Non-flow process with steam (Constant Pressure)

[voko]

I am not sure what problem you are trying solve now. Doing one at a time could be helpful.

 

[freshbox]

I am trying to solve:

In a closed system, 0.05.kg of dry saturated steam is heated at a constant pressure of 8 bar until the volume is occupied is 0.018m3
(A)Calculate the change in internal energy, the work energy transferred and the heat energy transferred during the process.

You told me to use perfect gas law to solve it, but i thought this question is about non-flow process with steam?

To solve using perfect gas law from the formula sheet:U₂-U₁=mc_v(T₂-T₁), C_v is not given at all, how do I solve?

 

[voko]

Do you have tables for superheated steam?

 

[freshbox]

Yes. How do you know it has turned into superheated or remain as dry saturated steam?


Thanks!

 

[voko]

What is "superheated steam" in your book?

 

[freshbox]

The specific properties of a superheated steam are normally tabulated in separate tables for selected values of pressure and temperature. For steam in the superheated region, temperature and pressure are independent properties. When the temperature and pressure are given for superheated steam then the state is defined and all the properties can be found.

 

[voko]

Yes, that is fine, but how does one MAKE superheated steam?

 

[freshbox]

From 1 of my book example, it says ts2>ts (stage 2 temp > stage 1) to be superheated.

So for this question, stage 1 at 8 bar=170.4°C. I am only given Stage 2 volume which is 0.018m³. How can I use it to help me find the temperature?

 

[voko]

You heat the steam at constant pressure, so you know that as well.

 

[freshbox]

is the stage 2 temperature 359.39°C?

 

[freshbox]

Should be correct, i got the final answer.. Hmm this type of question are harder than those guiding you to find "the dryness fraction of the steam after cooling"

Any tips for tackling this type of question? Sometimes I get confused+exam pressure then everything goes down hill..

 

[voko]

You seem to be a little unsure about what all those things really mean. Wet steam, dry steam, saturated steam, superheated steam, and how one changes into another. Review that. Make sure you can explain every step you made solving these problems.

 

[freshbox]

Thanks voko, thank you for your time and help.