Water can be cooled safely to near freezing point, using evaporators which have the refrigerant inside, with space for ice to form on the outside of the sur­face without causing damage. Two types are used:

1. Baudelot coolers (see Figure 7.13). The evaporator stands above a collection tank, and the water runs down the outside surface in a thin layer. Evaporator construction can be pipe coils or embossed plates. The latter are usually of stainless steel, to avoid corrosion. Evaporators may be flooded or direct expansion. During operation, a Baudelot cooler may sometimes build up a thin layer of ice, but this does no damage to the evaporator, and should melt off again when the load changes.

2. Pipe coils within a water tank (see Figure 7.8). Both flooded and direct expansion evaporators are in use. Water is circulated by pumps and/or special agitators. This type of water chiller may be operated without formation of ice, or ice may be allowed to accumulate intentionally (see below).

Water chillers of these two types are not usually made as single packages with their condensing unit, owing to the bulk of the system and subsequent difficulty of installation.

Posted in Refrigeration and Air Conditioning