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

Abstract

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 (Tin=50–70°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.