Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hi...Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.展开更多
Dry coal beneficiation using an air dense medium fluidized bed (ADMFB) requires the formation of a sta- ble and uniform bed from the dense medium. Others have shown that the structure and geometric parameters of the a...Dry coal beneficiation using an air dense medium fluidized bed (ADMFB) requires the formation of a sta- ble and uniform bed from the dense medium. Others have shown that the structure and geometric parameters of the air distributor have a significant influence on the experimentally observed fluidization quality. In this study we used a sintered metal distributor (SMD) in the ADMFB separator and study its effect on the fluidization quality. The results show that for the same open area ratio (OAR), a smaller aper- ture in the SMD will provide improved fluidization quality. If aperture size is held constant bigger open area ratios result in improved fluidization quality. And, the fluidization quality also improves when the pressure drop across the SMD increases. A model relating distributor pressure drop and the geometric parameters of the SMD is also proposed.展开更多
An experimental investigation was conducted to measure the temperature variation across the flow channel and to determine the performance of a natural convection solar air heater at various tilt angles from 15, 30 and...An experimental investigation was conducted to measure the temperature variation across the flow channel and to determine the performance of a natural convection solar air heater at various tilt angles from 15, 30 and 45°. The results of the temperature profile across the air gap showed that heat transfer from the absorber plate to the air stream was mainly by convection. At a particular section, mean air temperature could be calculated from the arithmetic mean of the temperature profile across the air gap to within ± 2 ℃. The axial air temperature distribution was non linear and did not increase much beyond 1 m of collector length. It tended to decrease towards the end of the collector. Overall glass, absorber plate and mean air temperatures over the entire length of the solar air heater could be determined by averaging the mean axial temperatures to within ± 2 ℃. The heater performed better as inclination increased.展开更多
文摘Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.
基金The financial support by the Natural Science Foundation of China for Innovative Research Group (No. 50921002) and Key Projects(No. 51134022) in Coal Joint Fund provided by National Natural Science Foundation-Shenhua Group
文摘Dry coal beneficiation using an air dense medium fluidized bed (ADMFB) requires the formation of a sta- ble and uniform bed from the dense medium. Others have shown that the structure and geometric parameters of the air distributor have a significant influence on the experimentally observed fluidization quality. In this study we used a sintered metal distributor (SMD) in the ADMFB separator and study its effect on the fluidization quality. The results show that for the same open area ratio (OAR), a smaller aper- ture in the SMD will provide improved fluidization quality. If aperture size is held constant bigger open area ratios result in improved fluidization quality. And, the fluidization quality also improves when the pressure drop across the SMD increases. A model relating distributor pressure drop and the geometric parameters of the SMD is also proposed.
文摘An experimental investigation was conducted to measure the temperature variation across the flow channel and to determine the performance of a natural convection solar air heater at various tilt angles from 15, 30 and 45°. The results of the temperature profile across the air gap showed that heat transfer from the absorber plate to the air stream was mainly by convection. At a particular section, mean air temperature could be calculated from the arithmetic mean of the temperature profile across the air gap to within ± 2 ℃. The axial air temperature distribution was non linear and did not increase much beyond 1 m of collector length. It tended to decrease towards the end of the collector. Overall glass, absorber plate and mean air temperatures over the entire length of the solar air heater could be determined by averaging the mean axial temperatures to within ± 2 ℃. The heater performed better as inclination increased.
