Effects of Combined Instantaneous High-Pressure and Medium Temperature on Peroxidase Activity in Wax Gourd Juices

Based on the instantaneous pressurization and depressurization produced by high pressure single pole cylinder pump and valve, the effects of the continuous processing on the peroxidase (POD) activity in wax gourd juices were investigated. Results showed that the processing factors such as pressure, temperature, pH and processing time are important to the POD activity. POD in crude juices could be inactivated apparently above 50 MPa(pH 4.6, 35℃, 4 min), and activated at 20 MPa ( P < 0.01). Its remarkable inactivation could also be observed at 45 and 55℃ (20 MPa, pH 4.6, 4 min), and the evident activation appears at the material temperature 35℃ ( P < 0.01). The pH 3.0 could destroy POD almost completely (20 MPa, 35℃, 4 min), while pH 6.0 could not influence apparently the POD activity in crude juices( P > 0.05). In addition, the rules of POD activity along with the treatment time are variational under different processing pressures. The higher the treating pressure is, the shorter the processing time is needed to inactivate POD.

Effects of Combined Instantaneous High-Pressure and MediumTemperature on the Retention of Total Vitamin Cin Wax Gourd Juices

Based on the instantaneous high-pressure(IHP)produced by high-pressure single pole-cylinder pump, the effects of combining this pressure with medium temperature on the retention of total vitamin C(Vc)in wax gourd juices were investigated under 20 - 80 MPa, 35 - 58℃, pH 3. 0 - 6. 0 and processing time 0-8 min. Results showed that the loss of Vc increased with elevated processing temperatures(50 MPa, 4 min). When the temperature of raw juices was 35℃, the retention of total Vc was higher under 40 - 60 MPa than that under the pressure < 40 MPa or > 60 MPa, and it was up to 94%(4 min). The retention of total Vc decreases slowly within 6 min, but rapidly after 6 min. The pH can also influence the retention of total Vc, and this retention can come to a highest point at pH 6.0.

Piezoelectric Power Harvesting Process via Phase Changes of Low-Boiling-Point Medium Together with Water for Recovering Low-Temperature Heats

Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures less than 373 K might be at least one of minimum roles for the current generations. Then, piezoelectric power harvesting process for recovering low-temperature heats was invented by using a unique biphasic operating medium of an underlying water-insoluble/low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) in small quantity and upper-layered water in large quantity. The higher piezoelectric power harvesting densities were naturally revealed with an increase in heating temperatures. Excessive cooling of the operating medium deteriorated the power harvesting efficiency. The denser operating medium was surpassingly helpful to the higher piezoelectric power harvesting density. Concretely, only about 5% density increase of main operating medium (i.e. water with dissolving alum at 0.10 mol/dm3) came to the champion piezoelectric power harvesting density of 92.6 pW/dm2 in this study, which was about 1.4 times compared to that with the original biphasic medium of pure water together with a small quantity of NOVEC.

Feasibility Demonstrations of Liquid Turbine Power Generator Driven by Low Temperature Heats

Lower temperature waste heats less than 373 K have strong potentials to supply additional energies because of their enormous quantities and ubiquity. Accordingly, reinforcement of power generations harvesting low temperature heats is one of the urgent tasks for the current generation in order to accomplish energy sustainability in the coming decades. In this study, a liquid turbine power generator driven by lower temperature heats below 373 K was proposed in the aim of expanding selectable options for harvesting low temperature waste heats less than 373 K. The proposing system was so simply that it was mainly composed of a liquid turbine, a liquid container with a biphasic medium of water and an underlying water-insoluble low-boiling-point medium in a liquid phase, a heating section for vaporization of the liquid and a cooling section for entropy discharge outside the system. Assumed power generating steps via the proposing liquid turbine power generator were as follows: step 1: the underlying low-boiling-point medium in a liquid phase was vaporized, step 2: the surfacing vapor bubbles of low-boiling-point medium accompanied the biphasic medium in their wakes, step 3: such high momentum flux by step 2 rotated the liquid turbine (i.e. power generation), step 4: the surfacing low-boiling-point medium vapor was gradually condensed into droplets, step 5: the low-boiling-point medium droplets were submerged to the underlying medium in a liquid phase. Experiments with a prototype liquid turbine power generator proved power generations in accordance with the assumed steps at a little higher than ordinary temperature. Increasing output voltage could be obtained with an increase in the cooling temperature among tested ranging from 294 to 296 K in contrast to normal thermal engines. Further improvements of the direct current voltage from the proposing liquid turbine power generator can be expected by means of far more vigorous multiphase flow induced by adding solid powders and theoretical optimizations of heat and mass transfers.

