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. A square microchannel (with wavy vertical walls) of length of 30 mm, and cross-section 0.4 × 0.4 mm2 is considered for the numerical simulation. The wavelength and amplitude of the vertical wavy shaped channel walls are 12 mm and 0.2 mm respectively. The working fluid is taken as water which enters the channel at 300 K, and constant heat flux boundary condition is imposed at the entire bottom surface of the substrate on which the microchannel was carved. All the remaining surfaces of the substrate 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 substrate thickness below channel bed to channel height ratio (δsf = 1) with varying solid to fluid conductivity ratio (ksf = 0.344 - 715). It is observed that ksf play a key role in controlling heat transfer due to axial wall conduction. Change of pulsation frequency corresponding to Womersley number (Wo = 1.414 - 3.163) does not affect local Nu. It is also found that overall Nu depends on Re and δsf at particular value of Wo. Overall Nu increases with ksf up to an optimum value, and then decreases due to the effect of axial wall conduction.