| Compared with the traditional cooling medium,nanofluids have two obvious advantages in energy transfer:1)The effect of heat transfer is higher than that of pure base liquid,which is related to the content,temperature and other factors,heat transfer system can be designed according to heat transfer requirement;2)The uniformity of the particles is better than that of millimeter and micron particles,and has better corrosion resistance and boiling resistance.Therefore,nano cooling liquid in the heat transfer enhancement performance,promote the efficiency of the cooling system,compact and lightweight,improve engine thermal efficiency,energy saving and environmental protection has a wide application prospect.In this paper,we focus on the heat transfer characteristics of three dimensionally constructed graphene nanofluids in automotive radiators:(1)Using two step method,ethylene glycol,50%ethylene glycol aqueous solution and propylene glycol were used as the base liquid respectively,and with the dispersant,stirring,ultrasonic vibration and other procedures to configure the 12 stable three dimensionally constructed graphene nano cooling liquid.(2)Setting up the automobile radiator heat transfer experimental bench,The experimental study on the heat transfer performance of each nanofluid was carried out under the condition that the flow rate was 6-14LPM(Liter Per Minute),the inlet temperature was 40℃、45℃、50℃、55℃.Results show that:1)The heat transfer coefficient of three dimensionally constructed graphene nanofluids increases with the increase of nanoparticle mass concentration(wt%),and then decreases,and reaches the maximum value at 0.1wt%;2)Heat transfer coefficient increases with the increases of initial temperature of the fluid,the heat transfer coefficient of 55 0C,0.05wt%graphene propylene glycol nanofluids increased by 31.6%more than 40℃;3)With the increase of velocity of flow,heat transfer and the heat transfer coefficient increases;4)Under the same conditions,the heat transfer performance of the three dimensional graphene nanofluids prepared from the three kinds of base liquid from superior to prioritize is 50%ethylene glycol aqueous solution,ethylene glycol,propylene glycol.(3)The numerical simulation of the flow process of three dimensional graphene propylene glycol nanofluids in the automotive radiator pipe was carried out by using the fluid simulation software.The simulation results are compared with the experimental results in terms of temperature difference,pressure drop and fluid heat transfer performance(positive/negative).The results show that with the increase of the mass concentration of nanoparticles,the difference between the simulation results and the experimental results of the temperature difference between the inlet and outlet of the cooling fluid becomes larger,this is due to the assumption that the nanofluid is a single-phase fluid,neglecting the effect of nanoparticle motion.As the growth of the flow,nanometer particle mass concentration,the system pressure drop increases,and the influence of velocity on the pressure drop is higher than that of nanoparticles.The performance indexes of nano cooling fluid is greater than 1,show that the preparation of nano fluid can be used as a good car radiator new alternative cooling fluid. |
