Low Thermal Load Research Articles

Modification of surface morphology during cryogenic turning of metastable austenitic steel AISI 347 at different parameter combinations with constant CO2 consumption per cut

For numerous cryogenically machined materials a hardness increase in the workpiece surface layer has already been reported due to strain hardening mechanisms and compressive residual stress. When machining metastable austenitic steels, these hardening mechanisms are overlaid by a deformation induced phase transformation from austenite to martensite. This phase transformation is favored by low thermal and high mechanical loads in the workpiece surface layer; thus the martensite content can be modified by varying the thermo-mechanical load.In this study, the cryogenic turning process is designed to maintain low workpiece temperatures during machining and to maximize the passive forces and consequently the martensite content. The passive forces are adjusted by using indexable inserts with strongly varying chamfer angles and therefore, also varying effective rake angles. The feed rate and thus the cutting cross-section are varied as well to further adjust the passive forces. As higher feed rates lead to shorter cutting times, the cooling time is also shortened, which increases the thermal load and worsens the surface morphology. Therefore, for each variation, the coolant supply was controlled to maintain a constant quantity of CO2 during each cut. Hence, low workpiece temperatures can be achieved even with high feed rates. By controlling the thermo-mechanical load, significantly more martensite can be generated while maintaining a constant CO2 consumption per cut.

Development and prospect of high-power doped fibers

Ytterbium-doped fibers have become the optimum gain media of high-power fiber lasers thanks to a simple energy structure, which strongly reduces the excited state absorption, and a low quantum defect and a high optic–optic conversion efficiency, which means the low thermal load. In this paper, we take a review of the current state of the art in terms of $\text{Yb}^{3+}$ doped fibers for high-power fiber lasers, including the development of the fabrication techniques. The research work to overcome the challenges for $\text{Yb}^{3+}$ doped fibers, which affect the stability of output power and beam quality, will be demonstrated. Direction of further research is presented and the goal is to look for a fiber design, to boost single fiber output power, stabilize the laser power and support robust single-mode operation.

Experimental testing of a small-scale two stage Organic Rankine Cycle engine operating at low temperature

Abstract This paper presents the testing results, both at partial and full load operation of a prototype two-stage, heat-to-power conversion engine based on the Organic Rankine Cycle with net capacity of 10 kWe at 130 °C. This engine has been developed to operate in a wide range of thermal load input, coming from thermal sources of variable heat supply. The intense fluctuation of the temperature and heat input dictates the use of a two-stage engine, so that the operation becomes flexible and efficient even at low thermal load. For the two-stage expansion, two scroll expanders have been connected in series with the first expander by-passed at low heat input. The engine has been tested in the lab supplied with heat from an electrical heater for several heat transfer fluid temperatures between 80 and 130 °C. The current work mainly focuses on the results of the operation at 130 °C, however a brief comparison of the results with other operating temperatures is also included. The measurements have shown that thermal efficiency is kept high enough even at low temperature, while the second expander operates with isentropic efficiency up to 66%. The maximum thermal efficiency reached is 8.87% and the maximum power production 7.53kWe for two-stage operation.

Predictive method for low load off-design operation of a lignite fired power plant

The increasing share of renewable energy sources and their stochastic attitude of power production force the conventional fossil fuel thermal plants to operate in a more flexible mode, with rapid load changes (ramp up/down rates) and in lower thermal loads than their current technical minimum. This can be achieved with the use of pre-dried lignite as a supporting fuel, in the place of conventional liquid fuels such as diesel. This study presents a thermodynamic methodology for the prediction of Agios Dimitrios V Greek lignite fired boiler at low power loads; even below the current technical minimum, when pre-dried lignite is employed. The calculations are based on measurement data provided for the current operating thermal loads of 100%, 80% and 60% (current technical minimum). Among the controlling values of critical operational parameters, this model takes into account the thermodynamic properties (pressure, temperature and steam quality) of SH and RH steam, the steam turbine properties, the heat transfer coefficient of the heat exchangers and the fuel combustion specifications. The model of the boiler is developed in Aspen Plus whereas the ST model was built in GateCycle. Furthermore, this house-built model is implemented to estimate the heat transfer coefficients for the theoretical scenario of 35% thermal load operation, which is far below the current technical minimum and no design or measurement data exist for them. Thermodynamic calculations reveal the boiler effective operation of the boiler even at a thermal load of 35% with a quite good overall thermal efficiency. The net efficiency of the theoretical new technical minimum load is 0.9 percentage points higher than the current one. Results of this approach are also compared against corresponding CFD results, with a fairly good accordance.

