Liquid Nitrogen Flow Boiling Critical Heat Flux in Additively Manufactured Cooling Channels

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Abstract
This paper presents an experimental characterization of liquid nitrogen (LN2) flow boiling in additively manufactured minichannels. There is a pressing need of concerted efforts from the space exploration and thermal transport communities to design high-performance rocket engine cooling channels. A close observation of the literature gaps warrants a systematic cryogenic flow boiling characterization of asymmetrically heated small ( 3000 kg/m2s and pressure > 1 MPa. As such, this work presents the LN2 flow boiling results for three asymmetrically heated additively manufactured GR-Cop42 channels of 1.8 mm, 2.3 mm, and 2.5 mm hydraulic diameters. Twenty different tests have been performed at mass flux~3805–14,295 kg/m2s, pressures~1.38 and 1.59 MPa, and subcooling~0 and 5 K. A maximum departure from nucleate boiling (DNB)-type critical heat flux (CHF) of 768 kW/m2 has been achieved for the 1.8 mm channel. The experimental results show that CHF increases with increasing LN2 flow rate (337–459 kW/m2 at 25–57 cm3/s for 2.3 mm channel) and decreasing channel size (307–768 kW/m2 for 2.5–1.8 mm channel). Finally, an experimental DNB correlation has been developed with 10.68% mean absolute error.
Funding Information
  • National Aeronautics and Space Administration (NASA) (80NSSC19P1100, 80NSSC20M0237)
  • NASA MIRO Cooperative Agreement number (80NSSC19P1100, 80NSSC20M0237)

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