Design and Development of a Parabolic Trough Solar Air Heater for a Greenhouse Dryer

Design and Development of a Parabolic Trough Solar Air Heater (PTSAH) for a Greenhouse Dryer (GD) was done to improve the dryer’s performance. The materials used for the fabrication of the PTSAH included galvanized sheets covered with aluminium foil, an absorber tube made of GI pipe painted matt black to increase heat absorbance at the focal line, mild steel square tubes, shutter plywood, and an axial fan to push air through the absorber tube. Key geometrical parameters used for the design of the PTSAH were a rim angle of 98 degrees, focal length of 0.2608 m, height of 0.3451 m, length of 2 m, and an aperture width of 1.2 m. The PTSAH’s total aperture surface area was 2.4 m2, while its absorber tube surface area was 0.1587 m2. The PTSAH was experimentally tested to establish its thermal performance. It was found that the ambient air recorded an average value of 31.1˚C and that the air heater could increase the air temperature by 45.6˚C above ambient with a thermal efficiency of 5.3%. It can, therefore, be concluded that the PTSAH can significantly improve the performance of a GD by supplying the GD with air at a higher temperature than ambient.

Application of an Artificial Neural Network Method for the Prediction of the Tube-Side Fouling Resistance in a Shell-And-Tube Heat Exchanger

The accumulation of undesirable deposits on the heat exchange surface represents a critical issue in industrial heat exchangers.Taking experimental measurements of the fouling is relatively difficult and,often,this method does not lead to precise results.To overcome these problems,in the present study,a new approach based on an Artificial Neural Network(ANN)is used to predict the fouling resistance as a function of specific measurable variables in the phosphoric acid concentration process.These include:the phosphoric acid inlet and outlet temperatures,the steam temperature,the phosphoric acid density,the phosphoric acid volume flow rate circulating in the loop.Some statistical accuracy indices are employed simultaneously to justify the interrelation between these independent variables and the fouling resistance and to select the best training algorithm allowing the determination of the optimal number of hidden neurons.In particular,the BFGS quasi-Newton back-propagation approach is found to be the most performing of the considered training algorithms.Furthermore,the best topology ANN for the shell and tube heat exchanger is obtained with a network consisting of one hidden layer with 13 neurons using a tangent sigmoid transfer function for the hidden and output layers.This model predicts the experimental values of the fouling resistance with AARD%=0.065,MSE=2.168×10^(−11),RMSE=4.656×10^(−6)and r^(2)=0.994.

Mathematical Modelling of Operating Temperature Variations of Shell-and-Tube Heat Exchanger (10-E-01)

The technique of modeling operating temperature variations of shell-and-tube heat exchanger 10-E-01 of kerosene-crude oil streams of Port Harcourt refinery crude distillation unit is presented in this research. Appropriate first-order model equations were developed applying principles of energy balance. The differential equations developed for the process streams which exchanged heat was evaluated numerically to predict the temperature variations as a function of time. The relevant parameters associated with typical heat exchanger works were calculated using plant data of 10-E-02. The model strives to predict the final kerosene temperature from 488 to 353.6 K. While the crude oil streams temperature rose from 313 to 353.6 K. The developed model enables the operator to predict the final temperature at the kerosene hydro-treating unit and thereby prevent regular emergency shutdowns due to excessive temperature rise.

Electrostatic Self-Assembly of Ti_(3)C_(2)T_(x) MXene/Cellulose Nanofiber Composite Films for Wearable Supercapacitor and Joule Heater

The titanium carbide nanosheets(MXene)hold great potential for fabricating high-performance electronics due to their two-dimensional layered structure,high electrical conductivity,and versatile surface chemistry.However,assembling the small MXene nanosheets into flexible macroscopic films for wearable electronics still remains a challenge.Herein,we report the hierarchical assembling of MXene nanosheets and cellulose nanofibers into high-performance composite films via an electrostatic self-assembly strategy induced by polyethyleneimine.Benefited from the nacre-like microstructure of MXene"bricks"and cellulose nanofibers"mortars"interlocked by polyethyleneimine via hydrogen bonding and electrostatic interaction,composite films possess integrated superior flexibility,high tensile strength,and stable electrical conductivity,which are advantageous for wearable electronic applications.To provide a proof-of-concept design,a symmetric quasi-solid-state supercapacitor with the as-prepared composite film as electrode is fabricated,which exhibits a specific capacitance of 93.9 mF cm^(-2)at a current density of 0.1 mA cm^(-2)and almost constant capacitive behavior under different bending states.In addition,the composite film possesses capacities of electrothermal conversion and complete degradation in a hydrogen peroxide solution.These results demonstrate that the electrostatically self-assembled composite films hold great promise in the development of highly flexible,mechanically robust,and environmentally friendly energy storage and conversion devices.

