TY - JOUR T1 - Experimental Investigation of Heat Transfer Coefficient and Pressure Drop of Carbon Nanotubes-Water Nanofluid under Constant Heat Flux TT - بررسی تجربی ضریب انتقال حرارت و افت فشار نانوسیال نانولوله‌ کربن-آب تحت بار حرارتی ثابت JF - mdrsjrns JO - mdrsjrns VL - 14 IS - 13 UR - http://mme.modares.ac.ir/article-15-870-en.html Y1 - 2015 SP - 19 EP - 26 KW - nanofluid KW - Carbon nanotubes KW - Gum arabic KW - Convective heat Transfer enhancement KW - Extra pressure drop N2 - In this study, forced convective heat transfer and pressure drop behavior of multi walled carbon nanotubes (CNT)-water nanofluid were evaluated under constant heat flux in a circular tube. For this purpose, first, homogeneous aqueous suspension of CNT using gum Arabic (GA) surfactant was prepared in concentrations 0.05%, 0.1% and 0.2% wt. Then, the above mentioned nanofluids were evaluated in Reynolds number range of 800-2000 under constant heat flux. The results indicate a significant increase in convective heat transfer coefficient of nanofluids with the addition of small amounts of CNT in deionized water. Also, heat transfer coefficient is enhanced with increasing concentration and Reynolds number. However, the effect of increasing concentrations of CNT is higher than the increase in Reynolds number. In addition, the pressure drop data on the different concentrations and Reynolds numbers are also investigated. At low weight concentrations of CNT, the deal of pressure drop of nanofluids containing CNT and base fluids is approximately similar and the gap between them is negligible. This means that no extra pump power is required for low concentration CNT/water nanofluid. The maximum increase in heat transfer coefficient is 42.8%, which occurred at Re=2027, and a concentration of 0.2% wt. M3 ER -