Y. Gianchandani, U. of Michigan Nellis and Klein, U. of Wisconsin Madison

1. Micromachined Si/Glass Heat Exchangers for Joule-Thomson CoolersSandip Tiwari, Cornell University, ECCS - 0335765 A micromachined perforated plate Si/glass heat exchangers intended for Joule-Thomson (J-T) coolers was fabricated. In order to have a high effectiveness, the heat exchangers require good stream-to-stream thermal conductance while restricting parasitic stream-wise (axial) conduction. The perforated plate design uses numerous high-thermal-conductivity silicon plates alternated with low-thermal-conductivity glass spacers. It was fabricated using a four-mask process including KOH on (110) silicon wafers, HF glass wet etching and anodic bonding. Platinum resistance temperature detectors (Pt RTDs) were embedded for in-situ temperature sensing. The perforated plate heat exchanger demonstrated an effectiveness as high as 0.91 in cryogenic temperature range 237-252 K and excellent robustness at working pressures up to 145 psia (1 MPa). In J-T self-cooling tests using ethane, the lowest temperatures achieved by this heat exchanger were 218.7 K at steady state and 200.3 K in a transient state, when a 0.015 inch dia. orifice was used for gas expansion. Micromachined perforated plate Si/glass heat exchanger. Die size ~ 10 × 10 mm2. Length ~ up to 35 mm. Effectiveness measurements in a temperature range of 237-252 K. Y. Gianchandani, U. of Michigan Nellis and Klein, U. of Wisconsin Madison Work performed at the U-Michigan Lurie Nanofabrication Facility (testing at UW-Madison)