寒区沼气工程地下水源热泵加热系统能效分析

在北方寒冷地区,沼气工程加热系统如何能有效、合理地利用能源,提高能源利用率,是沼气工程实现低能耗,高产能必须解决的现实问题。该文依据地下水源热泵加热系统在沼气工程中应用的实例,建立了以?效率、热效率以及能级系数为评价准则的沼气工程加热系统能效分析模型,并通过对加热系统实际运行参数的测试,得到了沼气工程用户系统?效率为97.8%,地下水源热泵机组系统?效率为13.4%,沼气工程加热系统总的?效率为13.1%;加热系统总的热效率为85.3%;沼气工程用户耗热量的能级系数为0.161,用户供给热量的能级系数为0.164,地下水源热泵机组的能级系数为0.567。结果表明,对于沼气工程低品位热能用户,采用低温水供热科学合理;热泵机组系统回收了地下水中低品位热能,节约了高品位电能,加热系统能的数量有效利用程度较高;但热源与用户之间供需能质存在差异,在能质利用方面还需进一步完善。该结论可为今后沼气工程选择合理的加热模式提供参考依据。     

磁制冷材料Ni-Mn-Ga合金的相变与奇异热膨胀特性

Ni-Mn-Ga合金是典型的磁制冷材料,其热膨胀系数是工程设计中最重要的参数之一。为深入研究Ni-Mn-Ga合金的热膨胀特性,该文利用SEM、XRD、DSC及PPMS系统分别对合金Ni_(54+x)Mn_(19–x)Ga_(27)(x=0、0.2、0.4、0.6)的组分、结构、相变温度、磁结构转变及热膨胀特性进行试验测试。结果表明,随着Ni含量的增加,Ni_(54+x)Mn_(19–x)Ga_(27)合金的马氏体相变温度逐渐升高。当x从0.0增至0.6时,正反马氏体相变峰温TM与TA分别从257、265 K增至292、299 K。零场热应变曲线表明,Ni-Mn-Ga合金具有各向同性的热膨胀特性。马氏体相与奥氏体相的热膨胀系数分别位于8.87~16.60×10–6/K与5.21~6.26×10–6/K之间。而在马氏体相变附近,合金出现了奇异的、明显的负热膨胀行为,且升、降温过程合金的负热膨胀系数分别位于–147.54~–17.60×10–6/K与–133.30~–88.72×10–6/K之间,分别约为马氏体相的1.47~16.63倍与6.63~12.89倍。这种奇异的负热膨胀行为很可能是由于马氏体变体的成核、重取向所引起的。研究结果对磁制冷材料Ni-Mn-Ga合金热膨胀系数的调控及其工程应用具有较好的指导意义。     

油菜秸秆灰分混凝土保温性能试验

选取砂率、水灰比及油菜秸秆灰分掺量为变量,在保障秸秆灰分混凝土设计强度为C20的条件下,采用稳态平板导热仪测试秸秆灰分混凝土试件的导热系数。结果表明:油菜秸秆灰分混凝土的导热系数与秸秆灰分掺量呈负相关关系,掺入油菜秸秆灰分后,导热系数比不掺秸秆灰分的混凝土试件的降低6.8%~21.0%,秸秆灰分的掺量越多,保温性能越好。当水灰比为0.52、秸秆灰分掺量为5%、砂率为30%时,油菜秸杆灰分混凝土抗压强度达22.8 MPa,并具有良好的保温隔热性能。     

Effect of thermal pretreatment on germination of seeds from different provenances of subalpine oriental spruce (Picea orientalis (L.) Link.) forest in Turkey

We examined the effect of thermal treatment at two temperatures (60 s of 90°C dry heat and 60 min in 40°C hot water) versus control conditions on the germination of oriental spruce (Picea orientalis (L.) Link.) seeds originating from different subalpine provenances. Cutting test results showed that there was wide variation (between 10% and 90%) in filled seed rates. The results revealed that highest germination yield was attained via the hot water treatment. The maximum germination percentages were observed in seeds from “tree 3” in the first tree collective of provenances 1 (85.33 ± 5.77 control; 88.67 ± 7.02 via the hot water treatment; 82.00 ± 10.58 via the dry heat treatment) and 3 (70.67 ± 17.24 control; 88.00 ± 4.00 via the hot water treatment; 86.67 ± 11.37 via the dry heat treatment). The mean germination percentages were significantly different (p-value < .05): percentage values were 32.57% in provenance 1, 23.22% in provenance 3, 12.25% in provenance 4, and 2.82% in provenance 2. Mean germination time of seeds from different provenances and experiencing various pretreatments showed significant variation. The best pretreatment increase in germination rates was achieved via the wet heat method (60 min in 40°C hot water).     

