【作者】 程可辉；

【导师】 白雪莲；

【作者基本信息】 重庆大学 ， 供热、供燃气、通风及空调工程， 2011， 硕士

【摘要】 江水源热泵是目前大力推广的可再生能源利用技术。在水质条件较好的情况下,直接式系统因其对能源利用的高效在工程应用中被广泛采用。但是江水在一定条件下,很有可能产生污垢、磨损、锈蚀以及由于微生物不断繁殖而产生生物污泥等问题,由此将造成管道堵塞、能耗增加、机组的正常运行受到影响、制冷制热效果降低以及设备使用寿命缩短等。因此,在利用时,应注意对水质的要求及处理,防止出现换热、管路腐蚀等问题。同时,要考虑长期运行时换热效率下降对系统的影响。因此,对直接式水源热泵系统的机组换热器污垢形成机理及其对流动换热特性的影响展开研究是水源热泵技术推广应用的重要基础。本研究针对重庆地区江水源热泵换热器,进行污垢成因与时变规律,及其对换热器流动换热特性影响的研究,并得到了相关结论。通过江水水质的测试与分析,得到了水质指标的变化规律。通过对比实际水质状况与现行标准中对水质的要求,提出了全年利用江水时的重点处理对象。根据江河水与地下水水质的不同,建议江河水源热泵宜增加COD、电导率以及溶解氧等水质指标的限定。通过对影响江水源热泵换热器结垢的因素分析,发现其关键因素是含沙量和浊度,引起结垢的因素不包括藻类的作用。参照江水近几年的泥沙粒径分布情况,分别配置不同含沙量和浊度的水样31组,实测分析并得到了江水含沙量与浊度的相互关系。对试验系统换热器的实际污垢分别进行烘干灼烧失重分析、EDS能谱扫描分析和扫描电镜分析,均表明换热管内的污垢以泥沙颗粒污垢为主,附着在换热管上的污垢密致,质地坚硬,以小粒径泥沙为主。在重庆嘉陵江磁器口段的游船上搭建了江水源热泵换热器污垢研究试验台,进行了热阻法监测管内污垢首次生长特性实验和污垢清洗后再次生长特性实验研究。研究发现,首次生长时换热管内水流速为0.6m/s、1.0m/s和1.5m/s对应的污垢诱导期分别为55h、74h和86h,并且对应污垢稳定热阻值分别为10×10^-5（m²·k）/w、6×10^-5（m²·k）/w和5×10^-5（m²·k）/w。诱导期与流速成正比关系,而污垢稳定热阻值与流速成反比关系。对于流速为0.6m/s、1.5m/s的换热管污垢清洗分别采用双倍流速反冲洗和尼龙刷清洗,分析论证了江水源热泵换热器污垢清洗的效果。新换热管管道内的污垢生长特性（忽略诱导期）呈现首次的指数函数式缓慢生长和再次的指数函数渐近式特性快速生长;而除垢后管内污垢生长特性仅呈现指数函数渐近式生长过程。研究表明,管内污垢层是由难以除掉的基层和易于清洗的附着层构成,污垢前期的指数函数渐近式缓慢增长特性反映了污垢基层的生长过程,而后期的指数函数渐近式生长特性反映了污垢附着层的形成过程。对于新换热管而言,污垢的生长首先是基层的形成,然后是难以清除的附着层的形成;对于除污后的换热管,污垢再次生长过程主要是附着层的形成。通过实际江水源热泵换热器污垢时变特性的分析,基于Zubair和Sheikh等人提出的渐近增长模型,针对管内流速为1.0m/s和1.5m/s两种工况,研究提出了分别包括首次渐近式增长阶段、暂时平衡阶段、再次渐近式增长阶段和再次平衡阶段的污垢预测模型,并且对该污垢预测模型进行了验证分析。对比分析换热管内流速为0.6m/s、1.0m/s和1.5m/s时的稳定污垢热阻值,确定重庆嘉陵江水源热泵稳定污垢热阻值可取5.5×10^-5（m²·k）/w。并且对污垢进行火用分析,发现在水浴温度一定的条件下（即恒定温度）,不同流速下的变化情况,从与污垢相关的三项火用损失系数之和的变化可以看出,就本实验而言取流速在1.0m/s¹.5m/s之间数据比较合适。针对江水源热泵在实际应用中对换热器污垢的考虑,试验对比分析了水源热泵换热器目前常用的两种清洗方法:尼龙刷清洗和小水量强力轮替冲洗。研究指出,尼龙刷清洗存在不能完全回笼的问题,而小水量强力轮替冲洗方法只局限于单管程和双管程壳管换热器除污,因此均需要更合理的新技术引进。并且根据实际江水的变化特点,在江水洪峰到来时,换热管污垢热阻在极短时间内即可达到稳定值。因此,需要在洪峰过后即进行除垢处理。而当江水水质较好,即洪峰到来之前或之后,江水仅需进行一般过滤即可直接进入机组。本研究完成了重庆地区嘉陵江和长江水质的空调制冷期与供暖期的测试与分析、江水源热泵换热器污垢研究试验台的搭建、热阻法监测管内污垢首次生长特性实验和污垢清洗后再次生长特性实验研究,提出了全年利用江水时的重点处理对象、影响江水源热泵换热器结垢的关键因素、江水含沙量与浊度的相互关系、管内污垢层的构成以及对应的污垢预测模型,得到了江河水源热泵宜增加限定的水质指标、污垢成份、不同流速下稳定污垢热阻值、新换热管管道内的污垢生长特性、江水源热泵水源侧换热管内推荐流速值以及机组的清洗周期。研究结论为水源热泵污垢的深入研究奠定了基础,也为相关标准的制定提供了依据,在实际工程应用中也可以此为参考。更多还原

【Abstract】 River water-source heat pump is the promotion of renewable energy technology. In the conditions of water quality better circumstances, open-type system are widely used because of the energy utilization efficiency in the engineering applications.But in certain conditions of water quality, fouling, wear, corrosion , biological sludge due to microbial continuous reproduction and and other issues may be produced, which will cause many problems such as pipeline is blockaged, energy consumption is incre-ased, the normal operation of the turbine is affectd, the refrigerating and heating effect is reduced and the service life of the equipment is reduced . Therefore, when in use, attention should be paid to the requirement of water quality and treatment to prevent the emergence of heat exchanger, pipeline corrosion problems and soJ on. Meanwhile, it must be considerd that the long-term operation may reduce influence of heat exchange efficiency on system. Therefore, fouling formation mechanism research on unit heat exchanger of water source heat pump system of open-type system and reserch on its effect on flow and heat transfer characteristics are important basisof water source heat pump technology popularization and application. his research is based on the Chongqing river water source heat pump heat exchanger.The pape