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Dedicated fan-duct-heatsink combinations have become a standard means of cooling computer processors. Most previous studies have considered optimization of fin geometry (pitch and thickness) with overall heatsink dimensions (width, height, length) fixed. The present study considers size requirements for the constraints of fixed air volume flow rate and pressure drop, fixed fan/blower power, and fixed thermal conductance. First, an ideal heatsink with infinite fin thermal conductivity is considered, providing simple power-law prediction of performance. Next, fins of finite thermal conductivity and thickness, as well as effects of developing flow are included in the analysis, permitting prediction and minimization of weight. Models of both levels of complexity can be used, previous to more detailed numerical and/or experimental studies, to design optimized heatsinks.

It is increasingly acknowledged that climate change is influencing terrestrial ecosystems by increased drought and rainfall intensities. Soil microbes are key drivers of many processes in terrestrial systems and rely on water in soil pores to fulfill their life cycles and functions. However, little is known on how drought and rainfall fluctuations, which affect the composition and structure of microbial communities, persist once original moisture conditions have been restored. Here, we study how simulated short-term drying and re-wetting events shape the community composition of soil fungi and prokaryotes. In a mesocosm experiment, soil was exposed to an extreme drought, then re-wetted to optimal moisture (50% WHC, water holding capacity) or to saturation level (100% WHC). Composition, community structure and diversity of microbes were measured by sequencing ITS and 16S rRNA gene amplicons 3 weeks after original moisture content had been restored. Drying and extreme re-wetting decreased richness of microbial communities, but not evenness. Abundance changes were observed in only 8% of prokaryote OTUs, and 25% of fungal OTUs, whereas all other OTUs did not differ between drying and re-wetting treatments. Two specific legacy response groups (LRGs) were observed for both prokaryotes and fungi. OTUs belonging to the first LRG decreased in relative abundance in soil with a history of drought, whereas OTUs that increased in soil with a history of drought formed a second LRG. These microbial responses were spread among different phyla. Drought appeared to be more important for the microbial community composition than the following extreme re-wetting. 16S profiles were correlated with both inorganic N concentration and basal respiration and ITS profiles correlated with fungal biomass. We conclude that a drying and/or an extreme re-wetting history can persist in soil microbial communities via specific response groups composed of members with broad phylogenetic origins, with possible functional consequences on soil processes and plant species. As a large fraction of OTUs responding to drying and re-wetting belonged to the rare biosphere, our results suggest that low abundant microbial species are potentially important for ecosystem responses to extreme weather events.

Abstract Methane dry reforming with CO2 using FeO powder in molten salt has been investigated at various flow rates of CH4/CO2 mixed gases (CH4/CO2=1) between 50 and 400 ml/min at 1223 K in an infrared furnace. This work is carried out to determine the usefulness of this method for the chemical storage of solar energy. The CH4/CO2 mixed gases passing through the molten salt (Na2CO3/K2CO3=1) containing the FeO powder were catalytically decomposed into CO, H2 and H2O. The product gas mole ratios, CO/H2/H2O, were shown to be 3:1:1 for a high flow rate of 200 ml/min and to be CO/H2=2:1 for a low flow rate of 50 ml/min. The results were explained in terms of the kinetics of the CH4-reforming reaction and the thermodynamics of the redox process of FeO powder mixed in the molten salt; CH 4 +2FeO⇒2Fe+H 2 +CO+H 2 O Fe+CO 2 ⇒FeO+CO for a high flow rate, and FeO+CH 4 ⇒Fe+2H 2 +CO Fe+CO 2 ⇒FeO+CO for a low flow rate.

Abstract Integration of solar photovoltaic (PV) and battery storage systems is an upward trend for residential sector to achieve major targets like minimizing the electricity bill, grid dependency, emission and so forth. In recent years, there has been a rapid deployment of PV and battery installation in residential sector. In this regard, optimal planning of PV-battery systems is a critical issue for the designers, consumers, and network operators due to high number of parameters that can affect the optimization problem. This paper aims to present a comprehensive and critical review on the effective parameters in optimal planning process of solar PV and battery storage system for grid-connected residential sector. The key parameters in process of optimal planning for PV-battery system are recognized and explained. These parameters are economic and technical data, objective functions, energy management systems, design constraints, optimization algorithms, and electricity pricing programs. A timely review on the state-of-the-art studies in PV-battery optimal planning is presented. The challenges, trends and latest developments in the topic are discussed. At the end, scopes for future studies are developed. It is found that new guidelines should be provided for the customers based on various electricity rates and demand response programs. Also, several design considerations like grid dependency and resiliency need further investigation in the optimal planning of PV-battery systems.

The concept of a high temperature fast reactor cooled by supercritical water (SCFR-H) was developed for achieving high thermal efficiency and a compact reactor system. The core characteristics were obtained from single channel thermal-hydraulic analysis. Thus, it is necessary to carry out subchannel analysis to estimate the effect of local power peaking and cross flows. For this purpose, a subchannel analysis code is developed. It is verified by comparing the results with experimental data of High Conversion Pressurized Water Reactor (HCPWR). Sensitivities of the outlet coolant and cladding temperature to the subchannel flow area and local power peaking are high. One of the reasons is that the ratio of the coolant flow rate of SCFR-H to the power is smaller than that of LWR. Another reason is that, temperature of supercritical water is more sensitive to the enthalpy change above 450°C. The outlet coolant temperature distribution can be flattened by reducing the area of the peripheral subchannels and by enhancing the mixing between the subchannels.

Abstract The goal of the safety design for the demonstration fast breeder reactor is to ensure that the safety level is equivalent to or higher than that of the light water reactors of the same period. The design of the safety features such as reactor shutdown, decay heat removal and confinement systems is of importance to reach the goal. The reactor core is equipped with two independent fast shutdown systems, the primary system and the backup system. In addition, it is planned to strengthen the passive shutdown capability by using self- actuated systems such as a Curie point device for the backup system. The decay heat is removed from the core to the atmosphere through the safety lines of the direct reactor auxiliary cooling system which is composed of four independent lines. Furthermore, under the severe conditions that no active function of the decay heat removal system is available, the heat can be removed by natural convection through the safety lines by taking advantage of the high boiling temperature of sodium. For the confinement function, the reactor vessel is surrounded by a containment vessel and a confinement area. The design concept of these safety features is described in this paper.

Corrosion-resistive conductive titanium oxide exhibited remarkably higher durability than a carbon support during electrochemical catalytic reactions under high potential conditions.