基于温度场模拟的大花洞火炕烟道构造形式优化设计   总被引：1，自引：1，他引：0  

张杰  陈丽珠  王伟栋 《农业工程学报》2019,35(17):233-239

针对内蒙古东部农牧区居住建筑中广泛使用的大花洞火炕普遍存在的炕面温度极不均匀、热效率低的问题,以流体力学和建筑热工知识为指导,遵循前引后导原则对火炕烟道形式进行改进设计。通过对大量新建火炕模型温度场的模拟,精选出改进火炕I和改进火炕II 2种优化方案。利用ANSYS模拟技术对现状大花洞火炕和改进火炕模型的烟气流场、温度分布状况进行模拟分析,结果表明:相比现状火炕,改进火炕I的排烟温度降低了10℃左右且接近炕板处高温烟气覆盖面增加了约55%,改进火炕II的排烟温度降低了20℃左右且接近炕板处高温烟气覆盖面增加了约40%,改进后的大花洞火炕的烟气流场分布和热效率较现状火炕有明显改善和提升。  相似文献   

温度和粉碎粒度对不同能量饲料原料热物理特性的影响   总被引：3，自引：3，他引：0  

孔丹丹  方鹏  金楠  段恩泽  陈计远  王红英 《农业工程学报》2019,35(6):296-306

为探究常见能量饲料原料在不同温度、不同粉碎粒度下的热物理特性差异,该文以4种谷物(玉米、小麦、大麦和高粱)和4种加工副产品(小麦麸、木薯渣、甜菜渣和米糠)原料为研究对象,分别粉碎过孔径1.5、2.0和2.5 mm筛片,得到3种不同粉碎粒度的粉料,利用差示扫描量热法(differential scanning calorimetry,DSC)和线热源法分别测定了不同粉料在25～100℃范围内的比热和导热率,通过计算得到相应的导温系数,分析了温度、粉碎粒度对原料热特性的影响以及不同原料之间的热特性差异,并建立了热特性参数关于温度的回归预测模型。结果显示:8种原料粉碎过1.5 mm筛孔的粉料比热、导热率和导温系数随温度的升高分别在1.580～2.671 kJ/(kg·K),0.054～0.362 W/(m·K)和6.694×10~(-8)～23.254×10~(-8) m~2/s范围内变化。整体上,原料的热特性均随温度的升高而呈线性或非线性上升趋势。不同粉碎粒度的同一原料,在相同温度下的比热差异均不显著(P0.05);随着粒度的增大,粉料的导热率和导温系数均有逐渐下降的趋势。4种谷物的比热与温度之间呈线性关系;小麦麸、木薯渣和米糠的比热可用温度的三次多项式表示;而甜菜渣的比热与温度呈二次关系。4种谷物和甜菜渣在3种粒度下的导热率均可用温度的三次多项式表示,而小麦麸、木薯渣和米糠的导热率则可用温度的二次多项式表示。小麦麸和米糠的导温系数与温度呈二次关系,其余6种原料的导温系数则可用温度的三次多项式表示。研究结果可为配合颗粒饲料配方变换所需的调质、制粒等热加工过程的工艺参数的调整、优化提供理论依据。  相似文献   

Novel models for simulating maize growth based on thermal time and photothermal units: Applications under various mulching practices          下载免费PDF全文

《农业科学学报》2023,22(5):1381-1395

Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world. Plant height (H), stem diameter (SD), leaf area index (LAI) and dry matter (DM) are important growth parameters that influence maize production. However, the combined effect of temperature and light on maize growth is rarely considered in crop growth models. Ten maize growth models based on the modified logistic growth equation (Mlog) and the Mitscherlich growth equation (Mit) were proposed to simulate the H, SD, LAI and DM of maize under different mulching practices based on experimental data from 2015–2018. Either the accumulative growing degree-days (AGDD), helio thermal units (HTU), photothermal units (PTU) or photoperiod thermal units (PPTU, first proposed here) was used as a single driving factor in the models; or AGDD was combined with either accumulative actual solar hours (ASS), accumulative photoperiod response (APR, first proposed here) or accumulative maximum possible sunshine hours (ADL) as the dual driving factors in the models. The model performances were evaluated using seven statistical indicators and a global performance index. The results showed that the three mulching practices significantly increased the maize growth rates and the maximum values of the growth curves compared with non-mulching. Among the four single factor-driven models, the overall performance of the Mlog_PTU Model was the best, followed by the Mlog_AGDD Model. The Mlog_PPTU Model was better than the Mlog_AGDD Model in simulating SD and LAI. Among the 10 models, the overall performance of the Mlog_AGDD–APR Model was the best, followed by the Mlog_AGDD–ASS Model. Specifically, the Mlog_AGDD–APR Model performed the best in simulating H and LAI, while the Mlog_AGDD–ADL and Mlog_AGDD–ASS models performed the best in simulating SD and DM, respectively. In conclusion, the modified logistic growth equations with AGDD and either APR, ASS or ADL as the dual driving factors outperformed the commonly used modified logistic growth model with AGDD as a single driving factor in simulating maize growth.  相似文献   

