155182 Bibcode: 1977ApJ...213..518M full text sources ADS |

Soft X-ray and microwave observations of hot regions in solar flares

Hot regions in solar flares produce X-radiation and microwaves by thermal processes. Recent X-ray data make it possible to specify the temperature and emission measure of the soft X-ray source, by using, for instance, a combination of the 1–8 A (peak response at about 2 keV) and the 0.5–3 A (peak response at about 5 keV) broad-band photometers. The temperatures and emission measures thus derived satisfactorily explain the radio fluxes, within systematic errors of about a factor of 3. Comparison of 15 events with differing parameters shows that a hot solar flare region has an approximately isothermal temperature distribution. The time evolution of the correlation in a single event shows that the hot material originates in the chromosphere, rather than the corona. The density must lie between 1010 and 2 × 1011 cm−3. For an Importance 1 flare, this implies a stored energy of roughly 2 x 1030-1029 ergs. A refinement of the data will enable us to choose between conductive and radiative cooling models.

Magma convection, temperature distribution, and differentiation

Normal heat fluxes from the Earth are sufficient to cause magma convection in plutons greater than 15 m for magma viscosities to 10 (super -8) poise. Convection increases markedly with size of the magma chamber and becomes the dominant method of heat transfer within the magma. Large solidifying intrusions have an approximately isothermal temperature distribution during part of the crystallization history. Natural convection also redistributes settling crystals. The population distribution (differentiation) of crystals in the vertical direction depends on the settling and convective back diffusion fluxes. An equation for population distribution is derived, and calculations made for olivine and quartz crystals in ultramafic and granitic magmas are in agreement with observed distribution of these minerals in corresponding solidified intrusions.

The atmospheric pressure wave generated by a nuclear explosion: 1.

The problem of describing the pressure wave detected by an observer on the ground a few thousand kilometers from a low-altitude nuclear explosion is formulated. To avoid numerical complications, the atmosphere is assumed to have an isothermal temperature distribution. With this simplification a Green's function for the problem is developed as an expansion in Legendre polynomials. This representation yields a time-dependent pressure function which satisfies the condition of causality but which converges far too slowly to be useful. An alternative scheme, which is entirely equivalent, makes use of a Watson transformation and requires the determination of the set of Regge poles. The behavior of the complete Green's function is then shown to be dominated by the so-called gravity wave mode, and the form of this approximate solution is developed.