How to read Thermodynamic property tables?

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Discussion Overview

The discussion revolves around how to read thermodynamic property tables, specifically focusing on steam tables and their application in determining properties like internal energy for given conditions. The scope includes conceptual clarification and practical guidance on using these tables.

Discussion Character

  • Conceptual clarification, Technical explanation, Homework-related

Main Points Raised

  • Rob expresses difficulty in understanding how to read thermodynamic property tables and seeks assistance in finding specific values for internal energy.
  • Some participants note that mass is typically not needed when looking up values in the tables, as the values are given per unit mass (kJ/kg).
  • It is mentioned that there are usually three separate tables for water: superheated steam, saturated liquid, and compressed solid, with a focus on the steam tables for Rob's inquiry.
  • Participants suggest looking for the chart corresponding to the pressure (10 bar) and then finding the relevant temperature for saturated steam.
  • One participant provides a link to a website discussing steam tables and explains the calculation of internal energy as the product of specific internal energy and mass, mentioning that interpolation may be necessary.
  • A tool called SteamTab is recommended by another participant for easier access to steam table data without manually searching through long lists.

Areas of Agreement / Disagreement

Participants generally agree on the structure of steam tables and the method of calculating internal energy, but there is no consensus on the best approach to learning how to read the tables effectively, as Rob's initial confusion remains unaddressed.

Contextual Notes

Some assumptions about the familiarity with thermodynamic concepts and the specific format of steam tables may not be explicitly stated, which could affect understanding for those new to the topic.

rc flyer uk
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I can't remember for the life of me how to read Themodynamic property tables!

I want to find answers to questions for example: What is the internal energy of 1kg of saturated steam at 10 bar or 3kg of water at 130C

Can anyone help or know of any good websites which has information on how to read the tables?

Thanks a lot,

Rob
 
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Mass is usually not part of what you need when looking up items in the tables since everything is pretty much per unit mass, i.e. kJ/kg.

Most tables I have seen are pretty straight forward. What exactly troubles you?
 
Yes, Fred is right, the units you are given will be per mass, kJ/kg. You are typically given three separate tables for water. Superheated steam, saturated liquid, and compressed solid (I think that's what it's called). Since you are looking for steam, you go to the steam tables. What you will typically have is a lot of little charts for each pressures. So, go and find the chart of 10 bar and then look for your temperature.
 
As Fred and minger pointed out, the thermodynamic properties in steam tables are given in terms of specific properties, or property per unit mass.

Here is as site that discusses steam tables - http://www.engineersedge.com/thermodynamics/steam_tables.htm

To get the internal enregy (U) of a mass (m) of water/steam - multiply the specific internal energy (u) by mass m, i.e. U = m u.

Some interpolation may be necessary.

The are other sites, but most require membership (often for a fee) to use their lookup tables or calculators.

Google on "steam tables".
 
SteamTab is the excellent tool I use day in and day out. I need not have to strain my eyes looking at the long list in the tables. Put the values and click the button, voila, the data appears. The fully functional demo version gives you data about water, saturated steam, subcooled superheated steam.

http://www.chemicalogic.com/steamtab/demo.htm

Good luck,
 
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