【作者】 王子云；

【导师】 付祥钊；

【作者基本信息】 重庆大学 ， 供热、供燃气、通风及空调工程， 2008， 博士

【摘要】 在国家大力提倡节能减排的形势下,发展可再生能源是缓解我国能源短缺局面、调整我国能源结构的不合理性、保护环境的有效方式,是实现社会和环境可持续发展的必由之路。相对于空气温度而言,江河水水温度更为稳定,冬季比室外气温高,夏季比室外气温低,是一种较好的建筑用冷热源。论文在对长江重庆段江水水源概况进行详细实验调研的基础上,对发展长江水源热泵的技术路线和关键技术展开了研究。应用湍流流动理论、计算流体力学、两相流和对流换热理论,对长江水源热泵用换热器进行理论和实验研究。研究方法、内容和成果如下:以长江重庆段江水为例,对江水温度的日逐时变化、日平均变化和月平均变化进行了详细实验调研和分析,得出江水日波动在0.5℃以内,与气温日波动10几℃相比,是一种稳定的冷热源;江水的横断面水温分布均匀;江水做水源热泵的冷热源的主要水质问题是泥沙含量和水中的悬浮物,长江悬移质泥沙主要为粉砂和粘土。三峡库区的形成对重庆段江水夏季水位影响较小,因此江水水质变化不大。通过对长江水源热泵系统的技术路线、节能性和环保性分析,提出了适合发展长江水源热泵技术的开式直接系统。开式直接江水源热泵可分别比冷水机组+燃气锅炉系统和空气源热泵系统节能减排33%和40%。由于江水的流动性,江水源热泵系统可有效缓解城市热岛效应。江水泥沙颗粒的运动规律是两相流研究的基础。论文对颗粒运动微分方程进行详细的分析讨论,建立了三维颗粒运动微分方程的直接模拟数值方法。分析了颗粒在液体中受到非线性曳力、Basset力以及虚拟质量力作用时的沉降规律。对颗粒在流体中的阻力和升力进行了量级分析,得到在液体中的颗粒运动,除了考虑惯性力、曳力、压力梯度力和重力外,需要考虑Basset力以及虚拟质量力,而Saffman升力和Magnus升力则主要在靠近壁面的附近起作用。应用大涡模拟和颗粒相直接模拟技术对颗粒在突扩管内的扩散进行了数值分析,结果表明随着St P数的增加,颗粒的扩散度是减小的,也可以看出由于湍流的作用,流场对小粒径颗粒的携带能力更强。对江水换热引起的污垢热阻,采用热力学第一、二定律和熵产分析法,分析污垢对管内对流换热过程性能的影响。从污垢的形成过程看,熵增率是逐渐增加的,同时引起整个对流换热过程的不可逆性的增加。在相关理论研究的基础上,论文首先根据江水的水质特点对适合于长江水源热泵的换热器型式进行了分析讨论,分别提出了适合大型机组换热器型式(专利申请号200810069811.1)和中小型机组的单流道套管式换热器。对影响套管式换热器泥沙分离的半圆环形折返管内流动、换热以及两相流进行了数值模拟,得出折返管内存在明显的二次流现象,并且由于二次流的作用,使得换热管的对流换热性能较直管有一定的增加。而含沙江水两相流采用两流体连续介质模型,对不同曲率折返管内含沙江水两相流进行了数值模拟,得到当R/r在10～40的范围内,泥沙分离出现极小值的结果。在以上分析的基础上设计内壁采用光滑,外壁带有螺旋槽的换热内管,折返管弯曲度为R/r=12的实验用套管换热器,并采用数值方法对换热器的换热性能、阻力以及泥沙两相流进行了分析,换热性能和阻力分析结果表明,采用计算流体力学分析方法可满足工程应用的要求,可作为工程辅助设计的参考,而泥沙两相流分析的结果表明换热器不会出现泥沙堵塞的现象。在换热器实验研究方面,为了验证数值模拟的结果,论文对换热器分离堵塞进行了实验研究,得到换热器在泥沙流动稳定后,不会出现由于泥沙的分离而产生堵塞现象。最后论文对所设计换热器进行了热泵机组的冬季实验和夏季实验研究,经过实际工况的分析,换热器没有出现堵塞现象,同时换热器性能良好,能够得到实际应用,有推广的价值。更多还原