Numerical examination of an operationally flexible lignite-fired boiler including its convective section using as supporting fuel pre-dried lignite

This work simulates the main furnace and the convective section of the lignite-fired Ag. Dimitrios V boiler located in Kozani, Northern Greece, under three different thermal loads (100%, 60% and 35% of the nominal one) using the Ansys Fluent 15.0® software program. The lowest thermal load investigated, i.e. 35% of the nominal one, is lower than the current technical minimum of the unit (~55%). In order to ensure the furnace stability and efficiency in this low thermal load, a co-combustion scheme of pre-dried with raw lignite is implemented. Due to sub-stoichiometric operating conditions in the main furnace zone in the full-load case and the formation of a two-stage over-fire air (OFA) system, the simulation of whole the furnace, including both the main furnace and the convective section of the boiler, is necessary, to investigate the char conversion and the furnace performance thoroughly. The simulation of the convective section is based on the porous media analysis using the Macro Heat Exchanger Model provided by Ansys Fluent 15.0®. The results regarding the total heat transfer towards the working medium and the flue gas average temperature at the main furnace outlet surface and at characteristic transversal surfaces of the convective section are compared against thermodynamic model predictions and experimental values showing good agreement, since the maximum percentage difference between the results of the two software tools and with the experimental values is approximately equal to 10%. Based on these results, it is indicated that the injection of pre-dried lignite fuel ensures the combustion stability and high efficiency of the boiler in lower thermal load (35%) than the current technical minimum of the unit.

On the Origin of Diamond Plates Deposited at Low Temperature

The crucial requirement for diamond growth at low temperatures, enabling a wide range of new applications, is a high plasma density at a low gas pressure, which leads to a low thermal load onto sensitive substrate materials. While these conditions are not within reach for resonance cavity plasma systems, linear antenna microwave delivery systems allow the deposition of high quality diamond films at temperatures around 400 °C and at pressures below 1 mbar. In this work the codeposition of high quality plates and octahedral diamond grains in nanocrystalline films is reported. In contrast to previous reports claiming the need for high temperatures (T ≥ 850 °C), low temperatures (320 °C ≤ T ≤ 410 °C) were sufficient to deposit diamond plate structures. Cross-sectional high resolution transmission electron microscopy studies show that these plates are faulty cubic diamond terminated by large {111} surface facets with very little sp2 bonded carbon in the grain boundaries. Raman and electron energy loss spectros...

Stability of large room airflow structures in a ventilated room

ABSTRACTThis paper presents a new set of experimental data for different kinds of room airflows in a ventilated room. The data are used to examine Archimedes number effects on the behaviour of large-scale flow structures and their stability versus time. All experiments are performed in a simplified room geometry, representing a small meeting room, a train or an airplane cabin. The supply air is introduced at the ceiling and the exhaust air leaves the room at the bottom zone. The heating power is realised by four controllable heat sources in the lower part of the model room. The experimental investigations apply different supply air set-ups as well as changing supply air velocities and a variation of the heating power. The data of the experiments indicate that the room geometry-based Ar number can be used to distinguish between unstable to stable room airflow structures. Low velocities and high thermal loads cause time depended, unstable room airflows. Neither the forced nor the free convection dominates the flow structure. By increasing the inlet velocity, the airflow structure gets more stable. Large eddies occur between the heat sources and the ceiling of the model room. This experimental investigation showed that it is possible to determine an Ar number for the room geometry under investigation, in the region where a transition takes place from instable to stable airflow. The value of this critical Ar number has been extracted from a qualitative velocity profile analysis.

