Reduction In Peak Temperature Research Articles

Compact Thermal Modelling Tool for Fast Design Space Exploration of 3D ICs with Integrated Microchannels

Integrated microchannel cooling is a very promising concept for thermal management of 3D ICs, because it offers much higher cooling performance than conventional forced-air convection. The thermo-fluidic simulations of such chips are usually performed using a computational fluid dynamics (CFD) approach. However, due to the complexity of the fluid flow modelling, such simulations are typically very long and faster models are therefore considered. This paper demonstrates the advantages of TIMiTIC—a compact thermal simulator for chips with liquid cooling—and shows its practical usefulness in design space exploration of 3D ICs with integrated microchannels. Moreover, thermal simulations of a 3D processor model using the proposed tool are used to estimate the optimal power dissipation profile in the chip and to prove that such an optimal profile allows for a very significant (more than 10 °C) peak temperature reduction. Finally, a custom correlation metric is introduced which allows the comparison of the power distribution profiles in terms of the peak chip temperature that they produce. Statistical analysis of the simulation results demonstrates that this metric is very accurate and can be used for example in thermal-aware task scheduling or dynamic voltage and frequency scaling (DVFS) algorithms.

Yearly analysis of peak temperature, thermal amplitude, time lag and decrement factor of a building envelope in tropical climate

Two similar building structures, one is with macrocapsules of PCM called the experimental building structure (EBS), while the other is without macrocapsules of PCM called the reference building structure (RBS) were developed using conventional construction materials. Both the structures were then monitored for one year in the outdoor tropical type of environmental conditions to evaluate the indoor thermal behavior based on indoor peak temperature, indoor thermal amplitude, time lag, and decrement factor. Additionally, the annual average peak heat flux and corresponding cost-savings in peak cooling load were also analyzed. The results depict that EBS shows a reduction in the indoor peak temperature round the year, ranging from 0.2 °C to 4.3 °C and a percentage reduction in indoor thermal amplitude ranging from -2.43% to 51.3%. The annual average time delay of 97.5 min and the annual average percentage reduction of 24.69% in the decrement factor was obtained by the EBS. The annual average peak heat flux reduction of 17.37% and corresponding yearly average cost-saving in peak cooling load of 1.47 rupees/kWh/m2/day was obtained in the EBS.

Microstructure and thermal characterization of aerogel–graphite polyurethane spray-foam composite for high efficiency thermal energy utilization

Aerogel is a superinsulating material with an extremely low thermal conductivity (<0.015 W/m·K), high porosity (>99 %), and extremely low density. In this study, a new closed-cell spray polyurethane (PU) foam with aerogel was developed and investigated. In particular, a PU foam with aerogel and graphite (PUAG) was prepared by mixing aerogel for reducing the thermal conductivity of the foam and a small concentration of graphite for improving its flame-retardancy performance. The performance of the prepared PUAG was analyzed via several tests, including density measurements, thermal-conductivity measurements, morphology examination, flame-retardancy evaluation, thermogravimetric analysis, and dynamic heat transfer analysis. A 20 % reduction in the thermal conductivity compared with traditional PU was observed. Additionally, the PUAG exhibited a reduction in the total smoke production and a 10 % reduction in the surface peak temperature.

Effects of Bismuth Content on the Microstructure, Shear Strength and Thermal Properties of Sn-0.7Cu-0.05Ni Solder Joints

The effects of bismuth content on the microstructure, shear strength and thermal properties of Sn-0.7Cu-0.05Ni solder joints were investigated. Adding 2 wt% elemental Bi to Sn-0.7Cu-0.05Ni solder joints reduced peak temperature by about 6.7 °C, increased pasty range by 4.2 °C and raised undercooling by 3.1 °C. The microstructure of the interfacial layer between solder and Cu substrate was composed of (Cu,Ni)6Sn5 and (Cu,Ni)3Sn intermetallic compounds (IMCs). The solder joint included a phase of SnBi and Cu6Sn5 IMCs. The addition of elemental Bi increased shear strength and suppressed the growth of IMCs in the interfacial layer of the solder joints.

Influence of graphene nanoplatelets on curing kinetics and rheological properties of a benzoxazine resin

The effect of two types of graphene nanoplatelets on the curing kinetics, gelation and vitrification behaviour of a benzoxazine resin was investigated by means of differential scanning calorimetry and rheological experiments. The results showed that the incorporation of graphene nanoplatelets did not change the autocatalytic nature of curing reaction. However, when benzoxazine was doped with the nanofiller supplied by XG-Sciences an acceleration effect in curing reaction was observed, especially when a 2 wt.% was added. This catalytic effect was demonstrated by the reduction of peak temperature, apparent activation energy and the shorter gelation and vitrification times.Finally, the curing kinetic equation for benzoxazine and its nanocomposites was obtained by linear model-fitting of non-isothermal experiments and it matched reasonably well with the experimental results from both non-isothermal and isothermal tests.

