【作者】 庄兆意；

【导师】 孙德兴；

【作者基本信息】 哈尔滨工业大学 ， 供热、供燃气、通风及空调工程， 2012， 博士

【摘要】 城市污水中蕴含有丰富的低位热能，将其作为热泵的冷热源为建筑供热空调具有巨大的开发利用价值。城市污水的水质极为恶劣。其热工与流动性能与清水有很大不同。污水处理厂中的二级出水（排放水）接近清水的水质，但由于污水处理厂多位于远离城市建筑群的郊区，因此真正具有巨大开发利用价值的是遍布城区污水渠中的原生污水。传统的热泵空调机组对水质有严格的要求。因此目前在利用原生污水的热泵系统中多为避免污水直接进热泵系统的蒸发器或冷凝器而设置一个中间换热的措施，即所谓“间接式系统”，这种间接式系统不仅要增加中间换热设备而且要增加系统的火用损失，故开发污水直接进机组的热泵系统，即所谓“直接式系统”，从污水源热泵技术产生以来就对学术与工程界具有巨大的诱惑力。直接式污水源热泵系统由于污水水质的特殊性，必须解决以下关键问题：（1）对过滤和防阻塞的效率和可靠性提出了更高的要求；（2）必须认清污水的流动、换热以及污垢热阻的特性与规律；（3）必须认清污水蒸发器、冷凝器的换热特性；（4）直接式热泵系统两换热器的合理匹配与性能。本文对此主要进行了下述研究工作：直接式污水源热泵系统能够长时间连续安全换热，首要前提是必须保证大尺度污物不进入机组的换热器中。针对已在间接式污水源热泵系统中普遍应用的污水防阻设备，通过工程实践和测试，总结发现：（1）丝状纤维类污物是阻塞滤面的最大诱因；（2）参考传统做法，仅靠过滤孔直径难以衡量防阻机滤面的过滤与再生能力；（3）不可避免的存在内漏混水的情况。论文建立了以缠绕长度、反冲效率、内漏率、换热保证率为核心的，包括滤孔直径、反冲面积比、转速、阻力等在内的防阻机设计指标体系，并通过工程测试确定了最佳的缠绕长度、反冲面积比和清洁周期，为防阻的科学合理设计及工程选用提供了合理依据。设计并在哈尔滨太平污水处理厂搭建了城市原生污水性能研究实验台，实验研究了城市原生污水在各种管材圆管内紊流流动时的污垢热阻特性，流动阻力特性及对流换热特性。通过大量实验数据总结出各种常用换热管内污垢热阻增长规律，以及污垢热阻稳定值与管内污水流速的函数关系、污水紊流流动的阻力系数计算式及换热准则关联式。实验表明污垢增长模型为时间的渐进型函数，在同管径同流速下污水的流动阻力系数约为清水的1.08~1.12倍，对流换热系数约为清水的0.75~0.82倍。这些基础数据与经验公式为污水源热泵系统的换热设备研发、系统设计等提供了较为可靠的依据。依据污水流动、换热及污垢热阻特性、换热管污水侧难以强化换热的特点，建立了污水蒸发器与冷凝器的分布参数模型，编制了仿真程序并进行了大量的数值研究，给出了污水蒸发器和冷凝器的传热系数范围，以及污水温度和流量变化对换热器换热特性的影响规律。发现与常规水源热泵的两换热器相比，污水蒸发器与冷凝器内污水以四流程为宜，冷凝器内蒸汽过热段所占比例较大，过热对冷凝换热影响明显，为系统换热器设计以及系统性能分析打下基础。通过直接式污水源热泵系统建模与数值仿真，给出了直接式系统的效能范围，以及污水温度对效能的影响规律。规定了污水源热泵机组的标准设计工况，并深入分析了污水蒸发器、冷凝器面积匹配比与机组制热量、制冷量、出力比之间的关系。由于污水源热泵机组具有更大的适宜面积比范围和出力比范围，提出不同地区采取不同面积比进行热泵机组设计的理念。最后给出了非标准工况下热泵机组的特性以及设计与选型原则。本文通过研究主要解决了直接式污水源热泵系统所面临的防堵塞可靠性、污水流动与换热计算方法、污水蒸发器与冷凝器的换热特性、机组换热器匹配等问题，为直接式污水源热泵技术的发展奠定了一定的理论基础。更多还原

