Studies on solar flat plate collector evaporation systems for tannery effluent(soak liquor)

Heat and mass transfer analysis of an incompressible, laminar boundary layer over solar flat plate collector evapora- tion systems for tannery effluent (soak liquor) is investigated. The governing equations are solved for various liquid to air velocity ratios. Profiles of velocity, temperature and concentration as well as their gradients are presented. The heat transfer and mass transfer coefficients thus obtained are used to evaluate mass of water evaporated for an inclined fibre-reinforced plastic (FRP) solar flat plate collector (FPC) with and without cover. Comparison of these results with the experimental performance shows encouraging trend of good agreement between them.

Thermodynamic Analysis and Optimization of Flat Plate Solar Collector Using TiO_(2)/Water Nanofluid

To research solar energy's efficiency and environmental benefits,the thermal efficiency,exergy,and entropy of solar collectors were calculated.The experiment involved two glass-topped collectors,fluid transfer tubes,and aluminum heat-absorbing plates.Glass wool insulation minimized heat loss.A 0.5% TiO_(2)/Water nanofluid was created using a mechanical and ultrasonic stirrer.Results showed that solar radiation increased thermal efficiency until midday,reaching 48.48% for water and 51.23% for the nanofluid.With increasing mass flow rates from 0.0045 kg/s to 0.02 kg/s,thermal efficiency improved from 16.26% to 47.37% for water and from 20.65% to 48.76% for the nanofluid.Filtered water provided 380 W and 395 W of energy in March and April,while the nanofluid increased it to 395 W and 415 W during these months.Mass flow generated energy,and the Reynolds number raised entropy.The noon exergy efficiency for nanofluids was 50%-55%,compared to 30% for water.At noon,the broken exergy measured 877.53 W for the nanofluid and 880.12 W for water.In Kirkuk,Iraq,the 0.5% TiO_(2)/Water nanofluid outperformed water in solar collectors.

Numerical Investigation and Optimization of a Flat Plate Solar Collector Operating with Cu/CuO/Al_(2)O_(3)–Water Nanofluids

Nanofluids are a potential alternative to significantly improving the performance of heat transfer applications. In this work, a numerical analysis to examine the eff ect of dispersing copper(Cu), copper oxide(CuO), and aluminum(Al2O3) nanoparticles in pure water on the performance of a flat plate solar collector(FPSC) and a numerical model was proposed. The influence of the nanofluid type on the thermal efficiency was critically investigated and discussed. The eff ect of the mass flow rate on the performance was also analyzed and discussed. Based on correlations of the thermophysical properties of nanofluids, a sensitivity analysis was used to analyze the impact of the nanoparticles on the base fluid. The results indicate that the performance of the FPSC with Cu/water nanofluid was better than that of FPSCs using CuO/water or Al2O3/water nanofluids. When the mass flow rate of the nanofluids was 8.0 L/min, the efficiency of the FPSC was much greater than those at the flow rates of 5.0 L/min and 2.0 L/min. Mean enhancements in thermal efficiency of 4.44%, 4.27%, and 4.21% were observed when 2.0 L/min was applied using Cu/water, Cu O/water, and Al2O3/water nanofluids, respectively. Improvements in thermal efficiency of 2.76%, 2.53%, and 2.47% occurred when 8.0 L/min was applied.

Solar Thermal Systems Performances versus Flat Plate Solar Collectors Connected in Series

This paper shows the modeling of a solar collective heating system in order to predict the system performances. Two systems are proposed: 1) the first, Solar Direct Hot Water, which is composed of flat plate collectors and thermal storage tank, 2) the second, a Solar Indirect Hot Water in which we added an external heat exchanger of constant effectiveness to the first system. The mass flow rate by a collector is fixed to 0.04 Kg·s–1 and the total number of collectors is adjusted to 60. For the first system, the maximum average water temperature within the tank in a typical day in summer and annual performances are calculated by varying the number of collectors connected in series. For the second, this paper shows the detailed analysis of water temperature within the storage and annual performances by varying the mass flow rate on the cold side of the heat exchanger and the number of collectors in series on the hot side. It is shown that the stratification within the storage is strongly influenced by mass flow rate and the connections between collectors. It is also demonstrated that the number of collectors that can be connected in series is limited. The optimization of the mass flow rate on cold side of the heat exchanger is seen to be an important factor for the energy saving.

