Why r traiangular/tapered longtudinal fins better than straight fins

[smukthiHT]

Hi All,

Why r triangular/tapered longtudinal fins more efficient than straight fins from a convection heat transfer standpoint? Could any one please let me know. I have done some literature search and all i could find is analyical equations which ay that trainagular/tapered fins are better than straight longitudnal fins. I am trying to understand the physcis would could have lead to that. Please comment.

Thanks
Sridhar

 

[racookpe1978]

Draw a tall triangular fin, with the wide side attached to a hot plate or tube, the two sides surrounded by a cooler air flow.

Heat "enters" the wide side of the triangle, flows up the ever-narrowing fin towards the cooler tip, right? The amount of cross section "area" of the fin decreases as the amount of energy that crosses each length of the fin decreases. Weight goes down, mass of metal needed goes down. Expense per fin might go up - depends on how you make the fins.

Is the decreased weight and slightly improved performance worth the effort? Depends.

 

[Compositepro]

Tapering the thickness of the fin will slightly increase the resistance to heat flow through the fin from base to the tip. However, it increases the gap between fins allowing more air flow. It is with closely spaced fins that the tapering becomes important. Tapering will also somewhat improve radiative cooling because the hotter base of the fins will be more exposed to cooler space.

 

[gruntguru]

The tapered fin also offers a much higher ratio of bending strength to self-weight, which is important for fatigue life in vibrating machinery - motors, IC engines, heat exchangers etc.

je suis charlie

 

[racookpe1978]

Well, if you get into the manufacturing side of the house, castings MUST have slightly angled fins (the molds are sloped) to allow the two halves to be separated. It's called a draft.

 

[Dougt115]

Thin fins weigh less than fat fins.

The heat conducted through the fin is a function of the cross sectional area. Fat high flux, thin low flux

By using tapered fins you save weight, get better air flow, and be injection molded and still have good heat sinking.