发酵秸秆碎料内乙醇平面热源法提取及其设备设计

为降低固态发酵后秸秆碎料料内乙醇提取能耗,用平面热源进行乙醇提取并设计相应设备,进行初步计算。基于热重试验,研究了固态发酵后的甜高粱秆粉碎料中乙醇的蒸馏规律。考虑料含湿量、湿分乙醇体积分数、加热温度对料中湿分质量变化速率的影响,得出在研究范围内(含湿量10%~90%,湿分乙醇体积分数3%~11%,加热温度20~100℃)料中湿分质量变化速率与乙醇体积分数关系不大,随料含湿量呈线性关系,随加热温度呈幂函数关系,并得出回归模型。基于乙醇挥发数据,得出乙醇挥发数学模型。基于以上两模型,推导出平面热源提取乙醇的乙醇提取率方程,根据加热温度、料含湿量和湿分乙醇体积分数,便可计算任意时刻的乙醇提取率。建立成本模型并进行成本分析发现,该提取方法成本显著低于原有蒸汽提醇法。最后设计了一套采用平面热源连续提取发酵料内乙醇的生产装置,给出其设计计算式,进行了初步设计,得到一套示例性质的工业级设备方案。     

基于累积热量单位的甜瓜幼苗生长和形态模拟模型

为了明确甜瓜(Cucumis melo var.reticulatus Naud.)种苗生长与形态建成对环境温度的要求,研究了甜瓜种苗生长、形态与累积热量单位之间的关系,构建了基于累积热量单位驱动的甜瓜幼苗形态和干物质积累模拟模型。结果表明幼苗生长至三叶一心期过程中,株高、茎粗与累积热量单位呈线性相关关系,子叶和真叶的长、宽、面积均与累积热量单位呈logistic曲线关系,干物质积累随累积热量单位增加呈指数增长。用独立的实验数据对模型进行检验的结果表明,模拟值与观测值的线性回归系数均接近1(R20.98),表明模型的预测性较好。     

圆锥形顶太阳能蓄热水箱锥顶结构及运行参数优化

为获得顶部为圆锥形结构的太阳能蓄热水箱最优锥顶结构及运行参数,对水箱在有内置隔板情况下的10种锥顶结构进行了数值设计,结果表明:在给定流动参数条件下,锥顶角在173.1°~118.1°间变化对水箱内热分层影响效果相当,高温热水区域范围略有增大;对于锥顶高度为0.09 m、锥顶角为159.6°的最佳结构水箱,水箱出口附近高温热水区域范围随冷水入口流速增大逐渐缩小、随热水入口温度提高而增大,但提高热水入口温度对于高温热水区域范围的增大程度在较高冷水入口流速时要小于较低冷水入口流速时的情况;在其他流体参数不变的情况下,冷热水出口温差随冷水入口流速增大呈上升趋势,但当冷水入口流速增大到一定值时其对增大冷热水出口温差的贡献趋于平缓;在冷水入口流速较小时提高热水入口温度对于增大冷热水出口温差的贡献要略大于冷水入口流速较大时的情况。热水入口温度为333 K、冷水入口温度为303 K、热水入口流速为0.05 m/s、冷水入口流速为0.9 m/s组合而成的工况以及热水入口温度为343 K、冷水入口温度为303 K、热水入口流速为0.05 m/s、冷水入口流速为0.9 m/s组合而成的工况适合于"小流量大温差"的热用户运行模式;热水入口温度为333 K、冷水入口温度为303 K、热水入口流速为0.05 m/s、冷水入口流速为0.1 m/s组合而成的工况以及热水入口温度为343 K、冷水入口温度为303 K、热水入口流速为0.05 m/s、冷水入口流速为0.1 m/s组合而成的工况适合于热用户对热水供应量需求较大的情况。     

Development and initial validation of a sensory threshold examination protocol (STEP) for phenotyping canine pain syndromes

Objective

To study the feasibility and test–retest repeatability of a sensory threshold examination protocol (STEP) and report the quantitative sensory threshold distributions in healthy dogs.

Sedative and antinociceptive effects of different combinations of detomidine and methadone in standing horses

Objective

To evaluate intravenous (IV) detomidine with methadone in horses to identify a combination which provides sedation and antinociception without adverse effects.

Evaluation on Air Environment of a Large Tower Type Cowshed for Dairy Cattle in Northern China

In this study, the air environment quality indicators of a large tower type cowshed for dairy cattle in North China were monitored and evaluated at all seasons of one year, including the indicators of thermal environment, the content of ammonia (NH₃), carbon dioxide (CO₂), microbe and the dust in the air. The objective was to study the change rules of the mentioned indicators, to evaluate whether this type of cowshed could meet the production requirements, and to provide theoretical basis for the design and daily management of the cowshed in the Northern region of China. The results showed that all the indicators mentioned above varied with seasons and time to some extent. The wind speed inside was below the standard of dairy cattle cowshed in summer, and the temperature in 14∶00 of summer was above 27 ℃, and THI was beyond 69, so the dairy cattle suffered slight heat stress in summer. The other air environment quality indicators monitored in any time and any space all met the standard. In conclusion, the tower type cowshed monitored was suitable for dairy cattle in North China, but some facilities should be added to decrease the temperature and the heat stress in summer.