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Classification of evaporators
Apr 15, 2020

Evaporator is an important part of the machine. What is the classification of evaporator?

 

1. Horizontal evaporator

 

Its structure is basically similar to that of horizontal shell and tube condenser. Horizontal shell and tube evaporator is widely used in closed brine circulation system. Its main characteristics are: compact structure, good contact between liquid and heat transfer surface, high heat transfer coefficient. However, it needs to be filled with a large amount of refrigerant, the liquid column will have a certain impact on the evaporation temperature. And when the brine concentration decreases or the salt pump stops for some reason, the brine may be frozen in the tube. If the refrigerant is freon, the lubricating oil dissolved in freon is difficult to return to the compressor. In addition, stop working while cleaning. The main difference between dry freon evaporators is that the refrigerant flows inside the tube while the refrigerant carrier flows outside the tube. After the throttle, the freon liquid enters the evaporator from the lower part of the end cover on one side, and then is drawn out from the upper part of the end cover after several processes. The refrigerant evaporates continuously with the flow in the tube, so part of the wall surface is occupied by the steam. Therefore, its heat transfer effect is not as good as that of the full liquid type. However, due to the influence of its anhydrous column on evaporation temperature, and the high velocity of freon (≥4m/s), the oil return is better. In addition, the risk of freezing is mitigated by the large quantity of refrigerant carrier being filled outside the tube. The refrigerant charge in the evaporator is only 1/2 ~ l/3 or less of the full liquid, so it is called "dry evaporator".

 

2. Vertical tube evaporator

 

The common point of vertical tube type and spiral tube type evaporator is that refrigerant evaporates in the tube. The whole evaporator tube group is immersed in the box (or pool or tank) full of refrigerant. In order to ensure the circulation of refrigerant in the box at a certain speed, the box is welded with longitudinal baffles and equipped with spiral agitators. The refrigerant carrier flow rate is generally 0.3 ~ 0.7m/s to enhance heat transfer.

 

These two types of evaporators can only be used in the open circulation system, so the refrigerant carrier must be non-volatile substances, usually saline and water. If salt water is used, the evaporator pipe is easy to be oxidized, and salt water is easy to absorb moisture and reduce the concentration. These two evaporators can directly observe the flow of refrigerant carrier and are widely used in brine refrigeration systems with ammonia as refrigerant.

 

The two types of evaporator introduced above are the two basic types of evaporator. I hope the above contents will be helpful for you to understand what the classification of evaporator is.

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