Comparative Study of the Types of Photovoltaic Panels Used in Solar Pumping Systems in Dry Tropical Zones: Case of Adamawa Region in Cameroon

In the dry tropical zone where access to water is increasingly difficult for populations, solar pumping units are increasingly installed to provide water to population. In the local market, there are essentially two types of solar panels, namely monocrystalline and polycrystalline. However, the part of the local market is more dominated by the polycrystalline panel. In this work, comparative studies are carried out in order to characterize the two types of solar panels with regard to local constraints. Tests were carried out over the course of the sun to establish the performance of each type. The panels used have the same electrical characteristics and are connected to loads with same characteristics. Under the set operating conditions, the monocrystalline panel presents more performance than the polycrystalline panel. Although the local market is dominated by the polycrystalline panel, dust deposition tests on the surface of the panels show that the performance of the polycrystalline panel is more affected compared to the performance of the monocrystalline panel.

Impacts of different drying strategies on drying characteristics,the retention of bio-active ingredient and colour changes of dried Roselle

The drying kinetics of Roselle （Hibiscus sabdariffa L） of variety Terengganu （UMKL-1） and the quality attribution of Roselle were studied. The experiments were conducted using four different drying methods, including solar greenhouse drying （SD）, solar greenhouse with intermittent heat pump drying （SIHP）, hot air drying （HA） and heat pump drying （HP）. Among the four drying methods, HP achieved the highest drying rate at a range from 0.054 g H20-（g DM）-1. rain-1 to 0.212 g H20-（g DM）-1. rain 1 while SD had the lowest drying rate, measured at 0.042 g H2O. （g DM） 1.min- 1. The analysis on colour kinetics revealed that there is no significant colour loss （p 〉 0.05） observed from HP＇s dried Roselle. Greater amount of flavonoid compounds i.e. protocatechuic acid was found in SD and SIHP dried finished product whereas HP＇s dried Roselle contains higher percentage of catechin as compared to other drying methods.

基于机器视觉的陈皮热泵干燥含水率预测模型研究

为定量预测陈皮热泵干燥过程中含水率的变化,基于机器视觉技术提取陈皮干燥过程中的图像特征,建立含水率预测模型。采集不同干燥时期的陈皮图像,采用图像处理的方法对陈皮图像进行预处理操作,提取陈皮图像的6个颜色特征和6个纹理特征共计12个图像特征,分析特征参数和含水率变化关系,将相关图像特征作为模型的输入,陈皮的含水率作为模型的输出,分别建立基于BP神经网络和支持向量机的陈皮干燥含水率预测模型进行对比分析,得到不同干燥时期含水率最佳预测模型。结果表明,支持向量机的预测效果更好,准确率达到99.01%,均方误差达到0.006 5,模型运行稳定,含水率预测结果准确且快速,能够为陈皮干燥过程中的含水率在线预测提供科学依据。

基于模糊控制的高温热泵果脯干燥系统设计

针对高温热泵干燥技术替代传统蒸汽或热风干燥在果脯烘干中的应用场景,研制高温热泵干燥系统。结合热交换器结构与换热特性,分析果脯干燥工艺特点,将模糊逻辑控制应用于热泵干燥过程;考虑干燥箱的热场分布、温度梯度控制与干燥时间的耦合,对模糊控制器、模糊规则表进行详细设计,采用可编程逻辑控制器(PLC)控制的热泵干燥控制系统进行龙眼干燥实验测试。结果表明,模糊控制具有良好的稳态和瞬态性能,具有温度调节快、误差小、干燥效率高、节能效果好等优势,适用于干燥工艺复杂、温度调节要求高、减少人为干预影响品质的果蔬类农产品深加工。

Experiment research on grain drying process in the heat pump assisted fluidized beds

A heat pump assisted fluidized bed grain drying experimental system wasdeveloped. Based on this system, a serial of experiments was performed under four kinds of air cycleconditions. According to the experimental analysis, an appropriate drying medium-air cycle for theheat pump assisted fluidized bed drying equipment was decided, which is different from the commonlyused heat pump assisted drying system. The experimental results concerning the drying operationperformance of the new system show that the averaged coefficient of performance (COP) can reach morethan 2.5. The economical evaluation was performed and the power consumption for removing a kilogramwater from grains was about 0.485 kW-h/kg (H_2O), which shows its reasonable commercial efficiencyand great application potentiality in future market.