Thermal performance of a hollow block with/without insulating and reflective materials for roofing in Mexico

The thermal analysis of a hollow block with/without insulation and reflective materials for roofing was studied during 24h (hottest and coldest days) considering environmental variables from a city in Mexico with hot weather. The traditional blocks used for roofs in Mexico with two and three hollows were considered. The different configurations of roof analyzed are: (C1) Reference or traditional block (hollow block+concrete slab), (C2) Traditional block with a reflective coating on the outer of the slab (hollow block+concrete slab+reflective coating), (C3) Traditional block with an insulating material between the outer surface of the block and the slab (block hollow+insulation+concrete slab) and (C4) Traditional block with a insulation material and a with a reflective coating on the outer surface of the slab (hollow block+insulation+concrete slab+reflective coating). The different coatings considered are: Gray, Black and White. The results show that the configuration C4 with a white reflective coating demand a lower thermal load for the block with two hollows (B2-Wins-RW) and three hollows (B3-Wins-RW) with a value of 1045.3 and 975.9Wh/m2, respectively. These values represent a decrease in the thermal load of 32.4 and 46.3% with respect to the traditional roof (C1). This result shows the advantage of using the combination of insulating material and reflective coating on roofs with hot climates.

Experimental study on the performance characteristics of a cylindrical heat pipe having a screen wick subject to multiple heat sources

In a simple model to predict heat pipe performance, uniform thermal loads are assumed over heat transfer surfaces. The validity of the simple model is limited in many application areas such as electronics cooling and space thermal control, where a heat pipe is often subject to multiple, unequal thermal loads. This study aims to experimentally identify the performance of a cylindrical heat pipe under various multiple heat source configurations and thus to quantitatively estimate the deviation from a heat pipe under uniform conditions. The model heat pipe was 9.53mm in diameter and 0.6m in length, with a 0.4m evaporator. The working fluid and the container wall were water and copper, respectively, and a wire mesh screen was inserted as a capillary structure. The fluid charge ratios tested were 100% and 120% based on the wick void volume. The heat pipe was in gravity-assisted mode with an inclination angle of 45° to extend the range of thermal input. Five small heaters were installed in the evaporator with equal spacing, and the power inputs were controlled individually. Three different thermal load configurations were imposed: equal, increasing and decreasing distributions toward the condenser. The results were compared from the viewpoints of thermal resistance and effective thermal conductance. The thermal resistance of the heat pipe with a 100% fluid charge exhibited excellent values from 0.16K/W (at 50W) to 0.03K/W (at 300W) for a uniform heat load. However, those with multiple thermal loads resulted in almost a 100% increase for the lower thermal load, and up to a 40% increase for the higher thermal loads, depending on the configuration. The behavior of the heat pipe with a fluid charge of 120% exhibited little difference. The results herein can be employed to estimate the performance deviation of a heat pipe due to thermal load distribution.

Utilization of Baggase Waste Based Materials as Improvement for Thermal Insulation of Cement Brick

Building materials having low thermal load and low thermal conductivity will provide thermal comforts to the occupants in building. In an effort to reduce the use of high energy and waste products from the agricultural industry, sugarcane bagasse and banana bagasse has been utilize as an additive in the manufacture of cement brick. The aim of this study is to investigate the insulation and mechanical properties of brick that has been mixed with bagasse and its effectiveness as thermal insulation using heat flow meter. Waste bagasse is being treated using sodium hydroxide (NaOH) and is characterized using SEM and XRF. The samples produced with two different dimensions of 50 mm × 50 mm × 50 mm and 215mm × 102.5mm × 65mm for thermal conductivity test. Next, the sample varies from 0% (control sample), 2%, 4%, 6%, 8% and 10% in order to determine the best mix proportion. The compressive strength is being tested for 7, 14 and 28 days of water curing. Results showed that banana bagasse has lower thermal conductivity compared to sugarcane bagasse used, with compressive strength of 15.6MPa with thermal conductivity 0.6W/m.K.

