The effect of solidification cooling rate on the size and distribution of inclusions in 12%Cr stainless steel was investigated. A wide range of solidification cooling rates（from 0.05 to 106 K·s^-1） was achieved...The effect of solidification cooling rate on the size and distribution of inclusions in 12%Cr stainless steel was investigated. A wide range of solidification cooling rates（from 0.05 to 106 K·s^-1） was achieved using various solidification processes, including conventional casting, laser remelting, and melt spinning. The size and distribution of inclusions in the steel were observed and statistically collected. For comparison, mathematical models were used to calculate the sizes of inclusions at different solidification cooling rates. Both the statistical size determined from observations and that predicted from calculations tended to decrease with increasing cooling rate; however, the experimental and calculated results did not agree well with each other at excessively high or low cooling rate. The reasons for this discrepancy were theoretically analyzed. For the size distribution of inclusions, the effect of cooling rate on the number densities of large-sized（〉 2 μm） inclusions and small-sized（≤ 2 μm） inclusions were distinct. The number density of inclusions larger than 1 μm was not affected when the cooing rate was less than or equal to 6 K·s^-1 because inclusion precipitation was suppressed by the increased cooling rate.展开更多
Extra cooling pads on the sidewalls are needed for larger poultry houses using tunnel ventilation system.Preliminary study showed that the airflow velocity going through different aisles varies greatly when the extra ...Extra cooling pads on the sidewalls are needed for larger poultry houses using tunnel ventilation system.Preliminary study showed that the airflow velocity going through different aisles varies greatly when the extra pads are installed at the end of sidewalls,making a“[”-shape air inlet.Combined with field tests,the CFD(computational fluid dynamics)technology was used to study the uniformity of airflow distribution in a tunnel-ventilated laying-hen house.The air distribution was first monitored in a layer house to find the main reason resulting in the variations of airflows in different aisles.Then CFD simulations were carried out with different distances(D=2 m,3 m or 4 m)between the pads on end-wall and the extra pads on side walls.The field test showed that airflow streams from the different groups of cooling pads collided vertically at the house corners,mixed with each other,then flew towards the center of the house.This was the main reason that the wind speed in the middle aisle was much higher than in other aisles,leaving large zones of lower ventilation in the aisles adjacent to the sidewalls.The results of CFD simulations indicated that air distributions could be significantly improved when the extra pieces of pads were moved away for an appropriate distance from the end coolingpads.As far as conventional poultry house with a span of 12 m,the air speeds in different aisles were more uniform when this distance was about 3 m.展开更多
基金financially supported by the National Basic Research Program of China (No. 2011CB012900)
文摘The effect of solidification cooling rate on the size and distribution of inclusions in 12%Cr stainless steel was investigated. A wide range of solidification cooling rates（from 0.05 to 106 K·s^-1） was achieved using various solidification processes, including conventional casting, laser remelting, and melt spinning. The size and distribution of inclusions in the steel were observed and statistically collected. For comparison, mathematical models were used to calculate the sizes of inclusions at different solidification cooling rates. Both the statistical size determined from observations and that predicted from calculations tended to decrease with increasing cooling rate; however, the experimental and calculated results did not agree well with each other at excessively high or low cooling rate. The reasons for this discrepancy were theoretically analyzed. For the size distribution of inclusions, the effect of cooling rate on the number densities of large-sized（〉 2 μm） inclusions and small-sized（≤ 2 μm） inclusions were distinct. The number density of inclusions larger than 1 μm was not affected when the cooing rate was less than or equal to 6 K·s^-1 because inclusion precipitation was suppressed by the increased cooling rate.
基金the China Agricultural Research System(CARS-41)and the National“Twelfth-Five Year”Research Program of China under Grant Number 2012BAD39B02.
文摘Extra cooling pads on the sidewalls are needed for larger poultry houses using tunnel ventilation system.Preliminary study showed that the airflow velocity going through different aisles varies greatly when the extra pads are installed at the end of sidewalls,making a“[”-shape air inlet.Combined with field tests,the CFD(computational fluid dynamics)technology was used to study the uniformity of airflow distribution in a tunnel-ventilated laying-hen house.The air distribution was first monitored in a layer house to find the main reason resulting in the variations of airflows in different aisles.Then CFD simulations were carried out with different distances(D=2 m,3 m or 4 m)between the pads on end-wall and the extra pads on side walls.The field test showed that airflow streams from the different groups of cooling pads collided vertically at the house corners,mixed with each other,then flew towards the center of the house.This was the main reason that the wind speed in the middle aisle was much higher than in other aisles,leaving large zones of lower ventilation in the aisles adjacent to the sidewalls.The results of CFD simulations indicated that air distributions could be significantly improved when the extra pieces of pads were moved away for an appropriate distance from the end coolingpads.As far as conventional poultry house with a span of 12 m,the air speeds in different aisles were more uniform when this distance was about 3 m.