Optically pumped wavelength-tunable lasing from a GaN beam cavity with an integrated Joule heater pivoted on Si

Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a Ga N-based laser with an integrated PN junction heater on Si is fabricated.The photoluminescence properties of the Ga N beam cavity are controlled by temperature, and the Joule heater provides electrically driven regulation of temperature. These two features of the cavity make it possible to realize convenient tuning of the lasing properties. The multi-functional Ga N beam cavity achieves optically pumped lasing with a single mode near 362.4 nm with a high Q-factor of 1394. The temperature of this device increases by 0–5℃ under the Joule heating effect. Then, electrical control of the lasing mode is demonstrated. The lasing resonant peak shows a continuous redshift of about 0.5 nm and the device also exhibits dynamic switching of its lasing mode. The lasing modulation can be ascribed to temperature-induced reduction of the bandgap. Our work may be of benefit for external optical modulation in future chip-based optoelectronic devices.

Simulation of Natural Convection Flow with Magneto-Hydrodynamics in a Wavy Top Enclosure with a Semi-Circular Heater

Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approach is used to solve two-dimensional governing mass, momentum and energy-equations for natural convection flow in the presence of a magnetic field on a roof top with semi-circular heater. In the enclosure the horizontal lower wall was heated, the vertical two walls were adiabatic, inside the semi-circular heater, the wavy top wall cooled. The parameters Rayleigh number, Hartmann number and Prandtl number are considered. The effects of the Hartmann number and Rayleigh number on the streamlines, isotherms, velocity profiles and average Nusselt number are examined graphically. The local Nusselt number and the average Nusselt number of the heated portion of the enclosure with the semi-circular heater are presented in this paper. Finally, for the validation of the existing work, the current results are compared with published results and the auspicious agreement is achieved.

CO_(2)电弧等离子加热器电热特性研究

对管状阴极轴线式CO_(2)电弧等离子加热器的电热特性进行了实验研究,得到了电流、气体流量、励磁电流和前电极长径比对电弧加热器的伏安特性和热效率的影响规律。采用相似理论模型,对实验数据进行回归分析,得到了加热器伏安特性和热损失系数的近似表达式。研究结果发现,CO_(2)气体流量和电弧电流对加热器的伏安特性和热效率都具有显著的影响,前电极的长径比和励磁电流则只对热效率具有影响。电弧加热器伏安特性和热损失系数的回归公式计算值与实验数据一致性较好,伏安特性回归误差<10.0%,热损失系数回归误差<18.2%。

家用空气源热泵热水器微通道冷凝器仿真研究

为提升家用空气源热泵热水器水箱外微通道冷凝器的性能,建立了家用空气源热泵热水器水箱外微通道冷凝器的准稳态模型,实验验证结果显示模型误差能控制在±9%以内。依据模型对微通道冷凝器的换热量、换热系数、压降等性能进行仿真研究。结果发现,微通道冷凝器为四流程时能够减小压降并保证换热量满足需要;关键参数微通道截面的最佳尺寸在1.6~2.6 mm^(2)系统性能最优,同时扁管内微通道数应控制在16~24根。研究结果为家用空气源热泵热水器微通道冷凝器的设计提供借鉴。

风机转速对CO_(2)空气源热泵热水器性能影响的试验研究

为了定量探究CO_(2)空气源热泵热水器系统性能随风机转速的变化规律,通过试验研究了不同工况下,改变风机转速对排气压力、过热度、CO_(2)质量流量、系统制热量、系统总功耗以及制热性能系数COP的影响;利用响应曲面法对试验进行了优化分析,同时利用试验数据拟合了COP回归模型,并进行可信度分析;通过回归模型预测了系统的最优运行工况并进行试验验证。结果表明:在压缩机频率和电子膨胀阀(EEV)开度一定的情况下,存在着最佳风机转速;在45~85 Hz范围内,随着压缩机频率的提高,COP先增大后减小,增幅最高可达8.97%,各频率下COP最大时对应的最佳风机转速不断减小;随着EEV开度在35%~55%范围内不断增大,COP先增大后减小,增幅可达到6.6%,各EEV开度下COP最大时对应的最佳风机转速不断增大;当压缩机频率为65 Hz、EEV开度为50%时,对应的最佳风机转速为1000 r/min,系统COP达到峰值(4.09)。本文所拟合的COP回归模型最大误差为4.5%;预测系统最优运行工况为:压缩机频率68 Hz、EEV开度52%、风机转速956 r/min,此时系统COP最大,可达到4.29,预测误差为3.7%。本研究可为CO_(2)空气源热泵热水器系统保持高效运行提供理论指导。

