PURPOSE: To maintain a moving speed of substance even if a flow speed of sucked liquid volume is reduced by a method wherein a covering part is contacted with a surface of a unit to fix a covered electrical line and at the same time an electric field is generated between a electric line of the covered electrical line and the surface of the unit.

CONSTITUTION: A covered electrical line 10 having an electrical line 20 covered with a covering part 11 made of insulation material is wound in a single winding in a helical form at a circumference of a surface of a thermal conducting pipe 2 through which cooling water for a covered flowing down type absorber flows and at the same time a voltage is applied by installing a power supply 21 between the thermal conducting pipe and the electrical line part of the covered electrical line. Therefore, a convection flow is generated within a liquid film under action of electrical field generated within an absorption liquid film 19 formed at a surface of the thermal conducting pipe 2, a mixing of concentrations at the surface of the absorption liquid film having a low flow speed and at the inner part is activated, resulting in that either absorbed gas or vapor present around it is always contacted with a new absorption liquid and an absorption and a movement of heat exchanging substance are promoted.