Heat Transfer Performance Of Various Nanofluids In A Double-tube Counter Flow Heat Exchanger

With the development of economy and the progress of science and technology,the demand for energy from human society is increasing,the problem of energy shortage is becoming more and more serious,the heat load of heat exchanger is also increasing.But the problem of low efficiency of heat exchanger restricts the development of industrial production.Therefore,in order to reduce the energy consumption and improve the energy efficiency of the heat exchanger,it is necessary to improve the heat exchanger.This article mainly improves the tube heat exchanger from two aspects:the heat transfer medium and tube structure.In terms of heat transfer work medium,nanofluid as a new heat transfer work medium is used to replace the traditional heat transfer work medium.For the tube structure,the smooth tube is replaced by the corrugated tube.In order to investigate the influence of the nanofluid and threaded tubes on the heat transfer,flow and comprehensive performance in double-tube heat exchanger,the Nussel number,friction factor and comprehensive performance index of seven nanofluids in smooth tube and threaded tube double-tube heat exchanger were analyzed by experimental method.In this paper,seven nanofluids were prepared first using a two-step method,which are Al₂O₃-water,Cu O-water,Fe₃O₄-water,Mg O-water,Si C-water,Si O₂-water and Zn O-water nanofluid.The prepared nanofluids have mass concentrations of 0.5%,1.0%,1.5%and2.0%.The stability of nanofluids was studied by sedimentation method and Zeta potential test method,and the results show that the nanofluid have good stability.The heat transfer capacity of nanofluids in the smooth double-tube heat exchanger was experimentally studied by building a double-tube heat exchanger experimental system.The study found that the Nusselt number and the comprehensive performance index of the nanofluid increased with the increase of the Reynolds number.Nanofluid has the best mass concentration,which makes the nanofluid have the best heat transfer capability and comprehensive performance.The friction factor of nanofluids decreases with the increase of Reynolds number and increases with the increase of mass concentration.This paper also designs three kinds of threaded double-tube heat exchangers with thread pitches of 4 mm,6mm,and 8 mm,and compares their heat transfer performance with smooth double-tube heat exchangers.The study found that with decreasing thread pitch,the Nusselt number,friction factor,and comprehensive performance index of nanofluids increase.The Si C-water nanofluid with a mass concentration of 1.5%has the best comprehensive performance in a threaded double-tube heat exchanger with the thread pitch of 4 mm,compared to the comprehensive performance of deionized water in a smooth double-tube heat exchanger,the comprehensive performance index increased by a maximum of 60.2%.