【作者】 石帅；

【导师】 阎昌琪；

【作者基本信息】 哈尔滨工程大学 ， 核能科学与工程， 2013， 博士

【摘要】 换热设备在核电厂、船舶动力系统中占有很大比重，提高换热设备的换热效率，使之具有高效节能的特点是当前的一个重要研究课题。实现上述特点就要依靠传热强化技术的应用，而应用什么样的传热强化技术要取决于工质的热力学特性和流体力学特性。本文采用水冷却68#润滑油的方式，研究了高粘性流体在一种新型针翅套管滑油冷却器内的传热与阻力特性。首先通过单管实验，研究了影响针翅套管元件传热与阻力的主要因素，并对其传热强化机理进行了分析；然后在此基础上制造针翅套管滑油冷却器，并对其进行实验研究；通过与其它类型滑油冷却器的比较，对针翅套管滑油冷却器的综合性能进行了评价；为了全面了解针翅套管元件内的流动与传热情况，最后还用数值模拟的方法对其进行了研究。得到的研究结果对针翅套管滑油冷却器的优化设计和工程应用具有实际意义。本文的主要研究工作如下：1.以高粘性润滑油为工质，对新型复合强化传热元件—针翅套管元件进行传热和阻力特性研究。探究它与普通流道的差别以及影响其性能的主要因素。建立针翅管针翅传热模型，在等壁温条件下对环形通道内充分发展层流对流换热问题进行研究，分析针翅套管强化传热的机理，推导针翅套管换热元件的优化参数。另外，对实验数据进行分析整理，拟合针翅套管在进行双侧强迫对流换热时的传热与阻力实验关联式。2.对针翅套管滑油冷却器进行实验研究，和相应的单管进行对比分析。水流量和油流量的分配不均、针翅管加工质量以及管束效应是导致单管和管束换热存在差别的主要因素。研究水流量对针翅套管滑油冷却器换热效果的影响，并确定了1#针翅套管滑油冷却器的最佳水流量范围为18~22m3/h。对两种针翅套管滑油冷却器进行了性能评价，结果表明，它们的同功耗下强化指标是对应光滑套管滑油冷却器的1.4~1.9倍，同时用“单位压降下的单位体积释热率”这一参数对换热器的综合性能评价进行了补充。3.对自支撑式、套管式和板壳式滑油冷却器进行实验研究，并将它们和实验用及工程用光管滑油冷却器进行对比分析。与光管滑油冷却器相比，它们的换热效果明显提高，体现了小型化与高效化的特点，并对其油侧换热与阻力实验数据进行了回归分析，得到的实验关联式能较好的兼顾关键因素对滑油冷却器换热与流动特性的影响，在一定范围内可推广使用。在Webb评价准则的基础上，以滑油冷却器壳程（油侧）流动为研究对象，推导适合本实验研究的性能评价指标计算公式，评价公式计算结果表明，针翅套管滑油冷却器的综合性能最佳，当压力损失和体积相同时，换热量约为基准滑油冷却器的1.86～2.16倍。同时，还从加工工艺出发，指出自支撑式滑油冷却器在石油化工等存在高粘性流体换热的领域应具有较好的应用前景。4.由于实验的方法存在成本高、效率低的缺点，本文最后用数值模拟的方法对针翅套管元件进行研究，探讨这种方法对具有复杂几何结构的针翅套管元件的可行性。通过模拟值与实验值的对比，表明二者的最大误差在20%左右，从物理模型的建立、计算域的离散等方面分析了误差来源。对计算域的温度分布云图、压力分布云图和速度矢量图进行分析，研究针翅套管元件强化传热的机理，由于针翅的扰动，增大了壁面处的温度梯度，使润滑油主流区的温度分布更加均匀，强化了传热。更多还原

