? asked in Science & MathematicsEngineering · 9 years ago

Thermodynamic help! - Steam tables?

For a certain experiment, R-410a vapor is contained in a sealed glass tube at 20°C. It is

desired to know the pressure at this condition, but there is no means of measuring it, since

the tube is sealed. However, if the tube is cooled to −20°C small droplets of liquid are

observed on the glass walls. What is the initial pressure?

1 Answer

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  • 9 years ago
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    Pi = ?

    Ti = 20°C

    Tf = - 20°C = T sat(saturated condition)

    Cooling process is a process of decreasing temperature with constant pressure. So, initial pressure and final pressure will be the same.

    Tf and Pf are dependent, you can look saturated pressure for saturated condition.

    T sat = -20°C, then P sat = 3.99551185 bar, so Pi = 3.9955 bar

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