This paper introduces a new kind of evaporators in which a self-rotating spiral and a driving wheel with spiral flange are installed in each heat transfer tube in heating chamber. The spiral can prevent and remove fouling at low flow velocity and the overall flow resistance is less than 10kPa. The modified boiling chamber has great depth, large cross-area and the area becomes bigger gradually. When the circulating mother solution flows though it at low flow velocity, it can begin to vaporize at greater depth and stay for a longer time. The sensitive heat got in the heating chamber can be changed into vaporizing heat as much as possible. Thus the kinetic energy loss can be reduced greatly to make the driving power of natural circulation reach 10similar to15kPa. The force-cycle pump can be removed, which will consume a great deal of energy. So, the new evaporator has great value to enhance heat transfer and save energy.