【Abstract】 Heat exchanger accounts for a large part in nuclear power plants and ship systems. Incurrent, it is a very important issue to improve heat exchanger’s compactness and itsefficiency. The heat transfer enhancement technology can be used to solve the problem. Whatkind of enhanced heat transfer technonlogy should be adopted is up to the performance ofthermohydraulics of the working fluid. The68#lubrication oil was cooled by water. In thepresent study, the heat transfer and flow performance of high viscosity fluid in the Pin-FinCasing (PFC) oil cooler is experimental and numerical studied. The major influencing factorsof the PFC on the heat transfer, pressure drop and the heat transfer enhancement theory isinvestigated, and a basis for the design of high efficiency bundle is provide. In addition, thecomparison of the transfer efficiency between the bundle and tube unit is also studied. On thebasis of comparison between PFC oil cooler and the others, the paper evaluated itscomprehensive properties. In addition, the numerical simulation on the performance of PFCwas adopted to supplement the experiment. The results show that PFC takes on the high heattransfer efficiency and structure security. The present work has a very important significancefor the PFC optimization and its application. The main experimental results and conclusionsare as follows:1. High viscosity lubricant was used as working fluid in this paper. Heat transfer andpressure drop performance of PFC (a new complex enhanced heat unit) were researched inthis paper. The results show that PFC has a very good heat transfer enhancement propertywith high viscosity fluid. Its property of bilateral forced convection heat transfer and pressuredrop is different from the common channel. The relative height and pitch of pin-fin in theannular space are the main influence factors. The paper established the heat transfer modelfor pin-fin tube, investigated the convection heat transfer of fully developed laminar inannular space at the same wall temperature, analyzed the heat transfer enhancement theory ofPFC, provided an optimal parameterb/dD0.5which including aspect ratio b/d andchannel width D. According to the analysis on the experiment data, a formula about heattransfer and flow resistance for PFC at bilateral forced convection heat transfer has been putforward in the peper, and which has a very good agreement with the experiment data. 2. The experimental research on PFC was carried out in the paper, and the heat transfercharacteristic was compared with that in the tube unit. The difference between bundle andtube unit was caused mainly by mass flow matching, pin-fin mass, and bundle effect. Whileat the same mass flow rate condition, the pressure drop of bundle is not different from that oftube unit. The influence of water mass flow rate on heat transfer efficiency is mainly up to itsthermal resistance. When the thermal resistance on oil side losts its dominance, the heattransfer efficiency can be improved greatly by increasing water mass flow. Looking for theoptimal water mass flow can obtain the greatest heat transfer efficiency. The paper evaluatedthe performance of the two lubricating oil cooler. The results show that, at the same powerconsumption, both of them show a better heat transfer property. The parameter heat load ofunit volume at unit pressure drop was supplied for estimating the evaluation criterion of heatexchangers. The evaluation criterion can be used to select one type of PFC oil cooler whichcan compared with other oil cooler.3. The experiments on three type enhancement lubricating oil coolers (Self-supporting,PFC, Plate-shell) were carried out in the paper. The three type lubricating oil coolers werecompared with plain tube used in experiment and engineering. These coolers take on highheat transfer efficiency and the advantage of miniaturization. The paper analysed the heattransfer and resistance data at oil side. The formula proposed in the paper estimate theinfluence of the critical factors on lubricating oil coolers, and it can be extend at a certainrange. On the basis of Webb criterian, the paper investigated the shell side of lubricating oilcoolers, and deduced an evaluation criterian formula which is appropriate for this experiment.The lubricating oil cooler property is estimated by the present formulation. The results showthat the performance of the three enhancemen lubricating oil coolers is better than that of theplain tube lubricating oil coolers and PFC is the best one among them. According to themachined processing, the self-supporting lubricating oil coolers have a good prospect ofapplication at high viscosity fluid field.4. The experiment cost is extremely expensive and its effiency is relatively low. Becauseof the above disadvantage, a numerical simulation on PFC has been carried out in the paper toinvestigate its heat transfer and fluid field at the condition of bilateral forced convection heattransfer. The numerical results were compared with the experiment data. The results showthat, numerical simulation can exactly predict the flow field, and the maximum error between numerical and experiment is about20%. The paper analyzed the error source from the viewof models and calculation zone dispersion. According to the analysis of the contours oftemperature, pressure and velocity vector, it is found that, there will be a wake region at thebottom of the pin-fin, which will deteriorate the heat transfer effect. The pin-fin can enhancethe temperature gradient at the tube wall, and make the lubricating oil temperature moreuniform. The temperature distribution at the tube takes on wave shape which can reinforcethe metal heat conduction. So, PFC can enhance the heat transfer effect.更多还原