Energy Analysis of Pid Controlled Heat Pump Dryer

In this experimental study, a heat pump dryer was designed and manufactured, in which drying air temperature was controlled PID. Manufactured heat pump dryer was tested in drying kiwi, avocado and banana from among tropical fruits and energy and exergy analyses were made. Drying air temperature changed between 40 oC - 40.2 oC while drying the tropical fruits. Before the drying process in heat pump dryer, initial moisture contents were determined as 4.31 g water / g dry matter for kiwi, 1.51 g water / g dry matter for avocado and 4.71 g water / g dry matter for banana. Then tropical fruits were dried separately in heat pump dryer. Drying air temperature was kept unchanged with the error of +0.2 oC. Drying air velocity changed between 0.3 and 0.4 m/s in a period of 310 min. COPws of the heat pump dryer was calculated as 2.49 for kiwi, 2.47 for banana and 2.41 for avocado during the experiments. EUR changed between 13 % and 28 % for kiwi, 18% and 33% for avocado and 13% and 42% for banana in heat pump dryer.

不同高温热泵干燥条件对龙眼干品质的影响

以龙眼为研究对象,考察了不同热泵干燥温度和干燥风速对龙眼干一般理化特性、色泽、质构和活性成分等品质的影响。结果表明:采用高温热泵干燥时,干燥温度越高,龙眼干的总酸含量越高,复水率越低;干燥风速相同时,龙眼干的pH值随着温度的升高而降低;龙眼干燥后总体色泽的变化主要在色泽的变暗及变黄,干燥温度的升高和干燥风速的增加都会导致龙眼色泽变化的增加;总体来说,不同高温热泵干燥条件下,龙眼干的弹性、回复性、硬度以及耐咀性的变化均不显著,干燥风速较低,龙眼干的黏性较大;当干燥温度为60℃时,龙眼干中保留的游离酚含量最高,不同干燥条件下,结合酚含量、多糖含量的差异不显著。

滹沱河断流区水环境劣变特征与地下调蓄潜力

本文通过对 2 0世纪 80年代以来滹沱河山前段的地表水和地下水环境劣变特征分析 ,阐明了山前拦蓄地表水和山前平原超采地下水对水环境影响的后果 ,并以大量实测资料为依据论证了被疏干地下含水介质空间的地下调蓄可利用性 ,系统阐述了研究区地下调蓄的基本条件和潜力 。

北京市第九水厂排泥水处理系统改造设计分析

随着排泥水处理技术研究的不断深入，以及净水厂排泥水处理工程设计经验的不断丰富，排泥水处理系统设计更加科学化和合理化。北京市第九水厂排泥水处理系统正式运行已十余年，运行中发现了一些需要改进的地方。在对北京市第九水厂目前所面临的水源水质情况及排泥水处理系统运行中存在的问题进行分析的基础上，提出了改造方案并总结了实际工程设计时应注意的一些设计要点。

基于电子鼻识别的热泵干燥鲢鱼品质评价模型的建立

为提高干制水产品品质评价的客观性,建立可靠的电子鼻评价模型。运用电子鼻技术根据总挥发性盐基氮(total volatile base nitrogen,TVB-N)值对不同干燥工艺条件下的腌制鲢鱼进行检测,通过主成分分析并结合统计模式识别方法和偏最小二乘(partial least squares,PLS)回归分析方法对输入的鲢鱼TVB-N值进行模式识别。结果表明:电子鼻对同一因素不同水平下干燥白鲢的TVB-N值产生不同的响应;建立的K最近邻分类算法判别模型对训练集和预测集的识别率均在90%以上,能够对样本进行准确的判断;PLS法分析不同条件下干燥的鲢鱼样品训练集(30个样本)和预测集(15个样本)的相关系数分别为0.913 5和0.933,训练集的交互验证均方根误差为3.67,而预测集的预测均方根误差为3.26,达到理想效果。结论:所建立的电子鼻PLS模型能根据TVB-N值实现不同腌干鲢鱼制品的电子鼻区分识别,可用于热泵干燥的白鲢鱼品质预测监督,为干制水产品品质客观的评价提供理论基础和技术指导。

