平流层飞艇昼夜驻空蒙皮热特性研究

目的分析平流层飞艇蒙皮在不同空速下的热特性,为平流层飞艇蒙皮材料的选择以及其驻空性能的分析提供参考和指导。方法基于CFD数值分析方法,建立外部热源模型,囊体内部自然对流和囊体外部强迫对流分析的综合方法。通过数值仿真分析典型飞艇在不同空速下的热特性,得出飞艇囊体内部的氦气平均温度随着热环境的周期变化,会产生周期性变化。结果在1m/s的较低空速下,飞艇昼夜氦气温差达到46 K,蒙皮昼夜最小温度出现在晚上,约为180 K,最大温度出现在正午时分,温度约为280 K。在10 m/s的空速下,飞艇昼夜氦气温差达到29 K,蒙皮昼夜最小温度约为190 K,最大温度为280 K。结论在飞艇设计中,蒙皮材料选择时考虑温度的影响。所建立的热分析方法以及得到的热特性,可为平流层飞艇蒙皮材料的选择提供参考和指导。     

岛屿地形下的核电厂护岸防洪设计研究

对国内第一个岛屿地形下核电厂的护岸防洪设计进行了研究,提出直立式护岸结构方案以满足核电厂防洪和避让毗邻海岛的要求。在波浪数值模拟计算结果基础上,开展了波浪整体物理模型试验、波浪局部整体物理模型试验和波浪断面物理模型试验,对护岸的越浪量和结构稳定性进行了优化验证。研究结果表明,岛屿地形下,波浪破碎和波能集中导致护岸堤身坡脚处波高增大,须加高挡浪墙和优化挡浪墙结构型式;在相同的越浪量标准下,采用直立堤结构相对斜坡堤结构对应的护岸挡浪墙的高程须明显加高;利用部分海岛地形斜坡高地作为厂区护岸一部分时,原状海岛地形斜坡高地处的波浪爬高效应明显,须加高邻近护岸挡浪墙的高程。     

Thermal modeling and analysis of novel twin-chamber community solar cooker as a replacement of biomass-based cooking

A novel design of twin-chamber community solar (TCCS) cooker is presented as a replacement of biomass-based cooking. The novelty of separating a single rectangular cooking chamber into separate twin chambers (of 1-m² aperture area each) improves the cooking performance as opening of one chamber for unloading of food cooked in lesser time (rice) does not disturb the stagnation temperature of the other chamber (pulses and meat) needing more time to cook besides resulting in reduction in side heat loss coefficient due to common wall. Aperture area and cooking volume of TCCS cooker are 9.54 and 35.33 times more as compared to single-chamber domestic solar (SCDS) cooker which makes it a community-scale large-capacity solar cooker. The developed solar radiation capture model and overall heat loss coefficient (U_l) computed for TCCS cooker have been used in a thermal model developed between various interactive components. First (F₁) and second figures of merit (F₂) values are 0.13 and 0.42, respectively, for TCCS cooker at par with ‘A’ grade category SCDS cooker. Techno-economic analysis shows that the net present value of TCCS cooker is Rs. 83,253 with break-even point occurring after cooking 43,461 meals with payback period of only 25, 50, and 72 months if used as a replacement for LPG, cow dung cakes, and wood-based cooking, respectively. Environmental impact analysis shows that the use of the proposed cooker can mitigate 2, 5.9, and 4.1 tonnes of CO₂ emissions every year by not burning LPG, cow dung cakes, and wood respectively.     

Thermal performance of ice-making machine with a multi-channel evaporator

An experimental investigation is presented in this paper on the vapor compression refrigeration cycle used in an ice-making machine with a multi-channel evaporator. To study the operation performance of the refrigeration system in the ice-making machine, the fluid temperature distribution in multi-channel evaporating coils are tested and the dynamic variations in each cooling loop are investigated during the ice-generating phase. The results show that the external cooling loops have the largest temperature fluctuations caused by the large initial refrigerant injecting mass flow and the external environmental disturbances. For the inner cooling loops, the related temperature profiles of different test points have relative stable variations. To reduce the temperature fluctuations of the outside loops, it is suggested to reduce the initial refrigerant mass flow and adjust the initial opening of the thermal expansion valve. Moreover, it is the normal phenomenon for the slight temperature variations for the temperature curves of different test points, caused by the adjustment of thermal expansion valve. During the ice-making process, both the sensible heat removal phase and latent heat removal phase are experienced successively. To remove the sensible heat of water, the refrigerant system is operating in high efficiency with test points having a rapid linear temperature reduction. While for eliminating the latent heat of ice, it requires much more power supply, the relating test points have a temperature decrease with fluctuations. To improve the operation performance of ice machine, some suggestions and improvements are proposed.     

