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Heat Load (heat + load)
Selected AbstractsMulti-Fluid Modeling of Low-Recycling Divertor RegimesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-5 2010R. D. Smirnov Abstract The low-recycling regimes of divertor operation in a single-null NSTX magnetic configuration are studied using computer simulations with the edge plasma transport code UEDGE. The edge plasma transport properties pertinent to the low-recycling regimes are demonstrated. These include the flux-limited character of the parallel heat transport and the high plasma temperatures with the flattened profiles in the scrape-off-layer. It is shown that to maintain the balance of particle fluxes at the core interface the deuterium gas puffing rate should increase as the divertor recycling coefficient decreases. The radial profiles of the heat load to the outer divertor plate, the upstream radial plasma profiles, and the effects of the cross-field plasma transport in the low-recycling regimes are discussed. It is also shown that recycling of lithium impurities evaporating from the divertor plate at high surface temperatures can reverse the low-recycling divertor operational regime to the high-recycling one and may cause thermal instability of the divertor plate (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Simulation Study of Radiative Cooling in the Divertor on JT-60 Super Advanced (JT-60SA)CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008Y. Suzuki Abstract A simulation study of the divertor for JT-60SA is discussed in both double-null (DN) and single-null (SN) configurations. In the DN case, the transition of peak heat load on the targets and divertor plasma states from CDN (connected double-null) to DDN (disconnected double-null) are shown in the simulation. The radiative cooling power in the divertor plasma is discussed in this study. The carbon impurity generated by the sputtering on the divertor target is included in the simulation. In the gas puffing cases of fueling gas (D2) and impurity gas (Ne), the reduction of heat load is confirmed consistently with increasing the radiative cooling loss power in the diverter plasma. The loss power and the distribution of radiative cooling in the divertor plasma are studied in this paper. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A dimensionless factor characterizing the ignition of pulverized coal flow: Analytical model, experimental verification, and applicationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2009Qulan Zhou Abstract An analytical model describing the ignition process of pulverized coal is proposed, and a dimensionless condition number (Ncom) is obtained to describe the comprehensive effect of factors governing the ignition of pulverized coal flow, such as the initial temperature of flow, the sectional heat load of the furnace, and the flux of primary air, secondary air and recirculation flue gas. An optimized concentration of pulverized coal flow is derived explicitly, upon which the earliest ignition of pulverized coal flow is possible. The model is verified in a hot furnace experiment, where it is shown that the derived criterion (Ncom) can be used for different kinds of coal and different types of burner. For given coal and sectional heat load of furnace, when the value of Ncom increases, the condition of ignition is improved and both unburned carbon and NOx emission are reduced. The employment of Ncom in the optimization of burner operating conditions is demonstrated through two applications. In practice, the criterion Ncom can be used to guide the selection of the concentration and type of pulverized coal, as well as the choice of burner and desired aerodynamic field, so as to achieve an optimized performance. Copyright © 2008 John Wiley & Sons, Ltd. [source] A fibre-mat catalytic burner for the heating system of PVC tilesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2002Yong Seog Seo Abstract This study aims to develop the low-temperature catalytic burner using Al2O3 fibre and Pt catalyst as a substrate and an active material, respectively, and then to apply it to the heating system of PVC tiles. Three types of fibre-mat catalytic burners,natural diffusion catalytic burner, forced diffusion catalytic burner and premixed catalytic burner,were tested. For the natural diffusion catalytic burner, the combustion efficiency was significantly affected by the installation method. Its combustion efficiency was above 99.5% when it was placed vertically and upward, whereas the combustion efficiency rapidly deteriorated to less than 80% when it was installed in downward position. When the forced diffusion combustion mode was employed, the combustion efficiency of the fibre-mat catalytic burner was successively improved over 99.5%. The optimal operation condition of the premixed fibre-mat catalytic burner was obtained when the excess air ratio is 4.3 and the heat load is 3.0 kcal h,1 cm,2. The heat load of the premixed catalytic burner was found to be twice as much as those of the natural and forced diffusion catalytic burner, meaning that the size of the catalytic burner can be reduced to its half if the premixed catalytic burner is used. We also performed the field test of the fibre-mat catalytic burner in the heating system of the PVC tiles. The combustion efficiency of the catalytic burners appeared to be satisfactory, above 99.5%, and the energy saving by replacing the existing electrical heaters with the fibre-mat catalytic burners were shown to be 27.7%. Copyright © 2002 John Wiley & Sons, Ltd. [source] Photovoltaic-powered cold store and its performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2001J. Nagaraju Abstract A photovoltaic-powered cold store