【作者】 卢艳华；

【导师】 王一平；

【作者基本信息】 天津大学 ， 环境化工， 2010， 博士

【摘要】 通风是改善室内空气品质最有效的方式之一。新风负荷目前已占空调负荷的30-40%,其中60-80%的能量可以回收利用。针对现有新风余热回收设备的不足,本文提出了一种薄膜式新风换热器,首次利用塑料薄膜在空气流动作用下产生的振动来强化传热,提高换热器性能。论文对新风换热器中蕴含的流-固耦合问题进行了实验和数值模拟研究。其中,实验研究主要包括:空气低速错流流过振动薄膜在人为激励振动及流致振动条件下的传热特性;设计样机,建立了整机性能测试系统,研究了不同工况下样机的传热性能及阻力性能。数值模拟研究包括空气-薄膜耦合问题的动力模型和传热模型的建立,探讨了二维逆流及三维错流条件下空气流动和薄膜的相互作用及其对传热的影响机理,并以薄膜变形为参数定量分析了振动对传热的影响。研究结果表明:实验工况下,新风换热器换热效率在0.65~0.85之间,最大压降低于20.0Pa,节能效果明显。空气流动引起的薄膜振动能有效地改善传热,强化传热的程度与薄膜振动的强度成正比,薄膜变形大小(振幅)是改善传热的主要因素,变形越大,薄膜的换热效率越高。对于每种厚度的薄膜,风量存在一个上限(此时,换热通道内上下薄膜发生接触,导致换热恶化)。稳态模拟条件下,空气流动引起的薄膜变形改变了通道形状,从而改变了通道内的速度场和温度场分布。二维逆流模拟条件下,薄膜变形使得通道形状呈突扩/突缩,但变形从整体上没有强化传热,却导致压降明显增加,在高流速下甚至成倍增加;三维错流时,薄膜不同区域的变形程度不同,使得通道形状整体上不是简单的突扩/突缩变形,通道内的流场变化更加剧烈,对温度场的影响也更大,从而整体上改善了传热。更多还原

【Abstract】 Ventilation is one of the most effective means which can improve the indoor air quality, and has already accounted for about 30-40% of the building heating and cooling energy demand but as much as 70% of this energy can be reclaimed by using Heat Recovery Ventilators (HRVs). Aiming at eliminating the shortages of existing heat recovery equipment, a novel film fresh heat exchanger was put forward, which uses airflow-induced vibration.Experiments as well as numerical simulation were carried out to study the fluid-structure coupling problem inherent in the fresh heat exchanger. The experimental studies mainly include: the heat transfer performance of the vibrating film induced by airflow and mechanical method, and the prototypes design of fresh air heat exchanger with different film thickness. The experimental systems for the performance of fresh air heat exchanger were set up. During the numerical study, the dynamic and heat transfer models of the airflow-film interaction were established, the interaction between the airflow and the film and its effect on heat transfer were studied under the flow styles of two-dimensional counter-current flow and three-dimensional cross-flow.The results show that the effectiveness of the heat exchanger varies from 0.65 to 0.85 with airflow rate, the pressure drop is less than 20.0 Pa, and has remarkable energy-saving effect. The film vibration induced by airflow can improve the heat transfer, and the enhancement extent is in proportion to the film vibration intensity. The amplitude of the film deformation is the major factor in improving the heat transfer. Larger air flow rate tends to decrease the effectiveness till some point where the channel films contact each other and makes for a worse heat transfer performance. The channel deformation induced by the steady fluid flow can change the velocity field and temperature field in the channels. The geometry of channel became converging-diverging configuration or diverging-converging configuration caused by the deformation of film, and the channel deformation did not improve the overall heat transfer performance relative to rigid channels, but the pressure drop doubles at high flow speed under the conditions of counter-current flow. Under the conditions of the three-dimensional cross-flow, the amplitude of the film deformation varies in different domain, which makes the geometry of channels are not the configuration of converging-diverging or diverging-converging in a whole. As a result, the velocity field in the channels varies more intensely, and leads to the improvement of heat transfer.更多还原