In the oil & gas industry, nozzles are the connections on heat exchangers and pressure-vessels which allow the process to flow in and out. They can also be used for venting, draining, inspection, instrumentation, and other things.

Single inlet and outlet shell-side nozzles are normally located at opposite ends of the exchanger with one on the top and one on the bottom of the shell. This arrangement allows vents and drains to be located in piping.