Investigations for the substantiation of high-temperature nuclear power generation technology using fast sodium-cooled reactor for hydrogen production and other innovative applications (Part 1)

Neutronics and thermal physics studies of BN-VT reactor installation with 600-MW thermal power demonstrated the possibility in principle to achieve the required parameters of high-temperature fast reactor for production of large quantities of hydrogen on the basis, for instance, of one of thermal chemical cycles or high-temperature hydrolysis with high thermal efficiency of use of electric power. Relatively small dimensions, the type of coolant, selection of fissile material and structural materials allow developing nuclear reactor with particular inherent properties (exclusion of prompt-neutron reactor power excursions, removal of decay heat in passive mode) while ensuring enhanced nuclear and radiation safety.Composition of BN-VT reactor facility includes sodium-cooled fast reactor, three cooling loops for emergency heat removal and three sets of equipment of the secondary cooling loop for heat transfer from the reactor to chemical installations generating hydrogen or to gas-turbine plant for supplying chemical equipment with electric power. Composition of each of the cooling loops includes intermediate heat exchanger arranged inside the reactor vessel, centrifugal pump and pipeline for removal and re-introduction of sodium in the reactor core. Contemporary requirements on the safety and financial performance of future generations of nuclear reactors were taken into consideration in the development of the reactor under study. Implemented calculation studies demonstrated that penetration of hydrogen within the limits of permissible allowances produce practically no effect on the neutronics and safety parameters of the reactor. Solution of the problem of fuel pin stability was mitigated due to the selection of low thermal load on fuel pins. Application of EP-912-VD steel as a possible optional structural material was examined.Continued studies of heat-resistant materials and their behavior under irradiation are required.

An experimental investigation of the influence of intermittent and continuous operating modes on the thermal behaviour of a full scale geothermal energy pile

Ground sourced heat pumps coupled with geothermal energy piles operate either continuously or intermittently depending on the heating or cooling needs of a built structure, giving rise potentially to variable thermal loads in the piles. This paper presents an experimental investigation on the influence of intermittent and continuous operations on energy extracted, ground and pile temperatures, and axial thermal strains and stresses of a full scale geothermal energy pile for daily cooling operation. Experiments were conducted for a 24 hours continuous operation (24 h mode), 16 hours operation with 8 hours rest (16 h mode), and 8 hours operation with 16 hours rest (8 h mode). It is generally found that the lower operating hours lead to higher energy extracted from the ground with lower thermal loads on the pile and the ground. The energy extracted was 40.9% and 14.8% higher in the 8 h and 16 h modes, respectively, compared to the 24 h mode. The ground temperatures for the 8 h and 16 h modes were 14.5% and 5.9% higher than the 24 h mode, respectively. The average thermal stresses in the pile for the 8h and 16 h modes were 42.3% and 12.2% lower than the 24 h mode, respectively. The results of the present study also showed that the soil did not affect the elasticity of the axial thermal strains between end of cooling and recovery of the intermittent modes for daily thermal cycles.

A scientific and interdisciplinary approach for high pressure processing as a future toolbox for safe and high quality products: A review

Abstract High pressure (HP) processing, typically at 600 MPa in combination with mild temperatures, makes it possible to produce safe and high quality foods while inactivating pathogenic microorganisms such as Enterohaemorrhagic Escherichia coli (EHEC). In the last decade much research was conducted to understand the inactivation of spores at high pressures and elevated temperatures. Bacterial spore inactivation by HPP in complex food matrices is assessed with an emphasis on mechanisms of inactivation and treatment of products that have low or non-uniform water activity (a w ) profiles. Low a w can be the result of a high concentration in solutes and the presence of oils/fats or other ingredients in the food. The synergistic effect of pressure and temperature leads to lower thermal loads applied to the product and consequently less unwanted compounds can be formed during the process. Future applications of high pressure and elevated temperature processes are assed. These processes could lead to healthier products, safer products and a smarter usage of emerging technologies. Industrial relevance The next step for high pressure processing in addition to pasteurization could be for food sterilization in combination with elevated temperatures. This would have a big impact on many sectors of the industry. Elevated temperatures could be used in existing “cold” HP systems using insulated carriers. The extra cost and construction problems could be minimized. Product quality and health attributes could be increased in comparison to conventional technologies.

