TY - JOUR A1 - Wu, Z. A1 - Guo, X. A1 - Xie, G. A1 - Yan, T. A1 - Wu, Dejian A1 - Zhang, F. A1 - Ang, R. T1 - Heat and electric flux coupling of closed-loop thermoelectric generator N2 - Thermoelectric generator (TEG) has been proved as a promising technology for directly converting heat into electricity based on Seebeck effect. On the contrary, this electricity can trigger a solid-state cooling based on conventional Peltier effect. However, these two effects induce a coupling between heat and electric flux, especially for the quantitative relationship still remaining a mystery. Here, we show experimental evidence and theoretical calculation for the coupling by monitoring transient response of fluid temperature and output power. The experimental maximum heat flow in open circuit is 1162 W at cold fluid flow rate = 0.3 m3/h and fluid temperature difference ΔTf = 70 °C, enhanced by 13% owing to heat compensation from intrinsic coupling in closed-loop circuit. Meanwhile, the measured maximum output power of TEG is 18.2 W, and subsequently decreases to 15.4 W due to the objective existence of coupling. This double-edged sword in coupling vigorously inspires the potential applications in heat-dissipation situation such as spacecraft, electronic components, photovoltaic, refrigerator and etc. Present findings open a novel avenue for manipulating heat-electricity conversion in practical engineering. KW - Thermoelectric generator PY - 2021 DO - https://doi.org/10.1016/j.enconman.2021.114529 SN - 0196-8904 VL - 244 SP - 1 EP - 13 PB - Elsevier Ltd. AN - OPUS4-53661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, W. A1 - Wei, A. A1 - Huang, W. A1 - Zhao, Peng A1 - Schmidt, Martin A1 - Krause, Ulrich A1 - Wu, Dejian T1 - Experimental and theoretical study on the inhibition effect of CO2/N2 blends on the ignition behavior of carbonaceous dust clouds N2 - Gaseous inhibitors are used in many industries for the explosion prevention of combustible dusts, mitigating the potential hazard to humans, properties and environments. This work experimentally and theoretically studied the inerting effect of gaseous inhibitors on the ignition process of dust clouds in O2/N2/CO2 atmospheres, with an emphasis on the role of the CO2/N2 ratio. 10 different combustible carbonaceous dusts were selected, including grain dust, biomass dust and coal dust. Experimental results showed that the inhibition effect of CO2/N2 is closely related to the ignition mechanism of dust clouds. Specifically, a higher ratio of CO2/N2 yields a stronger inhibition effect on the ignition process of dust samples with relatively low volatile matter contents predominated by heterogeneous ignition. In addition, two novel steady-state ignition mechanism models were developed to interpret the experimental observations. Maxwell-Stefan equations were used to describe the diffusivity in the ternary O2/N2/CO2 gas mixtures. The analytical results were in good agreement with the experimental data of the minimum ignition temperature of dust cloud (MITC) in oxygen-lean atmospheres. The mechanism modelling can be used to estimate the critical ignition temperature of all carbonaceous dust clouds with a wide range of volatile matter content under different inert atmospheres, which will provide a reference for the explosion hazard assessment of dust posed by a hot surface in the process industries. KW - CO2/N2 ratio KW - Inerting effect KW - Volatile matter content KW - MITC KW - Mechanism model PY - 2021 DO - https://doi.org/10.1016/j.psep.2021.07.005 SN - 0957-5820 VL - 153 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-53662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jiang, C. A1 - Xie, G. A1 - Wu, Dejian A1 - Yan, T. A1 - Chen, S. A1 - Zhao, P. A1 - Wu, Z. A1 - Li, W. T1 - Experimental investigation on an energy-efficient floor heating system with intelligent control: A case study in Chengdu, China N2 - The space heating system accounts for 20%~50% of building energy consumption, and may lead to energy waste due to unreasonable controls. In this study, an energy-efficient floor heating system with intelligent control was proposed to improve energy efficiency of the system. In order to validate the concept of the proposed intelligent control, an experimental system was designed and constructed in Chengdu, China. Temperature, control cycle and energy consumption were then studied under different control strategies. The result shows that a larger flow rate of supply water will result in a longer control cycle and a lower control frequency, i.e., the average control cycle at 7 L min−1 is 1.7 h during the test day, while it is 1.5 h at 5 L min−1. Moreover, adopting water with a higher temperature and flow rate could achieve a higher efficiency of the system. The energy consumptions in case 1 (5 L min−1, 50 °C), case 2 (5 L min−1, 55 °C), case 5 (7 L min−1, 55 °C) and case 6 (7 L min−1, 60 °C) are 4746 kJ, 3534 kJ, 3093 kJ and 3028 kJ, respectively. Based on the experimental data, the supply water temperature is suggested to set lower than 60 °C considering human comfort. KW - Floor heating KW - Intelligent control KW - Experimental KW - Energy consumption KW - Control strategy PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550522 DO - https://doi.org/10.1016/j.csite.2021.101094 SN - 2214-157X VL - 26 SP - 1 EP - 14 PB - Elsevier Ltd. AN - OPUS4-55052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xie, Y. A1 - Cui, Y. A1 - Wu, Dejian A1 - Zeng, Y. A1 - Sun, L. T1 - Economic analysis of hydrogen-powered data center N2 - The data center needs more and more electricity due to the explosive growth of IT servers and it could cause electricity power shortage and huge carbon emission. It is an attractive and promising solution to power the data center with hydrogen energy source. The present work aims to conduct an economic analysis on the hydrogen-powered data center. Configurations of hydrogen-powered and traditional data centers are compared and the differences focus on backup power system, converter/inverter, fuel cell subsystem, carbon emission, hydrogen and electricity consumptions. Economic analysis is conducted to evaluate the feasibility to power the data center with hydrogen energy source. Results show that electricity price increasing rate and hydrogen cost are the main factors to influence economic feasibility of hydrogen-powered data center. When the electricity price keeps constant in the coming two decades, the critical hydrogen price is about 2.8 U.S. dollar per kilogram. If the electricity price could increase 5% annually due to explosive growth of electric vehicles and economy, critical hydrogen price will become 6.4 U.S. dollar per kilogram. Hydrogen sources and transportation determine the hydrogen price together. Hydrogen production cost varies greatly with hydrogen sources and production technologies. Hydrogen transport cost is greatly influenced by distances and H2 consumptions to consumers. It could be summarized that the hydrogen-powered data center is economic if hydrogen could be produced from natural gas or H2-rich industrial waste streams in chemical plant and data center could not be built too far away from hydrogen sources. In addition, large-scale hydrogen-powered data center is more likely to be economic. Solar hydrogen powered data center has entered into a critical stage in the economic feasibility. Solar hydrogen production cost has restrained the H2 utilization in data center power systems now, since it could be competitive only when more strict carbon emission regulation is employed, hydrogen production cost reduces greatly and electricity price is increasing greatly in the future. However, it could be expected solar hydrogen-powered system will be adopted as the power source of data centers in the next few years. KW - Hydrogen KW - Date center KW - Economic analysis PY - 2021 DO - https://doi.org/10.1016/j.ijhydene.2021.06.048 SN - 0360-3199 VL - 46 IS - 55 SP - 27841 EP - 27850 PB - Elsevier Ltd. AN - OPUS4-53658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zang, N. A1 - Qian, X. A1 - Shu, C. A1 - Wu, Dejian T1 - Parametric sensitivity analysis for thermal runaway in semi-batch reactors: Application to cyclohexanone peroxide reactions N2 - The semi-batch reactors (SBRs) system, which is widely used in industrial processes, possesses an intrinsic parametric sensitivity, in which infinitesimal disturbances of input parameters can result in large variations in output variables. In this work, local parametric sensitivity analysis (PSA) was used to understand parameter variations and global PSA was conducted to examine the interaction of input parameters. The effects of these parameters on the output of the system model were analyzed based on the Monte Carlo method with Latin hypercube sampling and the extended Fourier amplitude sensitivity test model. The results showed that the evolution of thermal behaviors in SBRs were observed: marginal ignition; thermal runaway; and the quick onset, fair conversion, and smooth temperature profile. The threshold point of transition from marginal ignition to thermal runaway was at the maximal value of local sensitivity, for which the slope with respect to cooling temperature equaled zero. Moreover, the sequence of the global sensitivity of six common input parameters was computed and evaluated. The reliability of the numerical models was verified by using our previous experimental results of cyclohexanone peroxide reaction. This comprehensive sensitivity analysis could provide valuable operating information to improve chemical process safety. KW - Semi-batch reactor KW - Parametric sensitivity analysis