风冷冰箱蒸发器除霜特性及箱温回升的实验研究

为了探究风冷冰箱除霜过程动态特性及其对箱温回升的影响,对某单循环风冷冰箱稳定运行时的除霜过程进行了实验研究,结果表明:在蒸发器温度升高到0℃的预热阶段,霜层堵塞翅片间隙,箱温基本无回升;在温度维持在0℃左右的融霜阶段,除霜电加热被布置在蒸发器下方以及霜层"上疏下密"分布使底部霜层最早开始融化,融化结束时刻比顶部提前8min,融霜时翅片间空气流通面积逐渐增大,进入箱体内部的热空气量增多,箱温在9.34min内平缓上升5.7℃;在温度高于0℃的排水阶段,因蒸发器右上方冷藏送风风道存在凸起,热空气会积聚在此处,导致阶段结束时该部位比左上温度高17.1℃,此时翅片间空气流通面积达到最大,箱温在6.5min内快速上升6.6℃。     

疏水性铝翅片表面的结霜/融霜特性

为了揭示疏水性铝翅片表面特性对结霜/融霜过程的影响规律,构建翅片结霜/融霜实验平台,制备接触角为90°~160°的4组疏水性铝翅片,并对其表面的结霜/融霜特性进行研究。研究结果表明:翅片表面的接触角越大,凝结液滴越晚出现,抗凝结作用越明显。4组翅片表面霜晶形态相似,但霜层高度区别明显,接触角越大,霜层越薄,抑霜效果越好。翅片表面的接触角和接触角滞后对凝结液滴及融霜滞留液滴的形状、尺寸和分布密度具有重要影响。此外,疏水性强的翅片,表面融霜过程快且滞留水少,接触角为160°的表面其滞留水比接触角为98°的表面减少79.82%。因此,采用疏水性强的翅片,有利于减少蒸发滞留水耗热量和时间,从而提高热泵除霜效率。     

翅片管式蒸发器超声波除霜理论与技术研究

针对传统逆除霜技术能耗高、热舒适度差的问题,研究应用于翅片管式蒸发器的超声波除霜新技术。结合MATLAB数值求解方法与有限元压电结构耦合仿真方法,分析蒸发器结构中的频散曲线,确定蒸发器结构中的超声导波类型、模态及导波传播特性,并将超声频散曲线分析结果与有限元仿真结果进行对比。研究结果表明,在激励频率小于250kHz时,蒸发器翅片上存在Lamb波的A0和S0模态以及SH波的SH0模态,Lamb波在翅片与霜层界面处激发破碎应力,SH波激发剪切应力;翅片上振动以Lamb波的S0模态为主,铜管上可以清楚看到对称的纵向模态,有限元仿真结果与频散曲线分析结果完全吻合;超声除霜试验与能耗分析结果表明,超声除霜能耗不到传统逆除霜能耗的1/22,除霜效率至少提高了7倍,是一种高效、低能耗的翅管式换热器除霜新技术。     

翅片表面特性对结霜过程影响的实验研究

为研究翅片表面特性对空气源热泵结霜的影响,构建了翅片结霜实验平台,对接触角不同的4种翅片表面(亲水性铝翅片、普通铝翅片、疏水性铝翅片、超疏水性铝翅片)的结霜过程细微观特征进行了可视化研究,获得了翅片表面特性对结霜过程细微观物理特征及霜层热工特性的影响规律.结果表明,在霜晶生长初期,接触角越大,凝结形成的液滴粒径越小,分布越稀疏,液滴开始冻结的时间越滞后.霜层生长过程中,接触角大的表面霜晶相对矮小且疏松,枝晶分布不均匀,而接触角小的表面霜晶纤长且致密,枝晶多且分布均匀.随着接触角的增大,霜层的高度和导热系数减小,表面温度降低.超疏水性表面霜高比亲水性表面减少了45%,接触角越大的表面其抑霜效果越明显.     

环境湿度对超疏水翅片结霜特性的影响

为揭示超疏水翅片在不同环境湿度下的结霜特性及抑霜性能，制备了接触角为161.5°的超疏水翅片，并通过搭建翅片表面结霜实验平台，获取了环境相对湿度分别为65%、75%、85%和95%条件下，超疏水翅片的结霜特性及抑霜性能.实验结果表明：结霜初始阶段凝结液滴的生长行为受相对湿度影响，凝结液滴的冻结时间随着相对湿度的增加而减少，但湿度对液滴冻结前翅片表面覆盖率的影响并不明显；结霜时间为45 min时，几种环境相对湿度下的霜层高度分别为0.26, 0.42, 0.65, 0.93 mm,虽然超疏水翅片的霜层高度随着环境相对湿度的增加而增加，但与普通翅片相比，其在不同湿度条件下均能有效抑制结霜.     

光电耦合在线测霜技术的可行性试验研究

将光电子领域的光电耦合原理引入霜层厚度的在线监测技术中,并对其可行性进行了试验研究．试验结果显示,光电耦合器在线测霜技术的输出电压信号具有明显的“二值”、“线性”两大特性,可实现对霜层厚度的直接感应,满足空调、制冷设备除霜控制判据的要求．此技术的开发将为霜层厚度的测量提供新的方法,可解决空调、制冷设备存在的“误除霜”问题,具有较高的实用价值和开发潜力．     

风冷热泵除霜方法分析

本文分析风冷热泵霜层形成的机理和常用的除霜方法,供大家参考。     

显热除霜方式的能量分析与试验研究

针对现有逆向除霜方式的不足,提出了一种新型的除霜方式———显热除霜.分析了显热除霜的机理和作用过程,从霜层角度分析了蒸发器除霜过程中需要的热量组成.对显热除霜方式与逆向除霜方式除霜所需热量进行了理论比较,结果表明显热除霜方式所需的热量较少.从制冷系统角度对2种除霜方式除霜过程的能量进行了分析和试验验证.试验表明:逆向除霜方式因四通阀换向导致制冷系统压力、温度分布被破坏并重新建立而存在大量能量损失,显热除霜方式不存在这问题;在同样条件下显热除霜与逆向除霜相比,除霜时间缩短了26.7%,小时供热率提高2%,系统供热水温度波动在5℃以内.     

电冰箱的除霜方法及装置

文章介绍了电冰箱结霜的原因 ,霜层的影响 ,以及除霜的方式方法及设备 .     

风冷热泵冷热水机组热气旁通除霜与逆循环除霜性能对比

在制冷量为55kW的风冷热泵冷热水机组上，比较了热气旁通除霜和逆循环除霜的性能．结果表明：逆循环除霜的能量来自压缩机的输入功率以及从房间和循环水中吸收的热量，除霜时间为94s，但房间温度存在剧烈波动，舒适性较差；热气旁通除霜的能量只来自压缩机的输入功率，而且制冷荆流过分液器和分液毛细管的能量损失较大，除霜时间比逆循环除霜方式多178s，但不会从循环水和房间吸热，舒适性较好；在热气旁通除霜方式的融霜阶段，压缩机的吸气过热度一直在0℃左右，导致排气温度和过热度不断降低，可能会危及压缩机的安全．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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