Evaporation is one of the types of vaporization, which is a surface phenomenon compared to the boiling. Evaporation refers to a process by which a liquid turns into a gas or vapor below its boiling point occurring on the surface of the liquid. The equipment used for the evaporation is called evaporators, which have various types, such as rotary evaporators, falling film evaporators and other evaporators.
Types of Evaporation
Generally, there are three common classification methods when the types of evaporation are discussed, as follows:
In terms of the evaporation method, there are two types of evaporation, which are the natural evaporation and the boiling evaporation. The natural evaporation refers to that the solution evaporates below the boiling point. In this case, the vaporization rate of the solvent is low because the solvent only vaporizes on the surface of the solution. The latter means that the solution evaporates in the boiling state after heating the solution to the boiling point, which is commonly seen in industry.
In terms of the operating pressure, there are three types of evaporation, which are the atmospheric evaporation, pressure evaporation and vacuum evaporation. The pressure evaporation is suitable for high viscosity materials, while the vacuum evaporation is applicable for heat sensitive material.
In terms of the utilization of the secondary vapor, evaporation can be classified into two types, which are the single-effect evaporation and the multiple-effect evaporation. The single-effect evaporation refers to that the secondary vapor is directly condensed without one more utilization. If the secondary vapor is led into a lower pressure heating chamber of the evaporator and utilized as the heating vapor, this operation is known as the multiple evaporation.
Types of Evaporators
Evaporators are the equipment used for evaporation, which is used in the process of turning a liquid into a gas or vapor. Evaporators mainly consist of a heating chamber and an evaporation chamber. The former makes the liquid boil and vaporize by providing the heat required for evaporation. The latter separates the liquid and the gas completely.
There are several main types of evaporators, which are falling film evaporators, nucleate boiling evaporators, flash evaporators and direct contact evaporators. Among them, nucleate boiling evaporators can continue to be classified into six types, such as climbing film evaporators, short-tube vertical evaporators, long-tube vertical evaporators, etc. Though possessing similarities, they differ from each other in some aspects as well and are applicable for different types of evaporation.