The double tube condenser has the water tube inside the refrigerant tube. The coolant passes through the space between the two tubes, while water is pumped through the inner tube. Water flows in the opposite direction to that of the refrigerant, with the coldest water in contact with the coldest refrigerant and the warmest water in contact with the warmest refrigerant, avoiding thermal shocks. They are used where the refrigerant is ammonia, steel tubes are used, with diameters of generally 1 ¼ ”for the internal and 2” for the external. Although the countercurrent principle, made possible by this type of condenser, makes good use of the available water, the large number of connections and joints needed in large installations increases the possibility of leaks.
These condensers are difficult to clean and do not provide enough space for the separation of gas and liquid.
For these reasons, they are not widely used in large modern installations. Some small units are used in recent installations, however, they must be cleaned chemically. In the event of a leak, the entire unit must be replaced.
