Micro heat exchanger by using MEMS impinging jets

A micro impinging-jet heat exchanger is presented. Heat transfer is studied for single jet, slot arrays and jet arrays. In order to facilitate micro heat transfer measurements with these devices, a MEMS sensor chip, which has an 8/spl times/8 temperature-sensor array on one side, and an integrated heater on the other side has been designed and fabricated. This sensor chip allows 2-D surface temperature measurement with various jets impinging on it. It is found that micro impinging jets can be highly efficient when compared to existing macro impinging-jet microelectronics packages such as IBM 4381. For example, using a single nozzle jet (500-/spl mu/m diameter driven by 5 psig pressure), the sensor chip (2/spl times/2 cm/sup 2/) temperature can be cooled down from 70 to 33/spl deg/C. The cooling becomes more efficient when nozzle arrays (4/spl times/5 over 1 cm/sup 2/ area) are used under the same driving pressure. Interestingly, although higher driving pressure gives better cooling (lower surface temperature), the cooling efficiency, defined as h/0.5 /spl rho//spl nu//sup 2/, is actually higher for lower driving pressure.