12 replies to this topic

[Ankit_Kumar]

I am in the process of sizing RO for portable water service. Appreciate if someone can tell me that what is the limit for Beta ratio and flow coefficient for RO? Do we need to calculate Noise factor? If yes, how to calculate it?

Below is the calculations. Appreciate if someone can review and provide feedback.

 

Regards

 

Edited by Ankit_Kumar, 23 December 2015 - 05:53 AM.

[Lucian Gomoescu]

Hello,

According my calculations, the results are:

Discharge coeff.: 0.58;
Orifice diameter: 71.81 mm;
d1/d2: 0.354;

Crane Flow Coefficient:160;
cavitation index: 1.6 (< 2, thus cavitation may occur).

BR,
Lucian

[Ankit_Kumar]

@Lucian

 

Thanx for response. u r right. I checked my calculations and found the error.

 

Can you tell me how you calculated cavitation index and Crane Flow Coefficient?

 

Also what is the range of discharge coefficient, d1/d2 and crane flow coefficient ??

 

Regards

[S.AHMAD]

Hi

My calculation showed orifice diameter of 122.5 mm can let the pressure from 3 to 0.5 kg/cm2.

 

I attached the excel-file of previous version hoping you can oprn

[S.AHMAD]

Hi,

My computation showed an orifice of 71 mm Attached excel file fou you to check I am using C=0.625 at Re>4X10^{4._{. This Re is based on orifice diameter.}}

 

^_s.ahmad

 

Attached Files

•  orificerev3.xls   71KB   155 downloads

[S.AHMAD]

Normally beta between 0.2 and 0.7 is acceptable for orifice meter. However, if the noise is not acceptable you can install 2 or more RO i series.

 

Regads

 

s.amad

[Ankit_Kumar]

Many Thanks S Ahmad. 

 

Can you tell me how cavitation index and Crane Flow Coefficient is calculated? what is the importance?

[S.AHMAD]

Kumar pls see attached excel fil orificesize . The C value i However I am not fimilisr with csvitstion index but it is good idea for you to calculate the pressure at the orofice using Bernaulli's equation to ensure that the pressure is well above the vapor pressure at conditions.

 

 

s.ahmad

 

Attached Files

•  Orificesiize.xlsx   115.3KB   122 downloads

[Ankit_Kumar]

Many Thanks. I almost got 4 different spread sheets now to calculate orifice dia or flow whichever is required.

 

Just one Q. In 2ns sheet, at cell F11, orifice dia was calaulated? Why? As orifice dia is again being calculated at cell D13?  

[Lucian Gomoescu]

Hello,

Cavitation index is defines as the ratio (P2-Pv)/(P2-P1), where: P2, P1 are the upstream, respectively downstream static pressure (both locations being far enough from orifice in order to have a fully developed velocity field); Pv - liquid vapor pressure @ upstream temperature.

A value of at least 2 gives a safe margin from cavitation conditions. It isn't easy to accurately predict what is the minimum static pressure achieved along the fluid flow path from upstream to downstream, that's why this index value is used to determine if cavitation occurs or not.

The formula for Crane flow coefficient is attached. This coefficient can be used together with the other fittings' K values, e.g. if you want to determine pressure drop on a pipeline containing that restriction orifice.

Lucian

 

 

 

 

Attached Files

•  Orifice Crane K.PNG   9.54KB   38 downloads

[Ankit_Kumar]

Dear Lucian & Ahmad

 

I have done calculation for RO sizing based on the following values.

 

My main concern is regarding Reynold Number which is too much high. Can you guide is this point of concern? If yes, what is the solution?

[Ankit_Kumar]

Kindly reply

[breizh]

http://www.engineeri...turi-d_590.html

 

Your calculation is correct , the viscosity and density of your product are low ( based on temperature) , nothing wrong there ..Reynolds number is a consequence .

 

Breizh