The parallel-inlet holes with one-row, two-row and three-row film hole arrangements and different di- ameters are proposed to experimentally study their cooling characteristics. Detailed experimental processes and res...The parallel-inlet holes with one-row, two-row and three-row film hole arrangements and different di- ameters are proposed to experimentally study their cooling characteristics. Detailed experimental processes and results are described and carried out. Results indicate that heat transfer coefficient （HTC） is increased with the increase of blowing ratio. When the blowing ratio is lower, the distribution of HTC along the heated wall can be divided into three regions. For larger blowing ratio or diameter, the cooling characteristics oi parallel-inlet film holes are similar to those of convective heat transfer around flat. Furthermore, when hole diameter is deter- mined, the arrangement patterns of film hole and the blowing ratio take a great influence on HTC.展开更多
Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of th...Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of the geometric and system parameters on heat transfer characteristics in helically coiled tubes are investigated by collecting large amounts of experimental data and analyzing the heat transfer mechanisms. The existing correlations are divided into two categories,and they are calculated with the experimental data.The Dn factor is introduced to take into account the effect of a complex geometrical structure on flow boiling heat transfer.A new correlation is developed for predicting the flow boiling heat transfer coefficients in the helically coiled tubes,which is validated by the experimental data of R134a flow boiling heat transfer in them;and the average relative error and root mean square error of the new correlation are calculated.The results show that the new correlation agrees well with the experimental data,indicating that the new correlation can be used for predicting flow boiling heat transfer characteristics in the helically coiled tubes.展开更多
Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the el...Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the electrochemical hydrogen storage properties of the alloys before and after heat treatment. The results show that the maximum discharge capacity of heat-treated Ti2?xMgxNi alloy can reach 275.3 mA·h/g, which is 100 mA·h/g higher than that of the amorphous Ti2?xMgxNi alloy. The heat-treated Ti1.9Mg0.1Ni alloy presents the best cycling stability with a high discharge capacity of 210 mA·h/g after 30 cycles. The results of LP and potential-step measurement of the Ti1.9Mg0.1Ni alloy show that the exchange current density increases from 101.1 to 203.3 mA/g and the hydrogen diffusion coefficient increases from 3.20×10?11 to 2.70×10?10 cm2/s after the heat treatment, indicating that the heat treatment facilitates both the charge-transfer and hydrogen diffusion processes, resulting in an improvement in electrochemical hydrogen storage properties of Ti2?xMgxNi (x=0?0.3) alloys.展开更多
文摘The parallel-inlet holes with one-row, two-row and three-row film hole arrangements and different di- ameters are proposed to experimentally study their cooling characteristics. Detailed experimental processes and results are described and carried out. Results indicate that heat transfer coefficient （HTC） is increased with the increase of blowing ratio. When the blowing ratio is lower, the distribution of HTC along the heated wall can be divided into three regions. For larger blowing ratio or diameter, the cooling characteristics oi parallel-inlet film holes are similar to those of convective heat transfer around flat. Furthermore, when hole diameter is deter- mined, the arrangement patterns of film hole and the blowing ratio take a great influence on HTC.
基金The National Natural Science Foundation of China(No.50776055,51076084)
文摘Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of the geometric and system parameters on heat transfer characteristics in helically coiled tubes are investigated by collecting large amounts of experimental data and analyzing the heat transfer mechanisms. The existing correlations are divided into two categories,and they are calculated with the experimental data.The Dn factor is introduced to take into account the effect of a complex geometrical structure on flow boiling heat transfer.A new correlation is developed for predicting the flow boiling heat transfer coefficients in the helically coiled tubes,which is validated by the experimental data of R134a flow boiling heat transfer in them;and the average relative error and root mean square error of the new correlation are calculated.The results show that the new correlation agrees well with the experimental data,indicating that the new correlation can be used for predicting flow boiling heat transfer characteristics in the helically coiled tubes.
基金Project(51201089)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions of China
文摘Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the electrochemical hydrogen storage properties of the alloys before and after heat treatment. The results show that the maximum discharge capacity of heat-treated Ti2?xMgxNi alloy can reach 275.3 mA·h/g, which is 100 mA·h/g higher than that of the amorphous Ti2?xMgxNi alloy. The heat-treated Ti1.9Mg0.1Ni alloy presents the best cycling stability with a high discharge capacity of 210 mA·h/g after 30 cycles. The results of LP and potential-step measurement of the Ti1.9Mg0.1Ni alloy show that the exchange current density increases from 101.1 to 203.3 mA/g and the hydrogen diffusion coefficient increases from 3.20×10?11 to 2.70×10?10 cm2/s after the heat treatment, indicating that the heat treatment facilitates both the charge-transfer and hydrogen diffusion processes, resulting in an improvement in electrochemical hydrogen storage properties of Ti2?xMgxNi (x=0?0.3) alloys.