KW - Monte Carlo method KW - Thermal runaway KW - Cyclohexanone peroxide PY - 2021 DO - https://doi.org/10.1016/j.jlp.2021.104436 SN - 0950-4230 VL - 70 SP - 104436 PB - Elsevier Ltd. AN - OPUS4-53659 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, D. A1 - Ji, T. A1 - Jing, Q. A1 - He, W. A1 - Fan, Z. A1 - Wu, Dejian A1 - Qian, X. T1 - Experimental study and mechanism model on the ignition sensitivity of typical organic dust clouds in O2/N2, O2/Ar and O2/CO2 atmospheres N2 - To reveal and improve our understanding of the ignition behavior and mechanism, G-G furnace experiments of three typical organic dusts were performed to investigate the minimum ignition temperature (MIT) in O2/N2, O2/ Ar and O2/CO2 atmospheres with oxygen mole fraction from 8.4% to 50%. The experimental results were presented in oxygen-lean and oxy-fuel atmospheres to evaluate the ignition sensitivity of dusts in different atmospheres. It was found that CO2 is the strongest in terms of lowing the ignition sensitivity of the three dusts, and the dust explosion risk increases significantly with increasing O2 mole fraction for the three dusts through a logarithmically and significantly reducing MIT. However, for different dusts, inert gases show different suppression effects. In addition, a modified steady-state homogeneous ignition model was proposed and successfully applied to oxygen-lean atmospheres, and in oxy-fuel atmospheres, this model has also been improved to estimate the ignition mechanism. This ignition mechanism model could be used to successfully predict the minimum ignition temperature of high volatile dust under different inert atmospheres controlled by homogeneous ignition, which will provide a reference for the ignition hazard assessment of dust on hot surfaces. KW - Dust explosions KW - Gas explosions KW - Minimum ignition temperature KW - Hybrid mixtures PY - 2021 DO - https://doi.org/10.1016/j.jhazmat.2021.125108 SN - 0304-3894 VL - 412 SP - 125108 PB - Elsevier B.V. AN - OPUS4-53660 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Dejian A1 - Tan, X. A1 - Wei, A. A1 - Duan, Q. A1 - Huang, W. A1 - Schmidt, Martin T1 - Ignition temperature and mechanism of carbonaceous dust clouds: The roles of volatile matter, CH4 addition, O2 mole fraction and diluent gas N2 - Minimum ignition temperature of dust clouds (MITC) was studied experimentally and theoretically in different atmospheres. Three carbonaceous dusts were tested in both air and O2/CO2 atmospheres with CH4 mole fraction from 0 to 2%. Results showed that the ignition risk of the three dusts significantly increases (decrease of MITC by ~100 ℃) with increasing XO2 from 21% to 50%, but significantly decreases replacing N2 in air with CO2. The inhibition effect of CO2 on MITCs could be diminished by increasing XO2 or adding CH4. The addition of small amount of CH4 has different effects on the MITCs of different dust samples, following the opposite order of volatile matter content: anthracite>bituminous coal>starch. Two modified steady-state ignition models, considering the density of mixture gas and dust cloud, XO2 and its diffusivity, were developed to interpret the experimental observations. The analysis revealed that the global heterogeneous ignition model suits well for the hybrid mixtures of anthracite or bituminous coal dusts. In contrast, the proposed global homogeneous ignition model was found to be only valid for the pure starch dust, and the extra CH4 addition could strongly affect the ignition process of starch, particularly in O2/CO2 atmospheres with higher XO2. KW - Dust explosions KW - Gas explosions KW - Minimum ignition temperature KW - Hybrid mixtures PY - 2021 DO - https://doi.org/10.1016/j.jhazmat.2020.124189 SN - 0304-3894 SN - 1873-3336 VL - 405 SP - 1 EP - 10 PB - Elsevier CY - Amsterdam AN - OPUS4-53838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhao, P. A1 - Schmidt, Martin A1 - Krause, U. A1 - Duan, Q. A1 - Krietsch, Arne A1 - Wu, Dejian T1 - Experimental study on the minimum explosion concentration of anthracite dust: The roles of O2 mole fraction, inert gas and CH4 addition N2 - The explosion characteristics of anthracite coal dust with/without small amount of CH4 (1.14 vol %) were investigated by using a 20 L spherical explosion apparatus with an emphasis on the roles of oxygen mole fraction and inert gas. Two methods based on overpressure and combustion duration time were used to determine the minimum explosion concentration (MEC) or the lower explosion limit (LEL) of the pure anthracite coal dust and the hybrid coal-methane mixtures, respectively. The experiment results showed that increasing oxygen mole fraction increases the explosion risk of coal dust: with increasing oxygen mole fraction, the explosion pressure (Pex) and the rate of explosion pressure rise ((dp/dt)ex)) increase, while