12Cr2Mo1VR在电站辅机产品中的应用及制造工艺优化

本文主要介绍采用12Cr2Mo1VR材料短筒身的高压加热器,在制造过程中出现裂纹问题,针对此材料进行研究并采取措施,包括优化工艺、改进设计结构等,从而规避风险,保证产品质量。

输液加温仪结合手术室护理在宫腔镜手术患者中的应用

目的分析输液加温仪结合手术室护理在宫腔镜手术患者中的应用效果。方法选取2021年1月至2022年12月于滨州医学院附属医院接受宫腔镜手术治疗的80例患者作为研究对象,按照单双数分组法分为对照组(40例)与观察组(40例)。对照组予以常规手术室护理,观察组在对照组基础上联合输液加温仪干预。比较两组体温、凝血功能、并发症发生情况及满意度。结果麻醉即刻、麻醉30 min、麻醉60 min及完成手术即刻,观察组体温均高于对照组(P<0.05)。术后,观察组活化部分凝血活酶时间、凝血酶原时间、凝血酶时间均短于对照组(P<0.05)。观察组并发症总发生率低于对照组(P<0.05)。观察组总满意率高于对照组(P<0.05)。结论输液加温仪结合手术室护理在宫腔镜手术患者中的应用效果较好,可有效维持患者体温,改善凝血功能,减少并发症的发生,提高满意度,值得临床推广。

射流式太阳能空气集热器性能的数值模拟研究

为了提高太阳能空气集热器的性能,建立了射流太阳能空气集热器的数学模型,并分析了空气射流对太阳能空气集热器性能的影响。结果表明:在太阳能空气集热器内设置折流板形成射流流动,不仅可以增加集热板近壁面处的流动速度,还能减小垂直于空气流动方向的速度梯度。射流流动优化了流道内的速度分布,从而有效提高了空气与集热板的对流传热系数。与普通太阳能空气集热器相比,射流太阳能空气集热器的集热效率明显更高。当入口速度从0.5 m/s增加到3.0 m/s时,两者集热效率的差距从5.01%增加到15.38%。然而,射流太阳能空气集热器的压力损失较大,因此其有效效率随空气流量的增加呈现先增加后减小的趋势。在入口速度为2.5 m/s时,有效效率达到了极值63.75%,比普通太阳能空气集热器提高了11.21%。综上所述,利用折流板形成射流能显著提高太阳能空气集热器的集热效率与有效效率。

探究燃尽风对墙式对冲锅炉主再热汽温的影响

本文探究了燃尽风对墙式对冲燃烧锅炉主再热汽温的影响。关小燃尽风燃烧器拉杆,可以提高该区域的整体壁温,反之亦然。利用这一规律,可以有效调节主汽温度和再热汽温。

大流量高压燃烧加热器振动加速度测试分析

针对不同采样频率下(10、20、50、100、200 kHz)大流量高压燃烧加热器振动加速度差异较大的问题进行了研究,开展了冷吹试验、敲击试验、点火试验。采用时域分析法中的均方根、偏度、峭度,频域分析法中的功率谱密度,时频域分析法中的小波变换,并结合模态参数识别中的多参考最小二乘复频域法重点分析了10 kHz和200 kHz采样频率下的振动数据。获得了传感器的安装谐振频率、安装底座和待测设备组合体的固有频率以及加热器运行的主要频段,与声振频率计算公式的结果偏差小于5%。研究结果表明,采用10 kHz的采样频率能够有效表征加热器的振动情况,该方法可为大型复杂燃烧设备振动测试采样频率的选择提供参考。

Development and Experimental Study of Air Source Heat Pump Water Heater

The principle and development prospect of air source heat pump water heat were introduced,as well as the designation of condenser (storage water tank),experimental study on installations was also carried out.The results showed that air source heat pump water heater was superior to conventional system.Under the operation of cooling and heating,heat pump comprehensive utilization equipment could improve heating performance,reduce energy consumption,and recycle condensing heat to provide hot water.

