Below is a list of Tube Heat Exchangers manufacturers from Neenah, Wisconsin. A tube heat exchanger, also known as a shell and tube heat exchanger, consists of a series of tubes within a shell, or large pressure vessel. The tubes can be several different types of tubes, including plain or longitudinally finned, which can be either in a straight or U-tube bundle, or set of tubes. U-tubes are when the tube bundle is bent in a U-shape.