景区典型树种的热解特性及动力学研究

为了研究山林或景区中不同植物的热稳定性,选取了景区种植数量较多的6种典型树种:女贞、枇杷、竹子、松树、柏树和法桐的枝干和叶作为样品。借助同步热分析仪,在温升速率20℃/min的条件下,对未经干燥处理的样品进行热解特性及热解反应动力学研究。通过TG、DTG以及DSC曲线分析各样品的热解过程,并采用分阶段一级反应动力学模型Coats-Redfern法求得相应参数。研究结果表明:所取样品的热解过程都出现4个明显的热解阶段,即脱水阶段、综纤维素热解阶段、木质素热分解阶段、炭化阶段。根据6个树种的主要热解阶段和动力学分析,6种树种的热稳定性从低到高顺序依次为竹子、女贞、枇杷、法桐、柏树、松树。     

坝体动力抗震及尾矿动力特性分析

为研究尾矿坝的动力抗震特性以及为抗震措施提供理论指导,以四川某尾矿库为例,分析了该尾矿坝在EI Centro地震波、汶川地震波和人工地震波作用下的位移、加速度、液化、安全系数的动力响应特性。采用GDS动三轴仪对该尾矿库的3种典型尾矿进行动力实验,研究结果表明:随着动剪应变幅的增大动剪切模量比逐渐减小,阻尼比逐渐增大;3种尾矿的动压缩弹性模量的倒数与动轴向弹性应变之间的关系为直线关系,在双对数坐标系中,平均有效应力与动剪切弹性模量的关系为直线关系;尾粉质黏土抗液化强度较低,应优化尾矿排放工艺使其尽量沉积到库尾。     

矿井通风系统稳定性SD预测仿真分析

为了建立矿井通风系统稳定性水平评价体系,以常村煤矿为研究背景,结合常村煤矿多风井、大风量、高瓦斯等特点,从技术、安全、经济角度建立一系列完整的评价指标体系,利用层次分析法确立指标权重,并结合属性数学理论形成通风系统稳定性综合评价模型,通过构建的模型对其进行综合评价。以通风系统综合评价为基础,从系统动力学角度,对常村煤矿未来2 a的通风系统稳定性水平进行仿真预测,总结其动态变化规律。研究结果表明:通风系统总体稳定性评价结果为良好,属于较稳定水平。常村煤矿通风系统稳定性水平在未来2 a内随着安全投入的增加呈总体增加趋势,但随着矿山通风系统稳定性水平的逐渐增加,稳定性增长速率将会减小。     

矿井通风热阻力数值模拟研究

矿井风流流经井下热水、干热岩、火灾地点等局部高温区域时,风流吸收热量使其内能增加,高温风流在巷道内流动时会产生热阻力。针对如何确定井下风流加热流动时巷道内热阻力的实测范围这一问题,通过理论推导与数值模拟的方法对巷道内热阻力分布情况进行分析。由压力场的模拟结果得出风流加热流动时,所产生的热阻力不仅存在于加热区,高温风流向加热区下风侧流动时热阻力仍然存在。模拟结果表明:对于水平等截面管道,风流流经加热区时,风流速压增加,加热区内风流的静压降幅大于全压降幅;流出加热区的风流向管道出口处流动时,高温风流不断克服阻力做功,并与管道内的新鲜风流、壁面进行热交换,风流温度逐渐下降,当测定区间为加热区入口至模拟管道出口时,风流的静压降幅与全压降幅近似相等。研究结果对井下巷道、隧道及实际工程应用中热阻力的分析与研究都具有重要价值。     

归州河西沿江高切坡变形破坏及稳定性分析

为了掌握归州河以西沿江公路由于升级改造、工程开挖而产生的大量公路高切坡发育分布特征,总结其变形破坏模式,进而对其稳定性进行分析。在野外实地宏观调查、测量的基础上,通过数据处理,运用赤平投影法对调查区高切坡稳定性进行区划,其中不稳定切坡长约3.8km,占比39.6%,多发育在侏罗系遂宁组(J3s)和聂家山组(J1n)中,主要变形破坏模式为滑移型、倾倒型和剥落型,并根据其破坏模式的差异性提出相应防治对策。     

热等离子体技术在树脂废气处理中的应用

采用热等离子体技术处理佛山三水力泉树脂制品有限公司生产过程中产生的甲醇、甲苯等有机废气(反应器使用二箱蓄热式反应器),有效利用了VOCs废气焚烧产生的余热,废气经处理后,转化为CO、CO_2和H_2O等小分子气体。经第三方检测机构监测,甲苯平均去除率达到95.7%,VOCs总烃的平均去除率达到93.1%,其排放浓度达GB 16297—1996《大气污染物综合排放标准》的要求。采用热等离子体技术处理树脂生产过程中产生的有机废气,年运行费用在15.7万元左右。