Wall conduction as well as area variation leads to heat flux re-distribution.

A new parameter is proposed to analyse wall conduction in varying cross section microchannel.

Wall conduction reduces with divergence angle but depends weakly on convergence angle.

Wall conduction larger in converging microchannel compared to diverging microchannel.

The surface temperature gradient versus heat rate variation demarcates diverging and converging microchannels into two zones.

Standard deviation in heat rate distribution varies linearly with wall conduction number.