Heat transfer, pressure drop and fouling studies of multi-walled carbon nanotube nano-fluids inside a plate heat exchanger

This work presents the results of an experimental research on the heat transfer and pressure drop characteristics of multi-walled carbon nanotube (MWCNT), aqueous nano-fluids inside a plate heat exchanger (PHE), with the consideration of fouling formation of carbon nanotubes (CNTs). Influence of operating parameters such as flow rate (700 < Re < 25,000), volumetric concentration of nano-fluids (vol.% = 0.5-1.5), inlet temperature of nano-fluid (T-in = 50-70 degrees C) on the overall heat transfer coefficient and pressure drop was experimentally investigated. Results demonstrated that the heat transfer coefficient could be intensified, when flow rate and concentration of nano-particles increase. In addition, increase of temperature of inlet flow can cause a slight increase in heat transfer coefficient. In terms of pressure drop, it was seen that with increasing the flow rate and mass concentration of nano-fluids, pressure drop was intensified such that for flow rate, enhancement rate was significant, while for concentration, a small penalty was registered. Although MWCNT/water nano-fluids presented higher pressure drop and friction factor in comparison with the base fluid, they provided better overall thermal performance in comparison with the base fluid. For long-operating condition, significant fouling resistance was also measured, which was amplified by increasing the volumetric concentration of nano-fluids. A none-linear fouling behavior over the extended time was registered for nano-fluids and for the decrease of heat transfer coefficient as well. (C) 2015 Elsevier Inc. All rights reserved.