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Abstract An experimental investigation of the steady-state rates of heat transfer from an array of vertical rectangular fins of 3 mm thickness and 250 mm length, protruding 60 mm perpendicularly upwards from a 250 mm × 190 mm horizontal rectangular base, is reported. For constant (to ±0·1°C) base temperatures between 40°C and 80°C, in an ambient environment of 20±0·2°C, the optimal separation of the parallel fins, corresponding to the maximum rate of heat loss, is 10·5±1·0 mm. The effects of the extent of the fin protrusions on the thermal performances of such vertical fins, on the same base, which was arranged to be either vertical or horizontal , have been studied. The experiments were performed with three different fin protrusions, namely 32 mm, 60 mm and 90 mm, for a base temperature of 40°C above that of the ambient environment. The steady-state rate of heat dissipation from the fin array increased slightly less than linearly with the fin protrusion for both orientations, but the relationship became closer to linear as the fin spacing was increased. A comparison of the abilities to dissipate heat to the room air from the same geometrical configuration having a rectangular fin array but positioned with vertical fins on a vertical base, vertical fins protruding upwards from a horizontal base, or horizontal fins on a vertical base, has been made. The orientation with vertical fins protruding upwards from the horizontal base, is the preferred option because of the relatively high rates of heat transfer that can then be achieved.

The improvement of the energy efficiency of belt conveyor systems can be achieved at equipment and operation levels. Specifically, variable speed control, an equipment level intervention, is recommended to improve operation efficiency of belt conveyors. However, the current implementations mostly focus on lower level control loops without operational considerations at the system level. This paper intends to take a model based optimization approach to improve the efficiency of belt conveyors at the operational level. An analytical energy model, originating from ISO 5048, is firstly proposed, which lumps all the parameters into four coefficients. Subsequently, both an off-line and an on-line parameter estimation schemes are applied to identify the new energy model, respectively. Simulation results are presented for the estimates of the four coefficients. Finally, optimization is done to achieve the best operation efficiency of belt conveyors under various constraints. Six optimization problems of a typical belt conveyor system are formulated, respectively, with solutions in simulation for a case study.

Abstract For a cascade-arch low-NOx and high-burnout configuration designated as a solution to the currently incompatible problem of the ultra-low NOx combustion and high burnout in down-fired furnaces, numerical simulations, which were verified by real-furnace measurements of a 600 MWe down-fired furnace with a multiple-injection and multiple-staging combustion technology, were performed to evaluate its in-furnace flow, coal combustion, and NOx formation at various lower-arch location setups of CH = 0.65, 0.6, 0.55, and 0.5 (CH representing the ratio of the lower arch height to the front/rear wall height in the lower furnace). The aim was to evaluate its lower-arch location effect on the furnace performance and confirm its superiority compared with the prior art. With asymmetric combustion developing at extreme settings of CH = 0.65 and 0.5, the combustion symmetry and furnace performance originally improved but then worsened with decreasing CH, resulting in the exhaust gas loss, carbon in fly ash, and CO and NOx emissions all decreasing first and then increasing. Consequently, the CH = 0.6 location setup achieved the optimal furnace performance characterized as NOx emissions of 707 mg/m3 at 6% O2 and carbon content in fly ash of about 5.50%. In comparison to the prior art, the new combustion configuration owned an improved symmetrical combustion pattern, strengthened deep-air-staging conditions, and lengthened flame travel by positioning hopper air, applying flue gas recirculation, and introducing fine pulverized-coal reburning, thereby achieving the apparently improved low-NOx and high-burnout performance with a NOx reduction of 22% without affecting burnout.