Effects of temperature-dependent viscosity variation on entropy generation, heat and fluid flow through a porous-saturated duct of rectangular cross-section

Effect of temperature-dependent viscosity on fully developed forced convection in a duct of rectangular cross-section occupied by a fluid-saturated porous medium is investigated analytically. The Darcy flow model is applied and the viscosity-temperature relation is assumed to be an inverse-linear one. The case of uniform heat flux on the walls, i.e. the H boundary condition in the terminology of Kays and Crawford [12], is treated. For the case of a fluid whose viscosity decreases with temperature, it is found that the effect of the variation is to increase the Nusselt number for heated walls. Having found the velocity and the temperature distribution, the second law of thermodynamics is invoked to find the local and average entropy generation rate. Expressions for the entropy generation rate, the Bejan number, the heat transfer irreversibility, and the fluid flow irreversibility are presented in terms of the Brinkman number, the Péclet number, the viscosity variation number, the dimensionless wall heat flux, and the aspect ratio （width to height ratio）. These expressions let a parametric study of the problem based on which it is observed that the entropy generated due to flow in a duct of square cross-section is more than those of rectangular counterparts while increasing the aspect ratio decreases the entropy generation rate similar to what previously reported for the clear flow case by Ratts and Rant [14].

高温中压长输蒸汽管道的热补偿方式及支架约束

高温中压长输蒸汽管道热补偿方式有别于电厂内部短距离输送管道,既要考虑安全性,又要考虑项目的经济性。论文对比常用热补偿方式的优缺点,提出高温中压长输蒸汽管道采用旋转补偿器补偿为主、自然补偿为辅的热补偿方式较为合理。对直线线路段、平行线路段、转角及转角叠加标高微调段、直线高差段、直线跨越段这几种常见的管道布置形式,通过START应力计算软件建模分析,确定较优的热补偿方式及支架约束条件。

双碳目标下高温气冷堆替代中小型火电的思考

碳达峰碳中和是我国一项重要的国家战略决策,“双碳”目标的提出给能源行业带来了深刻的变革,我国能源结构将进一步优化,电力行业必须实现低碳转型,新能源取代火电已成为必然。本文分析了新形势下火电企业面临的巨大挑战、发电规模受到限制、经营成本不断上升,尤其是中小型火电机组,面临着淘汰和关停的局面,而高温气冷堆具有固有安全性、发电效率高、用途广泛的显著特点,使其替代中小型火电成为可能。本文通过厂址适应性、技术可行性、经济可行性三方面,分析了高温气冷堆替代中小型火电的可行性,并从相关法律法规适用性、内陆厂址所带来的问题、开展公众沟通等方面提出建议。

中压补气对R404A冷冻系统性能特性研究

针对纯电动冷藏车冷冻系统在低温工况下出现的排气温度过高、制冷效能较低等问题,研发并搭建了一套采用变频换热风机的微通道换热器新型冷冻系统,研究车厢外环境温度持续增长时,中压补气技术对冷冻系统性能的影响。结果表明:当压缩机转速为4200r/min,库外温度为32℃,库内温度为-15℃,车内换热器风量为80%时,通过试验数据对比分析发现主阀的过热度和补阀的开度分别为5K和25%时冷冻系统制冷性能最佳;当冷冻系统主补阀开度为最佳时,变化库外环境温度发现,与不补气系统对比,系统采用中压补气时,排气温度降低了12.53%~33.80%,制冷量提高了8.38%~16.73%,压缩机功率增加了5.71%~13.07%,COP值上升了2.94%~4.17%。

基于中低温相变材料的管壳式储热单元传热性能数值分析

针对管壳式相变储热单元换热效率低的问题,设计一种带有径向矩形翅片的复合盐管壳式相变储热单元,进行数值模拟并与实验研究对比验证,然后选择适当的性能指标分析模拟结果。采用ANSYS FLUENT进行三维瞬态仿真,改变换热流体入口温度及储热单元翅片间距进行储热过程的数值计算,对相变材料温度变化、传热过程及熔化情况进行对比分析。结果表明:提高换热流体温度和缩小翅片间距是有效强化换热的手段。在本工作中,换热流体与相变材料复合盐CH_(3)COONa·3H_(2)O-KCl相变温差每增加5℃,相变材料熔化速率分别提升54.98%、 34.67%、 23.92%、 18.13%、 14.45%,潜热储热速率分别提升61.56%、 45.79%、 35.15%、27.04%、22.31%,速率提升效果均逐渐减弱。翅片间距每缩短10 mm,相变材料熔化速率分别提升32.37%、41.26%、38.66%,储热量随之减少6.40%、11.95%、6.55%,储能密度降低0.53%、10.97%、1.57%,实际应用中需综合换热能力、成本等方面问题选择合适的翅片间距。本工作可为实际工程中储热单元的设计优化提供理论支持。

