PURPOSE: To increase the coefficient of heat transfer of the heat transfer element and to prevent the element from being damaged by a method wherein the corrugated intermediated section of the heat transfer element is formed to have such a cross- sectional configuration that the pitch is in the order of 10W16mm, the height of each corrugation is in the order of 3W10mm and the tangent line passing through the intermediate part between the top or the bottom of the corrugation intersects the tangent line at the top or the bottom of the corrugation.

CONSTITUTION: The corrugated intermediate section 4 of the heat transfer element is formed to have such a cross-sectional configuration that the pitch is in the order of 10W16mm, the height of each corrugation is in the order of 3W10mm and the tangent line M passing through an arbitrary point of the intermediate part between the top (a) and the bottom (b) of the corrugation intersects the tangent line N at the top (a) or the bottom (b) of the corrugation. As a result, the pitch becomes small and the surface area of heat transfer per unit volume increases so that the coefficient of heat transfer of the heat transfer element increases. Further, as the corrugated intermediate section of the element has substantially no horizontal section, the element hardly vibrates even when it is subjected to a strong washing force and there is no fear of its being damaged.