Which of the following statements is correct regarding the term 'Reduced Pressure'?

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HPCL Engineer Mechanical 04 Nov 2022 Official Paper (Shift 2)

It is represented by the ordinate (Y axis) of generalised compressibility chart.
It is the difference between the critical pressure and the existing pressure of a substance.
It is the ratio of the existing pressure to the critical pressure of a substance.
Its unit is MPa.

Answer 1

Explanation:

The reduced properties of a fluid are a set of state variables normalized by the fluid's state properties at its critical point.
Reduced properties are also used to predict the behavior of substances near the critical point.
They are also used as critical exponents, which describe the behaviour of physical quantities near continuous phase transitions.
The ratio of the actual pressure in the system (p) to the critical pressure (pc).
Therefore it is a dimensionless term.

Reduced pressure (p_r) -

p_r = p/p_c

P_c is the critical pressure of the gas.

The generalized compressibility chart's ordinate (Y-axis) is the compressibility factor (Z).
Reduced pressure is a unitless quantity.