MEC decreases. The explosion risk of anthracite dust was found to be lower after replacing N2 with CO2, suggesting that CO2 has a better inhibition effect on explosion mainly due to its higher specific heat. However, the addition of 1.14% CH4 moderates the inhibition effect of CO2 and the promotion effect of O2 on anthracite dust explosion for some extent, increasing explosion severity and reducing the MEC of anthracite dust. For hybrid anthracite/CH4 mixture explosions, Barknecht’s curve was found to be more accurate and conservative than Chatelier’s line, but neither are sufficient from the safety considerations. The experimental results provide a certain help for the explosion prevention and suppression in carbonaceous dust industries. KW - Lower explosion limit KW - Minimun explosion concentration KW - Explosion charasteristics KW - Hybrid mixture KW - Explosion regimes PY - 2021 DO - https://doi.org/10.1016/j.jlp.2021.104490 VL - 2021 SP - 1 EP - 10 PB - Elsevier Ltd. ET - 71 AN - OPUS4-54074 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Dejian A1 - Guoqing, Li A1 - Jun, W. A1 - Shimao, J. B. A1 - Sheng, Q. T1 - Effects of gas concentration and obstacle location on overpressure and Flame propagation characteristics of hydrocarbon fuel-air explosion in a semi-confined pipe N2 - Experiments were conducted in a semi-confined pipe to investigate the effects of obstacle location and gasoline vapor concentration on gasoline-air fuel explosions. The variations of internal overpressure, external overpressure, flame propagation and flame-overpressure coupling relationship were analyzed. The results showed thatthe internal overpressure histories existed three obvious peaks, and when the obstacle location was set at 0.4 m, the maximum absolute values of overpressure (pmax and pneg), overpressure rise rates ((dp/dt)ave and (dp/dt)max) and the deflagration index (KG) were obtained. Additionally, more than two positive overpressure peaks were observed in the external overpressure histories. The maximum values of external overpressures and overpressure rise rates were obtained at the obstacle location of 0.4 m. For the fuel concentrations of 1.3%,.1.7% and 2.1%, the shortest time to reach pmax appeared at the obstacle location of 0.4 m, 0.2 m and 0.6 m, respectively, while the shortest time to reach (dp/dt)max and the maximum flame propagation speed were obtained for all the fuel concentrations at the obstacle location of 0.2 m. Moreover, a coupling relationship between overpressure and flame propagation was found. lt could be tleduced that the formation of the positive overpressure peak ofthe external overpressure might be directly related to the gas explosion inside the pipe and the flow jet caused by the high-speed flame propagation. rat her than the external explosion (or secondary explosion) out of the pipe. These results improve our understanding on gas explosion dynamics in a semi- confined space. KW - Hydrocarbon fuel-air explosion KW - Gas concentration KW - Obstacle location KW - Explosion overpressures KW - Flame propagation PY - 2021 DO - https://doi.org/10.1016/j.fuel.2020.119268 VL - 285 SP - 119268 PB - Elsevier Ltd. AN - OPUS4-52446 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Song, Z. A1 - He, T. A1 - Li, M. A1 - Wu, Dejian A1 - You, F. T1 - Self-sustaining smoldering as a novel disposal approach for food waste with high moisture content N2 - This work aims to explore the self-sustaining smoldering treatment (SSST) for the destruction of food waste. The food waste used in this work mainly consists of cereal, vegetable, and meat. To examine the processing procedures and parameters, three experimental groups (raw food waste, food-waste paste and food-waste paste blended with anthracite) and five variables (moisture content, sand size, sand-to-food waste ratio, air flow and food waste-to-coal ratio) were extensively investigated. Results show that raw food waste with 40% moisture content can be disposed by SSST with the mass destruction ratio over 90%. However, the robustness of SSST for raw food waste is constrained by the heterogeneous issue due to a variety of components and sizes of food waste. This issue is addressed through stir pre-processing of raw food waste as food-waste paste. The robustness of SSST for food waste is significantly further enhanced only if a slight mass fraction of anthracite (<20% of raw food waste) is supplemented. This provides an alternative solution for employing SSST for raw food waste with very high moisture content. KW - Food waste KW - Waste disposal KW - Smoldering combustion KW - Self-sustaining propagation PY - 2021 DO - https://doi.org/10.1016/j.fuproc.2021.107144 SN - 0078-3820 VL - 228 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-55053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -