Enhancement of flow boiling of subcooled water on transverse ribbed surface
The present work deals with enhancement of flow boiling heat transfer using transverse ribs of rectangular cross section attached on a flat heating surface. High flux cooling is envisioned in the field of the leading edge technology such as high power laser applications, advanced metallurgical processes, fusion reactors, integrated circuit chips and so forth. In such advanced cooling devices subcooled boiling of water at high velocity is expected as one of most efficient and convenient means for heat removal exceeding 10{sup 7}W/m{sup 2}. In the present experiment, a sheet of stainless-steel (10mm wide, 0.2mm thick and 80mm in heated length) was flush mounted on one wall of a vertical rectangular channel (a cross-section 20mm x 30 mm) and used as a heating surface by passing a direct current. Transverse-ribs made of plastic plate (0.5mm thick and 30mm in lateral length) were attached at an equal longitudinal spacing on the heating surface. Longitudinal spacing of ribs was varied from 2.5, 5, 10, 20mm to infinity (a flat surface without ribs), and the rib height was 2.5mm and 5.0mm. Experiments were conducted with water at a pressure of 0.12MPa in the range of mass velocity from 500kg/m{sup 2}s to 2,000kg/m{sup 2}s (water velocity from 0.5m/s to 2m/s) and subcooling from 20K to 50K. It was found that the ribbed structure strongly affects heat transfer both in the non-boiling and partial nucleate boiling regimes. Enhancement rate of heat transfer coefficient varied from 5% to 50% in excess compared with that for the flat heating plate. According to visual observation of boiling bubbles the circulating flow occurred in a space between each consecutive ribs and seemed to enhance heat transfer. For narrow rib spacing a large coalesced bubble filled up each rib space and impeded the exchange of vapor with liquid, leading to heat transfer deterioration. In the present experimental range of the ribs, a 50% increase of heat transfer coefficient was attained on the ribbed surface with 5mm height and a spacing of 10mm.
- Research Organization:
- Kyushu Univ., Fukuoka (JP)
- OSTI ID:
- 20030455
- Resource Relation:
- Conference: 5th ASME/JSME Thermal Engineering Joint Conference, San Diego, CA (US), 03/14/1999--03/19/1999; Other Information: 1 CD-ROM. Operating system required: Windows i386(tm), i486(tm), Pentium (R) or Pentium Pro, MS Windows 3.1, 95, or NT 3.51, 8 MB RAM, MacIntosh and Power MacIntosh with a 68020 or greater processor, System software version 7.1, 3.5 MB RAM (5 MB for PowerMac) 6 MB available hard-disk space, Unix; PBD: 1999; Related Information: In: Proceedings of the 5th ASME/JSME thermal engineering joint conference, [3600] pages.
- Country of Publication:
- United States
- Language:
- English
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