烟管（5）中的水管（4）减小了烟道流动截面积、 加大了烟气流速，使得烟气传热性能增强、热效率高。
The water pipe (4) of the smoke pipe (5) reduces the flowing section of the smoke channel, speeds up the smoke flow, improving the heat transmission performance and efficiency.
在一个稳定的内部流动马赫数只能达到一在最低限度，在截面积。
In a steady internal flow the Mach number can only reach 1 at a minimum in the cross-sectional area.
依据压铸模具浇口计算的基本原理，给出了内浇口截面积和内浇口内金属液流动速度的计算公式。
In this paper, the principles of gate calculation in the die-casting mould are discussed, and the calculation formulas of gate area adn fiow velocity of metal in the gate are given.
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