Combustion and emission characteristics of a lateral swirl combustion system for DI diesel engines under low excess air ratio conditions

In order to improve the utilization of air in the cylinder, decrease the thermal load and improve the emission performance of diesel engines, a new lateral swirl combustion system (LSCS) has been proposed in this study. An experimental investigation of the LSCS at various excess air ratios was conducted using a 132mm single-cylinder direct injection (DI) engine. The experimental results indicate that, compared to a double swirl combustion system (DSCS), the LSCS achieves better fuel consumption and lower soot emissions. The fuel consumption was decreased by 4–5g/(kWh) at each excess air ratio, corresponding to a reduction of about 1.13–2.8%. The decreasing trend of soot formation was also clear, with a significant reduction in the range of 63.4–70.8%. The LSCS also showed excellent performance under an excess air ratio of 1.3–1.6. At an excess air ratio of 1.3, the brake-specific fuel consumption (BSFC) of the LSCS was 228g/(kWh), the soot emission level was 1.1 Filter Smoke Number (FSN) and the exhaust temperature was about 560°C. Related numerical research on the impact of in-cylinder fuel/air equivalence ratio, in-cylinder temperature and in-cylinder velocity of the DSCS and the LSCS was performed, and the results show that a large proportion of the fuel/air diffusion was at the bottom of the chamber in the LSCS (away from the cylinder head). The lower concentration of the fuel/air mixture near the cylinder head in the LSCS had a positive effect and reduced the thermal load so that less engine heat was taken away by the cooling water in the water jacket of the cylinder head. Due to the lower thermal load and higher efficiency, the exhaust temperature of the LSCS was higher than that of the DSCS. The higher exhaust temperature had a positive influence on soot oxidation, which caused the soot decrease in the LSCS. It is suggested that the LSCS, with its excellent fuel consumption and low soot emission, has better application prospects in diesel engines, than the DSCS under a low excess air ratio.

Heat for wounds - water-filtered infrared-A (wIRA) for wound healing - a review.

Background: Water-filtered infrared-A (wIRA) is a special form of heat radiation with high tissue penetration and a low thermal load to the skin surface. wIRA corresponds to the major part of the sun’s heat radiation, which reaches the surface of the Earth in moderate climatic zones filtered by water and water vapour of the atmosphere. wIRA promotes healing of acute and chronic wounds both by thermal and thermic as well as by non-thermal and non-thermic cellular effects. Methods: This publication includes a literature review with search in PubMed/Medline for “water-filtered infrared-A” and “wound”/”ulcus” or “wassergefiltertes Infrarot A” and “Wunde”/”Ulkus”, respectively (publications in English and German), and additional analysis of study data. Seven prospective clinical studies (of these six randomized controlled trials (RCT), the largest study with n=400 patients) were identified and included. All randomized controlled clinical trials compare a combination of high standard care plus wIRA treatment vs. high standard care alone. The results below marked with “vs.” present these comparisons. Results: wIRA increases tissue temperature (+2.7°C at a tissue depth of 2 cm), tissue oxygen partial pressure (+32% at a tissue depth of 2 cm) and tissue perfusion (effect sizes within the wIRA group). wIRA promotes normal as well as disturbed wound healing by diminishing inflammation and exudation, by promotion of infection defense and regeneration, and by alleviation of pain (with respect to alleviation of pain, without any exception during 230 irradiations, 13.4 vs. 0.0 on a visual analogue scale (VAS 0–100), median difference between groups 13.8, 95% confidence interval (CI) 12.3/16.7, p<0.000001) with a substantially reduced need for analgesics (52–69% less in the three groups with wIRA compared to the three control groups in visceral surgery, p=0.000020 and 0.00037 and 0.0045, respectively; total of 6 vs. 14.5 analgesic tablets on 6 surveyed days (of weeks 1–6) in chronic venous stasis ulcers, median difference –8, 95% CI –10/–5, p=0.000002). Further effects are: Faster reduction of wound area (in severely burned children: 90% reduction of wound size after 9 vs. 13 days, after 9 days 89.2% vs. 49.5% reduction in wound area, median difference 39.5% wound area reduction, 95% CI 36.7%/42.2%, p=0.000011; complete wound closure of chronic venous stasis ulcers after 14 vs. 42 days, median difference –21 days, 95% CI –28/–10, p=0.000005). Better overall evaluation of wound healing (surgical wounds: 88.6 vs. 78.5 on a VAS 0–100, median difference 8.9, 95% CI 6.1/12.0, p<0.000001). Better overall evaluation of the effect of irradiation (79.0 vs. 46.8 on a VAS 0–100 with 50 as neutral point, median difference 27.9, 95% CI 19.8/34.6, p<0.000001). Higher tissue oxygen partial pressure during irradiation with wIRA (at a tissue depth of 2 cm 41.6 vs. 30.2 mmHg, median difference 11.9 mmHg, 95% CI 9.6/14.2 mmHg, p<0.000001). Higher tissue temperature during irradiation with wIRA (at a tissue depth of 2 cm 38.9 vs. 36.4°C, median difference 2.6°C, 95% CI 2.2/2.9°C, p<0.000001). Better cosmetic result (84.5 vs. 76.5 on a VAS 0–100, median difference 7.9, 95% CI 3.7/12.0, p=0.00027). Lower wound infection rate (single preoperative irradiation: 5.1% vs. 12.1% wound infections in total, difference –7.0%, 95% CI –12.8%/–1.3%, p=0.017, of these: late wound infections (postoperative days 9-30) 1.7% vs. 7.7%, difference –6.0%, 95% CI –10.3%/–1.7%, p=0.007). Shorter hospital stay (9 vs. 11 postoperative days, median difference –2 days, 95% CI –3/0 days, p=0.022). Most of the effects have been proven with an evidence level of 1a or 1b.Conclusion: Water-filtered infrared-A is a useful complement for the treatment of acute and chronic wounds.