On Fundamental Principles for Thermal-Aware Design on Periodic Real-Time Multi-Core Systems

With the exponential rise of the transistor count in one chip, the thermal problem has become a pressing issue in computing system design. While there have been extensive methods and techniques published for design optimization with thermal awareness, there is a need for more rigorous and formal thermal analysis in designing real-time systems and applications that demand a strong exception guarantee. In this article, we analytically prove a series of fundamental properties and principles concerning the RC thermal model, peak temperature identification, and peak temperature reduction for periodic real-time systems, which are general enough to be applied on 2D and 3D multi-core platforms. These findings enhance the worst-case temperature predictability in runtime scenarios, as well as help to develop more effective thermal management policy, which is key to thermal-constrained periodic real-time system design.

Numerical assessment of brick walls` use incorporating a phase change material towards thermal performance in buildings during a passive cooling strategy

The integration of new building materials incorporating phase change material (PCM) into the building envelope leads to an increase of the heat storage capacity, which may have an influence on minimizing the cooling demand and heating of the building. This work addresses a thermal performance enhancement of brick walls with incorporated PCM. The improvement has been assessed through a numerical approach in dealing with a 1-D transient conduction problem with phase change, while leaning on experimental results from a transient guarded hot plates method. The simulations have been fulfilled using a hybrid method combining both the finite volume method and an enthalpy porosity technique. The results of this combined approach are in good agreement. In the light of the findings obtained, it appears that PCM incorporation into a brick masonry can both reduce peak temperatures up to 3?C and smooth out daily fluctuations. Thereby, the evaluation achieved can turns out useful in developing brick walls with an incorporated PCM for passive cooling, thus improving buildings thermal performance.

Conductive inserts to reduce nuclear fuel temperature

In an effort to develop better performing nuclear fuels, placement of conductive inserts in nuclear fuel pellets is being considered. Conductive inserts incorporated in the fuel pellets will dissipate heat more efficiently, allowing the fuel to operate at a lower temperature while producing the same amount of power. Calculation results reported in the present paper, show that placing a 6-finned molybdenum insert in a UO2 pellet will result in an 842 C reduction of the peak fuel temperature. Likewise, placing multiple equidistantly spaced 50 μm thick molybdenum discs in a UO2 pellet will result in a 995 C reduction of the peak fuel temperature. In both cases, the volume of the insert is limited to 5% of the volume of the pellet. While these results are preliminary in scope, the impact of the reduced peak temperature on expected fuel performance warrants initiation of experimental work that will include fabrication and irradiation of these and similar fuel designs at the Idaho National Laboratory.

Submerged friction stir welding of dissimilar joints between an Al-Mg alloy and low carbon steel: Thermo-mechanical modeling, microstructural features, and mechanical properties

Underwater dissimilar friction stir welding of an Al-Mg alloy (AA5005) and low carbon steel (ASTM A283) in butt joint configuration was studied. The effect of submerged temperature at three levels of 273, 298 and 333 K on the mechanical and metallurgical properties of the joints was investigated. An improvement in the properties of the submerged dissimilar joints as compared with air-processed specimens is shown. It is demonstrated that this improvement is due to the reduced peak temperature and finer grain structure caused by the cooling effect of the medium. However, the surface flow of the materials is smoother in the air-processed specimens, although processing at heated water yields better surface quality. The thickness of the interface is also reduced by the submerge friction stir welding. The strength of the dissimilar joints varies between 62–72% and 19–23% of the aluminum alloy and the steel, respectively. A lower hardness is attained in the submerged welding that can be improved by processing in warm water. The results of this study may pave a way for robust friction stir welding of dissimilar joints through controlling the temperature of the processing environment.

Seismic, thermal and compositional structures of the stagnant slab in the mantle transition zone beneath southeastern China

The structure of Earth’s mantle transition zone (MTZ) contains important information about how oceanic plates are recycled into the mantle. However, morphologies of stagnant slab in the MTZ inferred from seismic studies remain controversial. Here, we conduct combined geodynamic, mineral physical and seismologic modeling to infer fine features of the stagnant slab in the MTZ beneath southeastern China. This method applies mineral physics modeling in combination with geodynamically consistent thermal anomalies to predict seismic velocity structures in the MTZ that are used in triplication waveform modeling. The synthetic waveforms are systematically compared with observed data using a grid search optimization. Our best-fit model reveals a stagnant slab lying at the bottom of the MTZ with a peak temperature reduction of 350 ± 80 K and a thickness of 85 ± 20 km, indicating that it underwent little deformation. By joint modeling of the mineral physics and thermal history of the slab, our approach improves estimates of both the thickness and temperature of the stagnant slab and provides a better understanding of the paleo subduction system beneath southeastern China.

