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

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Discussion Overview

The discussion revolves around calculating the volumetric flows of dry steam and liquid water in a pipe given specific conditions, including mass flow rate, steam quality, and pressure. Participants explore the relationship between steam quality, specific volumes, and the necessary equations to solve the problem, with a focus on using steam tables.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant states the mass flow rate of steam is 100 kg/s with a quality of 80% at 90 atm and seeks to find the volumetric flows of dry steam and liquid water.
  • Another participant asks for the definition of steam quality and suggests using steam tables to determine the specific volumes of liquid water and vapor under the given conditions.
  • Some participants express uncertainty about how to find the temperature of the steam and liquid water at the specified pressure and discuss the implications of steam quality on the calculations.
  • There are questions about whether dry steam and liquid water are present together in the flow stream and how this affects the temperature and specific volumes.
  • One participant mentions needing to interpolate specific volumes from the steam tables as the exact values do not appear for the given pressure.
  • Another participant requests resources for steam tables and expresses frustration about not finding the specific volume of saturated liquid water at 9 MPa.
  • There is a discussion about calculating the total volume of a mixture of vapor and liquid based on the quality and specific volumes.

Areas of Agreement / Disagreement

Participants generally agree on the need to use steam tables and the importance of steam quality in the calculations. However, there is disagreement and uncertainty regarding the presence of dry steam and liquid water together, the specific volumes at the given pressure, and the methods for interpolation.

Contextual Notes

Participants express limitations in accessing specific values in steam tables and the need for interpolation. There is also a lack of clarity regarding whether the steam and liquid are at saturation temperature and how to approach the calculations based on the provided quality.

snowwhite
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1. Homework Statement

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 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?
 
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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.
 
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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.
 
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.
 
By the way, I always do everything different from everybody else that why I´m different
 
snowwhite said:
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.
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
 
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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 ?
 
snowwhite said:
The problem doesn´t mention if dry stream and liquid water are present together.
If they are in the same pipe, they must be present together, correct? Hint: they are at the saturation temperature at 90 atm.
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.
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
 
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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
snowwhite said:
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?
Linearly interpolate. That's good enough.

Chet
 
  • #11
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
snowwhite said:
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?
Look harder. It should be there. See the table Further Properties of Water and Steam.

Chet
 
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  • #13
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
snowwhite said:
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?
Probably, but in the tables you linked in one of your posts, the relevant section is Further Properties of Water and Steam
 
  • #15
Does this question only require you to find Vf and Vg?
 
  • #16
DownShift said:
Does this question only require you to find Vf and Vg?
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
Chestermiller said:
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

Thanks
 

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