Experiments were conducted to study the heat transfer characteristics of water flowing through triangular silicon microchannels with a hydraulic diameter of 155.3 μm.The ratio of axial heat conduction to the whole heating and the axial heat conduction number were used to evaluate the effect of axial heat conduction on heat transfer in microchannelsThe thermal entry lengths for all cases were calculated based on experimental resultsThe measurements by IR camera showed that the local wall temperature did not change linearly along the channel

which was mainly caused by the axial heat conduction in the wallAnd the local Nusselt number distributions along the flow direction were calculated based on experimental resultsThe ratio of the axial heat conduction to the whole heating varied from 0.106 to 0.275

indicating that the axial heat conduction might play an important role in heat transfer in microchannels

especially when Reynolds number was lowThe axial heat conduction number was modified in the present studyThe experimental study revealed that the axial heat conduction number decreased with increasing Reynolds number when keeping heat input and inlet water temperature nearly constant.