气液喷射升压有机朗肯循环特性

针对小型有机朗肯循环工质泵效率低、耗功大等问题,将气液喷射器取代工质泵作为升压设备,基于喷射器一维模型,构建了气液喷射升压有机朗肯循环(IORC)的热力模型。以140?℃的中低温热源为驱动力,R245fa为工质,研究了喷射器引射系数、喷射器面积比以及冷凝器出口过冷度3个参数对IORC性能的影响,并将IORC与基本有机朗肯循环(BORC)的热力性能进行对比。结果表明,存在一个最佳引射系数和过冷度,使IORC的净输出功达到最大值。引射系数和面积比的增加均会使喷射器升压比降低,而过冷度的增加会使升压比增加。3个参数的增加均会使喷射器?效率和换热器经济性降低。IORC的换热器经济性比BORC更好,当工质泵效率低于52%时,IORC净输出功更具优势。

GNSS PWV典型季风气候特征奇异谱分析

为了进一步研究利用全球卫星导航系统(GNSS)大气可降水量(PWV)分析不同气候类型特征,进行GNSS PWV典型季风气候特征奇异谱分析:选取中国中东部地区2016—2021年部分连续运行参考站(CORS)数据,提出将全球气压和温度(GPT(GPT3_1、GPT3_5))模型、欧洲中期天气预报中心第五代大气再分析数据集(ERA5)模型3种大气模型分别与GNSS解算的对流层总延迟(ZTD)数据融合获取的PWV值进行对比分析,得出中国3种典型季风气候类型GNSS PWV最优大气模型;然后提出利用奇异谱分析(SSA)法分解重构出GNSS PWV时间序列,从而基于GNSS PWV分析不同季风气候类型特征。结果表明,中国3种典型季风气候类型条件下ERA5模型精度较优,选择ERA5模型为最优大气模型,重构后的GNSS PWV变化趋势能够很好地反映出3种典型季风气候类型的特征;因此GNSS PWV可应用于气候特征分析。

储氢技术研究现状及进展

储氢环节是连接氢生产到应用的桥梁,也是高效利用氢能的基础。高压气态储氢技术最成熟、应用最广泛,研制轻质、高压、耐腐蚀性强、稳定性好的储氢容器将是未来高压储氢的研发热点。固态储氢是利用固体材料吸附方式实现氢的存储,主要包括金属材料、复合氢化物、碳基材料、有机框架储氢材料、无机多孔储氢材料等。从储能密度角度看,低温液态储氢是一种十分理想的储氢方式,但也存在能量损失大、成本高昂等问题。有机液态储氢具有储氢密度大、安全性好、载体可循环使用等显著优点,被认为是最有希望实现大批量、远距离氢储运的重要方式之一,甲基环己烷(MCH)、二苄基甲苯(DBT)、N-乙基咔唑(NEC)、甲醇/甲酸等是当前有机物储氢介质的研究热点且具有商业化前景。目前有机液态储氢还存在脱氢效率低、能耗大、氢纯度不足等问题,大部分技术仍处于研究或初期示范阶段。短期内高压气态储氢仍是储氢方式的主流选择。中期内发展的重点是有机液态储氢和固态储氢,低温液态储氢主要应用在大批量、长距离的特殊储运场景。长期来看,融合多种储氢方式的优点,开发集成式耦合储氢技术是未来发展的关键,高效、长寿命、经济性好的储氢介质/催化剂体系是未来储氢技术的研究重点。

Z世代青年需求的中小户型空间适应性研究——以禧瑞学府为例

随着我国城镇化的快速发展,土地市场竞争激烈,许多住房产品“被豪宅化”,住宅面积大,总价过高,致使刚刚步入社会不久的Z世代(GenerationZ)青年无法负担。经近几年政策调控,一线城市住宅户型开始从“大户型”向“中小户型”发展,小户型、总价低的“上车盘”已成为Z世代青年的首要选择。本文通过总结研究的空间适应性经验,并从精神—需求—场景进行对应落位至笔者所参与的项目中,针对青年人群的居住需求类型提出实现当下青年住宅小户型空间适应性的设计。

