【作者】 何克青；

【导师】 晋欣桥；

【作者基本信息】 上海交通大学 ， 供热、供燃气、通风及空气， 2012， 硕士

【摘要】 伴随着世界经济的快速发展以及人民生活水平的不断提高,空调系统的应用也越来越广泛。空调系统的广泛应用使得其系统能耗也与日俱增,有资料显示,当前建筑能耗占总能耗的20%左右,而空调系统能耗占建筑能耗的30～50%左右,因此,空调系统应用和发展的关键问题之一是要降低其能耗。当今的暖通工作者的任务不仅仅是满足空调的设计要求,而且要更多地关注系统的节能设计以及系统的优化控制策略。目前,中国的电子工业的迅速发展对电子厂房空调系统的需求也越来越高。电子厂房空调系统往往需要全年供冷且冬季机组能耗仍然很大,现有的电子厂房空调系统绝大多数均采用全年冷水机组供冷方式。而在上海地区,由于冬季及过渡季节室外空气焓值较低,因此可以利用自然冷源部分或全部替代冷水机组供冷,从而减少空调系统全年的运行能耗。在此背景下,本文针对上海地区电子厂房,开展了冷却塔自然供冷空调系统的节能分析、控制设计、结构优化设计和控制优化等方面的研究。首先,根据研究对象空调系统的组成和具体特性,建立冷却塔自然供冷空调系统各部件的数学模型,包括离心式冷水机组、横流式多风机冷却塔、分集水器、水泵、三通阀、逆流式板式换热器、空调负荷等,然后利用TRNSYS17软件平台,建立了电子厂房冷却塔自然供冷空调系统的数字仿真器。在冷却塔自然供冷空调系统设备部件仿真的基础上,本文还设计并仿真了冷却塔自然供冷空调系统的基本控制系统。包括冷水机组启停控制、冷却塔启停控制、冷却塔出水温度控制、供冷模式转换控制。合理的控制设计能够保证系统在期望的模式下运行。在空调系统能耗中,冷水机组能耗所占比重很大,采用冷却塔自然供冷可以减小冷水机组运行能耗,尽可能地采用冷却塔自然供冷可以最大程度地减少机组能耗,因此,本文针对基本控制系统,设计了冷却塔优先供冷的基本运行控制策略。其次,在仿真的基础上,以上海地区典型年气象数据为室外气象条件,以自然供冷率和系统全年运行能耗为主要评价指标,通过仿真实验对电子厂房冷却塔供冷空调系统的节能潜力进行了分析。研究了不同参数对系统能耗的影响,包括冷冻水供水温度、冷却塔设计效率和板式换热器面积。研究结果表明,电子厂房冷却塔自然供冷空调系统具有较大的节能潜力,采用基本控制策略的冷却塔自然供冷空调系统,相比于无自然供冷系统全年可以节能34.2%。同时,系统的冷冻水供水温度、冷却塔的设计效率和板式换热器的面积对自然供冷率影响较大,提高冷冻水供水温度、冷却塔的设计效率和增加板式换热器的面积可以明显地提高系统的自然供冷率。再次,在节能分析的基础上,本文对换热器的选型进行了优化设计。冷却塔自然供冷空调系统与常规空调系统的最大区别在于增加了一个板式换热器,如何设计板式换热器的大小直接影响系统的运行能耗。选择大的板式换热器意味着减小可以减少系统的运行能耗,但同时这也增加了初投资。本文从投资回报率和系统生命周期内减少的运行费两方面的综合衡量,研究并提出了基于经济性的系统优化设计方法,为工程设计提供了理论基础。最后,为了使系统实时运行能耗最优,本文针对冷却塔自然供冷空调系统,根据冷水机组和冷却塔在不同部分负荷率情况下性能系数的不同,提出了冷水机组和冷却塔最佳负荷分配优化控制策略,并在系统仿真平台上,通过单个试验日工况和全年工况,对该优化控制策略进行了验证和分析。研究结果表明,该优化控制策略能够稳定、可靠地对系统进行优化控制,相比于无冷却塔自然供冷和有冷却塔自然供冷并采用基本控制策略的情况,采用该优化控制策略能够进一步节省系统的运行能耗,全年运行工况下分别可以节能38%和5.7%。更多还原

【Abstract】 With developing of economy and the rising of the living standard, the air conditioning systems are equipped in more and more buildings. With wide use of air conditioning systems, the rapidly growth of energy consumption of the air conditioning systems becomes a big problem in the world. It was reported that the air conditioning systems had used 30~50% of the energy consumption of the buildings which was about 20% of total energy use. So, it is the key issue for using and developing air conditioning system to reduce its energy use. Currently, the mission of designers is not only to satisfy the basic design requirements, but also to develop new energy saving system and new optimal control strategies.Currently, with developing of electronic industry in China, the quantity the air conditioning systems for electronic manufactory building has grown rapidly. For electronic manufactory building, the air conditioning system usually runs at cooling mode in whole year and its cooling load is also large in winter. The normal air conditioning systems for electronic manufactory building is designed to cool by chillers. However, in Shanghai, the chillers can be replaced partially or entirely by free cooling in winter. The free cooling of using cooling tower can reduce the annual energy consumption of system.Based on those above, for the air conditioning system with free cooling, this study carries out the energy saving evaluation, control system design, optimal configuration design and optimal control strategy.Firstly, according to the characteristics of the air conditioning system with free cooling, the models of the components of system is setup, including centrifugal chiller, cross flow type cooling tower, water mixing and separator, pump, three way valve, count flow type plate heat exchanger, cooling load. They are linked by TRNSYS 17 and setup the simulation of the air conditioning system with free cooling for electronic manufactory building in Shanghai.Based on simulation, the local controllers are designed for the air conditioning system with free cooling, including operation mode controller, chiller on/off operation controller, cooling tower on/off operation controller and cooling tower outlet water temperature controller. Those local controllers can ensure the system to run at expected mode reliably and stably. To reduce chiller energy consumption as possible as it can, the control strategy of prior cooling tower is developed and set as the basic control strategy of system operation.Secondly, the energy saving of the air conditioning system with free cooling is evaluated by ratio of free cooling and annual energy consumption, and the potential of energy saving is analyzed by simulation. The effects of parameters, including supply water temperature setpoing, rated efficiency of cooling tower and size of plate heat exchanger, are studied. The study concludes that the air conditioning system with free cooling can save a large of system energy use and it is about 34.2% less than the air conditioning system without free cooling in one year. The study also concludes that the parameters of supply water temperature setpoint, rated efficiency of cooling tower and size of plate heat exchanger can strongly affect the energy saving of the air conditioning system with free cooling. Increasing supply water temperature setpoint, or using high rated efficiency of cooling tower, or enlarging size of plate heat exchanger can improve ratio of free cooling and can save more energy obviously.Thirdly, based on balance of return on invest and the total operation cost reduction in life cycle, the optimal configuration design method is presented. It can be used to select the size of plate heat exchanger and design of system. Finally, to make system more efficient, the optimal control strategy based on load allocation of chillers and cooling tower is presented. The optimal control strategy is designed to optimize the load ratio of chillers and cooling tower according their COP varying under the different loading. The optimal control strategy is tested and validated by a typical day and annual simulation tests. The results show that it can control system operation reliably and stably, and it can save 38% energy compared with the air conditioning system without free cooling, and save 5.7% energy compared with the air conditioning system with free cooling under the basic control strategy.更多还原