Manufacturing and Thermal Performance Test of (Compound) Solar Collector in Damascus City

Solar water collectors that uses for domestic and industrial applications within temperature up to, are classified under two main types: Flat Plate collector (FP), and Evacuated Tube collector (ET). Thermal performance test results showed that each type have different thermal features. Comparison between (FP & ET) collectors showed that they could take advantages of different thermal features of two types when they work in the same climatic conditions and overlap of these thermal features when they work in different operational conditions. They can take advantage of these features through (compound) solar collector. Compound solar water Collector (CO) composed of a part of flat plate collector shape (FP), and a part of evacuated tube collector shape (ET). Booth have equal reference area, and connected together to be as one Solar collector (CO). Water entered first flat part (FP), then evacuated tube part (ET) then to tank or end-use. In this paper, present design and manufacturing as well the thermal performance test of (compound) solar collector, according to Standard Specification of tests, was EN12975:2001. Mechanical test for (CO) collector conducted successfully according to durability, reliability, and safety requirements. In addition, thermal performance was tested in steady state at the climatic conditions of Damascus city, and concluded the thermal performance of (FP & ET) that constitute (CO) collector. The results showed enhancement of thermal performance.

Performance and Optimization of a Small Hybrid Solar-Thermal Collector

A hybrid solar collector was designed to investigate the effects of combining two different solar collector techniques on the overall collector’s effectiveness. While most solar collectors focus only on one solar collection method, the small hybrid system uses a flat plate collector in conjunction with five evacuated tubes to absorb the most energy possible from both direct and diffuse solar radiation. Data was collected over four months while the system operated at different flow rates and with various levels of available insolation from the sun to evaluate the performance of the solar collector. To understand the relative contribution of the flat plate collector and the evacuated tubes, temperature differences across each part of the system were measured. The results indicate the average first law efficiency of the hybrid system is 43.3%, significantly higher than the performance of the flat plate alone. An exergy analysis was performed for this system to assess the performance of the flat plate system by itself. Results of the second law analysis were comparable to the exergetic efficiencies of other experimental collectors, around 4%. Though the efficiencies were in the expected range, they reveal that further improvements to the system are possible.

拉萨地区平板太阳能集热系统变流量运行策略及效益分析

针对室外环境参数波动变化以及蓄热系统温度波动特性,提出一种太阳能集热系统变流量运行调控策略,建立最优流量优化模型,回归得到不同工况下最优流量值多项式函数,并与定流量运行策略下的系统运行性能进行对比分析。结果表明:与定流量运行方式相比,采用变流量调控策略时,集热系统净收益显著提升。对于拉萨地区100 m^(2)串并联形式平板太阳能集热系统,采用变流量运行策略时,虽然运行泵耗增加,但集热量增益更大,相比单位集热面积流量为0.02 m^(3)/(h·m^(2))时,集热系统净收益增加了468.7 MJ,提高了6.75%。

高寒地区平板热管式太阳能集热系统热性能研究

基于呼和浩特地区高寒气候条件,搭建两组完全一致的平板热管式太阳能集热系统,通过实验对比分析太阳辐射强度、传热工质流量、集热板表面积尘等因素对集热器瞬时集热效率以及系统热性能的影响。结果表明,在同等外界条件下,集热器的集热效率随着工质流量的增加而增大,集热效率与太阳辐射强度变化趋势相近,随积尘密度的增加,集热板表面积尘导致系统的得热量减少,集热性能下降。

平板集热器冬季高流速运行数值模拟研究

针对平板集热器(FPSC)冬季热水收集温度不足等问题提出高流速运行方案,以期提高系统的集热性能以及全年利用率.通过CFD技术数值模拟FPSC系统在不同流速工况下(0.02~0.15 kg/s)各组件温度的变化情况,计算系统的集热效率,结合温度云图对比高流速运行的优势.结果显示,高流速运行能够减少集热损失,具有更佳的集热性能.

