Double tube coolers consist of two tubes arranged so that one tube lies within the other. The cooled fluid flows in one direction through the inner tube while the cooler flows in the opposite direction through the annular space between the inner and outer tubes. The outer tubes are welded to the vertical conduits of the
refrigerant, while the inner tubes pass through the conduits, and are connected together by the removable return bends.
The advantages presented by this unit are rigid construction, elimination of refrigerant joints, and easy access of the internal pipes for cleaning.
Double-tube coolers can be operated by dry expansion. In each case. Backflow of fluids into the tubes produces a relatively high coefficient of heat transmission. However, this type of cooler has the disadvantage of requiring larger space, especially free height, than some of the other cooler designs. For this reason, the dual tube cooler is only used in a few special applications. A number has been used in the beverage industry by fermentation and in the manufacture of wine, to cool wine and unfermented beer and in oil industries, for the cooling of oils.
