Design optimization, sensitivity analysis and operational comparison of a duplex helical elliptical tube metal hydride reactor

The outstanding performance of DHER is confirmed and the radial projected area of its tubes is determined as the key design factor.

Study the Effect of Forming Media on the Hydroforming Process for Copper Tube

To observe the effect of media of the internal pressure on the equivalent stress distribution in the tube, an experimental study is done by constructing a testing rig to apply the hydraulic pressure and three dies are manufactured with different bulging configurations (square, cosine, and conical). In the other part, ANSYS APDL is generated to analyze the bulging process with hydraulic and rubber (natural and industrial) media. It was found that when the media is a rubber, the stress is decreased about 9.068% in case of cosine die and 5.4439% in case of conical die and 2.8544% in case of square die. So, it can be concluded that the internal pressure in the rubber media is much better than in hydraulic media. Also, the force needed for forming the shape using rubber is higher than that of hydraulic and the force needed to form using industrial rubber is higher than of natural rubber. The thickness distribution in the tube wall in case of rubber media is better than that for hydraulic media and for the industrial rubber is better than that for natural rubber for the same dies. In case of hydraulic, the lower forming pressure is needed to bulging process compared with the rubber media since height stress in the tube metal is existed, which causes the failure. For the case of rubber, the forming pressure that was needed to bulge process is higher when compared with the hydraulic media but with less stress in tube metal and the failure in the wall is not existed with rubber media for the same pressure of hydraulic.

The Modeling and Dynamic Simulation of U-Tube Steam Generator

For comprehensive research on the dynamics of U-tube natural circulation evaporator in plant, the modular and lumped parameters method is used to establish the mathematical model of U-tube steam generator. Steam generator is divided into three parts in the model: primary water side, U-tube metal side and secondary water side. Secondary water side includes five modules. Then, the dynamic simulation experiment can be made on the basis of the simulation model. The experiment results consistent with the actual data and the adaptability and rationality of the model are verified.

Research on Dew Point Corrosion of Materials

To solve the problem of power station boilers' high exhaust temperature and the demand of the dewpoint corrosion prevention and control in the process of flue gas deep cooling, We chose dewpoint corrosion resistant steels BNS, ND and 316L steel as studied objects, which were in situ tested on a boiler of 1000 MW pulverized coal-fired power plant. The results show that 316 L steel is performing superior corrosion resistance. Iron oxides and a small amount of sulphate and chlo-rate are the corrosion products, and the suitable tube metal wall temperature is recommended as 80°C which can avoid the coupling effect between dewpoint corrosion and viscous ash deposition.

TEMPERATURE DEPENDENCE OF ELECTRICAL RESISTANCE OF INDIVIDUAL CARBON NANOTUBES AND CARBON NANOTUBES NETWORK

We present a model to understand the effect of temperature on the electrical resistance of individual semiconducting single wall carbon nanotubes (s-SWCNTs) of various diameters under various electric fields. The temperature dependence of the resistance of s-SWCNTs and metallic SWCNTs (m-SWCNTs) are compared. These results help us to understand the temperature dependence of the resistance of SWCNTs network. We experimentally examine the temperature dependence of the resistance of random networks of SWCNTs, prepared by dispersing CNTs in ethanol and drop-casting the solution on prefabricated metallic electrodes. Examining various samples with different electrode materials and spacings, we find that the dominant resistance in determination of the temperature dependence of resistance of the network is the resistance of individual tubes, rather than the tube–tube resistance or tube–metal contact resistance. It is also found that the tube–tube resistance depends on the electrode spacing and it is more important for larger electrode spacings. By applying high electric field to burn the all-metallic paths of the SWCNTs network, the temperature dependence of the resistance of s-SWCNTs is also examined. We also investigate the effect of acid treatment of CNTs on the temperature dependence of the resistance of SWCNTs and also multi-wall CNTs (MWCNTs) networks.