Experimental Study On Enhanced Boiling Heat Transfer Of Nano-fluid In The Cooling Water Chamber Of Internal Combustion Engine

With the needs of industrial technology development, power in per liter of internal combustion engine (ICE) increases and that will lead to the increasing temperature in the cylinder of ICE. Excessive thermal load inside becomes a tough challenge for the stability and life of the engine. Therefore, reasonable solution to the ICE cooling problems becomes more important for the development of modern ICE. Nano-fluid is a type of heat transfer material, which is dispersed in the liquid with a certain proportion of the metal, metal oxide or non-metallic particles at the nanometer level (particle size 1?100nm). In the cooling chamber of ICE, the phenomenon of local subcooled boiling happens and nano-fluid has been proposed by the experts to help solve the heat transfer problems in the cylinder of ICE. Compared with traditional solid-liquid suspension (made of millimeter or micron sized solid particles), nano-fluid has many obvious advantages:effective thermal conductivity of nano-fluid is larger than traditional two-phase mixture. In addition, convective heat transfer coefficient of nano-fluid does not increase at the expense of the flow resistance. As the motion behavior of the nano particle is much closer to the molecular, it can avoid producing some adverse effects such as friction and jam.Most existing studies focus on the effects of nano-fluid on the process of saturated boiling heat transfer and researches on subcooled boiling heat transfer are not very rich. On the other hand, most researches on nano-fluid improving heat transfer in the engine cooling water chamber are numerical simulation. There are few experimental researches about that. This paper focuses on the existing problems to mathe main research contents are as follows:(1) Preparation of nano-fluids. Two-step method is used to prepare the nano-fluid. It is found that the nano-fluids prepared show well dispersion and suspension after suspension experiment and TEM observation experiment test and it can meet the needs of the next experiment.(2) Measurement of the nano fluid physical parameters. In order to describe the basic properties of nano-fluids better, viscosity and thermal conductivity of nano fluid are measured and the effects of the nano-fluids volume fraction, temperature, particle size are studied.(3) Nano-fluids saturated pool boiling experiment. Experiment system about pool boiling heat transfer of nano-fluids is built and the repeatability of it is confirmed at first. The results show that the nanoparticle addition deteriorates the deionized water boiling heat transfer thermal properties. The results of heat transfer deterioration of nano-fluids are analyzed by using high-speed photography. The results show that volume fraction of nano-fluids and turbulence intensity have great effects on the heat transfer performance.(4) Nano-fluids subcooled pool boiling experiment. This part focuses on subcooled pool boiling heat transfer process of nano-fluids. The feasibility of using nano-fluid in the cooling water chamber of internal combustion engine is tested by combining pool boiling heat transfer and turbulence. Results show that the addition of nanoparticles increases the boiling heat transfer performance of deionized water. High-speed photography is used to analyze bubbles behavior of both nano-fluids and deionized water under different turbulence intensity. It is found that the volume fraction of nano-fluids, turbulence intensity and particle size have great effects on nano-fluids subcooled boiling heat transfer performance.