Heat Transfer in Pulsatile Flow Through Square Microchannels With Wavy Walls

Abstract

A three-dimensional numerical analysis is performed to understand the effect of axial wall conduction on conjugate heat transfer during single phase pulsatile flow in a square microchannel with wavy walls (wall faces are parallel to each other). A microchannel of inner width and height are 0.4 × 0.4 mm2 and length of 30 mm is considered for the numerical simulation. The wavelength and amplitude of the vertical wavy shaped channel wall are 12 mm and 0.2 mm respectively. The working fluid is taken as water which enters the channel at 300 K temperature and constant heat flux boundary condition is imposed on the entire bottom surface of the microchannel. All the remaining walls of the microchannel exposed to surrounding are kept insulated. The velocity at the inlet of channel is the combination of a fixed component of velocity and fluctuating component of velocity which varies sinusoidally, thus causing pulsatile velocity at the inlet (amplitude, A = 0.2) with variation of frequency from 2 Hz to 10 Hz. Simulations has been performed for constant flow Reynolds number (Re = 100) and wall thickness to inner radius ratio (δsf = 1) with varrying solid wall to fluid conductivity ratio (ksf from 0.344 to 715). It is observed that ksf play a key role to enhance heat transfer due to axial wall conduction. Change of pulsation frequency corresponds to Womersley number (Wo = 1.414, 2, 245, and 3.163) does not affect local Nu. From the numerical simulation, it is obtained that overall Nusselt number function of Re and thickness ratio (δsf) at particular Wo. Overall Nusselt number increases with ksf up to an optimum value then decreases due to the effect of axial wall conduction.