includes fouling causes and time-varying regularity, and its effect on the heat exchanger of flo-wand heat transfer characteristics of impact studies, and the conclusion is obtained.The variation rule of water quality indexes is obtained by mean of the river water quality testing and analysis. By comparing the actual water quality status and current standards of water quality requirements, key treatment objects are put forward when annual water is used.Because the river water quality and groundwater quality is differ-ent, the index limit of the proposal COD, conductivity and dissolved oxygen of water quality should be increased into river water quality standard on source heat pump. Through the influence factor analysis of river water source heat pump heat exchanger fouling,it is found that the key factor is the sediment concentration and turbidity, and causing scaling factor does not include the role of algae.With reference to the sediment particle size distribution of the river in last few years, after 31 groups different sedi-ment concentration and turbidity of water are respectively prepard, the relationship of the river sediment concentration and turbidity is obtainde by experimental analysis. The test system of heat exchanger fouling includes drying calcination loss analysis, EDS spectrum scanning analysis and scanning electron microscope analysis.The resu-lts show that fouling of the heat exchange pipe mainly includes sediment particles of fouling.The fouling is dense and hard texture and its main component is small particle diameter silt.Experiment platform on heat exchanger fouling of river water source heat pump was built on segment cruise ship in Jialing River Ciqikou ,Chongqing.The experiment includes the thermal resistance method for monitoring fouling in pipes first growth characteristic experiment and dirt cleaning again after the experimental research on growth characteristics. Study found that when the first growth, flow rate on heat exch-ange tube water was 0.6m/s, 1.0m/s and 1.5m/s and the fouling induction period of its corresponds was 55h, 74h and 86h. And corresponding stable thermal resistance we-re 10×10^-5（m²·k）/w,6×10^-5（m²·k）/w and 5×10^-5（m²·k）/w.The induction period and velocity is directly proportional, and stable thermal resistance and velocity is inversel-y proportional.For the flow rate of 0.6m/s, 1.5m/s of tube heat exchanger fouling, the cleaning methods included using double flow backwashi-ng and nylon brush cleaning.The results showed cleaning effect of water source heat pump heat exchanger fouling is relatively good.New heat exchange tube within the conduit （ induction period of growth charact-eristics of fouling in neglect ） appears first exponential function type slow growth and exponential asymptotic characteristic again fast growth. And after scale removal gro-wth characteristics of fouling in pipes only presents exponential asymptotic growth process.Research shows that, fouling layer within the tube is made of grass hard to get rid of and the easy cleaning attachment layer.The linear slow growth characteristics of fouling reflect the fouling grass growth process. During the late exponential asym-ptotic growth characteristics reflect the fouling layer forming process. To the new heat exchange tube, first fouling growth is the basic form, and it is difficult to remove the adhesive layer formation. For the heat exchange tube after