不同护色处理对龙眼干制品品质的影响

以龙眼为原料,结合护色、热泵干燥工艺加工龙眼干制品,研究护色处理过程中护色剂的护色时间、干燥温度及干燥时间等因素对龙眼干制品品质的影响。结果表明:龙眼干制品中总糖含量随着护色时间的延长而上升,随着热泵干燥温度的升高先增加后下降;龙眼干制品的酸度随着干燥时间和温度的增加先升高后降低。以1%偏重亚硫酸钠+0.5%抗坏血酸的复合护色剂对去皮、去核的果肉护色,在此基础上热泵干燥制备龙眼干制品的最佳工艺为护色时间4 min、热泵干燥温度60℃、干燥时间12 h,所制得的龙眼干制品色泽均匀、总糖含量2.55%、酸度25.7%。因此,不同护色和热泵干燥工艺影响龙眼干制品的品质,响应面优化的热泵干燥制备龙眼干制品的最佳工艺较好,所得龙眼干制品品质较佳。

超声波辅助漂烫预处理对太阳能-热泵联合干燥南瓜片品质的影响

研究超声波辅助漂烫预处理方法对太阳能-热泵联合干燥南瓜片品质的影响,以超声波温度、功率、频率和处理时间为单因素,研究其对干燥南瓜片色差、硬度、β-胡萝卜素及抗坏血酸含量的影响。通过正交优化分析获得最优工艺条件,并与传统漂烫预处理进行干燥南瓜品质的对比实验。结果表明,在超声波温度70℃、超声波功率为300 W、超声波频率为35 k Hz、超声波处理时间为3 min条件下,干燥处理对南瓜片的颜色及营养物质含量的影响最小,色差值为9.95,相比于传统热烫的预处理方法减少61.64%;硬度值为36.61 N;抗坏血酸含量为13.00 mg/100 g,较传统热烫提高41.38%。因此,相比于传统热烫的预处理方法优势依然明显。证明超声波这一物理手段可显著减少南瓜热处理时色泽变化及抗坏血酸等营养物质的流失,超声波辅助漂烫预处理手段可用于南瓜片干燥加工中。

Stability of phenolic compounds and drying characteristics of apple peel as affected by three drying treatments

To realize high-value utilization of discarded apple peel,this study investigated the effects of three selected commercial drying methods on drying kinetics,microstructure,color,phenolic stability and antioxidant capacity of apple peel.Apple peel was dehydrated by hot air drying(AD)at 75,65 and 55℃,heat pump drying(HP)at 65,55 and 45℃,and vacuum freeze-drying(FD),respectively.The results showed that HP was superior to AD and FD in terms of drying rate.In addition,HP at 65℃provided high-quality dried apple peel due to less browning and brighter appearance,the highest retention of total phenolics(29.35 mg/g)and the strongest antioxidant activities,with the highest ABTS and FRAP value of 127.15 and 219.57μmol TE/g,respectively.The content of the six major individual phenolics,i.e.caffeic acid,(-)-epicatechin,hyperoside,rutin,phlorizin and quercitrin,were found to be the highest in HP dried samples.Interestingly,the content of rutin was even increased after HP compared to the fresh sample.Considering drying efficiency,organoleptic quality and phenolic stability of the products,HP at 65°C is suggested for drying of apple peel.

风干板栗太阳能-热泵联合干燥特性与数学模型研究

为研究风干板栗太阳能-热泵联合干燥特性,以新鲜板栗为原料,探讨干燥温度、干燥风速、装载量对风干板栗干燥速率和干基含水率的影响,在不同干燥温度、干燥风速、装载量条件下分别对新鲜板栗进行干燥,并比较了6种数学模型在风干板栗太阳能-热泵联合干燥的适用性,同时以Fick第二扩散定律为依据,确定风干板栗不同干燥条件下的有效水分扩散系数。结果表明:风干板栗干燥过程由调整阶段和降速干燥阶段控制,主要表现为降速干燥;干燥温度越高、干燥风速越高以及装载量越小,干燥至目标含水率所用时间越短,干燥速率越大;干燥过程中,有效水分扩散系数随干燥温度及干燥风速的升高、装载量的降低呈现增大的趋势,干燥温度从15℃升高到35℃,其有效水分扩散系数由3.00124×10^-10 m^2/s增大到8.42115×10^-10 m^2/s,干燥风速由1.0 m/s升高到5.0 m/s,其有效水分扩散系数由4.54717×10^-10 m^2/s增大到9.13767×10^-10 m^2/s;装载量从0.6 kg升高至5.4 kg,其有效水分扩散系数由1.14753×10-9 m^2/s降至3.20443×10^-10 m^2/s;通过比较决定系数(R2)、残差平方和及卡方(χ^2)得出,Page模型为描述风干板栗太阳能-热泵联合干燥的最优模型,验证发现试验值与模型预测值拟合度较高,Pearson相关系数为0.998,二者显著相关(P<0.05),说明Page模型能够较好地反映风干板栗干燥过程中水分变化规律。

