Experimental investigation on the heat transfer performance and pressure drop characteristics of γ-Al۲O۳/water nanofluid in a double tube counter flow heat exchanger

In this paper, overall heat transfer coefficient and friction factor of water based γ-Al۲O۳ nanofluid in a double tube counter flow heat exchanger have been measured experimentally under turbulent flow condition. For better dispersion of γ-Al۲O۳ nanoparticles in distilled water, magnetic stirrer and ultrasonic vibrator (with a power of ۲۴۰ kW and frequency of ۳۵ kHz) were implemented. The stabilized γ-Al۲O۳ /water nanofluid have been examined at the concentrations of ۰.۰۵ and ۰.۱۵ vol. % with variation of flow rates in the range of ۷–۹ l/min. Nanofluid enters the inner tube of the heat exchanger at different temperatures including ۴۵, ۵۵,and ۶۵ °C. Results demonstrated that increasing the nanofluid flow rate, concentration and inlet temperature can improve the overall heat transfer coefficient and heat transfer rate. Also, the ratio of the overall heat transfer coefficient of nanofluid to that of pure water decreased with increasing the nanofluid flow rate. Meanwhile, the maximum enhancements of the overall heat transfer coefficient and heat transfer rate and friction factor compared with those of base fluid (distilled water) are respectively equal to ۱۹.۳%, ۱۰% and ۲۵% which is occurred at the concentration of ۰.۱۵ vol. %.

Keywords:

Double tube heat exchanger , Nanofluid , Overall heat transfer coefficient