科研之友
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摘要
In recent years, fluids containing suspension of nanometer-sized particles (nanofluids) have been an active area of research due to their enhanced thermal properties over the base fluids. This makes them very attractive as heat transfer fluids in many applications. Bubble study through visualization during nanofluid flow boiling may provide valuable insight in the mechanisms by which the nanoparticles affect the heat transfer performance. In this study, experiments were performed in subcooled flow boiling of ZnO-water nanofluids with different low particle concentrations (a parts per thousand currency sign0.01 volume %) in horizontal annulus at heat fluxes from 100 to 450 kW/m(2) and flow rates from 0.1 to 0.175 lps at 1-bar inlet pressure and constant subcooling of 20 A degrees C to determine bubble behavior by optical method and to study the parametric effect of heat flux, flow rate and particle volume fraction of ZnO on bubble behavior. Bubble images were captured with high-speed video camera using XCAP SV-642 software. Images were analyzed with the purpose of finding bubble characteristics viz. bubble diameter and bubble density using National Instruments IMAQ Vision Builder 6.1 image processing software. The results show that increase in heat flux leads to increase in bubble diameter. Addition of nanoparticles into the base fluid enhances the maximum bubble diameter and decreases the bubble density. Bubble diameter and bubble density decrease in both water and nanofluids with increase of flow rate. The heat transfer coefficient increases with increase in heat flux and particle volume fraction of ZnO.
- 出版日期2013-5
