The Plate-Shell Heat Exchanger (PSHX) is a completely welded heat exchanger that combines the best features of a shell and tube heat exchanger with that of a plate heat exchanger. With this, a fully welded plate pack is inserted into the shell which distributes the stress and eliminates the need for gaskets. Designed and manufactured to meet the customers specific needs, this heat exchanger can withstand extreme operating temperatures; pressures; and works with liquids, gases, and transitioning phases of the two.