Flow and heat transfer characteristics inside a wavy tube

Hydrodynamic and thermal characteristics in a pipe with sinusoidal wavy surface for steady laminar flow are investigated numerically in the present study. Governing equations are discretized using control volume based Finite-Volume method with collocated variable arrangement. SIMPLE algorithm is used and TDMA solver is applied for solution of system of equations. A pipe of length equal to 4;, is considered where A is the wavelength. Effect of surface waviness, determined by wavelength-amplitude ratio lambda/a (=L*) on flow and thermal field is presented. The simulation work has been carried out for L*=11.0 - 30.0 for a Reynolds number ranging from 50 to 2000. Results are presented in the form of streamfunction, isothermal lines, velocity and vorticity profiles, Nusselt number with Reynolds number, wave number (n) and L*. For a particular geometry, length of circulation zone increases with Reynolds number and approaches a limiting value. Wall shear stress is smaller in the bulge part of the channel that affects largely the rate of heat transfer. These circulation zone increases with the increase of surface waviness showing high mean friction factor per wavelength. Mean friction factor inversely varies with Reynolds number. A correlation is proposed for calculating the friction factor in the form f=C/(Re)(m), where 'C' and 'm' represents two polynomials of degree 4 and 2 respectively and are function of L*.