time dependent analysis of micro-tubes conveying nanofluids under time-varying heat flux

in this paper the numerical analysis of flow and time dependent heat transfer of micro-tube conveying nanofluid in laminar flow is investigated. in this study, convection heat transfer of nanofluid and base fluid and transient analysis for time-varying heat flux for time step of 0.0001 second are elucidated. it is observed that the pumping power of nanofluid flowing and the maximum temperature of micro-tube wall, respectively, is increased and decreased with increases in the volume fraction of nanoparticle. the maximum temperature of base fluid (water) is 305.6k and the maximum temperature is 304.2k for alumina oxide nanoparticle af with volume fraction 3%. in addition, the results show that using nanofluid has the advantage of heat transfer despite periodic heat flux. however, the results show that these parameters are vital in investigation of the heat transfer of system. also, it is obvious that the maximum temperature of micro-tube wall decreases with increase in the reynolds number. for example, for reynolds numbers 180, 360 and 720, the maximum temperatures occur at 307.8k, 304.6k and 302.8k, respectively. in addition, it is indicated that the variation of temperature decreases when the volume fraction of nanoparticles increases. also the results of numerical modeling are compared with those available in literature and good agreement is observed.