Investigation on Insulation Performance of Thermally Aged Natural Ester Oil Impregnated Pressboard

An attempt is made to understand the effect of thermal ageing on natural ester oil impregnated pressboard material. Surface discharge inception voltage of natural ester oil impregnated pressboard material is reduced drastically under AC, harmonic AC voltages and with DC voltages with high ripple content. Phase-resolved partial discharge studies show an increase in the number of discharges for natural ester oil impregnated pressboard (OIP) aged at higher temperature, under AC and harmonic AC voltages with different total harmonic distortions. Surface potential measurement study complies with results obtained by surface discharge inception voltage. It indicates the presence of high-density charge traps evolved as a function of ageing time and temperature. Laser-induced breakdown spectroscopy analysis is carried out to understand the characteristic variation with thermally aged OIP material. A decrease in plasma temperature is observed for sample aged at higher temperature. Differential scanning calorimetric studies indicate reduction in peak temperature with thermally aged specimens. Ageing observed to affect mechanical strength of the cellulosic material, as indicated by tensile test. Dielectric response spectroscopy study indicates that with an increase in thermal ageing, the permittivity, tan(δ), DC conductivity and relaxation time have increased. A reduction in activation energy of the aged material is observed, which indicates the status of the OIP material.

Potential benefits of cool roofs in reducing heat-related mortality during heatwaves in a European city

Abstract Hot weather can exacerbate health conditions such as cardiovascular and respiratory diseases, and lead to heat stroke and death. In built up areas, temperatures are commonly observed to be higher than those in surrounding rural areas, due to the Urban Heat Island (UHI) effect. Climate change and increasing urbanisation mean that future populations are likely to be at increased risk of overheating in cities, although building and city scale interventions have the potential to reduce this risk. We use a regional weather model to assess the potential effect of one type of urban intervention – reflective ‘cool’ roofs – to reduce local ambient temperatures, and the subsequent impact on heat-related mortality in the West Midlands, UK, with analysis undertaken for the summer of 2006, as well as two shorter heatwave periods in 2006 and 2003. We show that over a summer season, the population-weighted UHI intensity (the difference between simulated urban and rural temperature) was 1.1 °C on average, but 1.8 °C when including only night times, and reached a maximum of 9 °C in the West Midlands. Our results suggest that the UHI contributes up to 40% of heat related mortality over the summer period and that cool roofs implemented across the whole city could potentially offset 18% of seasonal heat-related mortality associated with the UHI (corresponding to 7% of total heat-related mortality). For heatwave periods, our modelling suggests that cool roofs could reduce city centre daytime 2 m air temperature by 0.5 °C on average, and up to a maximum of ~3 °C. Cool roofs reduced average UHI intensity by ~23%, and reduced heat related mortality associated with the UHI by ~25% during a heatwave. Cool roofs were most effective at reducing peak temperatures during the daytime, and therefore have the potential to limit dangerous extreme temperatures during heatwaves. Temperature reductions were dependent on the category of buildings where cool roofs were applied; targeting only commercial and industrial type buildings contributed more than half of the reduction for heatwave periods. Our modelling suggested that modifying half of all industrial/commercial urban buildings could have the same impact as modifying all high-intensity residential buildings in the West Midlands.

Augmented Cross-Entropy-Based Joint Temperature Optimization of Real-Time 3-D MPSoC Systems

3-D multiprocessor system-on-chip (MPSoC) systems can offer higher integration density, lower interaction cost, better bandwidth, and greater performance. However, vertically stacked silicon layers and limited heat dissipation paths result in high peak temperature and large temperature variation, which incur reliability reduction, lifetime decay, and performance degradation. In this article, we propose an offline augmented cross-entropy (CE)-based task scheduling strategy to jointly optimize peak temperature and temperature variation under the constraint of timeliness. Specifically, based on the conventional CE method, a heuristic iterative sampling method is designed to explore task-to-core assignment for balanced heat distribution between the top-layer and the bottom-layer cores. Subsequently, thermal characteristics of 3-D MPSoC systems are used to judiciously swap tasks between the two layers to improve the conventional CE-based task assignment and accelerate the iterative process. The peak temperature of individual cores is further reduced via sequencing, splitting, and slacking task execution. The experimental results demonstrate that compared to the existing state-of-the-art methods, the proposed scheme can reduce peak temperature by up to 8.02 °C and temperature variation by up to 24.78% without violating the timeliness of tasks.

