A Study on the Performances of Solar Air Collectors Having a Hemispherical Dimple on the Absorber Plate

In order to increase the efficiency of solar air collectors,a new variant with a protrusion is proposed in this study,and its performances are analyzed from two points of view,namely,in terms of optics and thermodynamics aspects.By comparing and analyzing the light paths of the protrusion and the dimple,it can be concluded that when sunlight shines on the dimple,it is reflected and absorbed multiple times,whereas for the sunlight shining on the protrusion,there is no secondary reflection or absorption of light.When the lighting area and the properties of the surfaces are the same,the absorption rate of the dimple is 10.3 percentage points higher than that of the protrusion.In the range of Reynolds number from 3000 to 11000,numerical simulations about the effects of the relative height(e/Dh=0.033–0.1)and relative spacing(p/e=4.5–8.5)of protrusions on air heat transfer and flow resistance show that,in terms of comprehensive evaluation coefficient(PF),the best relative height is 0.085,when the relative spacing is 5.A correlation of Nu and f with Re,e/Dh and p/e is obtained by linear regression of the results,in order to provide a useful reference for the design and optimization of this kind of solar air collector.

Theoretical and experimental research on effect of fins attachment on operating parameters and thermal efficiency of solar air collector

Flat plate air collector is a type of heat exchanger which absorbs radiated solar energy and exchanges it to heat.According to low efficiency of this type of collectors,a suitable approach is investigated in this paper so as to increase thermal performance of the system.Thermal efficiency of solar collector for two models C1(without fins)and C2(with fins)both of 1 m^2 surface area with forced convection flow is studied theoretically and experimentally.Rectangular fins are attached over back board in air channel to create turbulence in air flow.In order to measure air temperature,17 thermal sensors(LM35)are exploited,among which 11 were mounted on absorber plate and the remaining 6 on the back board.Physical design of experimental model are performed in Solidwork and programming of theoretical work in Matlab software.In this research,a fan with constant mass flow rate of 0.033 kg/s is utilized for producing air flow.Results indicate that applying fins in air channel not only reduces Nusselt number from 19.67 to 16.23,but also due to decreasing hydraulic diameter and creating air flow turbulence,causes increase of heat transfer coefficient from absorber plate to air flow and consequently reduction of total heat loss and higher outlet air temperatures.Average difference of outlet air temperature between experimental and theoretical results for both collectors(C1 and C2)was recorded respectively as 7.6% and 9.4%.Thermal efficiency was respectively calculated 30% and 51% for experimental types with and without fins and 33% and 55% for those of theoretical work which generally seem reasonable.

Thermal performance of solar air collector with transparent honeycomb made of glass tube

Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate solar air collector. Experiments are performed for solar collectors with six different honeycomb sizes. The emphasis is to study the effects of diameter and aspect ratio of the honeycomb unit on the transmittance and efficiency of the solar collector. It is shown that for the same diameter but different aspect ratios, there are large temperature differences between the collector’s exits; the smaller the aspect ratio, the larger the exit temperature, with a maximum difference of 10℃; for the same aspect ratio but different diameters, the temperature differences are small; the maximum temperature difference between the collectors with and without honeycombs is 12℃. A theoretical expression for the honeycomb transmittance is derived with a simplified method. The result shows that the honeycomb transmittance is only related with the aspect ratio and the materials’ optical properties but not the actual size of the honeycomb.

Theoretical and Experimental Study of a Double Air-Pass Solar Thermal Collector with an Insulating Rod of Millet

In this article, we present the study of a double-pass air insulated by crushed millet stem mixed with gum arabic. The study is carried out based on mathematical models obtained by writing energy conservation laws in the various components of the system, which made it possible to determine the evolution of the air temperature as a function of the length of the absorber and to make a comparison with the experimental results. After comparing the results obtained with those found in the literature, the influence of some physical and geometrical parameters on the performance of the solar thermal collector is presented.

交叉V型吸热板-底板太阳能空气集热器热性能的数值模拟

应用太阳载荷模型,利用FLUENT软件对九个交叉V型吸热板-底板太阳能空气集热器进行了数值模拟,得到集热器的热效率、出口温度、热损和吸热板温度,并对其进行了对比分析,发现集热器的热效率随着空气流道高度的增大而减小,热损失、吸热板温度和出口温度随着空气流道高度的增大而增大,最大效率为34.60%,最高出口温度为355.13 K.