decontamination, process of fouling again growth is the main adhesive layer formation.Through time-varying characteristics analysis of the actual river water source heat pump heat exchanger fouling, based on the asymptotic growth model proposed by Zubair and Sheikh, inside the tube flow rate of 1.0m/s and 1.5m/s in two different conditions, Study suggests including asymptotic growth phase for the first time,temporary equilibrium stage, asym-ptotic growth stage again and again equilibrium stage model for prediction of fouling.And the prediction of fouling model has been validated and analysised.Stabilizing fouling thermal resistance on the heat exchanger tube flow rate of 0.6m/s, 1.0m/s and 1.5m/s is analysised.Stability of fouling thermal resistance of water source heat pump in Chongqing Jalingjiang can be valued 5.5×10^-5（m²·k）/w. Through exgery analysis,the results showed that under certain conditions of constant temperature and under different flow rate changes, velocity between the 1.0m/s¹.5m/s value is appropriate by the analysis of three exegry coefficients associated with fouling.Heat exchanger fouling of water source heat pump in practical applications are considered. The two currently-used methods of water source heat pump heat exchang-er cleaning are comparatively analysised by the test.The methods are nylon brush to clean and powerful rotation of small water flushing.The results showed that the meth-od of nylon brush to clean has problems of not completely withdrawn from circulation. And the method of small water, strong rotation processing is confined to single-tube and double-tube shell and tube heat. So more reasonable and new technology are needed to be introduced. In the flood peak of the river, fouling resistance of tube heat exchanger can achieve the stable value in a very short period of time.Therefore, cleaning after the flood peak is needed. When the river water quality is good, before or after the flood comes, water only general filter can be directly into the unit.Water quality testing and analysis of air conditioning and refrigeration and heati-ng period in Chongqing jialing River and Yangtze River have been done.Experiment platform on water source heat pump heat exchanger fouling research has been set up. Thermal resistance method for monitoring fouling in pipes first growth characteristic experiment and dirt cleaning again after the experimental research on growth charact-eristics have been done.Key treatment indexs of water quality have been put forward. Key factors that affect river water source heat pump heat exchanger fouling have beendetimered. Relationship between river sediment concentration and turbidity have been identified. Tube fouling layer and corresponding fouling prediction model have been put forward. The increased limit of water quality index on river water source heat pu-mp have been dertimered. Fouling composition, fouling thermal resistance under different velocity stability, the growth characteristics of fouling in new heat exchanger tube pipe, recommended velocity values of river water source heat pump the water side heat transfer tube and the cleaning cycle on unit has been obtained by experimentand analysis.The conclusion of the study laid the foundation for further study of water source heat pump fouling, provides the basis for formulation of related standards, and also is as a reference in practical engineering application.更多还原