This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Micro heat exchangers (MHXs) may achieve very high heat transfer coefficients thanks to their
small dimensions and high Area-to-Volume ratio even in laminar flow. The main drawback of these devices
is the high frictional losses – especially for liquid flows – that make viscous dissipation no longer negligible.
In order to enhance heat transfer, modification of the channels’ cross-section is a viable strategy. In the
present work the fully developed steady laminar flow of a Newtonian liquid through a microchannel subject
to H1 boundary conditions in the presence of viscous dissipation is investigated. Entropy generation numbers
and FG1a performance evaluation criterion are employed to assess the influence of smoothing the corners of
an initially rectangular cross-section, with an aspect ratio ranging from 1 to 0.03 under four different types of
geometrical constraints. The governing equations and the results are expressed in non-dimensional form, the
intensity of viscous dissipation being exemplified by the Brinkman number, which is demonstrated to
increase its maximum allowable value when corners are smoothed. The results are reported as a function of
the non-dimensional radius of curvature Rc and aspect ratio and show that smoothing the corners almost
invariably brings about a benefit for a fixed heated perimeter