计及AA-CAES与PTC集成的综合能源系统运行优化与性能分析

为进一步发挥综合能源系统的多能互补优势,提出一种计及先进绝热压缩空气储能(AA-CAES)与槽式太阳能集热器(PTC)集成的综合能源系统(IES-PTC-CAES)优化运行策略。首先,对AA-CAES、PTC以及系统中其他设备进行分析并建立相应模型;进而以经济性、环保性和能效性为优化目标,以设备运行的关键参数为优化变量,基于分时电价建立了协同优化策略,并通过K-means算法将模拟出的典型年负荷聚类为典型日负荷;最终,使用并行式的遗传算法对系统进行寻优,得到不同目标下IES-PTC-CAES的最优运行策略。结果表明:与参考系统相比,IES-PTC-CAES系统经济目标下总成本降低了14.61万元,环保目标下二氧化碳排放量减少了6194.38 kg。

滤筒除尘器喷吹孔孔径的优化

【目的】为控制各个喷吹管气流量的均匀性,对喷吹管上的喷吹孔径进行优化,提高滤筒除尘器清灰效果。【方法】自制高压脉冲喷吹气流量测量装置对现有喷吹管气流量进行测定,采用光纤传感分析仪测试除尘器滤筒各部分的侧壁压力峰值,分析各滤筒清灰效果不均匀的原因;以滤筒各部位侧壁压力峰值作为清灰均匀性效果评估指标,优化喷吹孔径。【结果】优化前4个喷吹孔径均为19 mm,喷吹孔的气流量依次为13.69、 14.78、 16.03、 16.93 L,对应4个滤筒上、中、下部侧壁压力峰值的最小值分别为最大值的37%、 26%、 20%,气流量均匀度标准差为1.41;优化后4个喷吹孔径分别为23、 20、 18、 17 mm,喷吹气流量依次为14.05、 15.08、 15.87、 16.13 L,对应4个滤筒上、中、下部测壁压力峰值的最小值为最大值的56%、 56%、 53%,气流量均匀度标准差降为0.93。【结论】优化后的喷吹管气流量均匀化程度提高,可实现滤筒除尘器的均匀清灰。

输煤皮带秤技术的优化与应用研究

在传统煤矿测量过程中,容易出现精确度低、稳定性差等问题。因此通过分析传统输煤皮带秤技术,提出了输煤皮带秤技术的优化方法。该方法深入剖析了影响计量皮带秤测量准确度和稳定性的因素,提出了提高计量皮带秤测量准确度和稳定性的电气仪表技术优化改进措施。结果表明,优化后的输煤皮带秤技术能够提高称重准确度和效率,为相关行业的生产和管理提供了有效的建议和改进空间。

吨水耗电量在太阳能空气源热泵热水系统的应用

随着建设绿色低碳校园的理念提出,太阳能空气源热泵技术在高校得到了广泛应用。为了更好地分析和评价太阳能空气源热泵热水系统的节能降碳效果,以某高校宿舍楼为研究对象,设计了并联式太阳能空气源热泵(SC-ASHP)热水系统,分析了该系统的年实际运行情况,并与单一热泵(ASHP)热水系统的运行情况进行了对比研究。结果表明:该高校宿舍楼典型用水高峰期在18:00-22:00时,这有利于并联式太阳能空气源热泵热水系统在白天利用太阳能加热水箱,剩余不足部分由热泵进行补热。吨水耗电量可作为评价该热水系统运行效果的关键参数,并联式太阳能空气源热泵热水系统吨水耗电量y随环境温度T_a升高在逐渐降低,随进水温度T_(in)升高先减小后增大。在T_a和T_(in)都是11.5℃时,系统吨水耗电量达到最小值,这是因为当T_(in)>11.5℃时,不利于热泵凝汽器放热,热泵效率降低,热水系统吨水耗电量随之增大。并联式太阳能空气源热泵热水系统吨水耗电量整体低于单一热泵热水系统,其中热泵对系统吨水耗电量的影响最大。并联式太阳能空气源热泵热水系统比单一热泵热水系统年平均节省电量为4.18万kW·h,年平均降低CO_(2)间接排放量为41.67 tCO_(2),具有明显的节能降碳效果。

助流气碟在布袋除尘器下料中的应用

布袋除尘器是粉尘物料制备系统中的重要设备之一,其作用是截留捕获干燥后的物料颗粒并将其均匀输送到高温焙烧反应区,因此其运行效果直接影响物料生产的质量和产能。本文提出了一种对布袋除尘器的箱体增加助流气碟的改造方法,在投入较小的前提下实现了布袋除尘器下料方式的优化,同时避免了目前常用的机械式振打器对湿涩物料振打作用差以及造成料斗裂纹的情况,改造后的布袋除尘器积料和架桥周期大幅增加,产品质量和装置产能都实现了提高。

