What is the Difference Between Saturated Liquid and Compressed Liquid?

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The main difference between a saturated liquid and a compressed liquid lies in their proximity to vaporization and the conditions under which they exist:

  • Saturated Liquid: A saturated liquid is a liquid that is about to vaporize, meaning it is at a temperature and pressure where it can exist in both the liquid and vapor phases simultaneously. At this state, the liquid is considered saturated because it has absorbed as much heat as possible without entering its vapor phase. For example, at 1 atm pressure and 100°C, water exists as a saturated liquid, ready to vaporize.
  • Compressed Liquid: A compressed liquid, also known as a subcooled liquid, is a substance that is not about to vaporize. It exists at a temperature and pressure where it remains in the liquid phase, without the need to absorb additional heat to vaporize. For example, at 1 atm pressure and 20°C, water exists in the liquid phase as a compressed liquid.

In summary:

  1. Saturated liquids are closer to vaporization, existing at temperatures and pressures where they can coexist with their vapor phase.
  2. Compressed liquids are further from vaporization, existing at temperatures and pressures where they remain exclusively in the liquid phase.

Comparative Table: Saturated Liquid vs Compressed Liquid

The main difference between a saturated liquid and a compressed liquid lies in their preparation methods and physical properties. Here is a summary of their differences in a tabular form:

Property Saturated Liquid Compressed Liquid
Definition A liquid whose temperature and pressure are such that it cannot hold any more solute. It is in a state where it cannot absorb additional solute. A liquid that has been compressed to a higher pressure than its natural state. Its specific volume is less than the specific volume of the saturated liquid at the same pressure.
Preparation Method Adding solutes to a solvent until no more solute can be added. Applying external pressure on the liquid.
Phase Liquid Liquid
Boiling Point Has a clear boiling point. No distinct boiling point.
Temperature and Pressure Dependence Temperature dependent. Temperature and pressure dependent.
Occurrence in Systems Common in vapor compression cycles. Found in hydraulic and power systems.
Common Working Fluids Water, refrigerants. Hydraulic fluids, drilling mud.

A saturated liquid is a liquid that has reached its maximum capacity for solute concentration, while a compressed liquid is a liquid that has been subjected to external pressure, reducing its volume and increasing its density. The properties of a compressed liquid depend on both pressure and temperature, and its transition to a compressed state occurs gradually, unlike the distinct boiling point for a saturated liquid.