多孔介质辅助平板式太阳能集热器热性能强化的数值仿真研究

多孔介质材料具有良好的传热和蓄热性能。设计了新型多孔介质辅助平板式太阳能集热器的二维数值仿真模型,对其内部热性能进行了数值模拟,研究多孔介质块的形状(矩形、梯形、三角形结构)、布置数量和渗透率(达西数Da=10^(-5)~10^(-2))等因素对平板式太阳能集热器热性能强化的影响;然后考虑到插入多孔介质伴随的压降和摩擦阻力损失,提出了评价集热器传热性能与阻力损失的性能评估标准。研究结果表明:在平板式太阳能集热器换热通道插入4种不同形状的多孔介质块,矩形多孔介质块背部附近区域更易产生涡区,集热器内传热性能最强,但通道内流动阻力系数大,从而导致阻力损失大。当多孔介质区域总长度一定时,随着多孔介质块布置数量的增加,涡区数量相应增加,集热器内传热性能加强,且通道内流动阻力损失呈现先增加后降低的规律。多孔介质块渗透率对集热器传热性能的影响显著,当Da=10^(-2)时,集热器传热性能最强。集热器内多孔介质块布置任意数量、高渗透率(Da=10^(-2))条件下,矩形多孔介质块的性能评估标准最佳;在多孔介质块布置数量(N=6)较多、低渗透率(Da=10^(-5)、Da=10^(-4))条件下,三角形多孔介质块的性能评估标准最佳。

分析太阳能平板集热器吸热板芯传热性能的一种简易方法

该文通过对太阳能平板集热器吸热板芯的传热分析 ,导出了一种能计算集热器吸热板温度场分布的简易方法 ,通过与有限元数值计算方法得出结果的对比 ,表明这种方法是可靠的 ,可以用于分析吸热板结构、气象参数等因素对太阳能集热器传热的影响 ,以利于优化集热器结构。

太阳能平板集热器件纵横比与板间距优化

为减小平板集热器件边框对吸热板的遮光损失,该文应用几何光学基本原理建立了平板型集热器件平均有效吸热面积系数的数学模型。利用此模型对年均有效面积系数随集热器件纵横比、板间距、倾角、纬度的变化进行了详细分析。结果表明,年均有效面积系数随板间距的增大而减小,纵横比越大越明显;倾角小于15°或大于75°对集热器件平均有效面积系数都是不利的。为便于应用,文中给出了年均有效面积系数不小于0.90的临界板间距。鉴于对流热损失较小的合理板间距为4～6cm,该文拟推荐合理纵横比≤2/1,北纬20°、30°、40°、50°使用的平板集热器件最大板间距分别约为5.8、5.4、4.7、4.2cm,相应年均有效面积系数均大于0.90。在设计平板集热器件时,可参照该文研究结果,尽量达到对流热损失和遮光损失最小化。

太阳能集热器研究进展

太阳能热水技术在太阳能利用技术中最为成熟、实际应用最多且在经济上能与常规能源竞争。太阳能集热器是太阳能热水器的核心部件,是用于吸收太阳辐射并使之转换为热能传递给热介质的装置。介绍了平板型太阳能集热器和真空管太阳能集热器,并对两者的优缺点进行对比,对其发展趋势进行了分析。

平板太阳能集热器热性能数学建模及模拟

以平板太阳能集热器作为研究对象,通过对平板太阳能集热器热性能进行理论推导,引入效率因子,构建更为准确、便捷的平板集热器的数学模型,进行计算机程序模拟。根据模拟数据得出吸热体板芯几何结构、板芯用材对平板太阳能集热器性能的影响。在不降低集热器效率因子的情况下,使翅片的单位面积质量降低45.8%;在材料消耗相同的情况下,集热器效率因子提高了0.03。

相变蓄能抗冻太阳能平板集热器的设计与研究

提出一种具有抗冻功能的相变蓄能太阳能平板集热器。该集热器在吸热板与保温层之间增加了一层相变潜热大、相变温度为277.15~281.15 K的相变蓄能材料。根据该集热器的传热机理,给出计算相变蓄能层设计厚度的公式。采用ANSYS Fluent软件建立该集热器的三维非稳态模型,模拟不同工况下集热器的出口温度及其内部水的最低温度。研究结果表明:在冬季环境温度最低日,相变蓄能抗冻集热器内水的最低温度高于275.15 K,能很好地起到抗冻作用;相变蓄能抗冻集热器与相同结构的普通集热器相比,冬季阴天和晴天代表日的净得热量分别高1.3 MJ/m^2和0.7 MJ/m^2。

