Research On Total Heat Recovery And Air Purification Of TiO₂-Ag Hybrid Nanofluids

Nanofluids have been widely used in energy,chemical,machinery fields due to their excellent heat transfer performance.In recent years,researchers tried to add different nanoparticles to a base fluid,and the resulting hybrid nanofluids have the characteristics of various nanoparticles.In this paper,Ti O2-Ag hybrid nanofluids were prepared and the influencing factors of stability,thermal conductivity and viscosity were explored.An experimental system was built to study total heat recovery and air purification performance preliminarily of Ti O₂-Ag nanofluids.The work of this paper is summarized as follows:(1)The effects of preparation methods,surfactants,ultrasonication and storage time on the stability of Ti O₂-Ag hybrid nanofluids were explored.As the storage time is prolonged,sedimentation appeared in the Ti O₂-Ag hybrid nanofluids which was more significant in the low volume fraction nanofluids and ultrasonication was beneficial to alleviate this phenomenon.(2)The thermal conductivity and dynamic viscosity of the Ti O₂-Ag hybrid nanofluid were measured in different volume fraction,temperature,ultrasonication and storage time.Artificial neural networks(ANNs)were established to predict the thermal conductivity and dynamic viscosity of the Ti O₂-Ag hybrid nanofluid.The maximum thermal conductivity improvement and viscosity ratio were 9.98%and 2.78,respectively.The maximum relative errors of thermal conductivity and dynamic viscosity predicted by ANNs were 1.44%and3.54%,demonstrating acceptable adaptability.(3)An experimental system was designed and built to study total heat recovery and photocatalytic air purification of Ti O₂-Ag nanofluids and the experimental equipment,total heat recovery and air purification experimental procedures were introduced.(4)The performance of total heat recovery and air purification was preliminarily explored considering volume fraction and type of nanofluids,gas flow rate,surfactants,spray,ultraviolet lamp and initial pollutant concentration.The results showed that the Ti O₂-Ag nanofluid with a volume fraction of 0.001%has the best performance in purifying organic pollutants in the air.The concentration of total volatile organic compound(TVOC)and formaldehyde in the final container decreased to 59.1?g/m³and 25.3?g/m³.Compared with deionized water,the Ti O₂-Ag nanofluids with a volume fraction of 0.010%increased the heat transfer efficiency of total heat recovery by 1.033%.