Development and Testing of Microscale Silicon Heat Exchangers for the MIT Micro Gas-Turbine Engine

Micro-scale silicon heat exchangers were designed, modeled using conventional heat transfer and fluid mechanics correlations, fabricated in the MIT Microtechnologies Laboratory, and tested as part of the MIT micro-gas turbine engine project. Heat transfer and pressure drop experiments were carried out to measure the performance of these heat exchangers, and to validate the predictions of the model. The tested heat exchanger was 2 centimeters by 3 centimeters by 4 mm in size, and housed 220 individual heat transfer passages (110 in each direction). The heat transfer passages were rectangular in cross-section, with lengths of 7mm, widths between 100 and 150 micrometers, and depths of about 190 micrometers. In actual microengine application, the heat exchangers might experience temperatures as high as 1400K. In the tests conducted for this project, the temperatures were limited to 350K. Results demonstrated a heat transfer rate of about 0.5 watts. Under the test conditions, this corresponds to a heat exchanger effectiveness of about 52%, which is within the experimental margin of error of the 50.5% value predicted by the model. These results indicate that the addition of a recuperative heat exchanger to the MIT micro gas turbine engine could provide a benefit to the fuel efficiency of the engine cycle. Thesis Supervisor: John G. Brisson Title: Professor of Mechanical Engineering