ent control is required .DESCRIPTION OF THE PREFERRED EMBODIMENTSReferring to FIG. 1, a heat exchanger 10 comprises an air or fluid cooling chamber 12, a chamber or duct 14 for reception of a liquid, gas or other fluid, identified by arrows 20, to be cooled or condensed, and a partitioning wall 16 separatingchambers 12 and 14.