Plate Heat Exchangers Definition Plate Heat Exchangers (PHE) are industrial cooling devices, containing very thin metal plates sealed by rubber gaskets that separate hot and cold fluids. The hot and cold fluids alternate between each of the plates, which have a corrugation pattern to create high turbulence in the fluids and thereby maximise the heat transfer. Because each of the plates has a large surface area, the plates provide each of the fluids with the maximum heat transfer area. Therefore a PHE, as compared to a similarly sized traditional shell and tube heat exchanger, is capable of transferring much more heat. PHE are also much easier to service than traditional shell and tube heat exchangers. Brazed PHE, semi-welded PHE and Plate and Shell HE, all variations on the gasketed PHE, are used for very high temperature and / or high pressure applications.