采用折叠扁管与挤压扁管的微通道换热器长效特性

对采用折叠扁管与传统挤压扁管的微通道换热器长效特性进行了对比研究。分别进行了标准盐雾腐蚀实验,对比腐蚀前后两个换热器样品的换热量、空气侧压降和总热阻变化情况,结果表明,折叠扁管的样品在腐蚀后的各项性能均优于挤压管的样品。传统挤压扁管样件的翅片与扁管连接处率先被腐蚀破坏,14 d腐蚀后就可观察明显的翅片脱落现象,且在28 d腐蚀后挤压扁管上出现泄漏;折叠扁管样件则是翅片率先被腐蚀,而翅片与扁管的连接处没有明显损坏,在49 d腐蚀后折叠扁管没有出现泄漏现象。这是由于折叠扁管能方便地配备保护层,实现牺牲翅片保护扁管的方法,在腐蚀过程中能有效地保护更为重要的扁管。折叠扁管的长效特性优于传统挤压扁管。     

阻燃聚氨酯硬泡的研究现状及发展趋势

聚氨酯硬泡被公认为是目前世界上最好的保温材料,但未经阻燃处理的聚氨酯硬泡常常引发火灾。介绍了聚氨酯硬泡的成分、燃烧机理及阻燃原理,阐述了阻燃技术的研究现状及最新进展,展望了阻燃硬泡的发展趋势。     

高温型α-淀粉酶对膨化米粉冲调性的影响

研究了在双螺杆挤压系统下应用高温型α-淀粉酶制备和改善膨化米粉冲调性能的工艺和方法,并比较了加酶挤压前后DE值、结块率、黏度、色泽的变化。结果显示,在挤压过程中添加高温型α-淀粉酶,可以提高原料淀粉的降解程度,产品在冲调复水时,膨化米粉的结块率降低。通过响应面优化实验,得到了添加高温型α-淀粉酶制备膨化米粉最佳挤压工艺条件:挤压温度136.2℃,螺杆转速100 r/min,加酶量36.35 u/g。在此条件下所得膨化米粉与未加高温淀粉酶的米粉比较,产品DE值由1.06上升到13.58,结块率由32.0%下降到11.25%,冲调后的黏度由113.9 mPa.s下降到88.6 mPa.s,产品色度△E值与对照样基本一致,冲调性得以改善。     

阻燃聚氨酯软质泡沫塑料中氯含量的测定

叙述了阻燃聚氨酯软质泡沫塑料中氯含量的测定方法:在助燃剂存在下,氧瓶燃烧使聚氨酯软质泡沫塑料中的有机氯转化为HCl,用稀NaOH吸收,使用硫氰酸汞分光光度法测定聚氨酯软质泡沫塑料中阻燃剂的氯含量。该方法简单快捷、精确度高,回收率为99.64%～102.41%。     

纳米颗粒提高泡沫稳定性机理研究

泡沫流体作为一种非牛顿流体,广泛应用在石油工业的钻井、油气井增产、修井、提高采收率等各个方面。纳米颗粒作为一种新兴的稳泡材料,可以明显提高泡沫的稳定性。本文分别从纳米颗粒与界面的相互作用、单一疏水颗粒稳泡影响因素、以及亲水颗粒与表面活性剂协同稳泡三个方面来阐述纳米颗粒在稳泡方面的机理,最后探讨了纳米颗粒在稳泡方面的前景以及研究方向。     

添加造孔剂法制备开孔泡沫铝及其性能研究

以球形尿素颗粒为造孔剂,采用传统的粉末冶金工艺制备开孔泡沫铝并研究了其性能.结果表明,添加造孔剂法制备的泡沫铝可以任意控制孔隙率及孔径的大小,且孔结构良好,保持了造孔剂的形状;高的烧结温度使泡沫铝的压缩强度提高,但过高的温度将导致孔壁熔化.本试验制成的泡沫铝其压缩曲线和泡沫金属典型压缩曲线相似,且抗压强度和经典理论计算结果一致.     

Assessment of space division strategies for generation of adequate computational models for solid foams

The present study is concerned with a competitive assessment of different strategies for the division of space in the generation of computational models for the microstructure of solid foams for a numerical analysis of their properties. The study includes the standard (Γ‐) Voronoi procedure, the δ-Voronoi procedure, a Voronoi procedure in Laguerre geometry as well as a simple foam evolution strategy. In addition to the basic versions of the individual strategies, smoothing and optimization approaches are used for a further improvement of the generated computational models. The quality of the models is assessed in terms of two quantitative criteria where the first criterion is the Kelvin parameter whereas the second criterion is based on the error in the statistical cell size distribution compared to experimental observations reported in the literature. All strategies are applied to the simplified case of two-dimensional model foams. Nevertheless, the results can be generalized to the three-dimensional case in a straight forward manner.     

Mechanical Properties of Silicon Oxycarbide Ceramic Foams

The mechanical properties of ceramic foams obtained through a novel process that uses the direct foaming and pyrolysis of preceramic polymer/polyurethane solutions were investigated. The elastic modulus, flexural strength, and compressive strengths were obtained for foams in the as-pyrolyzed condition; values up to 7.1 GPa, 13 MPa, and 11 MPa, respectively, were obtained. The strength of the foam was virtually unchanged at temperatures up to 1200°C in air; however, long-term exposure at 1200°C led to a moderate degradation in strength, which was attributed to the evolution of intrastrut porosity during the oxidation of residual free carbon, as well as devitrification of the foams struts.     

挤塑聚苯板外墙外保温施工工艺

结合工作实践，针对目前多层、小高层建筑多采用瓷砖镶贴饰面层的特点，介绍了改进后的挤塑板外墙外保温层施工工艺原理，具体阐述了工艺流程，安全注意事项及质量要求等内容，并结合具体实例进行了效益分析，指出该技术值得推广。     

Hydroxyalkoxy derivatives of oxamic acid: polyol substrates for polyurethane foams

BACKGROUND: The work reported aimed at obtaining hydroxyalkoxy derivatives containing oxalamidoester groups starting from oxamic acid (OA) substrate. These derivatives were then used for the synthesis of polyurethane foams. RESULTS: The hydroxyalkoxy derivatives were obtained by reaction of OA with 6 to 15 molar excess of ethylene carbonate (1,3‐dioxolane‐2‐one) or propylene carbonate (4‐methyl‐1,3‐dioxolane‐2‐one). The products obtained have good thermal stability and possess suitable physical properties for use as substrates for foamed polyurethanes. CONCLUSION: The rigid polyurethane foams obtained from the hydroxyalkoxy derivatives of OA possess enhanced thermal stability and good mechanical properties in comparison with traditional polyurethane foams. Copyright © 2009 Society of Chemical Industry