plant, the first of its kind, has been developed to store 10 tons of frozen fish at ,15°C. It consists of a photovoltaic array (4 kW peak), a battery bank (96 V DC, 180 A H), a vapour compression refrigeration system (1 ton), electronic controls for automatic operation of plant and an insulated cold chamber. Experiments were conducted on the system to evaluate its performance with no heat load (frozen fish at ,15°C) and with different heat loads. It is observed that the system can be operated with a maximum heat load of 2350 W to maintain the walk-in-cooler temperature below the freezing point of fish (,2°C). The performance studies conducted on these subsystems viz., photovoltaic array and battery bank showed that their output has deteriorated in 5 years. Copyright © 2001 John Wiley & Sons, Ltd. [source] A novel epitaxially grown LSO-based thin-film scintillator for micro-imaging using hard synchrotron radiationJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010Paul-Antoine Douissard The efficiency of high-resolution pixel detectors for hard X-rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron-based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency: a novel scintillator based on doped Lu2SiO5 (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO-based thin crystal together with the high stopping power of the material allows for high-performance indirect X-ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible-light and the afterglow are investigated. A set-up to study the effect of the thin-film scintillator's temperature on its conversion efficiency is described as well. It delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X-ray imaging systems based on different diffraction-limited visible-light optics and CCD cameras using among others LSO-based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high-resolution computed tomography for life sciences. [source] Quantitative estimation of thermal contact conductance of a real front-end component at SPring-8 front-endsJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2008Mutsumi Sano The thermal contact conductance (TCC) of a real front-end component at SPring-8 has been quantitatively estimated by comparing the results of experiments with those of finite-element analyses. In this paper one of the methods of predicting the TCC of a real instrument is presented. A metal filter assembly, which is an indirect-cooling instrument, was selected for the estimation of the TCC. The temperature of the metal filter assembly for the maximum heat load of synchrotron radiation was calculated from the TCC that is expected under normal conditions. This study contributes towards the ongoing research program being conducted to investigate the real thermal limitation of all front-end high-heat-load components. [source] The new HMI beamline MAGS: an instrument for hard X-ray diffraction at BESSYJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2006Esther Dudzik The Hahn-Meitner-Institute Berlin is operating the new hard X-ray diffraction beamline MAGS at the Berlin synchrotron radiation source BESSY. The beamline is intended to complement the existing neutron instrumentation at the Berlin Neutron Scattering Centre. The new beamline uses a 7,T multipole wiggler to produce photon fluxes in the 1011,1012,photons s,1 (100,mA),1 (0.1% bandwidth),1 range at energies from 4 to 30,keV at the experiment. It has active bendable optics to provide flexible horizontal and vertical focusing and to compensate the large heat load from the wiggler source. The experimental end-station consists of a six-circle Huber diffractometer which can be used with an additional (polarization) analyser and different sample environments. The beamline is intended for single-crystal diffraction and resonant magnetic scattering experiments for the study of ordering phenomena, phase transitions and materials science. [source] Performance of a cryogenic silicon monochromator under extreme heat loadJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2004Aleksandr Chumakov The performance of an indirectly cooled cryogenic silicon monochromator under heat loads up to 870,W has been studied. The investigation was performed over numerous parameters and included measurements of total flux, spectral density, rocking curves, angular beam profiles and crystal slope errors. An almost ideal monochromator performance was observed in the 270,570,W range of the heating power. At a heat load of ,400,W and under standard operation conditions, the crystal distortions did not exceed 1,µrad. At the highest available heat load of 870,W, the crystal distortions were about 7,µrad. [source] Performance limits of direct cryogenically cooled silicon monochromators , experimental results at the APSJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2000Wah-Keat Lee The successful use of cryogenically cooled silicon monochromators at third-generation synchrotron facilities is well documented. At the Advanced Photon Source (APS) it has been shown that, at 100,mA operation with the standard APS undulator A, the cryogenically cooled silicon monochromator performs very well with minimal (<2 arcsec) or no observable thermal distortions. However, to date there has not been any systematic experimental study on the performance limits of this approach. This paper presents experimental results on the performance limits of these directly cooled crystals. The results show that if the beam is limited to the size of the radiation central cone then, at the APS, the crystal will still perform well at twice the present 100,mA single 2.4,m-long 3.3,cm-period undulator heat load. However, the performance would degrade rapidly if a much larger incident white-beam size is