请高手帮我翻译下这段文献吧!谢谢了!在线等……

请高手帮我翻译下这段文献吧!谢谢了!在线等……
However, if a high degree of concentration is needed, it is advisable to use more than one smaller unit in series instead of a large one. Under these conditions, the vapor
and the solution leaving the first unit are, respectively, the heating medium and the process stream for the second one. For a suitable driving force to exist in the second
unit, the solution boiling point has to be reduced, and this is accomplished by reducing the pressure in the evaporation chamber. In this way, a train of evaporators of decreasing pressure in the direction of the heating vapor is obtained.