3 replies to this topic

[rjsn]

I am attempting to calculate the volumetric flowrate water which is boiling inside the tubes of a water tube boiler. I know the mass flowrate of the water but do not know the density as I am not sure how much of the fluid is gas/liquid. Is there a way of calculating the density of the whole stream or the vapour fraction of the stream?

 

Many Thanks

[serra]

one can solve energy balance,

i.e. estimate heat transfer, dH, guess the new condition (and all related properties).

[samayaraj]

Hi,

 

Find attached steam table in excel sheet. You can find out various properties of water/steam at various conditions. There are few examples given in the first sheet for your reference. Look for the adjacent sheet for more commands. Enable macros before using this excel.

 

Hope this will help you.

Attached Files

•  Steam_Tables.xls   546KB   14 downloads

[shantanuk100]

Hi Rjsn,

 

1. You need atleast Two state properties of the steam (P,T etc) to be known for you to find out the other properties.

I am assuming you know the steam inlet conditions (Pressure and Temperature).

 

2. The important step in all these is to find out the Steam Quality (Vapor fraction) because all other properties depend on the vapor fraction. Specific properties (Per unit mass/volume) of the Steam at certain P,T can be found easily from steam tables, but for steam mixtures, we need to know vapor fraction to estimate the actual property value.

 

3. For this there are 2 steps. First use a Mollier Diagram (Pressure/Temp - Enthalpy diagram) for your inlet conditions.

This will give you the exact Enthalpy of your inlet mixture.

 

4. Then use that Enthalpy value and apply the mixture property formula :

 

H(mix) = H(pure vapor) X Vapor Fraction  +  H(saturate liquid/water) X (1-Vapor Fraction)

Hmix = Hvap*xvap + Hliq*xliq

 

5. Now in the above step, you can get the specific enthalpies Hvap, Hliq from the Steam Tables at your inlet conditions.

So you can calculate the actual vapor fraction of the fluid mixture you have.

 

6. Once you have the mixture vapor fraction, the rest of the properties can be calculated straight forward from the Steam Tables. Your density will me nothing but the reciprocal of the Mixture's specific volume.

 

7. This exercise is for you to understand how to calculate the properties. If you wish to get all the results at once, you can also use the steam tables that Samayaraj has been kind enough to attach, where even the vapor fraction is calculated in it.

 

Regards,

Shantanu Kallakuri

Edited by shantanuk100, 08 April 2016 - 12:57 AM.