Evaporator :

蒸发器的功能是吸收来自空间或周围介质的热量，该介质将通过制冷来冷却。从蒸发器中完成了从要冷却或冷藏的物质中去除热量的过程。液体制冷剂在蒸发器（线圈或外壳）内部蒸发，以清除液体（例如空气，水等）的热量。蒸发器以不同的形状，类型和设计制造，以适合冷却需求的多样性。因此，我们有多种类型的蒸发剂，例如主要的表面类型，鳍管或延长的表面类型，壳和管液体冷水机等。

Construction of Evaporator :

如图所示的蒸发器是制冷系统的一部分，在该系统中，制冷剂在加热时会蒸发。加热的空气被迫穿过蒸发器的鳍和管。空气中的热量被沸腾的制冷剂接收，并在系统中携带到冷凝器。蒸发器通常安装在仪表板面板下的外壳中。

Working of Evaporator:

When the air conditioning system is turned on, warm air from the passenger compartment is blown through the coils and fins of the evaporator. The evaporator receives refrigerant from the thermostatic expansion valve or orifice tube as low pressure, cold atomized liquid. As the cold refrigerant passes through the evaporator coil, heat moves from the warm air into the cooler refrigerant. When the liquid refrigerant receives enough heat, a change of state – from a low-pressure liquid into a low-Pressure vapor – takes place.
恒温膨胀阀或孔管连续计，以保持最佳传热所需的精确量，这确保了所有液体制冷剂在到达蒸发器出口时都将变为蒸气。然后，蒸发的制冷剂继续延伸到压缩机的入口（吸入）侧。

蒸发器的类型：

Evaporators are divided mainly into three groups.

1.自然循环蒸发器

i) Evaporating pans

ii) Evaporating stills

iii）短管蒸发器。

2) Forced circulation evaporator.

3) Film evaporator

Types:

i) Wiped Film evaporator

ii）长管蒸发器

a) Climbing film evaporator

b) Falling film evaporator Types of Evaporators.

泛滥的蒸发器。

Flooded type of evaporator feeds excess of liquid refrigerant so that the exit of the evaporator will be a mixture of liquid and vapor refrigerant.

In the flooded type of evaporator coil remains completely filled with liquid refrigerant as shown in the figure. The level of liquid refrigerant is maintained constant in the surge chamber by using float control. The liquid refrigerant enters into evaporator coil from the surge chamber. In evaporator coil, part of liquid refrigerant boils and converts into vapor. The vapor formed is collected at the top of the surge chamber and the remaining liquid refrigerant is returned to the surge chamber. From the top of the surge chamber, refrigerant vapors are drawn in the suction line of the compressor. In the flooded type evaporator rate of heat transfer is very high as the whole evaporator coil remains in contact with liquid refrigerant but this type of refrigerant requires a large amount of refrigerant.

Applications of flooded type evaporator:-

这种类型的蒸发器用于
1) Large installations, where refrigerating capacity is high.
2）在制冷系统中，负载波动更高。
3）用于多蒸发器系统。

鳍蒸发器

The finned evaporators are the bare tube type of evaporators covered with the fins. When the fluid (air or water) to be chilled flows over the bare tube evaporator lots of cooling effect from the refrigerant goes wasted since there is less surface for the transfer of heat from the fluid to the refrigerant. The fluid tends to move between the open spaces of the tubing and does not come in contact with the surface of the coil, thus the bare tube evaporators are less effective. The fins on the external surface of the bare tube evaporators increase the contact surface of the of the metallic tubing with the fluid and increase the heat transfer rate, thus the finned evaporators are more effective than the bare tube evaporators.

The fins are the external protrusions from the surface of the coil and they extend into the open space. For the fins to be effective it is very important that there is very good contact between the coil and the fins. In some cases, the fins are soldered directly to the surface of the coil and in other cases, the fins are just slipped over the surface of the fins, and then they are expanded thus ensuring close thermal contact between the two. Tough the fins help increase the heat transfer, rate, adding them beyond certain numbers won’t produce any additional benefits, hence the only a certain number of fins should be applied on the external surface of the tube.
鳍蒸发器最常用于几乎所有类型的空调中，例如窗户，拆分，包装和中央空调系统。

干膨胀蒸发器

In the dry-expansion evaporator, the liquid refrigerant is generally fed by an expansion valve. The expansion valve controls the rate of flow of refrigerant to the evaporator in such a way that all the liquid is vaporized and the vapor is also superheated to a limited extent by the time it reaches the outlet end. At the inlet of the evaporator, the refrigerant is predominantly in the liquid form with a small amount of vapor formed as a result of flashing at the expansion valve.

当制冷剂通过蒸发器时，越来越多的液体会被负载蒸发。制冷剂到达蒸发器的末端时，纯粹是在蒸气状态下，并且过热。因此，其长度的蒸发器充满了不同比例的液体和蒸气。蒸发剂中的液体量会随蒸发器上的负载而变化。蒸发器的内部远非“干”，但用液体润湿。All the same, this type is called the ‘dry-expansion’ system to distinguish it from the ‘flooded’ system and also probably because by the time the refrigerant reaches the evaporator outlet it is no more wet (no liquid) but dry (superheated) vapor.

蒸发锅：（蒸汽外套水壶）

Principle :

参与这个蒸发过程的机制is conduction and convection. The material is placed in the jacketed kettle. Steam provides heat to a jacketed kettle in which the aqueous extract is placed. The raised temperature increases the tendency of the solvent molecules to escape into the vapors.