2

I would have posted this in Chemical or Petroleum Engineering board, but they don't exist.

The following webpage (http://www.fekete.com/SAN/WebHelp/Piper/WebHelp/c-te-pressure.htm) gives the calculation of $N_{vl}$ (Liquid Velocity Number) as:

$N_{vl} = 1.938 V_{sl} \left(\frac{\rho_L}{g\sigma}\right)^{0.25}$

This is supposed to be a dimensionless number, and I assumed that if all the entities were put in in their SI form, there would be no upfront constant. That is $V_{sl}$ in $\frac{m}{s}$, $\rho_L$ in $\frac{kg}{m^3}$, $g$ in $\frac{m}{s^2}$ and $\sigma$ in $\frac{N}{m}$.

However when these quantities are entered in the appropriate field units ($\frac{ft}s$, $\frac{lb}{ft^3}$, $\frac{ft}{s^2}$, $\frac{dyne}{cm}$) and the upfront constant calculated from the relevant conversion factors, it does not turn out to be 1.938, rather 4.615.

What am I missing?

Adrian
  • 424

1 Answers1

1

The website has an error. The correct equation is:

$N_{vl} = 1.938 V_{sl} \left(\frac{\rho_L}{\sigma}\right)^{0.25}$

The gravitational constant $g$ is bundled into the constant. So the new constant becomes:

$\frac{4.615}{32.174^{0.25}} \approx 1.938$

Adrian
  • 424