2 replies to this topic

[Sakthi Vel]

Dear Experts,

 

Can anyone explain the Gas Reynolds number factor below:

 

Re = K Re Gg

 

Where,

K Re = Gas properties factor, m² hr/ Kg

Gg = gas mass flux, Kg / m² hr which is used for performance analysis of air pre heater.

 

Regards,

Sakthi

[shantanuk100]

Hi Sakthi Vel,

 

1. The K Re is actually not K*Re but K suffix(Re).

This is a factor defined for a Gas, as a single value to account for the effect of Gas Properties.

 

2. Gg is the Mass flux which is nothing but the Mass flow Rate per Unit area.

 

3. Your reynolds number is actually nothing but the ratio of the inertial forces on a liquid to the viscous forces on the liquid. It measures the relative importance of each. 

 

4. It is usually written as Re = Rho * v * L / Mu where L is characteristic length where for pipe flow - L=D etc., v=velocity, Mu = dynamic viscosity

 

5. The other way of writing this Re = Rho * v * D / Mu  is also as  Re = G.D / Mu where G is the mass flux of flow or the Mass flow / sec / unit area.

 

6.  From this, they have defined the gas properties parameter as K = D/Mu. 

 

Regards,

Shantanu

Edited by shantanuk100, 27 April 2016 - 12:07 AM.

[Mahdi1980]

Sakthi

 

For a fluid through a duct or pipe as you know :

 

Re= (Rho).V.d/(mu)    that mu= gas viscosity and Rho= gas density

V=Q/A

That Q is volumetric flow rate (m3/hr)  and A is cross sectional area of duct (m2)

By substituting the 2nd equation into the 1st one  we have:

Re= (Rho).(Q/A).d/(mu)

by defining Gg as Mass flux we can get result that Gg=(Rho).(Q/A)

So:

Re= Gg.d/(mu)

from the above equation you can understand that Gg is Gas mass flux and K_Re= d/(mu) is the gas properties factor as mu is one of the important properties of gas.

 

Mahdi

Edited by Mahdi1980, 23 April 2016 - 05:08 AM.