Air conditioner evaporator classification
Depending on the type of medium being cooled, evaporators can be divided into two broad categories:
(1) An evaporator that cools the liquid brine. Used to cool liquid coolant - water, brine or aqueous glycol solution. Horizontal evaporators, riser evaporators, and spiral tube evaporators are commonly used in such evaporators.
(2) An evaporator that cools the air. This type of evaporator has a cooling drain and a chiller.
(3) Horizontal evaporator
The structure is basically similar to that of the horizontal shell-and-tube condenser. According to the liquid supply mode, it can be divided into a shell-and-tube evaporator and a dry evaporator. Horizontal shell and tube evaporators are widely used in closed brine circulation systems. Its main features are: compact structure, good contact between liquid and heat transfer surface, and high heat transfer coefficient. However, it needs to be filled with a large amount of refrigerant, and the liquid column will have a certain influence on the evaporation temperature. And when the brine concentration is lowered or the brine pump is shut down for some reason, the brine may be frozen in the tube. If the refrigerant is Freon, it is difficult for the lubricating oil dissolved in the Freon to return to the compressor. In addition, stop working when cleaning. The main type of dry freon evaporator is that the refrigerant flows inside the tube and the brine flows outside the tube. After the throttling, the freon liquid enters the evaporator from the lower part of the one end cap, and after several processes, it is taken out from the upper part of the end cap, and the refrigerant evaporates continuously with the flow in the tube, so a part of the wall is occupied by the vapor, so Its heat transfer effect is not as full as liquid. However, its liquid-free column has an effect on the evaporation temperature, and since the Freon flow rate is high (≥4 m/s), the oil return is better. In addition, since the outside of the tube is filled with a large amount of brine, the risk of freezing is reduced. The amount of refrigerant in the evaporator is only 1/2 to l/3 or less of the full liquid type, so it is called a "dry evaporator".
(4) riser evaporator
The common point of the riser type and the spiral tube type evaporator is that the refrigerant evaporates in the tube, and the entire evaporator tube group is immersed in the tank (or the tank and the tank) filled with the refrigerant, in order to ensure that the brine is in the tank. It is circulated at a certain speed, and the box is welded with a longitudinal partition and a screw stirrer. The flow rate of the brine is generally 0.3 to 0.7 m/s to enhance heat transfer.
These two evaporators can only be used in open circulation systems, so the coolant must be non-volatile, and brine and water are commonly used. If brine is used, the evaporator tube is easily oxidized and the brine is susceptible to moisture absorption to reduce the concentration. These two evaporators can directly observe the flow of the brine, and are widely used in brine refrigeration systems that use ammonia as a refrigerant.