In industrial plants, ships, and buildings, a large amount of gas and air ducts are applied for equipment connection, HVAC, medium transport, and exhaust, etc. These ducts can be designed in varied cross-sectional sha...In industrial plants, ships, and buildings, a large amount of gas and air ducts are applied for equipment connection, HVAC, medium transport, and exhaust, etc. These ducts can be designed in varied cross-sectional shapes, such as round or rectangle. The author reveals through geometric calculation of the duct cross-sectional shapes and engineering experiences that the round cross-section is an optimal shape in the duct system. The round duct has the shorter perimeter than the other cross-sectional shape ducts and the stronger structure in the same working condition. The material saving of the round duct due to the shorter perimeter is quantitatively determined. In the pater, it is shown that the round duct is economically attractive. The economic analysis for the material cost saving is illustrated by an example. For a long duct system, the material and material cost savings are significant. It is suggested that the round duct in the gas and air duct system should have priority as long as the field conditions are allowed. In the paper, the material cost saving is also converted to PW, AW, and FW used for LCC economic analysis.展开更多
The objective of this work is to estimate the accuracy of a predicted velocity profile which can be gained from experimental results, in comparison with the exact ones by the methodology of entropy generation. The ana...The objective of this work is to estimate the accuracy of a predicted velocity profile which can be gained from experimental results, in comparison with the exact ones by the methodology of entropy generation. The analysis is concerned with the entropy generation rate in hydrodynamic, steady, laminar, and incompressible flow for Newtonian fluids in the insulated channels of arbitrary cross section. The entropy generation can be calculated from two local and overall techniques. Adaptation of the results of these techniques depends on the used velocity profile. Results express that in experimental works, whatever the values of local and overall entropy generation rates are close to each other, the results are more accuracy. In order to extent the subject, different geometries have been investigated. Also, the influence studied, and the distribution of volumetric geometries is drawn. of geometry on the entropy generation rate is local entropy generation rate for the selected geometries is drawn.展开更多
The turbulent flow-field characteristics in a 180° curved duct with rectangular cross-section were investigated.The profiles of tangential velocity and pressure were measured by using five-hole probe and simulate...The turbulent flow-field characteristics in a 180° curved duct with rectangular cross-section were investigated.The profiles of tangential velocity and pressure were measured by using five-hole probe and simulated by FLUENT 6.2.The results showed that centrifugal force was generated as the fluid rotated,which contributed to the change of tangential velocity and pressure.Tangential velocity increased and pressure decreased in the section between 0° and 60° when the fluid rotation began,while tangential velocity decreased and pressure increased in the section between 60° and 180° near the inner wall.On the contrary,the tangential velocity decreased and pressure increased in the section between 0° and 60°,but tangential velocity increased and pressure decreased in the section between 60° and 180° near the outer wall.This investigation indicated that turbulent flow-field characteristics in the 180° curved duct could be understood by combined experiment measurement and numerical simulation.展开更多
文摘In industrial plants, ships, and buildings, a large amount of gas and air ducts are applied for equipment connection, HVAC, medium transport, and exhaust, etc. These ducts can be designed in varied cross-sectional shapes, such as round or rectangle. The author reveals through geometric calculation of the duct cross-sectional shapes and engineering experiences that the round cross-section is an optimal shape in the duct system. The round duct has the shorter perimeter than the other cross-sectional shape ducts and the stronger structure in the same working condition. The material saving of the round duct due to the shorter perimeter is quantitatively determined. In the pater, it is shown that the round duct is economically attractive. The economic analysis for the material cost saving is illustrated by an example. For a long duct system, the material and material cost savings are significant. It is suggested that the round duct in the gas and air duct system should have priority as long as the field conditions are allowed. In the paper, the material cost saving is also converted to PW, AW, and FW used for LCC economic analysis.
基金partly supported by a grant from the Center of Excellence on Modeling and Control Systems (CEMCS) of Ferdowsi University of Mashhad,Iran
文摘The objective of this work is to estimate the accuracy of a predicted velocity profile which can be gained from experimental results, in comparison with the exact ones by the methodology of entropy generation. The analysis is concerned with the entropy generation rate in hydrodynamic, steady, laminar, and incompressible flow for Newtonian fluids in the insulated channels of arbitrary cross section. The entropy generation can be calculated from two local and overall techniques. Adaptation of the results of these techniques depends on the used velocity profile. Results express that in experimental works, whatever the values of local and overall entropy generation rates are close to each other, the results are more accuracy. In order to extent the subject, different geometries have been investigated. Also, the influence studied, and the distribution of volumetric geometries is drawn. of geometry on the entropy generation rate is local entropy generation rate for the selected geometries is drawn.
文摘The turbulent flow-field characteristics in a 180° curved duct with rectangular cross-section were investigated.The profiles of tangential velocity and pressure were measured by using five-hole probe and simulated by FLUENT 6.2.The results showed that centrifugal force was generated as the fluid rotated,which contributed to the change of tangential velocity and pressure.Tangential velocity increased and pressure decreased in the section between 0° and 60° when the fluid rotation began,while tangential velocity decreased and pressure increased in the section between 60° and 180° near the inner wall.On the contrary,the tangential velocity decreased and pressure increased in the section between 0° and 60°,but tangential velocity increased and pressure decreased in the section between 60° and 180° near the outer wall.This investigation indicated that turbulent flow-field characteristics in the 180° curved duct could be understood by combined experiment measurement and numerical simulation.
