海水源热泵用双螺旋管海水换热器传热特性的研究

发布时间：2018-10-24 14:07

【摘要】：结合我国沿海建筑能源紧张的现状,高效、节能、环保的海水源热泵系统作为沿海建筑的冷热源具有重要的研究价值和应用前景。因此,本文提出了一种用于海水源热泵系统的新型双螺旋管海水换热器,并对该换热器的换热特性进行了实验与模拟研究。并且基于北方沿海地区,冬季海水温度接近冰点温度的特点,本文不仅研究了该换热器夏季工况与冬季非结冰工况的换热特性,还着重研究了冬季结冰工况的换热特性。首先,分别建立了双螺旋管海水换热器在冬季结冰工况、非结冰工况及夏季工况下的数学模型,并在天津国际邮轮母港搭建了双螺旋管海水换热器性能测试实验系统。在上述三种工况下,分别对双螺旋管海水换热器沿管长的温度分布进行了测试,并对冬季结冰工况下沿管长的冰层厚度分布进行了测量。将实验结果依次带入到相应的数学模型中,对该换热器的管外对流换热系数进行求解,获得该换热器在测试期间的管外对流换热系数变化范围:冬季非结冰工况下海水流速为0.07~0.38 m/s时,对应的管外对流换热系数为427.8~712.8 W/(m2?K);冬季结冰工况下海水流速为0.21~0.53 m/s时,对应的管外对流换热系数为582.8~853.9W/(m2?K);夏季工况下海水流速变化范围在0.09~0.47 m/s时,管外对流换热系数的变化范围为451.7~762.4 W/(m2?K)。其次,利用双螺旋管海水换热器夏季工况及冬季结冰与非结冰工况的数学模型,对其在海水中的传热特性进行了模拟预测,即通过数值模拟的方法,研究了换热器管长、管径、管内流体流速、入口温度以及海水温度等因素对该换热器换热特性的影响,并模拟了冬季结冰工况下该换热器管外冰层的结冰规律以及结冰对换热器换热特性的影响。最后,以天津港南疆港区内某办公楼应用的海水源热泵系统为例,给出了双螺旋管海水换热器详细的选配方法并对其管内流体流速的经济性进行了分析。利用Energyplus能耗模拟软件对该办公楼全年负荷进行模拟计算,以全寿命周期成本及费用年值为评价指标,对该办公楼选用直接取水模式的海水源热泵系统、渗滤取水模式的海水源热泵系统以及双螺旋管海水换热器的海水源热泵系统的经济性进行了对比分析,并对其节能环保效益进行了评价。
[Abstract]:Combined with the current situation of energy shortage in coastal buildings in China, the sea water source heat pump system with high efficiency, energy saving and environmental protection has important research value and application prospect as the cooling and heat source of coastal buildings. Therefore, a new type of double helical tube seawater heat exchanger for sea water source heat pump system is proposed in this paper, and the heat transfer characteristics of the heat exchanger are studied experimentally and numerically. Based on the characteristics that the sea water temperature is close to the freezing point temperature in the northern coastal area, this paper not only studies the heat transfer characteristics of the heat exchanger in summer and non-icing conditions in winter, but also focuses on the heat transfer characteristics of the freezing condition in winter. Firstly, the mathematical models of double-helical tube seawater heat exchangers in winter icing, non-icing and summer conditions were established, and the performance test system of double-helix sea water heat exchangers was built in Tianjin International Cruise Port. The temperature distribution along the tube length and the ice thickness distribution along the pipe length were measured under the above three conditions. The experimental results are introduced into the corresponding mathematical model in turn, and the convection heat transfer coefficient outside the tube of the heat exchanger is solved. The variation range of convection heat transfer coefficient of the heat exchanger outside the tube during the test period is obtained: when the seawater velocity is 0.07 ~ 0.38 m / s in winter, the corresponding convection heat transfer coefficient is 427.8 ~ 712.8 W / (m ~ (2) K), and the sea water velocity is 0.21 ~ (0.53) m / s under freezing condition in winter, and the corresponding convection heat transfer coefficient is 712.8 W / (m ~ (2) K) in winter when the water velocity is 0.07 ~ 0.38 m / s. The corresponding convection heat transfer coefficient is 582.8~853.9W/ (m ~ 2 ~ (2) K), and the variation range of convection heat transfer coefficient is 451.7N ~ (762.4) W / (m ~ (2) K) when the variation range of seawater velocity is 0.09 ~ 0.47 m / s in summer. Secondly, by using the mathematical model of double-helical tube seawater heat exchanger in summer and winter icing and non-icing conditions, the heat transfer characteristics in seawater are simulated and forecasted, that is, the tube length and diameter of the heat exchanger are studied by numerical simulation. The effects of flow velocity, inlet temperature and seawater temperature on the heat transfer characteristics of the heat exchanger were studied. The ice formation law of the outer ice layer and the effect of ice formation on the heat transfer characteristics of the heat exchanger in winter were simulated. Finally, taking the sea water source heat pump system used in an office building in Nanjiang Port of Tianjin Port as an example, a detailed selection method of double helical tube seawater heat exchanger is given and the economy of the flow velocity in the pipe is analyzed. The Energyplus energy consumption simulation software is used to simulate the annual load of the office building. Taking the life cycle cost and cost annual value as the evaluation index, the sea water source heat pump system with direct water intake mode is selected for the office building. The economy of the sea-based water source heat pump system based on leachate mode and the sea water source heat pump system with double helical tube seawater heat exchanger is compared and analyzed, and its energy saving and environmental protection benefit is evaluated.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU83

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