The influence of parameters pertaining to the confinant structure on water hammer had been less studied than those relative to the fluid. One of them is the inner pipe-diameter, a basic structural-parameter that makes...The influence of parameters pertaining to the confinant structure on water hammer had been less studied than those relative to the fluid. One of them is the inner pipe-diameter, a basic structural-parameter that makes its influence in essential hydraulic topics such as head loss, in pipelines. In this paper, the objective is to analyze the inner-diameter influence on water hammer phenomenon. An analytical algorithm for solving the unsteady-one-dimensional water hammer model had been applied. It had allowed estimating the instantaneous head at any point of a single pipeline. The model was solved by mean of the Laplace＇s Transformed application and the anti-transforming procedure into the complex field. To determinate the influence of internal-diameter conduit on the pressure oscillation, four distinct inside-diameter values were introduced into the solution, successively. The first overpressure-peak at each case was tabulated along with the corresponding inner^liameter and a mathematical relation had been founded. The obtained results show a close dependence between both, over-pressure peaks and internal-pipe diameter. It was founded that this dependence is given in terms of a non-linear relation between them. It was further founded that the wave frequency is sensitive to the variation of the pipe-diameter.展开更多
The dual-cooled nuclear reactor is currently considered for improving the designs of current/future nuclear reactors. Investigation of the thermal-hydraulic characteristics of the nuclear reactor via experiments is es...The dual-cooled nuclear reactor is currently considered for improving the designs of current/future nuclear reactors. Investigation of the thermal-hydraulic characteristics of the nuclear reactor via experiments is essential for commercializing the dual-cooled nuclear reactor. In this paper, the turbulent flow in square arrayed six-rod bundles in the form of magnified copies of the dual-cooled and current OPR-1000 nuclear reactor is experimentally investigated by means of hot-wire anemometry and smoke-wire generation methods. Vortex trains which do not exist in an ordinary reactor subchannel are presented in the subchannel of the dual-cooled reactor. The vortices are induced by a span-wise velocity gradient. This flow pulsation phenomenon increases the inter-channel mixing of the subchannel. To understand the periodic feature of the pulsation, axial/cross velocities are measured and the periodic characteristic frequencies are obtained by a Fast Fourier Transform (FFT) analysis. The peak frequency that represents the quasi-periodic pulsation of the flow is increased with an increase in the axial velocity while the wavelength of the pulsation remains constant within a tested range of the Reynolds number (9000 51000). The vortex trains are highly synchronized with each other, as confirmed by means of visualization.展开更多
In this paper a lumped parameter model of a two-pass gas-to-gas crossflow heat exchanger with high speed air flow has been presented for the investigation of its transieat behaviours. The effects of both the changes o...In this paper a lumped parameter model of a two-pass gas-to-gas crossflow heat exchanger with high speed air flow has been presented for the investigation of its transieat behaviours. The effects of both the changes of inlet temperature and flow rate on outlet temperature can be predicted with this model.The calculation results under typical conditions are compared with experimental results and good agreements are obtained.展开更多
文摘The influence of parameters pertaining to the confinant structure on water hammer had been less studied than those relative to the fluid. One of them is the inner pipe-diameter, a basic structural-parameter that makes its influence in essential hydraulic topics such as head loss, in pipelines. In this paper, the objective is to analyze the inner-diameter influence on water hammer phenomenon. An analytical algorithm for solving the unsteady-one-dimensional water hammer model had been applied. It had allowed estimating the instantaneous head at any point of a single pipeline. The model was solved by mean of the Laplace＇s Transformed application and the anti-transforming procedure into the complex field. To determinate the influence of internal-diameter conduit on the pressure oscillation, four distinct inside-diameter values were introduced into the solution, successively. The first overpressure-peak at each case was tabulated along with the corresponding inner^liameter and a mathematical relation had been founded. The obtained results show a close dependence between both, over-pressure peaks and internal-pipe diameter. It was founded that this dependence is given in terms of a non-linear relation between them. It was further founded that the wave frequency is sensitive to the variation of the pipe-diameter.
基金carried out under the Nuclear R&D Program supported by the Ministry of Education, Science and Technology of the Republic of Korea (Grant No. NRF-2012M2A8A5025824)the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (Grant No. 2012-0005727)
文摘The dual-cooled nuclear reactor is currently considered for improving the designs of current/future nuclear reactors. Investigation of the thermal-hydraulic characteristics of the nuclear reactor via experiments is essential for commercializing the dual-cooled nuclear reactor. In this paper, the turbulent flow in square arrayed six-rod bundles in the form of magnified copies of the dual-cooled and current OPR-1000 nuclear reactor is experimentally investigated by means of hot-wire anemometry and smoke-wire generation methods. Vortex trains which do not exist in an ordinary reactor subchannel are presented in the subchannel of the dual-cooled reactor. The vortices are induced by a span-wise velocity gradient. This flow pulsation phenomenon increases the inter-channel mixing of the subchannel. To understand the periodic feature of the pulsation, axial/cross velocities are measured and the periodic characteristic frequencies are obtained by a Fast Fourier Transform (FFT) analysis. The peak frequency that represents the quasi-periodic pulsation of the flow is increased with an increase in the axial velocity while the wavelength of the pulsation remains constant within a tested range of the Reynolds number (9000 51000). The vortex trains are highly synchronized with each other, as confirmed by means of visualization.
文摘In this paper a lumped parameter model of a two-pass gas-to-gas crossflow heat exchanger with high speed air flow has been presented for the investigation of its transieat behaviours. The effects of both the changes of inlet temperature and flow rate on outlet temperature can be predicted with this model.The calculation results under typical conditions are compared with experimental results and good agreements are obtained.
