Heat exchanger array for a step down return of condensate

A heat exchanger array for step down return of condensate in a vapor system having a vaporizer and a plurality of vapor sevices of different temperature and pressure having condensate reservoirs of relatively higher and lower pressures and temperatures, the array comprising:

• a plurality of straight tube heat exchangers each of which comprises a straight outer tubular shell with an inside wall, having a fluid inlet and a communicating fluid outlet, and, an inner conduit assembly with fluid inlet and a communicating outlet concentrically mounted within the outer tubular shell, the conduit assembly having an inner tube with an external fin structure displaced from the inside wall and a periodic baffle structure proximate to the inside wall of the tubular shell;
• wherein the straight tube heat exchangers are arranged with at least one heat exchanger having an inlet connected to a reservoir of relatively higher temperature and pressure and a communicating outlet connected to the inlet of at least one other heat exchanger the inlet of which is additionally connected to a condensate reservoir of relatively lower temperature and the communicating outlet of which is connected to a common return for the combined condensate, the array having further, pressure control means for regulating a pressure drop between the exchangers and cooling means for cooling the condensate in the exchangers.