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。     

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。     

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。     

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。     

29种湿地填料对氨氮的吸附解吸性能比较

为筛选出性能更好的人工湿地填料,采用等温吸附-解吸试验,测定了29种天然和非天然人工湿地填料的孔隙率、渗透系数及其对NH₃-N的吸附-解吸特性. 结果表明:锯末、瓷砖、鸡蛋壳、瓷砂陶粒、火山岩等材料的孔隙率较大,瓷砂陶粒、海绵铁、石灰石、页岩陶粒、砾石等材料的渗透系数较大;Freundlich和Langmuir等温吸附方程能较好地拟合各填料对NH₃-N的吸附特征,通过Langmuir等温吸附方程计算,对NH₃-N的理论饱和吸附量居前5位的填料依次是火山岩(1.700 0 mg/g)、瓷砂陶粒(1.620 0 mg/g)、生物炭(1.353 0 mg/g)、沸石(1.350 0 mg/g)、石榴石(1.190 0 mg/g). 吸附速率的变化与填料吸附NH₃-N的途径密切相关. 吸附饱和的生物炭、焦炭、大理黏土、沸石、磁铁矿、石英砂主要通过离子交换作用吸附NH₃-N,稳定性好,解吸率均小于20%;瓷砂陶粒和火山岩对NH₃-N的解吸率分别为24.50%和35.51%,既有物理吸附也有离子交换作用. 火山岩、瓷砂陶粒、生物炭、沸石对较高浓度NH₃-N的吸附效果较好. 研究显示,火山岩、生物炭、瓷砂陶粒、沸石等适合作为人工湿地中吸附NH₃-N的填料.      

丙胺类离子液体的合成及其脱硫性能

以廉价的正丙胺及苯酚、乳酸、四氮唑乙酸为原料,采用一步法合成了3种丙胺类离子液体(丙胺乳酸盐([PA]L)、丙胺苯酚盐([PA][PHE])、丙胺四氮唑乙酸盐([PA][TAA]),并将其用于SO_2的吸收。测定了3种离子液体的主要理化指标,系统考察了其脱硫性能,并对SO_2的吸收机理进行了探讨。实验结果表明:3种离子液体均具有较高的热稳定性;25℃下,[PA][TAA]的密度和表面张力均较高,而[PA][PHE]的黏度远小于[PA]L和[PA][TAA],仅为66 mPa·s;3种离子液体的脱硫能力均较高,且吸收速率快,30℃下吸收平衡时SO_2与[PA][PHE],[PA]L,[PA][TAA]的摩尔比分别为0.570,0.806,0.904;3种离子液体的解吸较容易,对SO_2的吸收具有高选择性,且循环使用性能较好;丙胺类离子液体对SO_2同时存在物理吸收和化学吸收作用。     

玻化微珠保温砂浆在隧道防火设计中的应用研究

针对当前多发的隧道火灾,探讨玻化微珠保温砂浆在隧道防火设计中的可行性。通过有限元计算分析,对设置玻化微珠保温砂浆隔热层的隧道衬砌结构防火性能进行研究,同时对不同火灾规模下隧道温度场的影响进行了分析。研究结果表明玻化微珠保温砂浆可以很好地阻止热量的入侵,初步验证了其在隧道防火应用的可行性,可为后续隧道防火设计及相关研究提供参考。     

风机风量对生物质气化套管采暖影响模拟研究

生物质气化站在气化间与净化间之间设置防火墙后,会使气化反应余热无法向净化间内传递,使得我国北方地区气化站在冬季严寒情况下出现湿式净化装置冻裂,进而发生燃气泄漏的情况,增加了火灾、爆炸、中毒隐患。提出了一种利用风机套管将反应余热送入净化间采暖的技术,采用CFD(computational fluid dynamics)技术对采暖效果进行数值模拟,分析风机风量对采暖效果的影响,得出在风机风量对应进气口空气流速9 m/s时可获得最佳采暖效果,可使室外温度243.15 K时净化间内温度达到277~281 K。该技术利用余热进行采暖,达到了低碳环保、节能减排的目的。