| Description |
Xurography is a relatively inexpensive rapid prototyping microfabrication method used to manufacture microfluidic devices. An experimental study of water flow in rectangular xurographic microchannel counterflow heat exchangers with different channels widths is reported. Four different microchannel heat exchangers having channel widths ranging from 350 m to 1000 μm and aspect ratios ranging from 0.1 to 0.29 were fabricated using double-sided adhesive Kapton® polyimide tape and two square copper substrates. A mechanical clamping system provided additional mechanical force to prevent leakage and to enable higher flow rates. The maximum Reynolds number , based on the hydraulic diameter, was approximately 4500. Reported data include heat rate, heat flux, overall heat transfer coefficient, overall volumetric heat transfer coefficient, heat exchanger effectiveness, net transfer units, and two exergy efficiencies. These data are reported for each heat exchanger with up to three capacity rate ratios . The maximum heat rate, achieved with the largest size channels with ~ 1, approaches 77 W, corresponding to a heat flux of approximately 120 W/cm2. The maximum overall heat transfer coefficient is 49.5 kW/m2/K for the 500 μm channel width heat exchanger, which corresponds to an overall volumetric heat transfer coefficient of 488 MW/m3/K. Strong agreement is found between the experimental heat exchanger effectiveness and net transfer units relationship and an analytical expression for the conventional concentric tube counterflow heat exchanger. The maximum experimental effectiveness of about 0.623 was found for the 1000 μm channel width heat exchanger with ~ 0.5. An exergy efficiency analysis suggests that laminar channel flows produce the maximum exergy efficiency for the heat exchanger. The study confirms that xurography can be used to create effective thermal devices, so long as maximum operating temperatures do not exceed the temperature limits of the adhesive. |
