Experimental Research On Heat Transfer Enhancement Of Casing-tube Lubrication Oil Cooler

Pin-fin tube one type of three-dimensional discrete fin tubes with excellent ability ofenhanced heat transfer for high viscosity fluid like lubricant oil. The Enhanced Heat TransferLab of HEU developed a new heat transfer element of casing pipe, which is consisted of apin-fin tube sheathed by a smooth tube and two specially designed joints. Lubricant oil flowsin the annular gap formed by the pin-fin tube and the smooth tube, while the cooling waterflows inside of the pin-fin tube and outside of the smooth tube, making the oil cooled fromboth sides. Meanwhile, the pin-fin tube can enhance the heat transfer due to its strongturbulence to oil flow. The heat transfer and frictional characteristics was investigatedexperimentally for both pin-fin casing element taking lubricant oil and water as working fluid.The velocities of lubricant oil and water are in the range of0.1-0.6m/s and0.2-1.3m/s,respectively.The effects of pin height, pitch, diameter of pin-fin tube on heat transfer and flowresistance were mainly conducted in the experiments. The results show that the heat transferand frictional characteristics of pin-fin casing are significantly influenced by the pin height,the heat transfer coefficient increases about40%when pin height increases from2.7mm to3.6mm, meanwhile, the friction factor also increases about80%. The pitch has little effect onheat transfer, but has significant effect on flow resistance, the heat transfer coefficientdropped by18%and the friction factor by25%in the increase of pitch from3mm to9mm.On the basis of experimental data empirical correlations were proposed for calculating theheat transfer coefficient and friction factor, with the errors about15%and10%respectively.Moreover, a test on lubricant-oil cooler which took pin-fin casing as the heat transferelement was also conducted. It is showed that the pin-fin casing lubricating-oil cooler is muchbetter in comprehensive performance than the traditional shell-and-tube cooler under highlubricating-oil flow rate conditions. Its volumetric heat transfer capacity is about1.6times asthat of the traditional shell-and-tube cooler in present experimental conditions.