Experimental results of a novel, variable roughness technique to enhance, on demand, heat transfer in a single-phase heat exchanger
A novel, active concept for a variable-roughness, heat-exchanger-tube insert that can enhance heat transfer was developed. The final design consists of shape-memory-alloy (SMA) wire coils that ride along a support structure in close proximity to the inner-tube wall of a double-pipe heat exchanger. At low tube-wall temperature, the coils are close-coiled. An excessive tube-wall temperature (low heat transfer coefficient) results in coil extension which produces substantial heat transfer enhancement. This concept could also be applied to the outside surface of a heat-exchanger tube. Experiments were conducted at three test-fluid flow rates [0.14 kg/s (18.52 lb/min), 0.30 kg/s (39.68 lb/min), 0.58 kg/s (76.72 lb/min)] while maintaining constant test-fluid inlet temperatures [30 C (86 F), 35 C (95 F), 40 C (104 F)]. Extension of the SMA coils does produce a heat transfer enhancement and a pressure drop penalty. The increase in heat transfer coefficient between compressed-coil and extended-coil states ranges from 28 to 64%. The corresponding increase in friction factor is between 18 and 25%. Most favorable results occur at a test-fluid flow rate of 0.14 kg/s (18.52 lb/min), Re {approximately}10,000.
- Research Organization:
- Rensselaer Polytechnic Inst., Troy, NY (US)
- OSTI ID:
- 20030443
- 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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