Thermo question -- volumetric flows of dry steam and liquid water

1. Nov 12, 2014

snowwhite

1. The problem statement, all variables and given/known data

Given the rate of pipe= 100 kg/s

The steam flow has quality x= 80% = 0.8, pressure= 90 atm

Find the volumetric flows of dry steam and liquid water

2. Relevant equations.

https://www.physicsforums.com/file:///C:\Users\Toshiba\AppData\Local\Temp\msohtmlclip1\01\clip_image001.gif [Broken] Volumetric flow= Area * v where v is the rate of pipe 100 k/s

3. The attempt at a solution

Volumetric flow= Av= (1metre square)(100kg/s)= (100metres square)8kg)/s

The part that is confusing me is the steam quality. What for I need the steam quality in the problem? Is there any formula that relates the steam quality and rate of the pipe to calculate the volumetric flow of dry steam and liquid water?

I don’t know what the problem is giving me the quality and pressure?

Last edited by a moderator: May 7, 2017
2. Nov 12, 2014

Staff: Mentor

Do you know the definition of steam quality? If so, let's hear it.

Do you know how to determine the temperature?

I assume you are using the steam tables to solve this. Correct?

What is the specific volume of the liquid water and the specific volume of the vapor under these conditions?

Chet
P.S., this has nothing to do with the area of the pipe.

3. Nov 13, 2014

snowwhite

No. I don´t know how to find the temperature of both. Looking at the pressure 90 atm for the liquid water and vapor, I will find the temperature of both.Then I will determine the specific volume of both?
Yes, exactly, I´m using the steam tables.

4. Nov 13, 2014

snowwhite

Steam flows down a pipe at a rate of 100kg/s. The steam flow has a quality of
80% at 90 atm. Determine the volumetric flows of dry steam and liquid water.

5. Nov 13, 2014

snowwhite

By the way, I always do everything different from everybody else that why I´m different

6. Nov 13, 2014

Staff: Mentor

If water vapor and liquid water are present together in the flow stream, then the temperature is (a) the saturation temperature (and they are at the same temperature) or (b) not the saturation temperature?

Chet

7. Nov 13, 2014

snowwhite

The problem doesn´t mention if dry stream and liquid water are present together.

The problem only provides me rate of pipe 100kg/s. The quality x=80 % =0.80
and the pressure= 90 atm. Determine the volumetric flows of dry steam and liquid water.

do u know any formula to find the volumetric flow of dry steam and liquid water ?

8. Nov 13, 2014

Staff: Mentor

If they are in the same pipe, they must be present together, correct? Hint: they are at the saturation temperature at 90 atm.
If the quality is 80%, it means that 80% of the mass flow rate is steam and 20% of the mass flow rate is water.

From your steam tables, what is the specific volume of saturated steam at 90 atm, and what is the specific volume of saturated liquid water at 90 atm?

Chet

9. Nov 13, 2014

snowwhite

First, I convert the pressure given to bar.

so: 9 atmx (1.01325bar)/1atm = 91.1925 bar

I look these temperature in the steam table for specific volume of saturated steam and saturated liquid water, and these temperature does not appear.

so I need to interpolate.How can I do it?

10. Nov 13, 2014

Staff: Mentor

Linearly interpolate. That's good enough.

Chet

11. Nov 13, 2014

snowwhite

looking at the steam tables:

at 90 atm= 9MPA specific saturated steam volume is =0.001418metres cube/kg

In my steam tables does not appear saturated liquid water volme. How can I find it?

12. Nov 13, 2014

Staff: Mentor

Look harder. It should be there. See the table Further Properties of Water and Steam.

Chet

Last edited: Nov 13, 2014
13. Nov 13, 2014

snowwhite

can u please provide me a web page to look at the specific volume of saturated liquid water at 9 MPa? or a good steam tables web page to look at it?

I have books with steam tables, steam tables in pdf and really DOES NOT APPEAR LIQUID WATER.

WHAT APPEARS ITS COMPRESSED WATER.?IS THAT IT?

14. Nov 13, 2014

Staff: Mentor

Probably, but in the tables you linked in one of your posts, the relevant section is Further Properties of Water and Steam

15. Jan 18, 2015

DownShift

Does this question only require you to find Vf and Vg?

16. Jan 18, 2015

Staff: Mentor

No. Suppose you have 100 kg of this mixture. We want to find the volume of this 100 kg of mixture. Knowing the quality, how many kg of vapor are there? How many kg of liquid are there? Knowing Vf and Vg, how many cubic meters of vapor are there. How many cubic meters of liquid are there? What's the total volume of the 100 kg mixture?

Chet

17. Jan 19, 2015

Thanks