Using Rogers & Mayhew Steam Tables to Calculate Internal Energy Change

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In summary, the person is studying for an engineering thermodynamics exam and is having trouble remembering the exact formulas necessary to use steam tables. They have a question about determining specific internal energy change for water and are unsure how to use the given information to find the answer. They are advised to use interpolation, specifically double linear interpolation, to make assumptions and find the necessary values.
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j.m.m
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Well, I am studying for my engineering thermodynamics exam, and i don't seem to have written down some of the information about steam tables.

Im fairly confident using them, except i can't remember the exact formulas we use to get the numbers in between the numbers given. For example, i have a question as follows:

Use Rogers and Mayhew to determine specific internal energy change for water from 17.5 degrees Celsius to 86 degrees Celsius.

Well, my problem is the steam tables only give temperatures of 17 and 18, and 85 and 90.
17 bar - Hf 71.3
18 bar - Hf 75.5
85 bar - Hf 355.9
90 bar - Hf 376.9

how can I use this information to get the Hf of water at 17.5 degrees Celcius, and 86 degrees Celcius??

Thanks in advance
 
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  • #3
thanks a million

nice and quick reply too
 

What are steam tables and how are they used?

Steam tables are a set of tables that contain thermodynamic properties of water and steam at different temperatures and pressures. They are used to calculate various parameters such as enthalpy, entropy, and internal energy change of water and steam.

What is the purpose of using Rogers & Mayhew Steam Tables?

Rogers & Mayhew Steam Tables are widely used in engineering and scientific fields to accurately calculate the properties of water and steam. They are based on the International System of Units (SI) and provide more precise values compared to other steam tables.

How do you calculate internal energy change using Rogers & Mayhew Steam Tables?

To calculate the internal energy change of water and steam using Rogers & Mayhew Steam Tables, you need to first determine the initial and final state of the water or steam. Then, using the given temperature and pressure values, you can find the corresponding values for enthalpy and entropy from the steam tables. Finally, the internal energy change can be calculated using the formula: ΔU = ΔH - Δ(PV).

What are some limitations of using Rogers & Mayhew Steam Tables?

While Rogers & Mayhew Steam Tables provide accurate values for a wide range of temperatures and pressures, there are some limitations to their use. These tables are only applicable for water and steam, and do not take into account any impurities or non-ideal behavior. Additionally, they may not be accurate for extreme conditions such as very high pressures or temperatures.

Are there any alternatives to using Rogers & Mayhew Steam Tables?

There are several alternatives to using Rogers & Mayhew Steam Tables, including other steam tables such as the NIST Steam Tables or the ASME Steam Tables. Additionally, there are computer programs and online calculators available that can perform the calculations using different methods and equations. However, it is important to ensure that the chosen method is appropriate for the given conditions and is accurate enough for the intended use.

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