Smart heat storage building material development with Loess and SSPCM for building energy saving

This experiment aimed at the development of energy efficient and sustainable building materials. The specimens were made using loess, styrene butadiene latex (SBL), shape stable phase change material (SSPCM) made from x-GnP and n-octadecane for mechanical and thermal performance improvement. Compressive strength test, FT-IR (Fourier-transform infrared spectroscopy) and dynamic thermal transfer experiment were performed. From the result of the compressive strength test, it was found that the addition of SBL increases the compressive strength and the addition of SSPCM reduces the compressive strength. FT-IR analysis revealed no chemical reaction between PCM and x-GnP, indicating only physical binding. As a result of the dynamic heat transfer analysis, peak temperature reduction was observed. According to energy analysis, storage capacity energy was improved and PCM 7.5 was the most energy efficient.

Dynamic Task Mapping and Scheduling with Temperature-Awareness on Network-on-Chip based Multicore Systems

Abstract Technology scaling has enabled integration of a large number of intellectual property cores, memory units and processing elements on a single chip. This has led to the evolution of multicore systems. In recent years, these systems have gained popularity as execution platforms for real-time applications. However, due to the close spacing of the cores and uneven heat dissipation among the processors of the multicore platform, thermal hotspots are formed. Ensuring thermal safety in real-time systems is a challenging task, especially when various applications are executed with different timing constraints. In real-time dynamic systems, applications unknown at design-time, are submitted by users at runtime. In order to perform on-the-fly task assignment to the processors of the multicore platform, different dynamic resource allocation approaches are reported in the literature. However, most of the dynamic task allocation approaches lack in thermal awareness and do not consider thermal safety of the chip. Also, most of the existing thermal-aware task mapping methods rely on offline thermal analysis which is either unavailable in dynamic scenarios or is computationally too expensive for providing end-to-end thermal-aware solution at runtime. In this work, we propose an improved algorithm for dynamic thermal-aware task mapping and scheduling using a non-profiling based strategy for NoC based multi-core systems. By using a combination of threshold based thermal management scheme and dynamic task (re)allocation, the proposed thermal-aware approach helps to maintain the thermal safety of the chip. Simulation results demonstrate that the proposed algorithm achieves 25.3% and 45.6% reduction in chip peak temperature compared to recent dynamic task allocation approaches ATM [1] and DEAMS [2] respectively. Also, the proposed thermal-aware strategy satisfies the task deadline while reducing the average packet delay of the allocated applications. When compared to other thermal-aware methods such as ATM [1] and TAPP [3], the proposed strategy improves the deadline satisfaction of the tasks by 37.8% and 67.3% respectively.

Quench Protection of the 16 T Nb3Sn Dipole Magnets Designed for the Future Circular Collider

Three different 16 T dipole magnet options for the Future Circular Collider (FCC) have been designed within the H2020 EuroCirCol collaboration, namely a cosθ-, a block-, and a common-coil -type of magnet. All magnets were designed using the same constraints related to magnetic field, cable parameters, mechanics, and quench protection. The quench protection analysis during the magnet design was centralized and done for all the options using the same tools and methods. This paper summarizes the final conceptual protection schemes. They are based either on the novel CLIQ-technology (Coupling Loss Induced Quench) or on traditional quench heaters. We compare the performance of the protection systems and show that while both can protect the magnet at nominal operation current, CLIQ is more efficient in reducing peak temperatures than heaters, and the system operation is simpler due to smaller amount of protection units. Therefore, CLIQ has been chosen as the baseline protection option for the FCC dipole magnets. The future development of heaters is considered as a back-up option.