自控热泵柿饼烘干房及快速干制出霜工艺研究

传统柿饼加工为自然晾晒生产,受天气因素影响,加工周期长,易受灰尘及细菌污染,劳动强度大,正逐步被人工烘干替代。为此进行了一种自控热泵柿饼烘干房研制及干制和出霜工艺研究,介绍了烘干房的系统设计、电气控制、结构设计及生产工艺试验过程。利用该设备和工艺技术,使柿饼烘干周期从自然晾晒的40多天缩短为5-6天,成品柿饼水分控制在30%左右,烘干柿饼色泽优于传统柿饼,口感与传统柿饼相当,而卫生程度与生产效率远高于传统工艺,为柿饼的清洁化工厂化生产奠定了基础。

凝血酶冻干粉联合质子泵抑制剂治疗消化性溃疡出血的临床效果

目的探讨凝血酶冻干粉联合质子泵抑制剂治疗消化性溃疡出血的临床效果。方法选取2018年1月~2019年1月江西省吉安市第一人民医院内科收治的60例消化性溃疡出血患者作为研究对象,按照动态化随机分组法将其分为对照组与试验组,每组各30例。对照组患者采用质子泵抑制剂治疗,试验组患者采用凝血酶冻干粉联合质子泵抑制剂治疗。比较两组患者的临床疗效、凝血指标、血小板参数指标以及不良反应发生情况。结果试验组患者的治疗总有效率高于对照组,差异有统计学意义(P<0.05)。治疗前,两组患者的血浆凝血酶原时间(PT)、国际标准化比值(INR)、活化部分凝血活酶时间(APTT)、凝血酶时间(TT)、纤维蛋白原含量(Fg)、血小板计数(BPC)、血小板比积(PCT)、平均血小板体积(MPV)比较,差异无统计学意义(P>0.05);治疗后,两组患者的PT、INR、APTT、TT、MPV均低于治疗前,Fg、BPC、PCT均高于治疗前,差异有统计学意义(P<0.05);治疗后,试验组患者的PT、INR、APTT、TT、MPV均低于对照组,Fg、BPC、PCT均高于对照组,差异有统计学意义(P<0.05)。试验组患者的不良反应总发生率低于对照组,差异有统计学意义(P<0.05)。结论凝血酶冻干粉联合质子泵抑制剂治疗消化性溃疡出血的效果显著。

基于真空冷冻-热泵联合干制鱼片的解吸-吸附等温线及热力学特性

为探讨超声波辅助聚葡萄糖渗透预处理结合真空冷冻-热泵联合干燥罗非鱼片的品质及其后期贮藏稳定性,采用静态称重法测定真空冷冻-热泵联合干制罗非鱼片在25、35、45℃时及水分活度(a_(w))为0.1116~0.8434时的解吸-吸附等温线,选取8种常见的数学模型对解吸-吸附等温线数据进行拟合,通过决定系数(R^(2))和均方误差(E_(MS))确定解吸-吸附等温线的最佳模型,再根据干制罗非鱼片在不同温度下的解吸-吸附等温线数据获取干制罗非鱼片的热力学性质。结果表明:干制罗非鱼片的水分解吸-吸附呈Ⅲ型等温线,Peleg模型是描述真空冷冻-热泵联合干制罗非鱼片解吸-吸附等温线的最佳模型,同时获得25、35、45℃条件下干制罗非鱼片的绝对安全含水率分别为16.30%、13.68%、13.64%,相对安全含水率分别为22.89%、19.21%、19.77%;干制罗非鱼片的净等量吸附热、等量解吸热、微分熵均随平衡含水率上升呈现指数递减,解吸与吸附过程均由焓驱动,且均属于非自发性。研究表明,不同贮藏温度和水分活度对干制罗非鱼片的解吸-吸附等温线及热力学性质有较大影响,该研究结果可为罗非鱼片的干燥工艺优化及贮藏条件的设置提供数据参考。

