4种用于温室除湿的亲水翅片管蒸发器热湿传递性能分析

温室冬季高效除湿需求已经成为制约中国温室产业高质量发展的技术难题之一。为了提高温室用冷冻除湿系统中亲水翅片管蒸发器的热湿传递性能,该研究建立了低温高湿工况下平翅片、带涡产生器平翅片、波纹翅片、开缝翅片4种亲水翅片管蒸发器空气侧的数值传热模型,采用蒸发器的换热量Q、努塞尔特数Nu、摩擦因子f、单位翅片面积析湿量和强化传热因子JF等评价参数,对比分析了低温高湿工况下4种亲水翅片管蒸发器空气侧热湿传递性能。结果表明,与平翅片相比,带涡产生器平翅片、波纹翅片、开缝翅片空气侧的Nu、Q和f均高于平翅片,且开缝翅片的Q和f在相同条件下均最大;4种翅片的f随入口风速的增大而大幅度减小,而相对湿度对f的影响较小;单位翅片面积析湿量均随入口风速和相对湿度的增大而增大,波纹翅片的除湿能力最优;在入口风速1～4 m/s和相对湿度80%～95%条件下,波纹翅片管蒸发器的JF因子平均值最大,其热性能最优;在冬季寒冷地区低温高湿的温室中,推荐选用波纹亲水翅片管蒸发器对温室内空气进行除湿。该研究可为温室低温高湿环境下除湿系统用亲水翅片管蒸发器的设计与应用提供参考。     

日光温室冷凝除湿系统用蒸发器强化传热数值分析

为提高日光温室冷凝除湿系统中蒸发器的综合换热性能,将三角翼型涡发生器强化传热技术引入到蒸发器中。该文针对平直肋片管翅式蒸发器和加装三角翼型涡发生器肋片管翅式蒸发器的热质传递与阻力性能,建立了这2种蒸发器的三维传热模型,运用平均努塞尔数、阻力系数、析湿量、肋片效率及强化传热因子等评价参数,对不同除湿工况下2种蒸发器的传热传质及阻力特性进行了对比分析。结果表明,涡发生器下游的空气通道两侧肋片表面凝结液主要分布于纵向涡流边界以外,边界形状分别呈条带状和椭球状;涡发生器降低凝结液尺寸和脱落直径的同时使蒸发器的析湿量平均增长了50.79%,增强了蒸发器排液能力和除湿能力;涡发生器使蒸发器肋片效率平均提高了2.00%,并将蒸发器空气侧平均努塞尔数平均提升了25.45%,强化传热因子平均提升了9.61%,但阻力系数平均增长了51.70%;在空气相对湿度高于70%的除湿工况下,蒸发器的入口空气流速推荐值取2 m/s。该研究可为日光温室冷凝除湿系统蒸发器的结构优化设计提供参考。     

温室吸湿剂喷淋除湿降温系统的影响因子分析

为了解决湿热地区夏季温室的降温问题,提出了利用CaCl2溶液除湿降温系统对温室进行降温的方法。在CaCl2溶液除湿降温系统运行条件下,确定了以喷淋室出口空气相对湿度为试验指标,分析了进口空气流量、除湿剂流量、除湿剂浓度和温度、进口空气温度和湿度等因子对试验指标的影响。通过影响因子的单因素试验和多因素正交试验,得出了系统运行时影响除湿效果的显著因素是除湿剂浓度和温度、进口空气温度和湿度。通过回归分析建立了CaCl2溶液喷淋除湿的数学模型,并通过试验验证了该模型的最大相对误差小于5%。该文为中国南方高温高湿的温室夏季降温提供参考。     

太阳能除湿系统中混合盐溶液的性能

溶液除湿和太阳能再生技术,是解决高温高湿地区蒸发降温技术难题的关键。该文利用建立的太阳能再生溶液除湿实验台,实验测量研究了氯化钙（CaCl2）和氯化锂（LiCl）混合盐溶液（物质的量比1∶1）的密度与不同质量分数之间的关系;研究了进口空气的温度、湿度、流量,盐溶液的流量,溶液的质量分数、水汽压差等参数与除湿量之间的关系。结果表明：混合溶液的密度与其中的某一组分的溶液（CaCl2）密度非常近似,两者有很好的线性关系;影响除湿量的关键因素是传热传质过程中混合盐溶液和空气的水汽压差的大小。根据Ertas的实验研究,论文得到了氯化钙（CaCl2）和氯化锂（LiCl）混合溶液质量分数为20%～40%的溶液水汽压的计算公式,以及水汽压差和除湿量之间的关系式。该研究为禽畜舍、温室等设施除湿技术提供了新的研究思路。     

农业基站室外自然冷能微热管阵列式空冷器性能

针对农业生产服务基站内通讯及储备电源等设施发热量高的问题,该文设计了一种基于微热管阵列的室外空冷器,在北方冬季及过渡季节利用自然冷能对通讯基站散热降温,节能降耗。利用多功能气候实验室模拟不同的室外环境温度,对空冷器在不同流程(顺流和逆流)和不同温度及流量下的换热性能、温度分布、?效率及阻力特性等进行分析。结果表明:逆流式空冷器的换热性能相较于顺流式提升了16.9%。微热管阵列传热单元具有优良的导热性能和均温性能。试验过程中空冷器最大换热量为7.5 kW,空气流动的平均压降为164.9 Pa,水循环管路平均压降为7.96 kPa,?效率最高为38.8%,相较于常规冷却塔,微热管阵列式空冷器适用环境温度范围广且阻力较小。与平直翅片的板翅换热器的流动特性与阻力特性对比结果表明,本文锯齿形翅片的空冷器综合性能提升了36.1%。研究结果可为微热管阵列式空冷器在农业基站的应用提供参考。     