夏热冬冷地区节能公共建筑墙体热桥效应影响研究——以嘉兴市为例     

张燕  罗义英  赵美红  徐丹妮  陈骆  汤俊雁 《绿色科技》2019,(12):210-212,215

基于嘉兴地区主流墙体构造,模拟墙体表面温度分布,分析了主体墙传热系数与热桥线传热系数的相关性,研究了热桥效应对墙体保温性能的影响。提出了在节能建筑墙体设计时,在满足墙体保温性能同时,不应只重视主体墙的保温,还要考虑热桥部位保温构造,使主体墙与热桥柱的传热系数相近,避免墙体外表面开裂现象。  相似文献   

基于无人机热红外的水分胁迫指数与土壤含水率关系研究   总被引：1，自引：0，他引：1  

尚晓英  张智韬  边江  林历星  李乐  洪苑琪 《节水灌溉》2019,(4):16-21

为了实时快速监测作物根系活动层的土壤含水率,利用低空无人机搭载的热红外相机获取经4种水分处理的棉花花铃期一天中5个时刻的冠层温度,并连续观测5 d,应用水分胁迫指数(CWSI)的理论模式、简化模式、定义模式计算得到3种CWSI,与棉花根系不同土壤深度含水率建立模型。研究表明:3种胁迫指数与土壤含水率具有幂函数关系,其中理论模式与土壤含水率的相关性最佳,定义模式次之,简化模式最差;在一天中不同监测时间点上,3种CWSI的监测精度在13∶00最高,9∶00和17∶00最差;在监测深度上,3种胁迫指数与0～60 cm处的土壤含水率关系最为紧密,0～30 cm次之,0～15 cm最差。该研究可大面积获取作物根系层土壤含水率,提高作物根系层土壤含水率的反演精度。  相似文献   

不同膜下滴灌定额对土壤水热效应及甜菜产质量的影响   总被引：1，自引：0，他引：1  

《灌溉排水学报》2019,(12)

【目的】探究内蒙古半干旱区膜下滴灌甜菜土壤水热高效利用与甜菜提质增效的协同效应,为内蒙古半干旱区甜菜高产高效栽培提供理论依据。【方法】设置8个不同滴灌定额和滴灌频次(A处理滴灌定额450 m~3/hm~2、滴灌1次;B处理滴灌定额900 m~3/hm~2、滴灌2次;C处理滴灌定额1 350 m~3/hm~2、滴灌3次;D处理滴灌定额1 800 m~3/hm~2、滴灌4次;E处理滴灌定额2 250 m~3/hm~2、滴灌5次;F处理滴灌定额2 700 m~3/hm~2、滴灌6次;G处理滴灌定额3 150 m~3/hm~2、滴灌7次;H处理滴灌定额3 600 m~3/hm~2、滴灌8次),动态监测甜菜全生育时期土壤水分和温度,分析行上、行间土壤水热变化,结合甜菜产质量研究膜下不同滴灌定额的水热效应。【结果】各处理出苗稳定后72 h内土壤温度从17:00—次日11:00表现为行上>行间;从12:00—18:00表现为行间>行上,行上和行间最大土壤温差点分别在06:00—07:00和14:00—15:00;3 a内土壤有效积温变化规律与日平均土壤含水率变化规律相反,即随土壤积温增加,含水率逐渐降低。以2016年甜菜块根及糖分增长期为例,B、C、D、E、F、G、H处理行上土壤有效积温分别较A处理提高了5.61、29.11、-23.10、42.68、-10.85、-4.46、-22.79℃,B、C、D、E、F、G、H处理行上日平均土壤含水率分别较A处理提高6.96%、11.73%、-1.01%、11.76%、5.19%、22.14%、13.62%;随滴灌定额的增加,甜菜产量增加,含糖率降低,产糖量呈先增后降的趋势,以2016年为例,B、C、D、E、F、G、H处理分别较A处理产量提高4.73%、13.82%、26.38%、29.33%、31.48%、27.43%、25.78%,产糖量提高5.90%、10.61%、18.07%、20.01%、15.73%、9.78%、4.14%。【结论】在甜菜生长关键期进行适宜的滴灌可有效地提高土壤水热效应,最佳滴灌定额为1 800～2 250 m~3/hm~2,滴灌次数为4～5次,促进滴灌条件下甜菜产质量水平提升。  相似文献   