Abstract Nonlinear systems may exhibit secondary resonances, which can provide an additional and thus broadened bandwidth for energy harvesting. However, the secondary resonances of nonlinear energy harvesters reported in the literature suffer from low-power output and limited bandwidth. This work proposes a novel magnetic rolling pendulum (MRP) with a large bandwidth and high power output in both primary and secondary resonances for energy harvesting. The MRP employs the rolling motion of a magnetically levitated permanent magnet with minimal mechanical damping. A prototype was fabricated and characterised. An analytical model combined with finite element analysis was developed and validated by experiment. Both experiment and simulation show that the MRP has a linear resonance frequency of 4.6 Hz and peak power of 3.7 mW. It exhibits strong nonlinear behaviours and broadband characteristics with excitation amplitude as low as 2 m/s2 in the primary resonance. As the excitation amplitude is larger than 5 m/s2, the secondary resonance (1/2 order subharmonics) is excited. The responses of the MRP at the subharmonic resonance take the same form as the primary resonance in terms of displacement and power outputs. This helps the subharmonic resonance to produce the same power level as the primary resonance but with a larger bandwidth. When excited at 14 m/s2, the MRP shows 1-mW-bandwidth of 9.7 Hz, 2/3 of which is attributed to the subharmonic resonance.

The purpose of this paper is to provide a broad overview of the social and environmental costs and benefits of biofuels in Asia. The major factors that will determine the impacts of biofuels are: (1) their contribution to land-use change, (2) the feedstocks used, and (3) issues of technology and scale. Biofuels offer economic benefits, and in the right circumstances can reduce emissions and make a small contribution to energy security. Feedstocks that involve the conversion of agricultural land will affect food security and cause indirect land-use change, while those that replace forests, wetlands or natural grasslands will increase emissions and damage biodiversity. Biofuels from cellulose, algae or waste will avoid some of these problems, but come with their own set of uncertainties and risks. In order to ensure net societal benefits of biofuel production, governments, researchers, and companies will need to work together to carry out comprehensive assessments, map suitable and unsuitable areas, and define and apply standards relevant to the different circumstances of each country. The greatest benefits may come from feedstocks produced on a modest scale as co-products of smart technologies developed for phytoremediation, waste disposal and emissions reduction.

Abstract The automotive operating protocols is a comprehensive expression of a country or a region’s road, climatic environment and driving habits. It is the foundation of energy consumption, test method and limit method for automobile products. It has direct impact on R & D, production and government access management of enterprises. For fuel cells vehicles, the lifetime is one of the main factors restricting their commercialization. Furthermore, the lifetime evaluation methods and its standard specifications of vehicular proton exchange membrane fuel cell are the critical factors to its technological development, but there is no authoritative recognized life evaluation method and test protocols so far. A logical fuel cell durability test protocol is the fundamental for developing the fuel cell life evaluation methods. A review on the state-of-art in the world for fuel cell accelerated test protocols was given, the research circumstances of different universities and research institutions in China, America, the European Union, Japan and so on are analyzed and summarized in detail. Then the essential characteristics and applicable environments of a comprehensive and effective durability test protocol are summarized based on the analysis and demonstration of the existing durability test protocols in literature. The work in this paper focuses on the research of durability test protocols of the fuel cell stack for the first time. The final conclusion will provide theoretical basis for establishing fuel cell durability test specifications and proposing life evaluation methods, and make a contribution to the long life research of vehicular fuel cells.

Abstract Microalgae have reported to be one of the most promising feedstock for biofuel production. However, microalgal cultivation for biofuel production is a costly process due to the large amounts of water, inorganic nutrients (mainly N and phosphate (P)), and CO2 needed. In this study, we evaluated whether the nutrient-rich ash and flue gas generated in biomass power plants could serve as a nutrient source for Chlorella sp. C2 cultivation to produce biolipids in a cost-efficient manner. When ash was incorporated in the culture medium and photosynthesis was enhanced by CO2 from flue gas, Chlorella cultures produced a lipid productivity of 99.11 mg L−1 d−1 and a biomass productivity of 0.31 g L−1 d−1, which are 39% and 35% more than the control cultures grown in BG11 medium. Additionally, the cultures reduced the nitrogen oxide (NOx) present in the flue gas and sequestered CO2, with a maximum ash denutrition rate of 13.33 g L−1 d−1, a NOx reduction (DeNOx) efficiency of ∼ 100%, and a CO2 sequestration rate of 0.46 g L−1 d−1. The residual medium was almost nutrient-free and suitable for recycling for continuous microalgal cultivation or farmland watering, or safely disposed off. Based on these results, we propose a technical strategy for biomass power plants in which the industrial wastes released during power generation nourish the microorganisms used to produce biofuel. Implementation of this strategy would enable carbon negative bioenergy production and impart significant environmental benefits.