Heat Transfer And Flow Characteristics Of SiO₂-H₂O Nanofluids In Triangular Tubes

With the rapid development of modern industrial economy and technology,the research on energy and power technology is becoming more and more important.With the increasing shortage of global resources and energy,the research and development of new energy and more efficient enhanced heat transfer technology are the primary goals at present,which play a crucial role in the development of national economy of all countries.China is rich in land,resources and resources,but due to the large population,the current energy is still very limited.The per capita share of fossil fuels is only 56%of the world average,among which the per capita share of oil and natural gas is only 8%of the world average.China's hydraulic resources are very few in the world,and the development amount is as high as 379 million kilowatts,but the per capita amount is less than 0.3 kilowatts.Coal resource is the main consumption of disposable energy,and it account for 70%of the total energy consumption,but due to the serious pollution,the consequences will be unimaginable if no effective measures are taken.Therefore,improving energy efficiency,developing clean energy and protecting the environment have become the main strategic goals of China's sustainable development[1].In the aerospace and other industries,the engine and other power transmission device operation will be accompanied by a large number of heat generation.In order to ensure the normal operation of its power transmission device,there must be a certain degree of cooling device work,hence,heat exchanger plays a vital role in the above work.According to statistics,the investment of heat exchanger equipment such as boilers in thermal power plants accounts for 70%of the total investment of power plant,the investment in petrochemical enterprises accounts for 40%?50%,the quality of evaporators in refrigerating machines accounts for30%?40%,and of the total power consumption accounts for about 20%?30%[2].The flow of working medium is the most common process in major industries,which shows that the design,improvement and operation of heat exchange play an important role in energy utilization[3].For traditional heat exchangers,the traditional heat transfer medium with low thermal conductivity,such as water,alcohol,oil,etc.,is still the main body,and shell and tube heat exchanger is still the mainstream of heat exchange equipment,while more than 80%of shell and tube heat exchangers still use smooth round or square tube structure with low heat transfer efficiency[4-7].Now,the heat load and heat transfer in heat exchange equipment have higher requirements of strength,water,ethylene glycol,oil and other traditional pure liquid heat transfer mediums,have been unable to apply to some special conditions of heat transfer and cooling,and it requires further improvement to strengthen heat transfer technology.How to strengthen heat transfer more effectively has become an urgent problem at present.In this paper,the SiO₂-H₂O nanofluids are used to replace the traditional heat transfer medium,and the enhanced heat transfer tube?triangular tube?is used instead of the traditional heat exchanger structure.The heat transfer and flow characteristics of SiO₂-H₂O nanofluids with different mass fractions in built-in twisted tape triangular tubes with different pore sizes and spacing ties are studied.Main research work and conclusions:?1?SiO₂-H₂O nanofluids with different concentrations??=0 wt%,?=0.1wt%,?=0.3wt%and?=0.5wt%?are prepared by two-step method,and their stabilities are analyzed by sedimentation observation.?2?Thermal and physical parameters of SiO₂-H₂O nanofluids with different mass fractions are measured,such as thermal conductivity and viscosity.?3?The enhanced heat transfer system of the triangular tube is designed,and the flow and heat transfer characteristics test bench of the enhanced heat transfer system of the triangular tube is established and the heat transfer and flow resistance characteristics of deionized water and nanofluids are studied.Compared with deionized water under the same conditions,the maximum comprehensive performance evaluation index can be improved to 1.36.?4?The flow and heat transfer characteristics test bench of enhanced heat transfer system with built-in smooth twisted tape triangular tube is built and the heat transfer and flow resistance characteristics of deionized water and nanofluids are studied.Compared with deionized water under the same conditions,the maximum comprehensive performance evaluation index can be improved to 1.39.?5?The flow and heat transfer characteristics test bench of triangular tube enhanced heat transfer system with built-in twisted tape including different size circular holes is built and the heat transfer and flow resistance characteristics of deionized water and nanofluids are studied.Compared with twisted tape with the minimum circular hole under the same conditions,the maximum heat transfer can be increased by 6.498%.?6?One of the diameters of hole is selected,the flow and heat transfer characteristics test bench of enhanced heat transfer system with built-in twisted tape triangular tube is built,and the heat transfer and flow resistance characteristics of deionized water and nanofluids are studied.Compared with twisted tape with the maximum circular hole under the same conditions,the maximum heat transfer can be improved by 11.309%.?7?Compared with the heat transfer effect of the tube without twisted tape,the highest comprehensive performance evaluation index can reach 1.59 based on a comprehensive analysis of the flow and heat transfer in the tube.