COMPARATIVE STUDY ON HEAT TRANSFER ENHANCEMENT OF LOW VOLUME CONCENTRATION OF Al2O3-WATER AND CARBON NANO-TUBE-WATER NANO-FLUIDS IN TRANSITION REGIME USING HELICAL SCREW TAPE INSERTS

This study reports the comparison of heat transfer and friction factor characteristics of helical screw inserts in Al2O3-water and carbon nano-tube-water nano-fluids through a straight pipe in transition regime with constant heat flux boundary condition. Experiments were carried out by using 0.15% volume concentration of Al2O3-water and carbon nano-tube-water nano-fluid with helical tape inserts of twist ratio, TR=1.5, 2.5, and 3. The thermal performance of helical screw tape inserts with the carbon nano-tube-water nano-fluid is found -to be higher when compared to the Al2O3-water nano-fluid. In addition, the maximum enhancement in heat transfer was obtained for the carbon nano-tube-water nano-fluid with helical tape inserts of twist ratio 1.5. The increase in pressure drop of the Al2O3-water nano-fluid with helical screw tape inserts is found to be higher compared to the carbon nano-tube-water nano-fluid helical screw tape inserts at lower value of twist ratio.