太阳能吸收式制冷系统及其蓄能技术研究

在分析国内外现有太阳能吸收式制冷系统的基础上,从太阳能集热器、蓄能形式、辅助热源、吸收式冷水机组以及太阳能集热器与吸收式冷水机组的匹配等方面详细阐述太阳能吸收式制冷系统及其蓄能技术的发展现状,并对太阳能制冷空调系统的控制策略、优化分析及理论研究进行总结,最后指出太阳能吸收式制冷系统及其蓄能技术的发展方向。

矿用湿式过滤除尘器过滤单元过滤技术优化研究

为提升矿用湿式过滤除尘器呼吸性粉尘除尘效率,以除尘器过滤单元过滤参数为实验对象,搭建过滤单元实验平台,研究除尘器过滤单元过滤形式、过滤网层数/除雾垫厚度、孔径、过滤风速等对呼尘除尘效果和阻力的影响规律。研究结果表明:相同条件下,10层20目金属过滤网过滤板过滤性能最佳,阻力1 370 Pa,呼尘除尘效率90.7%;过滤风速取7.8 m/s,除尘器呼吸性粉尘除尘效率最高;采用冲击式惯性分离器与滤网融合设计的过滤板能有效避免出现堵死导致除尘器风机损坏。研究结果可为优化矿用湿式过滤除尘器结构、提升呼尘除尘效率提供依据。

增设FEP薄膜对圆孔型太阳能空气集热器性能的影响研究

针对太阳能空气集热器热量损耗比较严重、热性能较差的缺点,提出一种在圆孔型太阳能空气集热器玻璃盖板处增设FEP薄膜的方法来减少集热器的热损失。利用Fluent软件建立数学模型,研究了运行参数和物性参数对太阳能空气集热器热性能的影响,并进行了敏感性分析。结果表明:当进口流量低于60 m^(3)/h时,增设FEP薄膜后,集热器对外传热损失减小,出口温度提高。随着室外环境温度和太阳辐照强度增大,增设FEP薄膜后,集热器出口温度越来越高。降低FEP薄膜发射率,对出口温度和集热效率的提高有很大的积极作用,敏感性分析结果表明,膜的发射率对集热效率的影响程度颇大,为进一步改善膜的性能提供了数据支持。

太阳能热泵联合系统的枸杞干燥特性与能耗分析

为降低碳排放,利用太阳能集热器与空气源热泵联合干燥代替传统的燃煤热风炉干燥。通过对比太阳能热泵联合干燥和热泵单独干燥试验,研究太阳能热泵系统除湿特性。同时,进行太阳能空气集热器辅助空气源热泵的枸杞干燥试验,验证其可行性。在相同干燥温度设定下,太阳能热泵联合干燥相比热泵单独干燥节电了28.8%,高干燥负荷试验组较中等干燥负荷试验组相比节电15%。与传统热风炉烘干房干燥相比,每吨枸杞干燥节约成本448元,同时节约标准煤121.14 kg,可减少CO_(2)排放量317.39 kg。

寒冷地区户用大平板太阳能集热器-空气源热泵系统性能研究

针对太阳能难以单独稳定供暖和空气源热泵供暖成本高的问题,提出空气源热泵辅助太阳能稳定供暖构想,在甘肃省兰州市七里河区魏岭乡绿化村研发搭建大平板太阳能集热器-空气源热泵系统,对比研究晴天、多云和阴天3种典型工况下大平板太阳能集热器的集热效率、太阳能热泵和空气源热泵COP、太阳能保证率、系统总供热量和系统能效比等性能参数。结果表明:晴天、多云和阴天系统集热效率分别为44.9%、38.7%和20.6%,3种工况下太阳能热泵COP均为4.0,空气源热泵COP分别为3.5、3.3和3.1,太阳能保证率分别为38.1%、32.3%和12.9%,系统全天供热量分别为142.52、135.22和120.96 kWh,系统能效比分别为3.5、3.4和2.7。研究结果证明大平板太阳能集热器-空气源热泵系统用于寒冷地区单体建筑供暖的可行性,可为寒冷地区农村单体建筑的供暖提供一种新途径。