Planar Lithographed Superconducting LC Resonators for Frequency-Domain Multiplexed Readout Systems

Cosmic microwave background (CMB) polarization experiments are increasing the number of transition edge sensor (TES) bolometers to increase sensitivity. In order to maintain low thermal loading of the sub-Kelvin stage, the frequency-domain multiplexing (FDM) factor has to increase accordingly. FDM is achieved by placing TES bolometers in series with inductor–capacitor (LC) resonators, which select the readout frequency. The multiplexing factor can be raised with a large total readout bandwidth and small frequency spacing between channels. The inductance is kept constant to maintain a uniform readout bandwidth across detectors, while the maximum acceptable value is determined by bolometer stability. Current technology relies on commercially available ceramic chip capacitors. These have high scatter in their capacitance thereby requiring large frequency spacing. Furthermore, they have high equivalent series resistance (ESR) at higher frequencies and are time consuming and tedious to hand assemble via soldering. A solution lies in lithographed, planar spiral inductors (currently in use by some experiments) combined with interdigitated capacitors on a silicon (Si) substrate. To maintain reasonable device dimensions, we have reduced trace and gap widths of the LCs to 4 \(\upmu \)m. We increased the inductance from 16 to 60 \(\upmu \)H to achieve a higher packing density, a requirement for FDM systems with large multiplexing factors. Additionally, the Si substrate yields low ESR values across the entire frequency range and lithography makes mass production of LC pairs possible. We reduced mutual inductance between inductors by placing them in a checkerboard pattern with the capacitors, thereby increasing physical distances between adjacent inductors. We also reduce magnetic coupling of inductors with external sources by evaporating a superconducting ground plane onto the backside of the substrate. We report on the development of lithographed LCs in the 1–5 MHz range for use with FDM systems. These resonators will be used by CMB polarization experiments such as Polarbear-2, Simons Array, and SPT-3G. Existing FDM systems have multiplexing factors up to 16\(\times \). We report the extension to 40\(\times \), i.e., Polarbear-2, and 68\(\times \), i.e., SPT-3G. We present the design criteria of Polarbear-2’s LC circuits, the fabrication techniques, and the testing. Concerns such as yield, accuracy in frequency, loss, and mutual inductance between spatially neighboring channels will be discussed.

