INFLUENCE OF VIBRATING ELEMENT ON HEAT-TRANSFER IN A THIN-LAYER EVAPORATOR

This paper contributes to the present knowledge on heat transfer during the boiling of liquids in thin layer evaporators (TLEs). The application of a vibrating element in TLEs of the static type substantially changes both the hydrodynamics and the rate of heat transfer. A total of 689 individual heat transfer coefficients (IHTCs) were determined experimentally in a TLE with an exchange surface area of 0.16 m2. They comprise 86 measurements in a TLE of the static type (without a vibrating element) and 603 measurements in the TLE equipped with two different spiral elements. Distilled water and pure ethylene glycol were investigated in the process of boiling at normal pressure and under vacuum. In the investigated range of frequency and amplitude of vibrations an increase in IHTC values of between 23.7% and 104.8% has been observed.