湿式除尘器中气水喷雾降尘效果试验研究

为提高煤矿井下湿式除尘器降尘效率,改善作业人员工作环境,提出了在湿式除尘器中安装内混式空气雾化喷嘴的降尘方法。首先,基于激光多普勒喷雾雾化特性测试平台,对比3种空气帽结构空气雾化喷嘴的雾化角和雾滴索特尔平均直径D_([3,2]),优选出了雾化效果最佳的喷嘴。其次,基于湿式除尘器与气水喷雾降尘试验平台,选定喷嘴与风机距离、喷嘴供气压力、喷嘴供水压力和风机供气压力进行单因素试验,得到单一最佳水平。最后,基于正交试验理论,设计4因素3水平正交试验,开展了不同工况下的降尘试验。结果表明:在同一工况下,孔径为2.0 mm的压力扇形喷嘴雾化角最大且雾滴粒径最小,D_([3,2])为33.20~50.51μm,更有利于微细粉尘的捕集与沉降;4因素降尘效率显著性水平排序对于全尘和呼尘均为:喷嘴与风机距离>喷嘴供水压力>风机供气压力>喷嘴供气压力;降尘系统最优参数组合为:喷嘴与风机距离2.25 m、喷嘴供气压力0.4 MPa、喷嘴供水压力0.4 MPa和风机供气压力0.2MPa,全尘与呼尘的降尘效率可分别达到90.06%和75.91%。研究成果可为矿井湿式除尘系统的优化及应用提供理论参考。

Modelling, Transient Simulation and Economic Analysis of Solar Thermal Based Air Conditioning System in Gujarat

Commercial building sector accounts for 8% of the total electricity consumption in India. Cooling activities (HVAC) in commercial buildings consume 55% of the total energy utilized. Consequently, CO2 emissions from conventional buildings in India were estimated to be 98 metric tonnes of CO2 per million ft2 in 2014. Solar thermal air conditioning can be the solution to these demands and can contribute to about 15% to 20% of India’s total oil consumption thereby reducing the dependence on fossil fuels. Hence, the main objective of the work is to model and simulate a solar absorption cooling system for GERMI office building located in Gandhinagar, Gujarat, India, using the transient simulation software ‘TRNSYS’. Cooling load estimation and comfort conditions required for the building were determined based on ASHRAE standards. Evacuated tube collectors were selected because of its market availability, ease of manufacturing and proven technology. Single effect absorption chiller was used because of its commercial availability. The effects of storage tank volume, collector area and collector slope were also investigated for parametric optimization. The results of the simulation and parametric analysis are analyzed and presented in the paper.

两种聚光器联合驱动的鼓泡加湿除湿型太阳能海水淡化系统实验研究

设计一个由太阳能空气集热器和曲面菲涅尔透镜联合驱动的鼓泡加湿除湿型太阳能海水淡化系统,介绍该系统的结构和运行原理,对多曲面聚光器的聚光特性进行光学仿真分析,对装置各部件的能量进行平衡计算,测试系统在实际天气条件下的产水性能,给出太阳辐照度、装置运行温度和产水效率随时间的变化关系。当太阳辐照度平均为795 W/m2时,该装置集热管出口温度最高为64.8℃,产水量约为9.48 kg/d,整体系统热效率为43.5%。

基于平板热管的太阳能-空气能双源集热蒸发器性能实验研究

设计一种基于平板热管的太阳能-空气能双源集热蒸发器及由其组成的新型直膨式热泵系统,并对其进行实验研究与分析。实验测试平板热管在制冷剂低温取热条件下的均温性与导热性能,热泵运行工况下集热蒸发器表面温度分布、光电光热性能,以及在不同天气条件不同运行模式下热泵系统性能。结果表明,平板热管在低温取热条件下当量导热系数可达6.8×10^(5)W/(m·℃),集热蒸发器运行时纵向最大温差为3.9℃;在夏季晴朗天气条件下运行太阳能模式制热水时热泵平均COP为3.62;在低辐照阴天下运行太阳能-空气能双源模式与太阳能模式相比,单位面积集热功率提高18.8%,系统平均COP提高5.7%;在无辐照的夜晚,运行空气源模式系统COP为2.54。

利用条缝射流强化无盖板型太阳能集热器性能

为提升无盖板型太阳能空气集热器热性能,设计一种条缝射流型太阳能空气集热器,并利用数值模拟和实验验证对其热性能进行分析。集热器内部流动及换热特性的模拟结果表明,利用圆孔和挡片形成的条缝射流能对集热板形成有效覆盖,进而提高进气与集热板的对流换热。射流条缝存在最优结构参数,当圆孔直径为25 mm时,条缝宽度在3 mm处接近最优;集热效率则随挡片直径的增大而增大,是由于射流贴附效应在变强。实验结果表明,条缝射流型集热器的全天热效率稳定且高效。当处理气量为39 m^(3)/h时,该集热器全天热效率稳定在约48%,优于传统的无盖板渗透型太阳能集热器。