【Abstract】 Municipal sewage contains so abundant low level heat that it will mean ahuge value for development and utilization when used as a cold and heat source ofheat pumps for heating and air-conditioning system of buildings.The water quality of municipal sewage is extremely poor and the thermal andflow properties of it are quite different from those of clear water. In contrast, thewater quality of secondary effluent from sewage treatment plants (discharge water)is close to that of clear water. However, sewage treatment plants are mostly locatedin suburbs far away from the city buildings, so it is exactly untreated sewage allover the city sewers that will mean the huge value for development and utilization.Traditional heat pump air conditioning units have strict requirements on waterquality. Therefore, measures of intermediate heat-transfer are often taken in thepresent heat pump system based on untreated wastewater to avoid sewage flowingdirectly into the evaporator or condenser of the system which is the so-called"indirect system" and not only introduces extra intermediate heat-transfer devicesbut also increases system energy loss. So the development of heat pump systemnamely the so-called "direct system" allowing sewage to enter the units directlyshows a great allure on the academic and engineering fields from the origin of thetechnology of sewage-source heat pumps.Considering the specialty of the water quality of sewage, direct sewage-sourceheat pump system must solve the following key problems. Firstly, higherrequirement is needed for efficiency and reliability of filtering and anti-blocking.Secondly, the feature and discipline of flow, heat-transfer and fouling heatresistance of sewage must be recognized. Thirdly, the heat-transfer performance ofsewage evaporator and condenser should be recognized as well. At last, reasonablematch and performance of the two machines of direct heat system need to be takeninto consideration. This paper mainly introduces the research work on thementioned techniques as follows.The primary precondition of safe and enduring heat-transfer for direct sewagesource heat pump set is to guarantee that large-scale contaminant of all shapescannot enter the heat exchanger of the set. Corresponding to the universally employed sewage clog-proof machine in indirect sewage source heat pump systems,we have performed engineering practice and test, according to which we makefollowing conclusions. Firstly, filamentous contaminant is the main incentive ofblocking filter surface. Secondly, referring to the traditional method, it is tough tomeasure the filtration and regeneration ability of the clog-proof machine’s filtersurface only with the diameter of filter hole given. Thirdly, the condition of internalleakage mixing water exists inevitably. The paper establishes a design index systemof clog-proof machine including filter pore diameter, recoil area ratio, rotatingspeed, resistance and so on, and winding length, recoil efficiency, internal leakagerate and heat-transfer guaranteed rate are the core of the index system. The paperalso defines the optimal filter pore size, recoil square ratio and cleaning period ofthe clog-proof device by engineering tests, all three of which provide reasonablefoundation for scientific and rational design of clog-proof device for engineeringapplication.An experiment table focusing on city untreated sewage properties research hasbeen designed and constructed in Harbin Taiping sewage treatment plant as to bementioned in the paper. Experiments have been executed on the fouling heatresistance performance, flow resistance characteristics and flow and heat-transfercharacteristics of urban untreated sewage turbulent flow in a variety of pipes.Through considerable experimental statistics, we can reach such conclusions asfouling heat resistance growth disciplines for kinds of common heat-transfer pipes,the function between the stable value of fouling thermal resistance and the sewageflow rate in the pipe, an expression for resistance coefficient of sewage turbulentflow and finally a heat transfer correlation formula. The experiment resultsdemonstrate fouling growth model as a progressive function of time. Specifically,experiments verify that with same pipe diameter and flow rate, the flow resistancecoefficient of wastewater is approximately1.08~1.12times that of clear water,whereas the convective heat transfer coefficient is about75~82percent of that ofclear water. These fundamental statistics and empirical formulas provide morereliable basis for heat-transfer device development and system design of sewagesource heat pump systems.Based on the sewage flow, heat transfer and fouling resistance properties andthe characteristic of difficulty in heat transfer enhancement at the sewage side ofheat transfer tube, a distributed parameter model of the sewage evaporator and condenser is established, and simulation programs have been developed andemployed to do amounts of numerical study which obtains the scope of sewageevaporator and condenser heat transfer coefficients and the law of influence exertedby sewage temperature and flow changes on their heat transfer properties. It is alsofound that compared with the two machines of the conventional heat pump, thesewage evaporator and condenser have following prominent characteristics. Fourprocesses are appropriate for wastewater inside the machines, and steamsuperheating segment in condenser takes up a great proportion. In addition, theimpact of superheating on condensation heat transfer is significant. All theachievements lay the foundation for system evaporator and condenser design andsystem performance analysis.Through direct sewage source heat pump system modeling and numericalsimulation, the efficiency range of direct system and the law of sewage temperature’sinfluence on performance are given. Then we set the standard designed workingcondition of sewage source heat pump units and do deep analysis on the relationshipbetween the matching ratio of sewage evaporator and condenser area and heat output,cooling capacity and power output of the units. For the greater range of suitable arearadio and power output radio of sewage source heat pump unit, we put forward theconcept that different area ratio will be adopted while designing heat pump units indifferent regions. Finally the characteristics of heat pump units and principles fordesign and selection are introduced under non-standard working conditions.By researching, this paper has mainly solved problems faced by direct sewagesource heat pump system such as the clog-proof reliability, sewage flow and heattransfer calculation method, heat transfer properties of sewage evaporator andcondenser and the matching of the two devices, all of which lay theoreticalfoundation for the development of direct sewage source heat pump system.更多还原