4 replies to this topic

[gvdlans]

I agree that there is a mistake in there. The Souders-Brown equation reads:

velocity = k ((liquid density-vapor density)/vapor density)^0.5 (Equation 1)

which can be rewritten as:

velocity = k (liquid density/vapor density-1)^0.5 (Equation 2)

Which is not the same as what is shown in the experienced based rules:
velocity = k (liquid density/(vapor density-1))^0.5 (Equation 3)
(look at the location of the parenthesis!)

Since normally liquid density>>vapor density, equation (1) can be simplified to:
velocity = k (liquid density/vapor density)^0.5 (Equation 4)

Since the experienced bases rules are meant to use simple forms of equations, I would recommend to use equation (4).

A derivation of the Souders-Brown equation is given in Derivation of Souders Brown equation

[mbeychok]

TO: gvdlans

velocity = k ((liquid density-vapor density)/vapor density)^0.5 (Equation 1)

which can be rewritten as:

velocity = k (liquid density/vapor density-1)^0.5 (Equation 2)

Your are correct in saying that your Equation 1 can be re-written as Equation 2, but your Equation 2 can still be mis-interpreted. It still needs another set of brackets as follows:

velocity = ((liquid density/vapor density) - 1)^0.5

Regards,

[gvdlans]

To mbeychok:

Didn't we all learn at primary school the basic math rule that you have to divide before you subtract? Please Excuse My Dear Aunt Sally?! For those who do not remember, please have a look at Math Mojo!

You only use parenthesis in case you want to deviate from this basic rule. Since I did not want to deviate from the basic rule, I did not use parenthesis.

[mbeychok]

TO: gvdlans

My only rule is to write equations so that they cannot be misinterpreted ... if that is at all possible. Keep in mind that many readers may never have heard of any rules regarding the precedence of math operations.