焙烧温度对Pt/Pd负载型催化剂结构及性能的影响

为了探讨焙烧温度对催化剂性能的影响,通过对不同焙烧温度的Pt/Pd负载型催化剂进行XRD涂层结构分析及催化剂活性评价检测.XRD分析结果表明,随着焙烧温度的升高,催化涂层中铈锆固溶体的特征峰趋于完整,经950℃焙烧后,催化剂涂层中γ-Al2 O3相的衍射峰仍十分明显,说明镧、铈、锫等添加剂对γ型氧化铝起到了很好的结构稳...     

Dynamic test on waste heat recovery system with organic Rankine cycle

Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle（ORC） system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rankine cycle was constructed and the dynamic behavior was presented. In the dynamic test, the pump was stopped and then started. In addition, there was a step change of the flue gas volume flow rate and the converter frequency of multistage pump, respectively. The results indicate that the working fluid flow rate has the shortest response time, followed by the expander inlet pressure and the expander inlet temperature.The operation frequency of pump is a key parameter for the ORC system. Due to a step change of pump frequency（39.49-35.24 Hz）,the expander efficiency and thermal efficiency drop by 16% and 21% within 2 min, respectively. Besides, the saturated mixture can lead to an increase of the expander rotation speed.     

An optical sensor for hydrogen sulfide detection in open path using WMS-2f/1f technique

An optical hydrogen sulfide (H2S) sensor based on wavelength modulation spectroscopy with the second harmonic (2f) corrected by the first harmonic (1f) signal (WMS-2f/1f) is developed using a distributed feedback (DFB) laser emitting at 1.578 µm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H2S line at 6 336.62 cm-1 in the fundamental absorption band of H2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s (in concentration range of 15.2—45.6 mg/m3), respectively. The maximum relative deviation for continuous detection (60 min) of 30.4 mg/m3 H2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m3 with optimal integration time of 32 s. The optical H2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.     

椭圆形套管-管翅式蒸发式冷凝器传热性能实验研究

本文搭建了蒸发式冷凝器性能测试系统,采用控制变量法实验研究了迎面风速、喷淋密度、湿球温度、循环水温度、冷却水流量各参数变化对椭圆形套管-管翅式蒸发式冷凝器传热性能的影响。实验结果表明：该冷凝器实验系统的最佳迎面风速和喷淋密度分别为3.1 m/s和0.005 6 kg/(m·s),冷凝器管外空气压降随迎面风速的增大而迅速增加;随着空气湿球温度升高,冷凝器外传热过程的热流密度(即外热流密度)降低67.5%,而内传热过程的热流密度(即内热流密度)增大47.5%,依靠内传热过程的增强,冷凝器性能良好;随着循环水温度升高,冷凝器的内热流密度降低率高达64.6%,传热性能急剧下降;随着冷却水流量增大,冷凝器的内热流密度大幅提高2.92倍,总热流密度增大21.1%,传热性能显著增强;该冷凝器在低湿球温度、低循环水温度、大冷却水流量的工况下传热性能较优。     

“球囊夹紧法”取出锁骨下动脉支架推送杆断裂残端一例

针对水平光滑管和微肋管,基于FLUENT平台对制冷剂管内沸腾传热特性进行了数值模拟,研究质量流量、热流密度及干度等因素对制冷剂R245fa沸腾换热系数的影响。模拟结果表明:沸腾换热系数随着制冷剂质量流速与热流密度的增加而提高;随着干度的增加,换热系数先增加再降低,并在x=0.7时达到极大值;相比光滑管,微肋管内制冷剂的沸腾传热系数能提高10%~25%。     

550kV罐式断路器在寒冷地区的保温方法

随着SF6产品越来越多在低温地区使用,SF6断路器在低温地区使用时存在气体液化现象,不可忽视。作为制造厂家,为了保证产品的安全运行,必须采取应对措施来解决。在断路器外壳上加装保温装置,当环境温度低于SF6气体液化温度时,加热装置投入使用,对断路器内SF6气体进行加热,保证断路器的各项性能。