制冷系统不同表面能微通道的流动沸腾传热特性试验

为了研究微通道壁面特性对流动沸腾传热的影响,该文以具有不同表面能的微通道为研究对象,制冷剂R141b为试验工质,在不同热流密度、质量流率下对微通道内的沸腾传热特性进行了试验探究。结果表明:在该试验工况下,质量流率的增加有利于沸腾传热,但微通道内过冷段长度也相应增加;在微通道饱和沸腾区传热系数较稳定,但沿工质流动方向有缓慢降低的趋势;相比于表面能为23.93 m N/m的3#的微通道,表面能为60.03和49.54 m N/m的1#和2#微通道沸腾传热系数分别提高18.42%和9.28%;根据试验值与关联式预测值的对比情况,对Lazarek关联式进行修正,拟合得到能很好预测该试验各工况下的传热关联式,平均绝对误差为9.76%。该研究为微通道换热器的设计提供了参考。     

冷库冰水混合间接换热器的传热与流动特性

北方地区冬季寒冷漫长,夏季炎热,冬季储冰夏季利用有利于节能减排。利用冰水混合间接换热系统进行冷量交换,不仅节能环保而且空气质量明显提高。采用有限体积法商业软件FLUENT,应用SIMPLE算法对翅片管式换热器平直翅片的换热与流动特性进行数值研究,计算结果与试验结果对比分析。结果表明:数值模拟与试验偏差不超过15%;迎面风速均匀分布情况下,随着迎面风速的增加,换热系数和压降分别增加了133%和428%;平均场协同角随迎面风速的增加而增大,速度场和温度场的协同程度变差,对换热不利;在相同的空气体积流量下,迎面风速沿冰水流动方向呈逐渐降低的分布方式对换热有利。     

气-气换热器对太阳能再生装置性能的影响

再生装置是太阳能蒸发除湿降温系统的重要组成部分,但普遍存在再生性能较低的问题。为了提高再生性能,将气-气换热器加装于再生装置中用于回收部分空气余热。讨论了两种再生装置的特点,测试了加装前后再生装置的性能。试验结果表明：再生装置的除湿增量、再生效率都随着太阳能热水温度的升高而提高;气-气换热器的加装能有效提高再生装置的再生性能,除湿量可以达到40～55 g/kg,较未加装时提高了35～45 g/kg;再生效率在热水温度90℃时可以达到60%,同等温度下高出未加装换热器50%。因此,余热的回收利用对于再生装置性能的提高至关重要。     

密闭温室半导体制冷除湿及蒸散水回收灌溉装置的研制

为了提高人工补光温室的水分的利用效率低下的问题,该文以盆栽辣椒为研究对象,在密闭温室中试验种植,采用半导体制冷热交换和空气露点除湿的方法,对辣椒在发育期、开花期和结果期的蒸散水回收效率进行研究,对比自然对流和强制对流方式除湿的效果以及温室内外盆栽辣椒的生长情况。结果表明:冷凝板温度最低达5.5℃,满足露点除湿条件。在盆栽辣椒的不同生长时期,强制对流进风方式下的室内温度变化范围为18.6~28.2℃,室内湿度变化范围为41%~61.7%,除湿效果随温度升高而显著提高;日回收量从35 m L增加到375 m L,日灌溉量从132 m L增加到540 m L,蒸散水回收率最高达69.4%。密闭温室中盆栽辣椒能够正常生长,而室外盆栽辣椒生长受到抑制。人工补光密闭温室系统除湿效果明显,有效的利用回收水进行盆栽辣椒灌溉。结果表明,人工光密闭温室内半导制冷除湿和蒸散水回收的研究对提高温室作物水分利用效率有积极的推动作用。     

半封闭热泵干燥系统的热力学分析与试验

为实现谷物干燥装置的车载移动功能,必须通过提高设备性能来实现装置小型化,为此,基于前期谷物干燥试验和理论研究,设计出一种半封闭热泵流化床谷物干燥系统。该系统采用蒸汽压缩式热泵(热泵工质为R134a)提供热量,以卧式多室流化床为干燥器,让热泵蒸发器回收流化床前段排气中水蒸气潜热,鼓入环境状态的新风以回收干燥后物料的热量。针对该系统建立了集流化床内的流动、颗粒传热传质、床层干燥过程与热泵系统耦合为一体的综合数学模型。计算表明：干燥室入口空气温度在60～90℃之间变化时,干燥系统的除湿能耗比（SMER）存在一个最大值。开发出了干燥样机。试验表明：干燥过程中,干燥室入口空气温度在64.4～71.7℃间波动,新风比约为30%,平均热泵性能系数 （COP）为3.34,SMER可达1.935 kg/(kW?h)。模型计算与试验结果吻合良好,采用该装置进行谷物干燥节能效果明显。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.     

Genetic similarities among Spanisch populations of Agropyron, Elymus and Thinopyrum, using PCR-based markers

Arbitrary oligonucleotides were used as primers to amplifygenomic DNA of 48 wild Spanish populations of Agropyroncristatum, Elymus hispanicus,E. caninus,E. repens,Thinopyrum curvifolium, Th.junceum and Th.intermedium. Genetic diversity was analysedusing nineteen primers. The number of amplified products ranged from8 to 18 per primer and a total of 240 markers were scored. Differentlevels of intraspecific genetic diversity were found, the allogamousspecies E. repens andTh. intermedium being themost variable. Jaccard's similarity coefficients for internalmeasure within and between populations were used to produce a clusterdiagram. The results demonstrate differences in the degree ofsimilarity between taxonomic units. Interpopulational variability andinterspecific genomic relationships of these species arediscussed.     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.