复杂硫化铜镍渣中温氧压浸铜镍—同步沉铁研究

针对复杂硫化铜镍渣进行了中温氧压浸铜镍—同步沉铁试验,查明了硫化铜镍渣中主要元素的存在形式,考察了氧压浸出工艺条件对铜、镍、铁、硫浸出率的影响。获得硫化铜镍渣高效浸铜镍—同步沉铁的最佳工艺参数为:硫酸(98%)20 g(即每吨铜镍渣硫酸200 kg)、浸出温度170℃、氧分压0.4 MPa、液固比5 mL/g、浸出时间5 h,在该条件下,铜、镍、铁、硫的浸出率分别为98.73%、98.86%、26.69%、93.17%,浸出液残酸浓度1.28 g/L,浸出液中铜、镍、铁质量浓度分别为77.04、18.80、0.67 g/L。

5.5 MW半直驱中速永磁风力发电机温度场分析

本文建立了半直驱中速永磁风力发电机的三维流体与传热耦合模型,进行了数值模拟,获得了电机内部温度场,并与试验样机实测数据进行了对比。总结了大功率中速永磁发电机内部传热规律,为发电机冷却结构优化设计提供理论依据。

加氢制备对苯二甲胺工艺研究

以对苯二甲腈为原料,甲醇为溶剂,雷尼镍为催化剂,采用低温中压催化加氢工艺制备了对苯二甲胺。探究了反应溶剂、催化剂、温度、压力等因素对加氢反应转化率、选择性和产品质量的影响,实验结果表明:溶剂比例为1∶4,催化剂质量分数15%,反应温度60~95℃,压力7~8 MPa条件下,反应转化率为100%,选择性为97%~98%,副产物大幅减少,预期经济和环境效益明显,为工业化实施提供了支撑。

低温甲醇洗工艺系统设计要点

分析了低温甲醇洗工艺设计的关键内容,讨论了低温甲醇洗低温塔及甲醇/水系统材质选择、再沸器疏水优化、CO_(2)解吸塔及H_(2)S浓缩塔的两相流计算,位差设计和布置确定、热再生塔进料换热器管程前增加精密过滤器优化、中压闪蒸区的设计优化,总结了设计要点,以期为相关工程设计提供参考。

超超临界1 050 MW机组中压缸超温原因分析与处理

文章介绍了超超临界1050MW机组中压缸进汽室超温情况,以及发电厂利用机组A级检修机会,对中压缸解体检修,发现内缸、隔板套、隔板多处变形,通流部件有碰磨痕迹,随后将第1级隔板返厂增加切向旋流冷却孔,对隔板套、隔板等进行加工,对通流间隙进行调整。机组检修结束启动后,中压缸超温问题顺利解决,中压缸效率也得到恢复。

从迪拜光热+光伏综合电站项目浅谈温度仪表新应用

迪拜光热+光伏综合电站项目是目前世界上集光能发电之大成,既有光伏发电又集成了光热发电,且光热发电涵盖了目前世界上仅有的2种光热发电形式——槽式、塔式,其是一个成体系的完整光能发电项目,极具代表性。通过对光热发电原理的解读,结合迪拜光热综合电站项目知晓光热发电的测温需求,通过工程案例论述了光热镜场传热介质的测温方案,以及测温技术应用的关键点,对测温技术在光热发电方面的应用有着积极的意义。

15CrMo在含NaCl高温高压水/水蒸气中的腐蚀行为

为研究15CrMo钢在高温高压含NaCl工质中的腐蚀行为,搭建了高温高压反应釜实验台。利用SEM,EDS,XRD测试方法对在不同工况下的15CrMo腐蚀样品进行了分析。结果表明,当腐蚀温度为280℃时,相比于饱和水,Fe_(3)O_(4)的晶体结构在饱和蒸汽中的生成速率更快。当腐蚀温度上升到360℃时,15CrMo在含盐饱和蒸汽与含盐饱和水中腐蚀产物的晶体结构均已无明显变化,其表面的晶体结构各自趋于稳定。在饱和蒸汽中FeOCl的生成反应对温度变化的敏感性较高,温度为280℃时,该生成反应仅在腐蚀工质为含盐饱和水时发生,而在360℃,含盐饱和蒸汽中的样品表面也能够发生。在280~360℃,15CrMo在含NaCl饱和水中的腐蚀程度相较其在饱和蒸汽中更高。