Advanced Materials Research Vols. 354-355

Abstract: A shell-and-tube heat exchanger which is widely used for the heat recovery of air in a coal gasification system is investigated. FLUENT6.3 software is used and the RNG k−ε turbulence model is adopted for modeling turbulent flow. The porosity rate, the distribution of the resistance and the distribution of the heat source were introduced to FLUENT by coupling the user defined function. The variation of local heat transfer is studied under the effects of the baffles arrangement. The result shows that the porous media model can be applied in shell side of the air cooler in IGCC and the reasonable arrangement of the baffles can decrease the pressure drop with little influence on the heat transfer.

Abstract: Abstract Diammonium Phosphate (DAP) is an important crop nutrient for plants and its use is increasing day by day with increase in population. Life cycle assessment (LCA) is an important tool in the evaluation of the environmental performance of the product/ system throughout the life cycle. In this paper, LCA has been used to evaluate the performance of the Diammonium Phosphate (DAP) fertilizer production. The system investigated includes DAP production process. The quantification of environmental emissions, material and energy usage are quantified and environmental effects are assessed. The impact categories most affected by the DAP production, are respiratory inorganics and terrestrial acid/nitrification. Interpretations have been made and recommendations are given for operational improvements in DAP production

Abstract: The management decision fault during prophase demonstration, design and operation on power station can be avoided effectively by technical and economic evaluation of power station project. In this paper, the sintering circular-cooler waste heat power station in WISCO is taken as an example. Through analyzing the two methods of technical and economic evaluation on power plant and constructing the evaluation system of sintering waste heat power plant, the technical evaluation on overallcondition of power plant is made by adopting the ways of contrastive analysis, and index weight value of power plant is computed by analytic hierarchy process, then power station is evaluated through combining the two evaluation methods. And the bandwidth of net power output basic parameters of per ton of sinter waste heat is determined. The study results can provide reference basis for the initiating project and technology decisions of waste heat power station.

Abstract: OTEC has the advantages of large reserves, renewable, stable and clean without pollution. However the smaller ocean temperature-difference results in the lower thermal efficiency. Based on the research of Rankine cycle, Kalina cycle, Uehara cycle, a new closed-cycle system (GuoHai cycle) has been studied, this cycle system uses ammonia-water mixtures as working medium. Indirect regenerative cycle and poor ammonia solution regenerative cycle is adopted in order to improve the thermal efficiency of the system.

Abstract: CuO/graphene oxygen carrier models were built to investigate the reaction stoichiometry mechanism between the fuel gas CO and oxygen carrier CuO. The results show that the energy barrier of the single metal oxide CuO oxidation CO is 127.17kJ/mol, while energy barrier is only 42.64 kJ/ mol for the CuO/graphene. From the point view of chemical reaction dynamics, the oxidation activity of CuO/graphene much higher than single-metal oxide CuO, which indicate that graphene can improve the reaction performance of oxygen carrier. And analysis results for the oxidation of fuel gas CO has an important understanding of the process of scientific significance, and will promote the fundamental understanding and applications of the oxygen carrier CuO.

Abstract: A one dimensional unsteady mathematical model for predicting the air mass flow rate in a solar chimney has been proposed. The thermal resistance and thermal inertia of both the glass cover and heat absorbing wall were considered in the present model. Crank-Nicolson finite difference numerical method was used to solve the differential equations. The variation of the air temperature in the solar chimney was solved by integrating the controlling equation for the air along the chimney height. Results show the absorber wall reaches its peak temperature 2 hours later with respect to the maximum ambient temperature. The air temperature in the channel varies with the solar radiation in a day and researches its peak value at about 2:00pm. The air mass flow rate increases remarkably with the increase of the channel depth when the solar radiation is higher from 11:00 am to 3:00 pm. The maximum of air mass flow rate occurs at around 2:00pm

Abstract: According to the analysis of the characteristics of the biomass straw in its pneumatic drying process, some reasonable assumptions concerning the pneumatic drying are made and the mathematical model of heat and mass transfer in the biomass straw’s pneumatic drying process in the horizontal straight tube. Besides, the numerical method is adopted to solve the model and the analog simulation concerning the moisture content, temperature and the speed changes of the material and the air is conducted. Meanwhile influence of the gas-solid ratio and the air flow’s initial temperature on the drying effect is the analog simulated and the reason for this phenomenon is also analyzed.

Abstract: One of the worst accidents that may occur in a high-vacuum-multilayer-insulation (HVMLI) cryogenic tank is a sudden, catastrophic loss of insulation vacuum (SCLIV). it is obvious that the different gas leaking into the insulation jacket have some influence on the heat transfer process. However, this problem has not been studied systematically so far. In this paper, a test rig was built up and experiments were conducted on a SCLIV cryogenic tank by using the nitrogen, helium, oxygen, carbon dioxide and air as the leaking medium, respectively. Some important phenomena and heat transfer characteristics in a vacuum-lost HVMLI cryogenic tank have been obtained. The effects of the insulation layer numbers and the type of gases on venting rate and heat flux into the cryogenic liquid have been measured, analyzed and discussed. It indicates that the heat transfer performance of the HVMLI cryogenic tank after SCLIV is strong related to the type of gases leaking into the insulation jacket.

Abstract: In this paper, a new process of using high grade ores, such as magnesite and water magnesium stone etc, to produce magnesium is proposed from the thermodynamic point of view. For the ores, the main component of calcined products is MgO. Considering the reaction activity, price and material stability, CaC₂ is chosen as the reductant in the new process. Furthermore, the optimal reaction is determined as the reduction of MgO by CaC₂ adding SiO₂ based on the principle of Gibbs free energy. It is found that the initial reaction temperature is 947°C under ordinary pressure showing the reaction taking place without vacuum condition. Compared with the traditional silicothermic process, the new process is not only simple but also can achieve continuous production due to the thermal reduction under ordinary pressure, as a result that it is easy to industrial application in the present technological level and conditions.

Abstract: Based on the first and second laws of thermodynamics as well as exergo-economic theory, comprehensive performance evaluation criterion has been proposed for enhanced tube under the condition of equivalent pump (fan) power consumption, accounting for a variety of factors such as heat transfer, flow and investment costs. Performance evaluation criterion formula, namely, net profit value (NPV) has been derived from the perspective of the exergy recovery. Take spirally corrugated tube as an example, the results show that the exergo-economic performance of the spirally corrugated tube is superior to smooth tube for the range considered in the present study. From the viewpoint of NPV, although NPV of enhanced tube is greater than that of smooth tube, there exist critical values of Re and Nq exceeding which NPV of enhanced tube would be less than zero, showing no engineering significance.