Once-through heat exchanger and heat recovery steam generator including the same

A combined power generation system comprising:

• a gas turbine configured to generate rotational force by combusting fuel and discharge combustion gas;
• a heat recovery steam generator configured to generate and heat steam using the combustion gas discharged from the gas turbine;
• and
• a steam turbine using the steam heated by the heat recovery steam generator,
• wherein the heat recovery steam generator comprises a plurality of heat exchangers,
• wherein each of the heat exchangers comprises:
• a tube stack comprising a plurality of tubes;
• a plurality of heads connected to the tube stack via a connection module and configured to accommodate the heated steam;
• the connector module comprising a plurality of tube connectors and configured to connect the tubes and the heads;
• and
• a manifold connected to the heads via a plurality of link pipes and configured to accommodate heated steam;
• wherein the connector module comprises a first tube connector and a second tube connector having different shapes,
• wherein each of the heads is a pipe that extends parallel to the manifold and has both longitudinal ends blocked, and
• wherein the heads are spaced at different distances from the manifold,
• wherein the heads adjacent to each other in a longitudinal direction of the manifold are spaced apart at different distances from the manifold,
• wherein the first tube connector comprises a first connection part connected to an associated one of the heads, and the second tube connector comprises a second connection part connected to an associated one of the heads, and the first connection part has a smaller length than the second connection part,
• wherein the first tube connector further comprises a first extension part extending in a longitudinal direction of the link pipes from the first connection part, a first intermediate part extending in a longitudinal direction of the first connection part from the first extension part, and a first tip part extending in a longitudinal direction of the first extension part from the first intermediate part.