基于可靠度的冷却水泵网络操作优化
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摘要
离心泵是高耗能通用设备,以降低能耗和提高可靠度为目标对离心泵网络进行操作优化对化工装置节能很有益处。构建了基于可靠度的泵网络操作优化命题,同时考虑泵网络系统总功率最小和可靠度最大的目标,采用乘积消元方法将两个目标统一为单目标。分别建立了决策变量为开停不变频的混合整数线性规划问题Problem1和决策变量为开停加变频的非线性规划问题Problem2;提出了面向工业应用的经验规则算法,求解Problem1并与穷举搜索法获得的全局最优解对比。结果表明,在整个流量和压头变化范围,经验规则法获得的最优解方案与穷举搜索获得的全局最优解方案相比,方案调整少,容易人工操作。除了较低负荷之外,经验规则法提供的最优解方案的冷却水功耗平均比穷举搜索法的全局最优解高11%左右,功耗和可靠度波动明显较大。采用开停和变频为决策变量时,Problem2的平均冷却水功耗比Problem 1的全局最优解低8%左右,泵可靠度的波动也更小。最低的冷却水功耗可以达到0.105 kW·h·m~(-3)。
Centrifugal pumps are widely used in industry with high energy consumption. Operational optimization of pump networks to minimize energy consumption and maximize reliability is necessary for energy saving. In this study, operational optimization of a parallel pump network was investigated. Maximizing reliability and minimizing work consumption were the two objectives which were combined together by multiplication. A mixed-integer linear program(Problem 1) was built with turning on/off as the decision variable, whereas a mixed-integer nonlinear program(Problem 2) with both turning on/off and frequencies of pumps as decision variables was also built. Heuristic rule was proposed to solve Problem 1 for industrial usage.The results obtained by heuristic rules were compared to the global optima of problem 1 by enumeration searching. The results show that optimal solution of heuristic rules is easier to operate manually than the global optima among the total flowrate and head region, while the average work consumption is about 11% higher.Fluctuation of work consumption and reliability of the whole system obtained by heuristic rules were higher as well. When both turning on/off and frequencies were selected as the decision variables, average optimal work consumption of Problem 2 was about 8% lower than that of global optima of Problem 1. Less fluctuation of reliabilities was obtained as well. The minimum work consumption of cooling water was 0.105 kW·h·m~(-3).
Centrifugal pumps are widely used in industry with high energy consumption. Operational optimization of pump networks to minimize energy consumption and maximize reliability is necessary for energy saving. In this study, operational optimization of a parallel pump network was investigated. Maximizing reliability and minimizing work consumption were the two objectives which were combined together by multiplication. A mixed-integer linear program(Problem 1) was built with turning on/off as the decision variable, whereas a mixed-integer nonlinear program(Problem 2) with both turning on/off and frequencies of pumps as decision variables was also built. Heuristic rule was proposed to solve Problem 1 for industrial usage.The results obtained by heuristic rules were compared to the global optima of problem 1 by enumeration searching. The results show that optimal solution of heuristic rules is easier to operate manually than the global optima among the total flowrate and head region, while the average work consumption is about 11% higher.Fluctuation of work consumption and reliability of the whole system obtained by heuristic rules were higher as well. When both turning on/off and frequencies were selected as the decision variables, average optimal work consumption of Problem 2 was about 8% lower than that of global optima of Problem 1. Less fluctuation of reliabilities was obtained as well. The minimum work consumption of cooling water was 0.105 kW·h·m~(-3).
引文
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[5]陈福利,王彧斐,冯霄.带有辅泵的循环水系统研究[J].计算机与应用化学,2017,34(3):213-216.CHEN F L,WANG Y F,FENG X.Study on an auxiliary pump network for recirculating cooling water system[J].Computers and Applied Chemistry,2017,34(3):213-216.
[6]SUN J,FENG X,WANG Y F.Cooling-water system optimization with a novel two-step sequential method[J].Applied Thermal Engineering,2015,89:1006-1013.
[7]SUN J,FENG X,WANG Y F.Simultaneous optimization of cooler and pump networks for industrial cooling-water systems[J].Chemical Engineering Transactions,2015,45:1915-1920.
[8]MA J Z,WANG Y F,FENG X.Energy recovery in cooling water system by hydro turbines[J].Energy,2017,139:329-340.
[9]GAO W,FENG X.The power target of a fluid machinery network in a circulating water system[J].Chemical Engineering Transactions,2017,205:847-854.
[10]祝铃钰,施佳琪,郑成霖,等.离心泵网络的节能设计与操作优化:综述与展望[J].高校化学工程学报,2017,31(6):1245-1258.ZHU L Y,SHI J Q,ZHENG C L,et al.Energy saving design and operational optimization of centrifugal pump network:A review[J].Journal of Chemical Engineering of Chinese Universities,2017,31(6):1245-1258.
[11]KOOR M,VASSILJEV A,KOPPEL T.Optimization of pump efficiencies with different pumps characteristics working in parallel mode[J].Advances in Engineering Software,2016,101:69-76.
[12]MA Z J,WANG S W.Energy efficient control of variable speed pumps in complex building[J].Energy and Buildings,2009,41(2):197-205.
[13]TIRMIZI S A,GANDHIDASAN P,ZUBAIR S M.Performance analysis of a chilled water system with various pumping schemes[J].Applied Energy,2012,100:238-248.
[14]BARAN B,LUCKEN C V,SOTELO A.Multi-objective pump scheduling optimization using evolutionary strategies[J].Advanced Software Engineering,2005,36(1):39-47.
[15]Hydraulic Institute,Europump,the U.S.Department of Energy’s Office of Industrial Technologies.Pump life cycle costs:A guide to LCC analysis for pumping systems[M].Parsippany:Hydraulic Institute,2001.
[16]BARRINGER H P.An overview of reliability engineering principles[M].Houston:Barringer&Associates,Inc,1996.
[17]武鹏.并联泵组高效高可靠性运行问题研究[D].杭州:浙江大学,2013.WU P.Study on the parallel pump unit with high efficiency and high reliability[D].Hangzhou:Zhejiang University,2013.
[18]WESTERLUND T,PETTERSSON F,GROSSMANN I E.Optimization of pump configurations as a MINLP problem[J].Computers&Chemical Engineering,1994,18(9):845-858.