Exploring the Role of Large Centralised Caches in Thermal Efficient Chip Design

In the era of short channel length, Dynamic Thermal Management (DTM) has become a challenging task for the architects and designers engineering modern Chip Multi-Processors (CMPs). Ever-increasing demand of processing power along with the developed integration technology produces CMPs with high power density, which in turn increases effective chip temperature. This increased temperature leads to increase in the reliability issues for the chip-circuitry with significant increment in leakage power consumption. Recent DTM techniques apply DVFS or Task Migration to reduce temperature at the cores, the hottest on-chip components, but often ignore the on-chip hot caches. To commensurate the high data demand of these cores, most of the modern CMPs are equipped with large multi-level on-chip caches, out of which on-chip Last Level Caches (LLCs) occupy the largest on-chip area. These LLCs are accounted for their significantly high leakage power consumption that can also potentially generate on-chip hotspots at the LLCs similar to the cores. As power consumption constructs the backbone of heat dissipation, hence, this work dynamically shrinks cache size while maintaining performance constraint to reduce LLC leakage, primarily. These turned-off cache portions further work as on-chip thermal buffers for reducing average and peak temperature of the CMP without affecting the computation. Simulation results claim that, at a minimal penalty on the performance, proposed cache-based thermal management having 8MB centralised multi-banked shared LLC gives around 5°C reduction in peak and average chip temperature, which are comparable with a Greedy DVFS policy.

Charting pathways to climate change mitigation in a coupled socio-climate model.

Geophysical models of climate change are becoming increasingly sophisticated, yet less effort is devoted to modelling the human systems causing climate change and how the two systems are coupled. Here, we develop a simple socio-climate model by coupling an Earth system model to a social dynamics model. We treat social processes endogenously—emerging from rules governing how individuals learn socially and how social norms develop—as well as being influenced by climate change and mitigation costs. Our goal is to gain qualitative insights into scenarios of potential socio-climate dynamics and to illustrate how such models can generate new research questions. We find that the social learning rate is strongly influential, to the point that variation of its value within empirically plausible ranges changes the peak global temperature anomaly by more than 1°C. Conversely, social norms reinforce majority behaviour and therefore may not provide help when we most need it because they suppress the early spread of mitigative behaviour. Finally, exploring the model’s parameter space for mitigation cost and social learning suggests optimal intervention pathways for climate change mitigation. We find that prioritising an increase in social learning as a first step, followed by a reduction in mitigation costs provides the most efficient route to a reduced peak temperature anomaly. We conclude that socio-climate models should be included in the ensemble of models used to project climate change.

Insight into the potentiality of big biochar particle as an amendment in aerobic composting of sewage sludge

To assess the potential of big biochar as composting amendment, the study was performed on aerobic composting of sewage sludge amended with litchi wood biochar (10% of fresh mixture weight, 20–40 mm) in a 400 L bioreactor system. Physicochemical properties and microbial activities were monitored during the first fermentation process of aerobic compost. Application of big biochar reduced peak temperature and shortened thermophilic phase, but increased the activities of aryl-sulfatase, β-glucosidase, and dehydrogenase, which led to higher removal efficiency of total carbon, nitrogen, and sulphur. Big biochar inhibited degradation of organic matters in composting. Therefore, a comprehensive assessment including physicochemical and microbial properties can help to better understand the effect of big biochar on sewage sludge composting.

Potential benefits of cool roofs in reducing heat-related mortality during heatwaves in a European city

Hot weather can exacerbate health conditions such as cardiovascular and respiratory diseases, and lead to heat stroke and death. In built up areas, temperatures are commonly observed to be higher than those in surrounding rural areas, due to the Urban Heat Island (UHI) effect. Climate change and increasing urbanisation mean that future populations are likely to be at increased risk of overheating in cities, although building and city scale interventions have the potential to reduce this risk.We use a regional weather model to assess the potential effect of one type of urban intervention – reflective ‘cool’ roofs – to reduce local ambient temperatures, and the subsequent impact on heat-related mortality in the West Midlands, UK, with analysis undertaken for the summer of 2006, as well as two shorter heatwave periods in 2006 and 2003.We show that over a summer season, the population-weighted UHI intensity (the difference between simulated urban and rural temperature) was 1.1 °C on average, but 1.8 °C when including only night times, and reached a maximum of 9 °C in the West Midlands. Our results suggest that the UHI contributes up to 40% of heat related mortality over the summer period and that cool roofs implemented across the whole city could potentially offset 18% of seasonal heat-related mortality associated with the UHI (corresponding to 7% of total heat-related mortality).For heatwave periods, our modelling suggests that cool roofs could reduce city centre daytime 2 m air temperature by 0.5 °C on average, and up to a maximum of ~3 °C. Cool roofs reduced average UHI intensity by ~23%, and reduced heat related mortality associated with the UHI by ~25% during a heatwave. Cool roofs were most effective at reducing peak temperatures during the daytime, and therefore have the potential to limit dangerous extreme temperatures during heatwaves. Temperature reductions were dependent on the category of buildings where cool roofs were applied; targeting only commercial and industrial type buildings contributed more than half of the reduction for heatwave periods. Our modelling suggested that modifying half of all industrial/commercial urban buildings could have the same impact as modifying all high-intensity residential buildings in the West Midlands.