Thermal-hydraulic performance of multiport microchannel flat tube with a sawtooth fin structure

• Multiport microchannel flat tubes with fin structure have an earlier transition.
• The value of H/P has the most significant effect on heat transfer and flow.
• The maximum enhancement on Nusselt number can reach 5.1 times.
• The good values of performance evaluation criterion are obtained by calculation.

This work experimentally studied the single-phase flow and heat transfer characteristics of a type of multiport microchannel flat tube (MMFT) with a sawtooth fin structure. This MMFT consisted of numerous parallel rectangular microchannels and is widely used in industry as the heat transfer unit of a heat exchanger. Three samples with different dimensions and varied fin sizes were used as test sections to perform the experiment with water as a working fluid. The Reynolds number was varied from 110 to 6100 to cover the laminar, transition, and early fully developed turbulent regions. Moreover, a smooth MMFT of the same dimension as one of the three samples with a fin structure was tested as the control experiment. The experimental results show that the fin structure can enhance the heat transfer at the expense of increasing the pressure drop and earlier induction of the laminar–turbulent transition. The degree of heat transfer enhancement and the pressure drop increase both depend on the raised degree of the fin structure. Finally, the performance evaluation criterion (PEC) was calculated to comprehensively assess the performance of the MMFT with fins. The values of the PEC indicate that the MMFT with fins improves the heat transfer performance.