Retrieving Soil Moisture Using Spectral Mixture Analysis of Landsat8 and the Moderate Resolution Imaging Spectroradiometer北大核心CSCD     

Gong W.  Guo Y.  Wang W.  Heng W. 《灌溉排水学报》2019,(7):123-128

【Objective】Soil moisture plays a critical role in many hydrological and ecological processes and understanding its spatiotemporal changes is imperative to ecosystem management and irrigation design. This paper presents and tests a method to estimate soil moisture distribution using satellite technologies.【Method】We took Guangli Irrigation District at Jiaozuo in Henan Province as our study area. The Landsat-8 and MODIS imageries from the area were used to retrieve soil moisture with the apparent thermal inertia and vegetation water supply index, respectively. Using the abundance of vegetation and soil moisture decomposed by the spectral mixture analysis as weighting factors, we retrieved the soil moisture distribution in the area using the two methods.【Result】The correlation coefficient between the measured soil moisture and the retrieved using the vegetation water supply index method and the apparent thermal inertia method was 0.47 and 0.51 respectively. We found that combining the two methods could improve the correlation coefficient between the measured and retrieved soil moisture to 0.73. 【Conclusion】Our results showed that the proposed method is reliable and can adequately estimate soil moisture in irrigation district grown with a diverse of crops. © 2019 Authors. All rights reserved.  相似文献   

冀南冬小麦冬前热量条件变化研究   总被引：2，自引：0，他引：2  

孙东磊  杨雪川  陈文晖  梁钰  陈杰  杨永胜  甄文超 《中国农学通报》2009,25(19):257-262

近50 a来,冀南冬麦区日平均气温≥0℃终日、冬小麦冬前≥0℃积温和10-12月平均气温年际间波动较大,总体线性增长趋势不明显。但近5 a来,日平均气温≥0℃终日明显推迟,冬小麦冬前≥0℃积温显著增加。小波分析表明：日平均气温≥0℃终日变化存在4-7 a和14-17 a尺度周期变化规律,冬前≥0℃积温存在5-10 a和15-20 a尺度周期变化规律,未来3-5 a日平均气温≥0℃终日将处于偏晚期,冬前≥0℃积温呈增加趋势;10-12月平均气温存在3-5 a、8-10 a和20-25 a三类尺度周期变化规律,未来8-10 a升高趋势比较明显。综合分析表明,未来3-8 a冬小麦冬前热量仍呈增加趋势,但年际间波动明显,冬小麦播种期应根气象部门中长期气候预测年际间适当调整,避免热量资源波动对冬小麦生长发育的影响。  相似文献   

Thermal process model identification based on radial basisfunction neural networks     

LI Pan feng  YANG Chen 《保鲜与加工》2009,(9):1032-1036

In order to accurately reflect the dynamic behavior and realize the whole optimal control of the thermal process, a novel modeling method of the RBF NN (Radial Basis Function Neural Networks) model is proposed to build nonlinear model. This method is based on entropy clustering and competitive learning algorithm, combined with nonlinear autoregressive moving average (NARMA) model to identify the RBF NN stucture, and the power vector is gotten by the least square algorithm. Two simulation experiments show that the proposed method of the identification based on NARMA model and RBF NN can accurately describe the non linearity of the process and has less hidden nodes.  相似文献   

Impacts of natural ventilation on indoor thermal environment for residential housing   总被引：2，自引：0，他引：2  

LI Nan  LI Bai zhan  SHENG Yan  YU Wei  DING Yong 《保鲜与加工》2009,(7):736-742

A typical residential housing in Chongqing is taken as an example, which is with worse natural climate conditions and absent of wind resource. A feasibility study on improving the thermal environment by natural ventilation is analyzed based on the i d chart. By the on site tests,the indoor thermal comfort is evaluated based on the PMV PPD methodology. Better natural ventilation can not only save the building energy consumption, but also improve indoor thermal environment, especially in the rain and transition seasons, even in the urban area with poor wind resource.  相似文献