Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enh...Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enhanced thermo-hydraulic performance. Thermo-hydraulic design of CHEs （Compact heat exchangers） is strongly dependent upon the predicted/measured dimensionless performance （Colburnj factor and Fanning friction vs. Reynolds number） of heat transfer surfaces. This paper describes the numerical analysis to study the heat transfer coefficient and friction factor of Serrated fins in water medium. CFD （Computational fluid dynamics） methodology has been used to develop the single phase water heat transfer coefficient and friction factor correlations for serrated fins using ANSYS Fluent 14.5. The results are compared with previous air-cooled models and experimental results of water. The water cooled CFD analysis results shows that the Prandtl number has a large effect on the Nusselt number of the serrated fin geometry. Finally, the generalized correlations are developed for serrated fins taking all geometrical parameters into account. This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications.展开更多
Aims Leaf size and shape as objects of natural selection can play adaptive roles,and can change with the age of leaves.They can differ between sexes in dioecious species,and in most cases,females have larger leaves.Pr...Aims Leaf size and shape as objects of natural selection can play adaptive roles,and can change with the age of leaves.They can differ between sexes in dioecious species,and in most cases,females have larger leaves.Previous studies showed that sexes of Adriana tomentosa differed in their leaf lobing.In this study,we investigated whether there were other differences between sexes in leaf size,shape and ecophysiology,and if those differences were connected with adaptations and reproductive roles in the sexes of A.tomentosa.Methods Physical and chemical features of young and old leaves originating from female and male A.tomentosa plants growing in two disjunct populations in eastern Australia were measured.We determined leaf area,perimeter length,serration,circularity,aspect ratio(AR),roundness and the ecophysiological factors:specific leaf area,dry matter content,leaf moisture,relative water content,δ^(13)C,δ^(15)N isotope compositions,carbon and nitrogen contents and C:N ratio.Leaf lobing,the degree of lamina damage and the content of photosynthetic pigments were also determined.Important Findings In both populations studied,the sex of plants significantly influenced almost all parameters connected with leaf morphology such as area,perimeter length,circularity,AR and roundness.Contrary to expectations,males from both populations had a greater leaf area that was independent of leaf age.Male leaves were more lobed with a longer perimeter,but they were less elongated and less serrated.Only small differences between female and male leaves were observed for the ecophysiological factors.The degree of leaf damage differed between sexes but also with population.Differences between sexes in leaf area and shape were not compensated by measured ecophysiological factors.However,leaf area may be compensated by other ecophysiological mechanisms related to leaf morphology,because females had greater leaf serration in comparison to males despite the smaller leaf area.展开更多
文摘Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enhanced thermo-hydraulic performance. Thermo-hydraulic design of CHEs （Compact heat exchangers） is strongly dependent upon the predicted/measured dimensionless performance （Colburnj factor and Fanning friction vs. Reynolds number） of heat transfer surfaces. This paper describes the numerical analysis to study the heat transfer coefficient and friction factor of Serrated fins in water medium. CFD （Computational fluid dynamics） methodology has been used to develop the single phase water heat transfer coefficient and friction factor correlations for serrated fins using ANSYS Fluent 14.5. The results are compared with previous air-cooled models and experimental results of water. The water cooled CFD analysis results shows that the Prandtl number has a large effect on the Nusselt number of the serrated fin geometry. Finally, the generalized correlations are developed for serrated fins taking all geometrical parameters into account. This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications.
基金supported by the Department of Education and Training,Australian Government(Endeavour Research Fellowship,2017 to M.R.),the University of New England in Armidale,Australia and the Institute of Dendrology,Polish Academy of Sciences,Poland.
文摘Aims Leaf size and shape as objects of natural selection can play adaptive roles,and can change with the age of leaves.They can differ between sexes in dioecious species,and in most cases,females have larger leaves.Previous studies showed that sexes of Adriana tomentosa differed in their leaf lobing.In this study,we investigated whether there were other differences between sexes in leaf size,shape and ecophysiology,and if those differences were connected with adaptations and reproductive roles in the sexes of A.tomentosa.Methods Physical and chemical features of young and old leaves originating from female and male A.tomentosa plants growing in two disjunct populations in eastern Australia were measured.We determined leaf area,perimeter length,serration,circularity,aspect ratio(AR),roundness and the ecophysiological factors:specific leaf area,dry matter content,leaf moisture,relative water content,δ^(13)C,δ^(15)N isotope compositions,carbon and nitrogen contents and C:N ratio.Leaf lobing,the degree of lamina damage and the content of photosynthetic pigments were also determined.Important Findings In both populations studied,the sex of plants significantly influenced almost all parameters connected with leaf morphology such as area,perimeter length,circularity,AR and roundness.Contrary to expectations,males from both populations had a greater leaf area that was independent of leaf age.Male leaves were more lobed with a longer perimeter,but they were less elongated and less serrated.Only small differences between female and male leaves were observed for the ecophysiological factors.The degree of leaf damage differed between sexes but also with population.Differences between sexes in leaf area and shape were not compensated by measured ecophysiological factors.However,leaf area may be compensated by other ecophysiological mechanisms related to leaf morphology,because females had greater leaf serration in comparison to males despite the smaller leaf area.