平板型太阳集热器热性能的快速测试方法研究

对快速测量平板太阳集热器热性能的瞬态测试方法进行研究,并将快速测试方法的测试结果与国标GB/T4271-2000(平板型太阳集热器热性能试验方法)规定的测试方法所得的结果进行比较。通过对比可见,基于瞬态测试的快速测试方法可以得到与稳态测试同样的结果,考虑到现有太阳辐射表的精度,只要太阳辐照度大于300W/m2瞬态测试即可有效,且对测试期间太阳辐照度的变化无要求。在除雨雪天的情况下,整个测试可以在1d内完成。

平板太阳集热器热性能模拟分析

为对平板太阳集热器进行热性能分析及优化设计,建立平板太阳集热器的稳态性能数学模型,编制热性能模拟程序,分析环境参数、运行参数及结构参数对集热器瞬时效率的影响特性。模拟结果表明,环境温度升高、工质入口温度降低均可显著提高集热器瞬时效率;降低盖板发射率和吸热板表面发射率有利于提高集热器瞬时效率;减小工质质量流量和增大集热管间距会使集热器瞬时效率减小;环境风速变化对集热器瞬时效率影响较小;夹层间距变化对集热器瞬时效率的影响随工质入口温度的增大而增大;太阳辐射强度对集热器瞬时效率的影响跟集热器与环境间的热交换有关。

微热管阵列平板太阳能集热器中空保温层厚度优化

为分析微热管阵列平板太阳能集热器的热性能，该文建立了集热器的CFD模型，对其进行数值模拟，将模拟结果与试验结果进行对比，验证了模型的可靠性。采用该CFD模型对集热器保温层厚度进行优化，结果表明，当实心保温层导热系数分别为0.02、0.03、0.04、0.05 W/（m·K）时，优化的实心保温层厚度分别为4.5、5.0、5.5、5.5 cm。合理设计的中空保温层（空气层与实心保温层相结合的保温层形式）集热器能够达到与实心保温层集热器相当的保温隔热效果，同时可使集热器保温层成本及质量降低25%～50%。最后，该文给出了保温层总厚度分别为4、5、6 cm时的中空保温层厚度优化结果，为该类集热器保温层的设计提供了理论依据。

碳塑太阳能平板集热器热损系数的研究

传统金属平板集热器因水质影响易发生管路腐蚀,而碳塑平板集热器的塑料管道具有良好的抗腐蚀性能,可以极大延长集热器的使用年限。基于碳塑太阳能平板集热器对其热损系数进行研究,通过对平板集热器的热损系数理论分析,提出在无太阳辐射的室内条件下进行热损系数的测定试验方法,本文提出的碳塑平板集热器测得的热损系数约在7.2 W/(m^2·K),顶部热损系数在4.3 W/(m^2·K)左右,顶部热损系数约占总热损系数的60%,结构设计基本上合理,最后对比分析理论值与试验值,发现误差均在10%以内,说明测定方法可靠。该研究简化集热器热损系数的测定步骤,在设计集热器时可参考该研究降低热损失。

吸热板参数对平板太阳集热器热性能的影响

建立单层盖板平板太阳集热器的一维稳态数学模型,用Visual Basic语言编写程序模拟研究吸热板各参数对平板太阳集热器热性能的影响。在综合考虑集热器效率因子与金属消耗量的基础上,设集热器总热损失系数为变量,对铜铝复合平板太阳集热器的吸热板厚度与管间距进行了优化。研究表明,用导热系数大的铜板代替铝板的优势并不明显;吸热板厚度在0.3 mm以上增加时,平板太阳集热器热性能的提升很小;随着管间距的增加,平板太阳集热器性能下降;吸热板涂层的改进对于平板太阳集热器热性能的提高至关重要;排管内/外径、盖板透过率、涂层吸收率分别为0.0108/0.012 m、0.916、0.89时,在全年运行的平均工况下,保证集热器效率因子为0.9,优化得到吸热板厚度、管间距分别为0.25 mm、11 cm时,金属材料消耗量最小,为2.27 kg/m2。