If the heat transfer surface area of the single-effect evaporator is equal to the heat transfer surface area of the single-effect evaporator, and the same amount of water is evaporated, the productivity of the multi-effect is N times that of the single-effect. 若单效蒸发器的传热表面积与多效中单台的传热表面积相等，对蒸发同样多的水分，则多效的生产强度为单效的n倍。（ ）