Comparative study on heat transfer enhancement of low volume concentration of Al2O3-water and carbon nanotube-water nanofluids in laminar regime using helical screw tape inserts

Abstract

An experimental study has been carried out to evaluate the heat transfer and friction factor characteristics of helical screw inserts in Al 2O3-water and carbon nanotubes (CNT)-water nanofluids through a straight pipe in laminar flow regime with constant heat flux boundary condition. Tests have been performed by using 0.15% volume concentration Al 2O3-water and CNT-water nanofluid with helical tape inserts of twist ratio (TR) = 1.5, 2.5, and 3. The helical screw tape inserts with CNT-water nanofluid exhibits higher thermal performance compared to Al 2O3-water nanofluid. The maximum enhancement in heat transfer was obtained for CNT-water nanofluid with helical tape inserts of TR = 1.5. The increase in pressure drop of Al2O3-water nanofluid with helical screw tape inserts is found to be higher compared to CNT-water nanofluid with helical screw tape inserts at lower value of TR. For both the nanofluids (CNT-water and Al2O3-water), the thermal performance factor was found to be greater than unity for all TRs. Copyright © 2013 by ASME.