closure 14 of the dryer drum 10 the thickness and circumferential spacing of the spoiler bars 25 may be calculated in accordance with the teachings of the beforementioned u s pat no 3 724 094 a distinct advantage of these spoiler bars is that they permit the condensate depth to be thicker than where the heat chamber surface of the drum wall 11 is plain because the condensate layer may be thicker the siphon to shell clearance may also be greater and facilitates use of the stationary siphon with its advantageous relatively low differential pressure requirements while allowing more tolerance for the stationary siphon mounting a problem nevertheless occurs because it is not practical to extend the spoiler bars 25 into and across the narrow annular area identified at 27 in fig1 along which the siphon intake draws off the condensate 24 in the operation of the rotating dryer drum 10 the tips of the spoiler bars 25 must terminate adjacent to the area 27 far enough removed from the siphon intake 23 to avoid the risk of mechanical interference and possible damage as the bars 25 rotate past the stationary siphon intake 23 without the condensate turbulence effect of the spoiler bars 25 in the area 27 there is a tendency for rimming of the condensate especially in the layer which remains at the offrunning side of the siphon head 23 having regard to the direction of rotation of the drum wall 11 and therefore the heat transfer through the area 27.