Electromagnetic simulation and experimental analysis of microwave heaters for asphalt pavements

In order to study the thermoelectric efficiency of microwave heating and reproduction of asphalt pavements and the uniformity of reproduction temperature distribution, a waveguide excitation cavity is designed and applied to the structural design of a microwave heater. The structural sizes of the incentive cavities are determined based on the waveguide transmission line theory. Using IE3D software, electromagnetic simulations are respectively carried out in four different situations, including the distances between the magnetron probes （antennas） and a short-circuit board, different horn electric lengths and aperture sizes, different dielectric properties of the asphalt mixture, and the distances between the asphalt surface and the mouth cavity. The results show that, when the distance between the magnetron probe and the short-circuit board is 32.5 ram, it is the best installation site; reduction of aerial length is the main factor in improving the heating uniformity. When the aggregate is limestone, the best heating effect can be produced. Maximum radiation efficiency can be realized by adjusting the space between the heater radiation port and the asphalt pavement. The experimental results of asphalt mixture heating in four different situations have a substantial agreement with the simulation results, which confirms that the developed microwave heater can achieve better impedance matching, thus improving the quality and efficiency of heating regeneration.

Structural design and experimental research of microwave radiation heater for asphalt pavements

In order to improve the efficiency of heating and the uniformity of temperature distribution in recycling asphalt mixtures, a pyramidal radiation heater is designed. The principles of designing horn surface size and antenna length are established according to the law of energy conservation and microwave antenna radiation theory. Modeling and simulation are carried out using IE3D software. The simulation results demonstrate that, with a fixed horn surface size, the shortened electric antenna length is the main factor leading to the improved heating uniformity. On the other hand, with a fixed antenna length and diminished surface size, the standing wave ratio decreases with the improved radiation efficiency. Furthermore, the efficiency of radiation drops with increased distance between the horn surface and the asphalt pavement. Microwave heating experiments are carried out using this type of heater. The temperature distribution of asphalt samples is obtained by the grid temperature measurement method, and Matlab simulation is performed. The experimental results are in good agreement with the simulation.

尾气处理装置烟气加热器腐蚀失效原因分析

目的分析某天然气净化厂康索夫(Cansolv)尾气处理装置烟气加热器出现严重腐蚀失效的原因。方法分析了烟气加热器管束的腐蚀环境,开展了材料理化性能、腐蚀产物成分及微观形貌等失效原因分析。结果失效管束的理化性能符合要求,管束泄漏处呈坑状和蜂窝状,部分沟槽尖端有裂纹,且深入基体,呈现应力腐蚀的特征。结论烟气加热器在高温、高酸液含量的环境下发生了电化学腐蚀和应力腐蚀,导致管束出现腐蚀泄漏。

辅助燃煤机组AGC调节的熔盐电加热器动态性能研究

燃煤机组耦合熔盐电加热器系统可大幅提升其调频调峰能力。基于Modelica语言建立了熔盐电加热器的动态模型并完成了试验验证,揭示了熔盐电加热器在熔盐流量扰动和机组自动发电控制(AGC)负荷扰动下的动态特性。基于其动态特性提出了“前馈+PID”调节的温度控制方法,计算分析了熔盐电加热器辅助燃煤机组AGC调节时的电负荷变化特性和热力参数变化特性。研究结果表明,配置10 MW熔盐电加热器可使660 MW燃煤机组AGC变负荷速率提升340%,且所提控制方法能够维持电加热器热力参数的稳定。

基于聚类算法的热试验加热器布局设计与优化

针对目前航天器热试验中热流模拟需求复杂、加热回路设计效率低以及不易量化等问题,文章以某型号中的一组热控模拟件为典型对象,通过有限元方法建立不同特征长度组件和薄膜电加热器组合所对应的温度不均匀度模型;提出基于温度不均匀度距离的聚类方法,并开展基于MATLAB的聚类仿真。与欧几里得距离聚类的对比表明,在同等条件下温度不均匀度距离算法可将温度不均匀度降低30%左右。此外,对比了聚类簇数、加热表面细分数及待加热表面数量等参数对聚类结果和温度不均匀度的影响,可为未来热试验中的加热回路布局设计与优化提供参考。