FULLY-DEVELOPED LAMINAR HEAT-TRANSFER IN CIRCULAR-SEGMENT DUCTS WITH UNIFORM WALL TEMPERATURE

Heat transfer to constant-property, fully developed, laminar flows in circular-segment ducts with uniform wall temperature (T) has been anal yzed. Besides representing a compact surface, the segment duct geometr y models the flow cross section of a circular tube with a straight-tap e insert. Two variations in the T thermal boundary condition are consi dered: constant axial and circumferential wall temperature, and consta nt temperature on the curved surface but an adiabatic flat wall. These two conditions model the extremes of the fin effects of a straight-ta pe insert, i.e., 100% and zero fin efficiencies, respectively. Numeric al solutions, obtained by using finite difference techniques, are pres ented for both the velocity and temperature fields. The isothermal fri ction factors are in excellent agreement with analytical solutions rep orted in the literature. The Nusselt number results for the two therma l boundary conditions are presented for different segment shapes, 0-de gree less-than-or-equal-to theta less-than-or-equal-to 90-degrees, and they represent the lower limits of the heat transfer enhancement due to twisted-tape inserts.