Preparation of Nanometer Nd3＋,Y3＋ Co-doped CaF2 Powder by Coprecipitation-azeotropic Distillation Technique

The synthesis of Nd3＋,Y3＋：CaF2 nanopowder was conducted by azeotropic distillation method,which effectively dehydrated hydrous CaF2 and prevented forming hard agglomerates.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,scanning calorimetries-thermalgravimetry（DSC-TG）,Fourier transform infrared spectroscopy（FT-IR） and absorption spectroscopy were performed to characterize the powder properties.The experimental results showed that products obtained by azeotropic distillation were single phased,rather monodispersed,successfully prevented the hard agglomerate formation and effectively removed the residual water inside the as-prepared precipitate than that of the direct drying.The absorption spectra showed a wider and stronger absorption bands around 792 nm,which should be profitable for LD pumping.

Optimization of chanterelle mushroom drying kinetics under heat pump dryer using Taguchi design method

The optimum drying conditions with regard to minimum color changes, high rehydration ratio and drying rate for chanterelle mushrooms is inadequately known. To address this problem, drying kinetics for chanterelle mushroom samples with sizes of 20 mm×20 mm×20 mm cube, 20 mm×20 mm×30 mm cuboid, and Ø40 mm×20 mm cylindrical shape were experimented. Drying air temperatures of 40℃, 48℃, and 56℃ at superfluous humidity and velocity of 2.2 m/s were used. Initial color pixels for each sample were determined using Note 8 Pro Xiaomi smartphone camera and image processing tool in Matlab R2019a. Triplicate experimentation was done based on L9 Taguchi orthogonal arrays with drying rate, specific moisture extraction rate, color change, and rehydration ratio being the response parameters. The drying rate increased from 1.1174 g/g∙min to 1.3478 g/g.min as the temperature rose from 40℃ to 56℃. The mushroom cube had the highest drying rate of 1.2860 g/g∙min while the cylindrical shape had the lowest rate of 1.1764 g/g∙min. Similarly, SMER increased from 0.006 326to 0.013 27 g/kWh with the temperature rise. Contrary, SMER decreased from 0.006 92 to 0.013 63 g/kWh in cylinder to cube respectively. Color change was highest at 40℃ (13.49) and lowest at 56℃ (11.94). The mushroom cube had the lowest color change of 9.28 on average when compared to other shapes. Rehydration ratio was highest at 56℃ (3.824) as compared to 48℃ and 40℃. Additionally, the mushroom cube had the highest rehydration ratio of 4.55 on average as compared to other shapes. Temperature variation significantly influenced the drying rate and SMER. However, temperature variation had insignificant differences in color change and rehydration ratio. Mushroom shape variation had a significant difference in all the response variables tested. Conclusively, mushroom cubes at the drying temperature of 56℃ gave optimized drying conditions for chanterelle mushrooms with minimal quality deviations. Thus, chanterelle mushrooms can be sliced into cubes to allow quick drying rate, better SMER, rehydration ratio, and have minimal color change.

Study on friction performance and mechanism of slipper pair under different paired materials in high-pressure axial piston pump

High-pressure axial piston pumps operate in high-speed and high-pressure environments. The contact state of the slipper against the swashplate can easily change from an oil film lubrication to a mixed oil film/asperity contact, or even dry friction. To improve the dry friction performance of slipper pairs and to avoid their potentially rapid failure, this study examined the effects of material matching on the dry friction performance of the slipper pair for high-pressure axial piston pumps. A FAIAX6 friction and wear tester was developed, and the dry friction coefficients of the slipper pairs matched with different materials were studied using this tester. Based on the thermo-mechanical coupling of the slipper pair with the working process, the contact surface temperatures of the slipper pairs matched with different materials were calculated and analyzed for the same working conditions. Following this, the effects of the material properties on the temperature increase at the slipper sliding contact surfaces were revealed. The reliabilities of the temperature calculations and analysis results were verified through orthogonal tests of slipper pairs matched with different materials. The results indicate that the influence of the material density on the friction coefficient is greater than that of the Poisson's ratio or the elastic modulus, and that the slipper material chosen should have a high thermal conductivity, low density, and low specific heat, whereas the swashplate material should be high in specific heat, density, and thermal conductivity;in addition, the slipper pair should be a type of hard material to match the type of soft material applied;that is, the hardness of the swashplate material should be greater than that of the slipper material.