Friction and Forced Convection Heat Transfer Characteristics in Tubes by Use of Helical-Wire-Coil Inserts.

This work summarizes the results of experimental investigation of convective heat transfer and friction loss characteristics of air flow in a horizontal circular copper tube of diameters 13.5/22 mm., using helical wire-coils , of diameter 1.4 mm, inserted in. The helix angle (a) of the helical-wire-coil is varied from 65° to 86.7o. The outer surface of the test tube is heated by superheated steam (degree of superheat 2:3 oC) at atmospheric pressure. During the experimental work, Reynold's number is changed from 6000 to 120000 and Prandti number is about 0.7. The heat transfer enhancement of the inserted helical-wire-coil is ranging from 30 % to 145 %. However, A quantitatively increase in hydrodynamics resistance is noticed. Correlations of Nusselt number and friction factor has been made. It was found that the nusselt number and friction factor were dependent on both Reynold's number and helix angle.