This steam heater is a shell-and-tube heat exchanger. The two pipes on the side of the water tank are tube side, and the general medium is water, one is the inlet and the other is the outlet. A nozzle at the top is a steam inlet, and the bottom is not a waste gas outlet, but a steam outlet or a condensed water outlet, depending on the temperature and pressure of the heating steam and the inlet and outlet temperatures of the heated medium.
For this kind of heater, the steam is located in the shell side and the heating medium is located in the tube side. Using the condensation heat of steam to heat the medium in the pipeline is not "using its own steam to heat its own steam to obtain superheated steam" because it is uneconomical. Both the high-pressure heater and the low-pressure heater in the power plant are such devices.