Preliminary experimental studies on evaporation of Gengnian’an liquid extract of traditional Chinese medicine(TCM)with vapor-liquid-solid flow boiling technique were carried out in a transparent natual circulating three-phase evaporator. The height of the heating tube is 2.5m with an inner diameter of 0.038m and an outer diameter of 0.045m. The cylindrical solid particles with a diameter of 0.0025m and a length of 0.0025 m is made of a kind of inert material that does not interact with the liquid of Gengnian’an. The heat energy for the evaporator was supplied by the electric heating system. It was shown that the presence of the solid particles could enhance the process of heat transfer since the heat transfer coefficients in vapor-liquid-solid boiling system was about 1.5—2.0 times that of the vapor-liquid boiling system when the heat flux was constant. On the other hand

fouling prevention and a lower wall temperature were also seen when the solid particles were present. The quality of concentrated liquid of TCM would be improved.