PURPOSE: To cause the tapered part at one end to be closely abutted against an edge end of a thermal conducting pipe, a static pressure near an outlet port is decreased and a reversing of pressure between water chambers is prevented in a heat exchanger having a plurality of thermal conducting pipes passed between a pair of upper and lower water chambers in which the interior of a cylinder is partitioned by two pipe plates by a method wherein a metering structure having fine holes is arranged at the thermal conducting pipes adjoining the lower water chamber through supporting members.

CONSTITUTION: A disk 34 supporting a metering structure is removably fixed to a surface of a pipe plate 22b facing to an outlet water chamber 24 through bolts 35, and the disk is provided with through-pass holes 36. A threaded part 38 at an outer circumference of the metering structure 37 is threadably engaged with a through-pass threaded hole 36 and then fixed. Its tapered part 39 is directly contacted with an edge end of the thermal conducting pipe 25 at its metal to each other. Liquid naphtha injected from a spray nozzle 30 is heated while passing through each of the thermal conducting pipes 25 together with its accompanying gas and then is discharged to an outlet side water chamber 24. In this case, a reduced flow is generated at the fine hole in the member 37 and a pressure loss is generated. With this arrangement, no reversing of pressure is generated between both water chambers 23 and 24 and then no recirculation of water from an outlet water chamber 24 to an inlet water chamber 23 is generated.