How does an air conditioner evaporator coil work?

- Jun 11, 2018-

How does an air conditioner evaporator coil work?


Evaporator coil is an important part of the four major air conditioner components. The low-temperature condensate “liquid” body passes through the evaporator and exchanges heat with the outside air. The “gas” heat absorption achieves the cooling effect.


The commonly used evaporator coil is generally a heat transfer evaporator with partitions. If the solution stays in the evaporator, it can be roughly classified into two types: circulating type and single-pass type.


The central circulation tube is an evaporator: this type of evaporator is also called a standard evaporator. Its heating chamber is composed of vertical tube bundles. In the middle, there is a central circulation tube with a large diameter, and the other tubes with smaller tube diameters are called boiling tubes. Due to the larger central circulation pipe, the heat transfer surface per unit volume of the solution occupies less than the unit solution in the boiling pipe, that is, the heating degree of the solution in the central circulation pipe and other heating pipes is different, so that the density of the vapor-liquid mixture in the boiling pipe is The density of the solution in the central circulation tube is smaller than that of the solution in the central circulation tube, and the upward suction action of the rising vapor causes the solution in the evaporator to form a circulating flow that descends from the central circulation tube and rises from the boiling tube. This cycle is mainly caused by the density difference of the solution, so it is called the natural cycle. This effect is beneficial to the improvement of the heat transfer effect in the evaporator.

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The film-lift evaporator has a heating chamber consisting of a number of vertical tubes. The diameter of the commonly used heating tube is 25-50mm, and the ratio of the length of the tube to the diameter of the tube is about 100-150. After the preheated feed solution is introduced from the bottom of the evaporator, it is heated and boiled in the heating pipe and quickly vaporized. The generated steam rises at a high speed in the heating pipe, and the suitable outlet steam speed is 20-50 m/s under normal pressure operation. The steam speed can reach 100 to 160m/s or more under the following operation. The solution is driven by the rising steam, rising in a film-like shape along the tube wall and continuing to evaporate. The vapor and liquid mixture is separated in the separator 2, the liquid is discharged from the bottom of the separator, and the secondary steam is led out at the top. It should be noted that if the amount of water evaporated from the feed liquid is not large, it is difficult to achieve the above-mentioned required steam speed, that is, the film-lift evaporator is not suitable for the evaporation of concentrated solutions; it is very viscous, easy to crystallize or easy Scaled materials are also not suitable.