Why can we assume the temperature of a fluid is T_sat?

[zachdr1]

For example, in this question..

A 11 L rigid container contains 10-kg of R134a at 100kPa. Determine the temperature and total enthalpy in the container.

Why can we just assume that the temperature we're looking for is T_sat, how do we know this isn't a compressed liquid? How do we know it isn't a superheated vapor?

The answer (-26.37) is found by looking it up in the saturated R134a table.

 

[Chestermiller]

The specific volume of your sample is 1.1 L/kg = 0.0011 m^3/kg. Look in your tables and see if you find any compressed liquid or superheated vapor with this specific volume at 100 kPa. But it does lie between the specific volume of saturated liquid and the specific volume of saturated vapor at 100 kPa.

 

[zachdr1]

The specific volume of your sample is 1.1 L/kg = 0.0011 m^3/kg. Look in your tables and see if you find any compressed liquid or superheated vapor with this specific volume at 100 kPa. But it does lie between the specific volume of saturated liquid and the specific volume of saturated vapor at 100 kPa.

Ohhh okay that makes sense. Thank you.

This doesn't relate the the original problem I posted, but what happens if when using the equation v=v_f + x(v_fg) with the values from the saturated tables, I get a quality that is greater than one? Does that mean that the substance is actually a vapor or what?

 

[Chestermiller]

Ohhh okay that makes sense. Thank you.

This doesn't relate the the original problem I posted, but what happens if when using the equation v=v_f + x(v_fg) with the values from the saturated tables, I get a quality that is greater than one? Does that mean that the substance is actually a vapor or what?

Sure. In fact you should be able to see that from the superheated tables.