【Abstract】 Under the national energy saving and emission reduction situation, the development of renewable energy is the effective way of releaseing national energy shortage, adjusting the un-reasonable national energy structure, environmental protection, and is the only way of society and environment sustainable development.Compared with the air temperature, the temperature of river water is more stable,higher than air temperature in winter and lower in summer, and is a better cold and heat source used in building. Basing on the detailed investigation of Yangtze River water source in Chongqing,P.R.China, the technical route and key technology of river water source heat pump are studied.Using turbulent flow, computational fluid dynamics, two-phase flow and convection heat exchange theory, the heat exchanger used by river water source heat pump is studied theoretically and experimentally, which is a key technical problem of the development of river water source heat pump technology. Research methods, contents and Achievements are as follows:Hourly, daily and monthly average water temperature of Yangtze River in Chongqing,P.R.China are investigated and analysed Detailedly. The results show that the water temperature fluctuation is below 0.5℃, river water is a better cold and heat source than air , whose temperature fluctuation is larger than 10℃.Yangtze River cross section water temperature is well distributed. The quality problem is that river water contains much sediment and suspended matter. Yangtze River suspended sediment is mainly silt and clay. The formation of Three Gorges Reservoir Region has little influence on Yangtze River water level in Chongqing, P.R.China. So the water qulity changes little.By analysis technical route, energy saving and environmental protection of river water source heat pump system, the open-direct system of reasonablely developing of river water source heat pump technology is presented. Open-direct river water source heat pump system could save 33% energy than chiller and gas-fired boiler system, and 40% than air source heat pump system. River water source heat pump system can release the urban heat island effect because of the river water fluidity.The motion law of river sediment particle is basis of the river water two-phase flow research. The particle motion differential equation is analysed detailedly and the three-dimensional direct numerical method of particle motion differential equation is established. the settlement regularity of particle under non-linear drag force, Basset force and virtual mass force is analysed. By analysing magnitude of resistance force and lift force, the results show that the inertial force, drag force, pressure gradient foree, gravity alse with Basset, virtual mass force should be considered in particle-liquid motion. The Saffman force and Magnus force is only significant near wall.Using the large eddy simulation and particle direct simulation, the diffusion of particle in sudden expansion pipe is modeled. The results show that the diffusion degree of particle decreases with increase of St P number. Because of turbulence effect,the small particle can be taken more easily .Using the first and the second laws of thermodynamic, the entropy generation analysis, the influence of fouling on performance of convection heat transfer process inside pipe is analysed. Entropy production increased with the formation of fouling and caused the irreversibility of convection heat transfer process increased.Based on the water quality characteristics of Yangtze River, the heat exchanger type used in river water source heat pump is analysed and discussed, heat exchanger type used in large unit(patent application number 200810069811.1) and double pipe heat exchanger used in middle and small unit is presented.The flow,heat exchange and two-phase flow inside semi-annulus reentry pipe, which affected the sediment separation in pipe double pipe heat exchanger, is simulated numerically. The results show that secondary flow phenomenon is significant in semi-annulus reentry pipe. The performance of convection heat transfer will increase because of secondary flow phenomenon. Using two-fluid continuum model,the flow of the river water with sediment in semi-annulus reentry pipe of various curvature is simulated. The results show that separation of sediment has minimum when R/r ranges from 10 to 40.Using smooth inner wall and spiral groove exine pipe, whose R/r is 12, the experimental double pipe heat exchanger is designed. With numerical method, the heat transfer performance, resistance and two-phase flow of heat exchanger are analysed.the heat transfer performance and resistance analysis show that the CFD technology could meet heat exchanger design engineering application and could be used as computer assistant design reference. The result of two-phase flow simulation shows that the heat exchanger is not blocked by sediment.To validate numerical simulation result, the separation and blocking of heat exchanger is studied experimentally. Experimental results show that there are not blocking phenomenon caused by the sediment separation.At last, using the designed heat exchanger, the heat pump unit is studied experimentally in winter and in summer. The heat exchanger is not blocked and the heat pump unit operated well, it can be applied and popularized practically.更多还原