Assessment of Rear-Surface Processing Strategies for III–V on Si Multijunction Solar Cells Based on Numerical Simulations

The manufacturing of high-efficiency III–V on Si multijunction solar cells needs the development of hybrid, i.e., adapted to both families of materials, solar cell processing techniques, able to extract the full photovoltaic potential of both the subcells. This fact especially impacts the processing of the silicon rear surface of the tandem, which cannot receive treatments commonly used in the single-junction Si solar cell industry [Al-back surface field (BSF), thermal SiO2, and so on], since these would result in an excessive thermal load that would deteriorate the III–V upper layers (top cell, tunnel junction, and buffer layer). However, the Si bottom cell requires an advanced design with good rear passivation, a good ohmic contact, and good carrier selectivity, so that its contribution to the efficiency of the tandem is maximized. Accordingly, in this paper, several low-temperature compatible rear-surface passivation techniques for the Si bottom subcell in a monolithic III–V/Si tandem solar cell are explored. In particular, aluminum BSFs, passivated emitter and rear cell (PERC)-like architecture, passivated emitter and rear locally diffused (PERL)-like architecture formed with low thermal loads, and heterojunction with intrinsic thin layer (HIT)-like processes are assessed using numerical simulations, and a comparison of the Si bottom cell performance for the mentioned alternatives in a GaAsP/Si dual-junction solar cell is presented.

高速炉配管のLBB評価におけるスクリーニングルール

Since the piping of fast reactor is used at low internal pressure and its material has high ductility, LBB is easily satisfied in general. Especially when the internal pressure is low and thermal expansion reaction force is small, both crack driving force and fracture load are small, then it is easily imagined that LBB might be easily satisfied. However, the crack opening displacement and leak rate dynamically evaluated are small in such conditions. For this reason, the contradiction occurs that LBB evaluation is not satisfied despite the crack driving force and the fracture load are small. To eliminate such inconsistencies, screening rules to determine the necessity of a detailed LBB evaluation were proposed. According to the rules, the detailed LBB evaluation can be omitted for the cases of low internal pressure and small thermal expansion load as the fracture of pipes do not occur. Based on the piping design of the constructed fast reactor plant, the applicability of the proposed screening rules was examined.

Design of LD in-band direct-pumping side surface polished micro-rod Nd:YVO4 laser

To diminish the thermal load, two ways, that is, in-band direct pumping and micro-rod crystal, could be adopted at the same time. The efficiency of LD in-band direct-pumping side surface polished micro-rod Nd:YVO4 laser is numerically analyzed. By optimizing parameters such as crystal length, laser mode radius, pump beam radius, doping concentration and crystal cross-section size, the overall efficiency can reach over 50%. It is found that with micro-rod crystal implemented in the laser oscillator, high overall efficiency LD in-band direct-pumping Nd:YVO4 laser could be realized. High efficiency combined with low thermal load makes this laser an outstanding scheme for building high-power Nd:YVO4 lasers.

Conceptual design of divertor and first wall for DEMO-FNS

Key issues of design of the divertor and the first wall of DEMO-FNS are presented. A double null closed magnetic configuration was chosen with long external legs and V-shaped corners. The divertor employs a cassette design similar to that of ITER. Water-cooled first wall of the tokamak is made of Be tiles and CuCrZr-stainless steel shells. Lithium injection and circulation technologies are foreseen for protection of plasma facing components. Simulations of thermal loads onto the first wall and divertor plates suggest a possibility to distribute heat loads making them less than 10 MW m−2. Evaluations of sputtering and evaporation of plasma-facing materials suggest that lithium may protect the first wall. To prevent Be erosion at the outer divertor plates either the full detached divertor operation or arrangement of the renewal lithium flow on targets should be implemented. Test bed experiments on the Tsefey-M facility with the first wall mockup coated by Ве tiles and cooled by water are presented. The temperature of the surface of tiles reached 280–300 °С at 5 MW m−2 and 600–650 °С at 10.5 MW m−2. The mockup successfully withstood 1000 cycles with the lower thermal loading and 100 cycles with higher thermal loading.