Research On Heat Transfer Enhancement And Friction Characteristic Of Lubricating Oil Cooler

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.