<p>A jet–film contact device with organized jets and a liquid film flowing down the surface of transverse perforated partitions holding downcomer cups has been developed. Mathematical modeling of liquid motion in the downcomer cup of the jet–film contact device has been performed. The effect of the speed of liquid film flow along the specified surfaces on its mass output coefficient is determined. A dependence of the liquid mass output coefficient on the width of the downcomer cup of the contact device has been proposed. It has been established that the peripheral speed of rotation of the liquid in the downcomer cup is comparable with the speed of the film flowing into this liquid, which ensures high intensity of mass exchange on the liquid surface. To increase the coefficient of mass output of the liquid phase, it is recommended to design devices so as to maintain the ratio of the geometric dimensions of the downcomer cup and its filling with a value of h/b = 0.5.</p>