In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless...In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless maximum thermal resistance as a performance index,and the heat transfer performance of the twice Y-shaped assemblies of fins under various conditions with different freedom degrees are analyzed. The results show that the twice assemblies can improve the heat transfer performance of Y-shaped fin remarkably,and the minimum maximum thermal resistance of the twice Y-shaped assemblies of fins decreases by 36.37% compared with that of once Y-shaped assembly of fins. It is also proved again that the larger the number of freedom degrees for evolving is,the more perfect the system performance is. The effects of different characteristic parameters of geometry on the performance of the twice Y-shaped assemblies of fins are different,one should pay different attention to these parameters in practical engineering designs. The effects of two angles on the maximum thermal resistance are larger,but the optima of the two angles are robust. The effects of two height ratios on the maximum thermal resistance are more remarkable than those of two thickness ratios.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.10905093)the Program for New Century Excellent Talents in University of China(Grant No.NCET-04-1006)the Foun-dation for the Author of National Excellent Doctoral Dissertation of China(Grant No.200136)
文摘In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless maximum thermal resistance as a performance index,and the heat transfer performance of the twice Y-shaped assemblies of fins under various conditions with different freedom degrees are analyzed. The results show that the twice assemblies can improve the heat transfer performance of Y-shaped fin remarkably,and the minimum maximum thermal resistance of the twice Y-shaped assemblies of fins decreases by 36.37% compared with that of once Y-shaped assembly of fins. It is also proved again that the larger the number of freedom degrees for evolving is,the more perfect the system performance is. The effects of different characteristic parameters of geometry on the performance of the twice Y-shaped assemblies of fins are different,one should pay different attention to these parameters in practical engineering designs. The effects of two angles on the maximum thermal resistance are larger,but the optima of the two angles are robust. The effects of two height ratios on the maximum thermal resistance are more remarkable than those of two thickness ratios.
文摘为了解饲喂壳聚糖后鲤鱼体内部分组织中壳聚糖的沉积情况，将210尾鲤鱼随机分为7组，即对照组和试验Ⅰ-Ⅵ组。试验Ⅰ-Ⅵ组饲料中分别添加0.50%、1.00%、1.50%、2.00%、3.00%、4.00%的壳聚糖，对照组饲喂常规饲料。正试期60 d，每隔10 d 分别从各试验组及对照组的每个重复中随机选取1尾鲤鱼，测定并比较不同处理组鲤鱼鱼鳞、鱼鳍、鱼肌肉组织中的壳聚糖沉积量。结果表明，随着养殖时间的延长和饲料中外源性壳聚糖添加量的增加，对照组和所有试验组鲤鱼的鱼鳞、鱼鳍、鱼肌肉组织中的壳聚糖沉积量均有不同程度的提高。但当饲料中外源性壳聚糖的添加量≥3.00%时，鱼鳞中壳聚糖沉积量的变化不显著（P＞0.05）；当添加量≥1.50%时，鱼鳍中壳聚糖沉积量的增加差异不显著（P＞0.05）；在相同的试验阶段，各试验组与对照组之间、各试验组之间鱼肌肉组织中壳聚糖的沉积量差异均不显著（P＞0.05）。结果提示，当饲料中外源性壳聚糖的添加量达到一定程度时，鱼鳞及鱼鳍中壳聚糖的沉积量不会随着添加量的增加而显著增加，且添加不同水平的外源性壳聚糖，对鲤鱼肌肉组织中壳聚糖沉积量的影响较小。
