191,166 research outputs found
Analytical solution for heat conduction due to a moving Gaussian heat flux with piecewise constant parameters
We provide an analytical solution of the heat equation in the half-space
subject to a moving Gaussian heat flux with piecewise constant parameters. The
solution is of interest in powder bed fusion applications where these
parameters can be used to control the conduction of heat due to a scanning beam
of concentrated energy. The analytical solution is written in a dimensionless
form as a sum of integrals over (dimensionless) time. For the numerical
computation of these integrals we suggest a quadrature scheme that utilizes
pre-calculated look-up tables for the required quadrature orders. Such a scheme
is efficient because the required quadrature orders are strongly dependent on
the parameters in the heat flux. The possibilities of using the obtained
computational technique for the control and optimization of powder bed fusion
processes are discussed
Aerated blast furnace slag filters for enhanced nitrogen and phosphorus removal from small wastewater treatment plants
Rock filters (RF) are a promising alternative technology for natural
wastewater treatment for upgrading WSP effluent. However, the application
of RF in the removal of eutrophic nutrients, nitrogen and phosphorus, is very
limited. Accordingly, the overall objective of this study was to develop a lowcost
RF system for the purpose of enhanced nutrient removal from WSP
effluents, which would be able to produce effluents which comply with the
requirements of the EU Urban Waste Water Treatment Directive (UWWTD)
(911271lEEC) and suitable for small communities. Therefore, a combination
system comprising a primary facultative pond and an aerated rock filter
(ARF) system-either vertically or horizontally loaded-was investigated at
the University of Leeds' experimental station at Esholt Wastewater
Treatment Works, Bradford, UK.
Blast furnace slag (BFS) and limestone were selected for use in the ARF
system owing to their high potential for P removal and their low cost. This
study involved three major qperiments: (1) a comparison of aerated
vertical-flow and horizontal-flow limestone filters for nitrogen removal; (2) a
comparison of aerated limestone + blast furnace slag (BFS) filter and
aerated BFS filters for nitrogen and phosphorus removal; and (3) a
comparison of vertical-flow and horizontal-flow BFS filters for nitrogen and
phosphorus removal.
The vertical upward-flow ARF system was found to be superior to the
horizontal-flow ARF system in terms of nitrogen removal, mostly thiough
bacterial nitrification processes in both the aerated limestone and BFS filter
studies. The BFS filter medium (whieh is low-cost) showed a much higher
potential in removing phosphortls from pond effluent than the limestone
medium. As a result, the combination of a vertical upward-flow ARF system
and an economical and effective P-removal filter medium, such as BFS,
was found to be an ideal optionfor the total nutrient removal of both nitrogen
and phosphorus from wastewater.
In parallel with these experiments, studies on the aerated BFS filter effective
life and major in-filter phosphorus removal pathways were carried out. From
the standard batch experiments of Pmax adsorption capacity of BFS, as well
as six-month data collection of daily average P-removal, it was found that
the effective life of the aerated BFS filter was 6.5 years. Scanning electron
microscopy and X-ray diffraction spectrometric analyses on the surface of
BFS, particulates and sediment samples revealed that the apparent
mechanisms of P-removal in the filter are adsorption on the amorphous
oxide phase of the BFS surface and precipitation within the filter
Two-Stage Multi-Objective Meta-Heuristics for Environmental and Cost-Optimal Energy Refurbishment at District Level
Energy efficiency and environmental performance optimization at the district level are following an upward trend mostly triggered by minimizing the Global Warming Potential (GWP) to 20% by 2020 and 40% by 2030 settled by the European Union (EU) compared with 1990 levels. This paper advances over the state of the art by proposing two novel multi-objective algorithms, named Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-Objective Harmony Search (MOHS), aimed at achieving cost-effective energy refurbishment scenarios and allowing at district level the decision-making procedure. This challenge is not trivial since the optimisation process must provide feasible solutions for a simultaneous environmental and economic assessment at district scale taking into consideration highly demanding real-based constraints regarding district and buildings’ specific requirements. Consequently, in this paper, a two-stage optimization methodology is proposed in order to reduce the energy demand and fossil fuel consumption with an affordable investment cost at building level and minimize the total payback time while minimizing the GWP at district level. Aimed at demonstrating the effectiveness of the proposed two-stage multi-objective approaches, this work presents simulation results at two real district case studies in Donostia-San Sebastian (Spain) for which up to a 30% of reduction of GWP at district level is obtained for a Payback Time (PT) of 2–3 years.Part of this work has been developed from results obtained during the H2020 “Optimised Energy
Efficient Design Platform for Refurbishment at District Level” (OptEEmAL) project, Grant No. 680676
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