PURPOSE: To quickly exclude the condensed liquefied seed agent adhering to the outside of a cooling pipe from among the group of a cooling pipes and quickly exclude and collect the liquefied seed agent having dropped to the lowermost part of the room outside the pipe to the outside of the room outside the pipe.

CONSTITUTION: This is a shell and tube type heat exchanger which is positioned after the rare gas containing the seed being the operating fluid of the closed cycle MHD generating system using rare gas has passed, and for the direction of the cooling pipes 11, those are arranged approximately vertically. Moreover, the pipe plate 16 below the cooling pipes 11 is inclined to the horizontal plane, and the reservoir 17 where the condensed seed stay is provided at the lowermost part of the inclined plane.