Experimental investigation of convective heat transfer inside tube with stable plasmonic TiN nanofluid and twisted tape combination for solar thermal applications

The present experimental study involves a convective heat transfer performance analysis of the fully developed laminar flow of TiN nanofluid through a uniformly heated U pipe with and without twisted tape (H/D = 5) combination. The TiN nanofluid, with its enormous thermophysical properties, opens up a new dimension in solar thermal applications. TiN nanofluid pretends to have photoabsorption properties (localized surface plasmon resonance). The preparation of stable, efficient, low-cost TiN nanofluid and its application is an emerging area of research. Titanium nitride (TiN) nanoparticles with sizes of 40–50 nm were used to make distilled water-based nanofluid at concentrations of 0%, 0.025%, 0.05%, 0.075%, and 0.1%. The two-step preparation method is preferred to prepare a stable nanofluid. The thermophysical properties are evaluated experimentally over a wide temperature range. The experiments were performed at flow rate (0.25–1.25 LPM), volume concentration (0–0.1%), inclination angle (35 degree), and heat flux (1000 W/m2). The nusselt number, convective heat transfer coefficient, and friction factor were evaluated at a bulk mean temperature. The convective heat transfer performance increases with volume concentration and Reynolds number. The friction factor decreases with a rise in volume concentration and Reynolds number. The nusselt number of the entire test section increased by 30.04% for a 0.1% volume concentration of TiN nanofluid and 42.8% for 0.1% of TiN nanofluid with twisted tape (H/D = 5) combination. The convective heat transfer performance enhancement is obtained at a cost of 2% pressure drop. The correlation has been developed to estimate the nusselt number and friction factor.