等差数列的N项和及其应用

Methodology for Sum of N Terms of an Arithmetic Series and Its Application

摘要: 本文通过计算实例，介绍了等差数列N项和的计算方法。双心螺线概念在本文重新提出，用以確定螺旋板换热器和其它板卷的长度与直径。四心螺线作图法及其计算与本課题相关，在此一并作了介绍。

Abstract: This paper introduces the methodology for calculating the sum of N terms of an arithmetic series with practical examples. The concept of the double-center spiral is introduced again to determine the length and diameter of a spiral heat exchanger and other plate coils as well. A related topic, the drawing and its calculation of a four-center spiral, is also presented.