preheating boiler

例句：

1. 1.The preheating boiler is essential for the operation of the furnace.
   预热锅炉对于炉子的运行至关重要。
2. 2. The preheating boiler was designed to improve the efficiency of the heating system.
   预热锅炉的设计目的是为了提高供暖系统的效率。
3. 3.The preheating boiler was used to heat up the water before it was pumped into the pipes.
   预热锅炉被用来在将水泵入管道之前加热水。