Heat transfer characteristics of silver/water nanofluids in a shell and tube heat exchanger

An experimental study is carried out to investigate the heat transfer characteristics of silver/water nanofluids in a shell and tube heat exchanger. The test matrix is worked out in the turbulent regime with Reynolds number varying between 5000 and 25,000, particle volume concentrations of 0.01%, 0.03% and 0.04% and for heat flux varied between 800 W/m2 and 1000 W/m2, which is sourced from a solar flat plate collector. The influence of mass flow rate, inlet temperature and volume concentration on the LMTD, effectiveness, convective heat transfer coefficient and pressure drop are studied. The results showed an increase in convective heat transfer coefficient and effectiveness of silver/water nanofluids as the particle volume concentration is increased. A maximum enhancement in convective heat transfer coefficient of 12.4% and effectiveness of 6.14% is recorded. It is also observed that the apparent increase in the heat transfer coefficient is due to the enhanced thermo-physical properties of the nanofluids, and delayed development of boundary layer in the entrance regions due to the addition of nanoparticles.