﻿ 船舶中央冷却系统淡水侧水力计算分析
 舰船科学技术  2023, Vol. 45 Issue (24): 74-79    DOI: 10.3404/j.issn.1672-7649.2023.24.013 PDF

1. 中国船舶科学研究中心 船舶振动噪声重点实验室，江苏无锡 214082;
2. 深海技术科学太湖实验室，江苏无锡 214082

Hydraulic calculation and analysis of the fresh water side of the ship central cooling system
WANG Bin1,2, WU Chang-mai1,2, LIU Yuan-hui1,2
1. Key Laboratory of Ship Vibration and Noise, China Ship Scientific Research Center, Wuxi 214082, China;
2. Taihu Laboratory of Deepsea Technological Science, Wuxi 214082, China
Abstract: In view of the problem that the actual flow and the design flow will be greatly different when the central cooling system delivers fresh water to each cooling branch, taking four cooling equipments as examples, the calculation model of fresh water side is constructed. Based on the flow, impedance and other characteristics of the simple pipeline, the impedance balance calculation method is proposed, and the calculation steps are demonstrated with an actual example. The example is simulated with Flowmaster. The simulation results are in good agreement with the theoretical calculation results, which verifies the correctness of the impedance balance calculation method. Finally, impedance balance method is used to calculate the impedance and local resistance coefficient of each branch pipe under the design flow. The conclusion shows that the impedance balance method can accurately calculate the pipeline hydraulics, and can be applied in the design of ship central cooling system.
Key words: central cooling system     series parallel connection     hydraulic calculation     impedance balance
0 引　言

1 船舶中央冷却系统介绍

 图 1 某PLG船中央冷却系统原理图 Fig. 1 Schematic diagram of central cooling system of a PLG ship
2 冷却管路水力及流量分配计算

2.1 物理模型

 图 2 中央冷却系统淡水侧计算模型图 Fig. 2 Calculation model of fresh water side of central cooling system
 \left\{ \begin{aligned} & {Q_{{b_2}{b_1}}} = {Q_{{a_1}{a_2}}} = {Q_1}，\\ & {Q_{{b_3}{b_2}}} = {Q_{{a_2}{a_3}}} = {Q_1} + {Q_2}，\\ & {Q_{{b_4}{b_3}}} = {Q_{{a_3}{a_4}}} = {Q_1} + {Q_2} + {Q_3}，\\ & Q = {Q_1} + {Q_2} + {Q_3} + {Q_4}。\end{aligned} \right. (1)

 ${z_1} + \frac{{{p_1}}}{\gamma } + \frac{{u_1^2}}{{2g}} = {z_2} + \frac{{{p_2}}}{\gamma } + \frac{{u_2^2}}{{2g}} + {H_{{w}}}。$ (2)

 ${S_{{b_2}{b_1}{a_1}{a_2}}} = {S_{{b_2}{b_1}}} + {S_{{b_1}{a_1}}} + {S_{{a_1}{a_2}}}。$ (11)

 $\frac{1}{{\sqrt {{S_{1,2}}} }} = \frac{1}{{\sqrt {{S_{{b_2}{b_1}{a_1}{a_2}}}} }} + \frac{1}{{\sqrt {{S_{{b_2}{a_2}}}} }} 。$ (12)

 图 5 计算步骤分析图① Fig. 5 Analysis of calculation steps ①

 ${S_{{b_3}{b_2}{a_2}{a_3}}} = {S_{{b_3}{b_2}}} + {S_{1,2}} + {S_{{a_2}{a_3}}} 。$ (13)

 $\frac{1}{{\sqrt {{S_{1,2,3}}} }} = \frac{1}{{\sqrt {{S_{{b_3}{b_2}{a_2}{a_3}}}} }} + \frac{1}{{\sqrt {{S_{{b_3}{a_3}}}} }}。$ (14)

 图 6 计算步骤分析图② Fig. 6 Analysis of calculation steps ②

 ${S_{{b_4}{b_3}{a_3}{a_4}}} = {S_{{b_4}{b_3}}} + {S_{1,2,3}} + {S_{{a_3}{a_4}}}。$ (15)

 $\left\{ \begin{gathered} {Q_3}:{Q_{1,2}} = \frac{1}{{\sqrt {{S_3}} }}:\frac{1}{{\sqrt {{S_{1,2}}} }}，\\ {Q_3} + {Q_{1,2}} = {Q_{1,2,3}}。\end{gathered} \right.$ (17)

5 结　语

1）阻抗计算法可根据管路基本特征，准确计算出在初始状态下各支管的流量、流速、压头损失等参数，利用Flowmaster软件对算例进行了仿真，仿真流量与理论计算流量最大误差为1.23%，仿真流速与理论计算流速最大误差为1.31%，仿真计算得出的压头损失与理论计算压头损失最大误差为3.51，二者吻合良好，验证了阻抗平衡法理论计算数据的正确性。

2）管路流量可采用改变阀门开度进行调节，可利用阻抗平衡法反向计算出在设定流量下的各支管阻抗以及局部阻力系数，精准进行流量控制。

3）阻抗平衡法在计算过程中，充分考虑到每一管段的影响因素，并且无需求解复杂方程，可作为中央冷却系统水力的计算工具。

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