Approximate Optimum Fin Design for Boiling Heat Transfer

1971 ◽  
Vol 93 (1) ◽  
pp. 19-23 ◽  
Author(s):  
D. R. Cash ◽  
G. J. Klein ◽  
J. W. Westwater
Keyword(s):  
Cross Section ◽  
Atmospheric Pressure ◽  
Design Method ◽  
Circular Cross Section ◽  
Film Boiling ◽  
Optimum Shape ◽  
Base Temperature ◽  
Extended Surfaces ◽  
Predicted Values ◽  
Fin Design

For extended surfaces used in boiling liquids, the specified fin-base temperature may be such as to result in simultaneous nucleate, transition, and film boiling at adjacent positions on the fins. If the fins are spines of circular cross section, the optimum shape to minimize the volume of metal resembles a turnip, as shown by Haley and Westwater. The object of the new study was to develop easy-to-machine shapes using cones and cylinders. It was shown mathematically that two cones, base-to-base, give an excellent approximation to the turnip shape. Three such fins were constructed of copper and tested in Freon-113 at atmospheric pressure. The measured, peak heat duties were 5 to 70 percent higher than the predicted values, proving that the design method is conservative.

Differential Equations Governing the Geometry of a Diamond Mesh Cod-end of a Trawl Net

1997 ◽  
Vol 64 (1) ◽  
pp. 7-14 ◽  
Author(s):  
F. G. O’Neill
Keyword(s):  
Differential Equations ◽  
Cross Section ◽  
Good Description ◽  
Circular Cross Section ◽  
Mesh Size ◽  
Force Balance ◽  
Special Cases ◽  
Theoretical Predictions ◽  
Predicted Values ◽  
Simple Points

A new surface, made up of an infinite number of infinitesimal meshes, is defined to approximate the cod-end. The force balance on a mesh element of this surface is considered in the limit as the mesh size tends to zero and the differential equations governing the geometry of a diamond meshed cod-end of circular cross section are derived in cartesian coordinates. The parametric form of the equations in terms of a, the distance along the cod-end profile, is then deduced and some special cases examined. In particular the case of a partially filled cod-end hanging under gravity is investigated and experimental measurements are compared with numerically obtained theoretical predictions. The numerical results are shown to provide a good description of the cod-end geometry except where the cod-end diameter is at its narrowest where there is a systematic departure of the predicted values from those measured. It is demonstrated that a probable explanation of this discrepancy is the assumption that the knots are simple points of intersection rather than finite well-defined structures.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

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