Laminar Flow versus Turbulant Flow

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zelph
Posts: 15746
Joined: Tue Aug 14, 2007 1:53 pm

Re: Laminar Flow versus Turbulant Flow

Postby zelph » Fri Sep 19, 2008 1:17 pm

seudo_411 wrote:Hi guys, Been away for a while,, and the top the outlet with gauze as this will reduce the gas velocity and allow more contact with the pot. looking to get a Jetoil PCS type cup with heat exchanger.

Here's the Quick and Dirty drawing.

Image

I would appreciate any input you guys have.


Good to have you back and good to see you still are stove designing. :D

Putting gauze in the top outlet is going to act just like the simmer ring. Reduce oxygen flow.

Nice going on the purchase of Jetboil PCS type cup. I need to treat myzelph better and me one. :D
"Nothing Ventured Nothing Gained" stove store = http://www.woodgaz-stove.com/

BrokenAeroVT
Posts: 54
Joined: Fri Sep 18, 2009 5:49 pm

Re: Laminar Flow versus Turbulant Flow

Postby BrokenAeroVT » Sat Sep 19, 2009 12:19 am

Turbulent flow around the pot is more desirable because the boundary layer allows for greater heat transfer between the gas and the pot.

The purpose of jets is to draw in air by the Venturi Effect. Fast moving air creates vacuum that draws air into it. If the flame has no jet to draw air in, the flame will grow to increase the area of the combustion surface until it does burn up. If it grows too large, the flame cools and becomes yellow. A compact hot blue flame is more desirable.

The type of jet determines how much velocity is conserved. If the jet is just a hole in sheet aluminum, the velocity will drop 60% due to the back pressure created outside the hole. Nozzles are more efficient, keeping about 98% of their velocity for the same flow. A faster jet draws in more air.

A brilliant blue flame with a violet aura is ideal and indicates that a jet is drawing in a stoichiometric balance of air to fuel. The air to fuel ratio for methanol is 6.45 : 1. Increasing that 5 to 10% is common practice to guarantee full combustion.


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