In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition und...In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition under a constant pressure condition.The criticality conditions for a slab,an infinite cylinder,and a sphere are determined and discussed using dimensionless temperatures under constant ambient and surface temperatures for a non-uniform temperature system.Exact solution for a Semenov model with convection heat loss was also presented.The solution of the Semenov problem for constant volume or density as a solid and constant pressure were compared.The critical parameterδis calculated and compared with those of Frank-Kamenetskii solution values.The validation of the calculated ignition temperatures with other exact solution and experimental results were offered.The relation between critical parameters form Semenov and F.K.models solution was introduced.展开更多
Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils. Its thermal performances could be improved by improving the unifo...Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils. Its thermal performances could be improved by improving the uniformity of the phase change material （PCM） temperature distribution. Thus, a novel non-equidistant helical-coil structure was proposed in this study. Its coil pitch decreased along the flow direction of heat transfer fluid, which made the heat exchange area in unit volume increase to match the decreasing temperature difference between the heat transfer fluid and PCM. The structure was optimized using numerical simulation. An experimental system was developed and the experiment results indicated that the proposed non-equidistant helical-coil heat accumulator was more effective than equidistant helical-coil for latent heat storage. The uniformity of the temperaalre distribution was also confirmed by simulation results.展开更多
文摘In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition under a constant pressure condition.The criticality conditions for a slab,an infinite cylinder,and a sphere are determined and discussed using dimensionless temperatures under constant ambient and surface temperatures for a non-uniform temperature system.Exact solution for a Semenov model with convection heat loss was also presented.The solution of the Semenov problem for constant volume or density as a solid and constant pressure were compared.The critical parameterδis calculated and compared with those of Frank-Kamenetskii solution values.The validation of the calculated ignition temperatures with other exact solution and experimental results were offered.The relation between critical parameters form Semenov and F.K.models solution was introduced.
基金supported by the National Natural Science Foundation of China(Grant No.51576187)Fundamental Research Funds for the Central Universities(Grant No.WK2090130016)
文摘Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils. Its thermal performances could be improved by improving the uniformity of the phase change material （PCM） temperature distribution. Thus, a novel non-equidistant helical-coil structure was proposed in this study. Its coil pitch decreased along the flow direction of heat transfer fluid, which made the heat exchange area in unit volume increase to match the decreasing temperature difference between the heat transfer fluid and PCM. The structure was optimized using numerical simulation. An experimental system was developed and the experiment results indicated that the proposed non-equidistant helical-coil heat accumulator was more effective than equidistant helical-coil for latent heat storage. The uniformity of the temperaalre distribution was also confirmed by simulation results.
