Retardation of CaCO3 fouling on heat exchanger surface using water-based cloves-functionalized multiwall carbon nanotubes (C-MWCNT) nanofluids

Abstract

Fouling is defined as unwanted deposition on the heat exchanger surfaces which retards the heat transfer and declines its performance. In this investigation calcium carbonate (CaCO3) fouling mitigation was achieved by adding clove-treated multiwall carbon nanotubes (C-MWCNT) additive at three variable concentrations (i.e., 0.0143%, 0.0071%, and 0.0036% mass). Water based C-MWCNT nanofluid was selected for its ability to resist the foulant deposition without imposing any corrosion on the heat exchanger surfaces. MWCNT was functionalized with clove extracts for obtaining its suspension in distilled water. After functionalization, thermo-physical properties of all the three different C-MWCNT concentrations of nanofluid and water were investigated with Thermal conductivity meter, density meter, and viscosity meter, which demonstrated the increase in density and thermal conductivity with the increase of C-MWCNT concentration. After that fouling investigation was conducted at a constant heat flux boundary condition where the supersaturated solution of CaCO3 at 300 mg L-1 was used as a fouling liquid. After the fouling experiments, the test coupon was dismantled from the test section for morphological study of the fouling deposits. Field Emission Scanning Electronic Microscopy (FESEM) was used to investigate the morphology of the deposits. The results of CaCO3 mass deposition at variable concentrations of C-MWCNT such as 0%, 0.0143%, 0.00714%, and 0.00357% were 0.1652 g, 0.0993 g, 0.0805 g, and 0.0 584 g respectively, which revealed the inverse relationship between the concentration of water-based C-MWCNT nanofluid and the deposition of CaCO3 foulants on the heat transfer surfaces.