化工用换热器的应用与研究

在国内社会经济飞速发展的阶段,化工产业也有了不小的突破,社会对化工换热器方面提出的需求量也不断提升.因此,相关领域对此方面的应用研究愈加关注与重视.     

基于GA-BP神经网络的土壤-空气换热器换热量预测分析

文章对位于太原市一个日光温室内的土壤-空气换热器进行夏季工况试验,获得了不同运行工况下换热管内空气的温度和湿度的分布数据.试验结果表明:土壤-空气换热器具有一定的除湿效果;当换热管长度为17.2 m,换热管内空气流速为2 m/s时,土壤-空气换热器潜热换热量占全热换热量的31.37％,且潜热换热量在全热换热量中的占比随...     

组合式相变材料储热换热器的特性实验研究

本文介绍了一套搭建的储热换热器性能测试装置和数据采集系统,主要研究由HR-35、月桂酸和HR-50这3种相变材料组合而成的储热换热器的特性。测试结果表明,与单一相变材料的储热单元换热器相比,组合式相变材料的储热换热器的储热速率有一定的提高。     

浦东国际机场空调系统诊断与改善

针对浦东机场前年夏季部分空调区域出现较热的现象,对空调系统现状进行了调查,分析造成这一现象的原因。对发现的水力失调等问题进行了相应的整改。整改后的流量分配趋于合理,室内温度基本满足了要求。     

基于换热单元非均匀流动的换热器整体等效计算方法研究

为了解决因翅片与换热器整体尺寸跨度较大、新型换热器设计过程中缺乏试验数据而难以进行换热器整体性能模拟预测的问题,提出了一种基于换热单元非均匀流动的油冷器等效计算方法。该方法利用油冷器单元模型进行数值模拟,从中提取出换热单元的流动与换热特性参数,将该参数代入简化为多孔介质的油冷器整体模型中进行等效计算。结果表明,该方法在大范围内获得与试验数值相一致的结果,换热功率平均误差在试验工况范围内为3.5%。此外,等效计算换热的准确性受到换热参数拟合精度的影响,该影响可通过增加单元换热模拟工况点得到改善。     

三角小翼V形阵列换热特性实验研究

在Re=4800~10200范围内,实验研究了矩形通道内圆管侧后方两排三角小翼V形阵列布置的强化换热特性,比较了三角小翼V形阵列布置和单排大三角小翼布置的换热差异,研究了攻角、翼高和排列间距对换热的影响。结果表明:三角小翼V形阵列的Nu数比单排大三角小翼平均增加4.9%,且随着阵列中翼片前后排间距的增加,换热呈增强趋势。对于三角小翼V形阵列和单排大三角小翼,随着小翼攻角的增加,通道换热先增加后减小,最佳攻角均为α=60°,随着小翼翼高的增加,通道换热单调增加。实验数据拟合得到了V形三角小翼阵列和单排大三角小翼的Nu数无量纲关联式,为管翅式换热器中三角小翼的布置提供了依据和参考。     

Optimization to the tube-fin contact status of the tube expansion process

The tube-fin contact status is an important factor influencing both thermal resistance and service life of the tube-fin heat exchanger. Tube expansion process brings forming defects of gaps at the tube-fin interfaces. And elimination of this forming defect is proved to be difficult. This paper presents a novel method in improving the tube-fin contact status of heat exchanger. From simulation results, distribution of the contact pressure along the tube-fin interface can be obtained. Then, an optimization process integrated with FE simulation is established for the sectional profile of the fin collar. The fin collar is represented with spline curves. Results show that after the optimization, the gap at the tube-fin interfaces is basically eliminated and the tube-fin contact status is significantly improved. Furthermore, flanging process for the optimized sectional shape of the fin collar is discussed.     

Iodide substitution in lithium borohydride, LiBH4-LiI

The new concept, anion substitution, is explored for possible improvement of hydrogen storage properties in the system LiBH₄-LiI. The structural chemistry and the substitution mechanism are analyzed using Rietveld refinement of in situ synchrotron radiation powder X-ray diffraction (SR-PXD) data, attenuated total reflectance infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC) and Sieverts measurements. Anion substitution is observed as formation of two solid solutions of Li(BH₄)_1−xI_x, which merge into one upon heating. The solid solutions have hexagonal structures (space group P6₃mc) similar to the structures of h-LiBH₄ and β-LiI. The solid solutions have iodide contents in the range ∼0-62 mol% and are stable from below room temperature to the melting point at 330 °C. Thus the stability of the solid solutions is higher as compared to that of the orthorhombic and hexagonal polymorphs of LiBH₄ and α- and β-LiI. Furthermore, the rehydrogenation properties of the iodide substituted solid solution Li(BH₄)_1−xI_x, measured by the Sieverts method, are improved as compared to those of LiBH₄. After four cycles of hydrogen release and uptake the Li(BH₄)_1−xI_x solid solution maintains 68% of the calculated hydrogen storage capacity in contrast to LiBH₄, which maintains only 25% of the storage capacity after two cycles under identical conditions.     

Membrane heat exchanger in HVAC energy recovery systems, systems energy analysis

The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system.     

国产600 MW机组高加管座焊接缺陷分析

介绍了某厂新建2×600MW机组6台高压加热器管座角焊缝发现的严重裂纹,从多方面分析了裂纹的成因,提出了工艺改进办法和检验方法,为今后新机组高压加热器的检验工作积累了经验。