Solar Assisted Small-Scale Biomass District Heating System in the Northern Part of Sweden

Abstract

This article presents a case study of a projected solar assisted biomass district heating system in the north of Sweden. It is generally known that a biomass district heating system combined with solar heat brings many important benefits. The most common system solution is to install a heat store and a large solar collector field near the heating central. No plant of this type is however in operation in the northern part of Sweden. The main reason for this is that the solar irradiation at these latitudes is very low when the demand for heat is high. Solar heat could however be useful during summer in order to generate hot tap water. One problem is that the heat losses, calculated as percentage of the delivered heat, become very large during these months. This article presents the idea of allowing the connected households to generate their own hot tap water using solar collectors and heat stores installed in each house. The district heating network can therefore be closed in summer, which eliminates the heat losses outside the heating period. A case study of a projected plant has been carried out and it is shown that it is possible to reduce the heat losses by 20% compared to a conventional system. This idea also provides many other important technical and economic benefits.     

NUTRIENT MASS BALANCE FOR THE ALBEMARLE-PAMLICO DRAINAGE BASIN,NORTH CAROLINA AND VIRGINIA, 19901

ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and phosphorus and watershed nitrogen retention and processing capabilities. Basin total nitrogen and phosphorus input estimates were calculated for atmospheric deposition (which averaged 27 percent of total nitrogen inputs and 22 percent of total phosphorus inputs); crop fertilizer (27 and 25 percent); animal-waste (22 and 50 percent, respectively); point sources (3 percent each of total nitrogen and total phosphorus inputs); and biological nitrogen fixation (21 percent of total nitrogen inputs). Highest in-stream nitrogen and phosphorus loads were measured in predominantly agricultural drainage areas. Intermediate loads were observed in mixed agricultural/urban drainage areas; the lowest loads were measured in mixed agricultural/forested drainage areas. The difference between the sum of the nutrient input categories and the sum of the in-stream nutrient loads and crop-harvest nutrient removal was assigned to a residual category for the basin. The residual category averaged 51 percent of total nitrogen inputs and 54 percent of total phosphorus inputs.     

Justified Predictions about New (Different) Species Confirm the Theory

Russian Journal of Ecology -     

Thermal neutron fluence from ultra low-level γ-ray spectrometry of spoons activated during the JCO criticality accident at Tokai-mura in 1999

During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of ⁵¹Cr and ⁶⁰Co in stainless-steel spoons using γ-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable ⁵¹Cr in three samples and ⁶⁰Co in four samples taken from locations at distances of up to 430 m from the accident location despite the elapse of 4 half-lives of ⁵¹Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible.     

石化废水污泥实用焚烧处置技术

介绍了石化废水污泥焚烧处理的工艺流程、主要影响因素,分析了该项技术的优缺点。     

模拟SO_4~(2-)沉降对河口潮汐湿地甲烷排放通量的影响

2008年每月小潮日原位定期向闽江河口鳝鱼滩咸草(Cyperus malaccensis)潮汐湿地试验样地施加25,50,100kgSO42--S/(hm2·a)的硫酸钠溶液,探讨模拟SO42-酸沉降对河口潮汐湿地甲烷排放通量的影响.结果表明,SO42-酸沉降对于河口潮汐湿地甲烷排放通量基本无抑制作用.添加SO42-室内厌氧培养试验结果显示,虽然SO42-输入对湿地土壤CH4产生量具有一定的抑制作用,但相对对照组,下降幅度仅为8.5%~15.4%.室内添加甲烷产生基质的厌氧培养试验结果表明,非竞争性途径甲烷产生基质(甲醇和三甲胺)的添加可刺激并增加土壤的甲烷产生量,解释了原位施加SO42-对于河口潮汐湿地甲烷排放通量的基本无抑制作用的试验结果.     

系留气球整流罩散热数值仿真

目的解决系留气球整流罩散热设计问题。方法通过建立三维几何和离散模型,利用FLUENT开展热-流数值仿真计算,结合编制UDF同时实现整流罩外部对流、外部太阳辐射和内部对流、内部红外辐射和内部热源的实时耦合计算(双向耦合)。筛选环境最严酷状态(风速、温度和太阳辐射),对系留气球整流罩在3000 m和6000 m高度的散热性能进行分析。结果按最严酷状态进行分析后,在3000 m和6000 m工作高度,必须引入外界空气向整流罩内强制通风对流,才能保证任务设备工作环境要求。升空后,由于环境温度下降,整流罩散热增加,任务设备(雷达)散热所需引入外界通风量减少。3000 m^-3 m/s工况下,在整流罩进气口质量流量为1.0 kg/s时,整流罩内部维持在39~40℃;6000 m^-3 m/s工况下,在整流罩进气口质量流量为0.5 kg/s时,整流罩内部维持在25.5~26℃。整流罩上强制通风进气口应布设在任务设备发热部件下方,同时在整流罩上部和后部开设专用排气口,保证整流罩内部空气流通。结论双向耦合计算方法可快速获取系留气球整流罩在各状态条件下的散热详情,为整流罩散热设计及内部任务设备的热设计提供详实设计依据,相比工程估算和单向耦合更加贴近实际状态,计算精度更高。双向耦合计算方法和仿真数据可为同类型系留气球整流罩散热设计提供参考。     

焚烧法和厌氧消化法处理制革污泥中热值、硫、铬的比较

焚烧法和厌氧消化法都是利用制革污泥中热量的有效方法。比较两种方法所产生的热量,以及污泥处理过程中向大气排放的硫和铬,同时对铬的迁移作了初步的讨论。试验表明:焚烧法产生的热量多于厌氧消化方法,而厌氧消化方法中硫以及重金属铬的排放量明显小于焚烧法。     

Nitrous oxide fluxes from upland soils in central Hokkaido, Japan

Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November),for three years,in a total of 11 upland crop fields in central Hokkaido,Japan.The annual mean N2O fluxes ranged from 2.95 to 164.17 μgN/(m2·h),with the lowest observed in a grassland and the highest in an onion field.The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall eve...     

池火灾热辐射计算及模拟

在油罐火灾中,着火罐所释放的热辐射对附近的人员以及设备造成一定的危害,分别采用经验公式以及FDS模拟来计算热辐射强度,并对计算结果进行比较及分析,结果表明两种方法可互相补充完善。