utilized. [source] Eurosiberian meadows at their southern edge: patterns and phytogeography in the NW Tien ShanJOURNAL OF VEGETATION SCIENCE, Issue 2 2009Viktoria Wagner Abstract Question: What are the community types, underlying gradients and phytogeographical affinities of montane meadows in the western Tien Shan? Location: Aksu-Jabagly Nature Reserve, South Kazakhstan, Middle Asia. Methods: Species composition, structural and environmental variables were studied in 98 plots. Species composition was classified by cluster analysis and gradients explored using NMDS. Relationships between species richness, environmental and structural variables were investigated with regression analysis. Phytogeographic patterns were assessed by examining species distribution types. Results: Seven community types were distinguished by cluster analysis. Three axes of the NMDS explained 77% of the variation, showing different overlap of communities with environmental and structural properties. Species richness showed linear relationships with pH, altitude, heat load, soil skeletal content and structural variables. Middle Asian and Eurosiberian species constituted the majority of the species pool and cover. Conclusion: The studied communities represent a unique mixture of Middle Asian and Eurosiberian species that exhibit structural and environmental similarities to Eurosiberian meadows. The Tien Shan mountain meadows can thus be considered an endemic-rich southern outlier of the broader Eurosiberian meadow formation. Shifts in land-use patterns pose a potential threat that deserves more attention from conservationists. [source] CONSTRAINING HEAT INPUT BY TRAJECTORY OPTIMIZATION FOR MINIMUM-FUEL HYPERSONIC CRUISEASIAN JOURNAL OF CONTROL, Issue 4 2006M. Wächter ABSTRACT Unsteady heat input effects are considered for the range cruise of a future hypersonic vehicle equipped with a turbo/ram jet engines combination. A realistic mathematical model for describing the unsteady heat effects has been developed. It is coupled to the model for the dynamics of the vehicle. To compute the heat load in hypersonic flight, several points on the vehicle surface are treated simultaneously. A two-step technique consisting of an efficient optimization algorithm and an ordinary differential equations (ODE) solver is applied to generate a solution. The results show that the heat load can be significantly reduced, with only a small increase in fuel consumption. [source] Exposure of non-target tissues in medical diathermyBIOELECTROMAGNETICS, Issue 1 2010N. Leitgeb Abstract With different prevalence in different regions, radio frequency (RF) electromagnetic fields (EMF) are widely used for therapeutic tissue heating. Although short-wave diathermy (27.12,MHz) is the most popular treatment modality, quantitative data on patient's exposure have been lacking. By numerical simulation with the numerical anatomical model NORMAN, intracorporal distributions of specific absorption rates (SAR) were investigated for different treatment scenarios and applicators. Quantitative data are provided for exposures of target treatment areas as well as for vulnerable regions such as the eye lenses, central nervous system, and testes. Different applicators and distances were investigated. Capacitive and inductive applicators exhibit quite a different heating efficiency. It could be shown that for the same output power therapeutic heat deposition can vary by almost one order of magnitude. By mimicking therapist's practice to use patient's heat perception as an indicator for output power setting, numerical data were elaborated demonstrating that muscle tissue exposures may be several times higher for inductive than for capacitive applicators. Presented quantitative data serve as a guide for power adjustment preventing relevant overexposures without compromising therapy; they also provide a basis for estimating target tissue heat load and developing therapeutic guidelines. Bioelectromagnetics 31:12,19, 2010. © 2009 Wiley-Liss, Inc. [source] Photovoltaic-powered cold store and its performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2001J. Nagaraju Abstract A photovoltaic-powered cold store plant, the first of its kind, has been developed to store 10 tons of frozen fish at ,15°C. It consists of a photovoltaic array (4 kW peak), a battery bank (96 V DC, 180 A H), a vapour compression refrigeration system (1 ton), electronic controls for automatic operation of plant and an insulated cold chamber. Experiments were conducted on the system to evaluate its performance with no heat load (frozen fish at ,15°C) and with different heat loads. It is observed that the system can be operated with a maximum heat load of 2350 W to maintain the walk-in-cooler temperature below the freezing point of fish (,2°C). The performance studies conducted on these subsystems viz., photovoltaic array and battery bank showed that their output has deteriorated in 5 years. Copyright © 2001 John Wiley & Sons, Ltd. [source] Performance of a cryogenic silicon monochromator under extreme heat loadJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2004Aleksandr Chumakov The performance of an indirectly cooled cryogenic silicon monochromator under heat loads up to 870,W has been studied. The investigation was performed over numerous parameters and included measurements of total flux, spectral density, rocking curves, angular beam profiles and crystal slope errors. An almost ideal monochromator performance was observed in the 270,570,W range of the heating power. At a heat load of ,400,W and under standard operation conditions, the crystal distortions did not exceed 1,µrad. At the highest available heat load of 870,W, the crystal distortions were about 7,µrad. [source] | ||||||||||