Abstract: A heat exchange unit, adapted to performing heat exchange between first and second fluids at different temperatures, comprises a heat exchange apparatus provided with a tube bundle, crossed internally by said first fluid, and containing means of the second fluid, adapted to receiving the exchange apparatus so that at least one portion of the tube bundle is externally surrounded by the second fluid. The exchange apparatus further comprises connection means which are structurally separate from said retainer means and to which one end of the tube bundle is operatively connected.