Microchannel Experimental Structure for Measuring Temperature Fields During Convective Boiling

This work designs and fabricates a microchannel structure for measurement of wall temperature fields in two-phase flow. The microchannel with hydraulic diameter of 100 micrometers is etched into a suspended beam of silicon with three independently heated regions and integrated doped silicon resistors sensitive to channel temperature. Doped silicon resistors are also sensitive to strain in the silicon caused by pressure transients in the channel, so sensors are designed with two different orientations and thus two different piezoresistive coefficients to allow decoupling of pressure and temperature effects. Use of a 400 micrometer wide suspended beam reduces side-wall conduction compared to a bulk sample and provides better opportunities to measure the influence of flow regimes on heat transfer coefficients in future work. Use of the central heater reduces fluid preheating in the inlet plenum. The measured temperature distributions at flowrates up to 0.25 ml/min with heat fluxes into the silicon beam up to 78 W/cm2 show initial capabilities of the structure.