【作者】 刘灿；

【导师】 方玉堂； 顾军；

【作者基本信息】 华南理工大学 ， 化学工程， 2011， 硕士

【摘要】 换热器广泛应用于冷冻、空调、空间采暖以及化学工程等领域。以翅片管换热器为例,在其翅片表面涂上吸湿涂层后,与同类型换热器相比,不仅能进行显热交换,也能进行潜热交换,因此,可提高其换热效率,应用于空调系统,能显著提高空调能效比,降低系统能耗。本文对翅片管换热器铝箔表面吸湿涂层进行了研究。本文首先采用静电喷涂工艺,以干燥剂硅胶粉和胶粘剂粉末涂料的混合物做喷涂料,将其喷涂到铝箔表面,经加热固化得吸湿涂层;然后采用浸渍方法,将含有吸湿涂层的铝箔浸渍到含氯化锂、氯化钙、氯化镁等吸湿性盐溶液中,以进一步改善涂层吸湿性能;系统探讨硅胶粉质量分数、浸渍盐浓度、浸渍温度和浸渍时间对翅片涂层性能的影响;采用扫描电子显微镜及其能谱(SEM-EDS)、比表面积孔隙分析等手段对改性吸湿涂层的组成、表面形态、孔结构进行表征;采用热失重(TG)评价改性吸湿涂层的热稳定性。实验发现,随着喷涂料中硅胶粉质量分数的增加,吸湿涂层吸湿性能增加,但是当硅胶粉质量分数过大时,形成的吸湿涂层易开裂,并影响硅胶颗粒在铝箔表面的分散性;浸渍吸湿性盐溶液后的改性吸湿涂层,能显著提高其吸湿量。SEM表征显示吸湿涂层能均匀地分散在铝箔表面,EDS分析显示出吸湿涂层各成分组成;孔隙分析显示,改性后吸湿涂层,平均孔径略有增大,孔容和比表面积略有减小;TG分析表明,吸湿涂层失重主要集中在较低温度段(30~200℃)和较高温度段(300~600℃),前者与吸附剂脱附有关,后者与涂料热分解有关。静态、动态吸附测试结果显示,在较低温度、湿度,或在较高温度、湿度下,改性吸湿涂层的吸附性能与未改性相比,都有较大的改善。在铝箔表面吸湿涂层研究基础上制作的翅片管除湿换热器,应用于空调系统,测试结果显示出较好的空调系统能效比。更多还原

【Abstract】 Heat exchangers are widely used in the fields of refrigeration, air conditioning, space heating, and chemical engineering, etc. For example, the finned tube heat exchanger which coated hygroscopic coating on the finned surface, can exchange sensible heat and latent heat simultaneously, therefore, it can improve the heat exchange efficiency. Used in air conditioning system, it can significantly improve air-conditioning’s coefficient of performance (COP) and reduce energy consumption. This paper is focus on aluminum foil desiccant coating in the finned tube heat exchanger.By means of electrostatic spraying, the hygroscopic coating on the aluminum foil surface was accompolished by spraying and thermosetting the mixture of silica gel powder for dehumidifying and powder coating for bonding. In order to further improve the adsorption performance of desiccant coating, by means of impregnation, the modified hygroscopic coating was finished by impregnating the aluminum foil with hygroscopic coating into the salt solution of LiCl, CaCl2 and MgCl2, The effects of the silica gel mass fraction, the impregnation conditions such as the salt concentration, the impregnation temperature and time on the adsorptive performance of the finned coating were investigated systematically. The composition, surface morphology and pore structure of the modified hygroscopic coating were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM-EDS) and porous medium analysis. Thermogravimetry (TG) was used to evaluate the thermal stability of the modified hygroscopic coating.The experimental results showed that the adsorption performance of hygroscopic coating enhanced with the increase of mass fraction of silica gel powder. However, the excessive silica gel resulted in the cracks’ appearance on the hygroscopic coating surface, and also influenced the dispersity of silica gel particles on the aluminium foil surface. The adsorption ability of the hygroscopic coating was significantly improved by impregnating hygroscopic salt solution. SEM image showed that desiccant coating can evenly scatter on the aluminium foil surface, EDS analysis revealed the component of the hygroscopic coating. Pore structure analysis showed that, after impregnation, the average pore diameter of the hygroscopic coating slightly increased, while its pore volume and specific surface area slightly reduced. TG analysis showed that the thermal weight loss of the hygroscopic coating mainly concentrated in the lower temperature period (30~200℃) and the higher temperature period (300~600℃). The former corresponded to the desorption of silica gel desiccant and the latter corresponded to the decomposition of epoxy- polyester coating. The result of the static and dynamic state adsorption tests showed that, under lower temperature and humidity, or under higher temperature and humidity, the adsorption performance of modified hygroscopic coating was higher than that of no modified hygroscopic coating.The finned tube heat exchanger with aluminum foil desiccant coating was used in air conditioning system, the test result showed that the novel air conditioning system has a excellent COP.更多还原