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He K.,University of Science and Technology Beijing | Zhu H.,Hanbao Steel Energy Center | Wang L.,University of Science and Technology Beijing | Wang L.,State Key Laboratory of Technologies in Space Cryogenic Propellants
Applied Energy | Year: 2015

Inspired by energy storage systems for peak load shifting (PLS), this study proposes a PLS utilization mode of electricity-generating coal gas resources for the steel industry in China. The proposed mode can help the steel industry save electricity bills (2.4%) through the introduction of a time-of-use tariff. Data of a steel enterprise are used to prove the economic benefit of the coal gas utilization mode. Given that China produces more than half of converter steel of the total production worldwide, their coal gas resources are abundant. The PLS utilization mode will have a great effect on balancing the power grid. A simulated operation model for PLS coal-fired power units is used to calculate the energy conservation and emission reduction effect of coal-fired power plants under different scenarios. The annual coal savings are 1.7-3.1%, and the annual SO2 and NOX emission reductions are 2.9-12.4% and 44.6-14.1% of the total reduction amount of the steel industry in China, respectively. © 2015 Elsevier Ltd. Source


Wang L.,Xian Jiaotong University | Li Y.,Xian Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Zhao Z.,Xian Jiaotong University | Zheng J.,Xian Jiaotong University
Asia-Pacific Journal of Chemical Engineering | Year: 2014

The pressurization performance of cryogenic tanks during discharge is investigated by a computational fluid dynamic approach. A series of cases accounting for the effects of various influence factors such as inlet gas temperature, ramp time of inlet gas temperature, wall thickness, outflow rate, injector structure, and liquid supercooling on pressurization behaviors are computed and analyzed successively. Several valuable conclusions have been drawn as follows: (1) Increasing inlet gas temperature, applying a thin wall to construct the tank, and increasing the outflow rate are beneficial to the reduction of gas requirements, (2) Ramp process and use of a straight pipe injector may lead to an excessive pressure drop at the beginning of discharge, (3) Use of straight pipe injector can remarkably reduce the gas requirement but lead to a large loss of liquid propellant as well as a large weight of final ullage gas, and (4) The mode of mass transfer within the tank is close related to the injector structure and liquid supercooling. A trend of mass transfer toward evaporation can be observed by increasing the liquid temperature, especially for the straight pipe injector case. Generally, the results of this paper might be beneficial to the design and optimization of a pressurization system. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd. Source


Wang L.,Xian Jiaotong University | Li Y.,Xian Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Li C.,Xian Jiaotong University | Zhao Z.,Xian Jiaotong University
Cryogenics | Year: 2013

Predictions of thermal and pressurization performance in a liquid hydrogen (LH2) tank during liquid discharge is of significance to the design and optimization of a rocket pressurization system. In this paper, a computational fluid dynamic (CFD) model is introduced to simulate the pressurized discharge event of LH2 tank. The wall region together with the fluid region is simultaneously considered as the computational domain, and low-Re k-ε model is applied to account for the fluid-wall heat exchange effect. Liquid-vapor phase change effect is also involved in the model. Comparison of the numerical results with existing experimental data suggests that the CFD model has a good adaptability in pressurization computation. Detailed characteristics, such as pressurant gas requirement, pressure altering history, and temperature distribution inside the tank, can be obtained by the model. The difference of pressurant gas, selecting helium or vapor H 2, may result in the variations in pressure and temperature histories. Pressurization by vapor H2 supplies a higher pressure and also a temperature rise, which is significant to consider the selection of pressurant gas. The influences of phase change effect and injector structure on pressurization behaviors are also analyzed. The computational results show that liquid-vapor phase change has a slight influence on the pressurization behaviors. Significant pressure decay at the beginning stage of process may occur in the case of no-diffuser injector application since the incoming gas is excessively cooled by cold LH2. The results show that the present CFD model has a good adaptability in the prediction of pressurization behaviors and is a useful tool for the design and optimization of a pressurization system. © 2013 Published by Elsevier Ltd. All rights reserved. Source


Wang L.,Xian Jiaotong University | Li Y.,Xian Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Zhang F.,Urbana University | Ma Y.,Xian Jiaotong University
Cryogenics | Year: 2015

Two finite difference computer models, aiming at the process predictions of no-vent fill in normal gravity and microgravity environments respectively, are developed to investigate the filling performance in a liquid hydrogen (LH2) tank. In the normal gravity case model, the tank/fluid system is divided into five control volume including ullage, bulk liquid, gas-liquid interface, ullage-adjacent wall, and liquid-adjacent wall. In the microgravity case model, vapor-liquid thermal equilibrium state is maintained throughout the process, and only two nodes representing fluid and wall regions are applied. To capture the liquid-wall heat transfer accurately, a series of heat transfer mechanisms are considered and modeled successively, including film boiling, transition boiling, nucleate boiling and liquid natural convection. The two models are validated by comparing their prediction with experimental data, which shows good agreement. Then the two models are used to investigate the performance of no-vent fill in different conditions and several conclusions are obtained. It shows that in the normal gravity environment the no-vent fill experiences a continuous pressure rise during the whole process and the maximum pressure occurs at the end of the operation, while the maximum pressure of the microgravity case occurs at the beginning stage of the process. Moreover, it seems that increasing inlet mass flux has an apparent influence on the pressure evolution of no-vent fill process in normal gravity but a little influence in microgravity. The larger initial wall temperature brings about more significant liquid evaporation during the filling operation, and then causes higher pressure evolution, no matter the filling process occurs under normal gravity or microgravity conditions. Reducing inlet liquid temperature can improve the filling performance in normal gravity, but cannot significantly reduce the maximum pressure in microgravity. The presented work benefits the understanding of the no-vent fill performance and may guide the design of on-orbit no-vent fill system. © 2015 Elsevier Ltd. Source


Zhao Z.,Xian Jiaotong University | Li Y.,Xian Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Wang L.,Xian Jiaotong University | And 2 more authors.
Cryogenics | Year: 2014

Ambient air condensation on a cryogenic horizontal tube is investigated using a newly built mathematical model, in which the liquid film and the vapor boundary layer are coupled together with a major emphasis on the effect of buoyancy. Based on the model, the heat transfer coefficients and the film thickness as well as the interfacial shear are obtained under different conditions to investigate the effects on the flow and heat transfer characteristics of the superheating between vapor and film, the buoyancy in the boundary layer and the subcooling between wall and film. In addition to the flow and heat transfer characteristics of air, the other four different vapors, i.e. H2O, R134a, methane (CH4), argon (Ar), are also discussed. The results show that the superheating has a more significant contribution to the increase of heat transfer coefficient for air comparing to the other vapors, e.g. in the cases of superheating ΔTA¢. © 2014 Elsevier Ltd. All rights reserved. Source

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