Experimental investigation of an evaporator enhanced with a micro-porous structure in a two-phase thermosyphon loop
2009 (English)In: HT2008: PROCEEDINGS OF THE ASME SUMMER HEAT TRANSFER CONFERENCE - 2008, VOL 2, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2009, 327-334 p.Conference paper (Refereed)
Following is an experimental study of six different evaporators in a closed two-phase thermosyphon loop system, where the influence of various evaporator dimensions and surfaces was investigated. The evaporators featured a 30 mm long rectangular channel with hydraulic diameters ranging from 1.2-2.7 mm. The heat transfer surface of one of the tested evaporators was enhanced with copper nano-particles, dendritically connected into an ordered micro-porous three dimensional network structure. To facilitate high speed video visualization of the two-phase flow in the evaporator channel, a transparent polycarbonate window was attached to the front of the evaporators. Refrigerant 134A was used as a working fluid and the tests were conducted at 6.5 bar. The tests showed that increasing channel diameters generally performed better. The three largest evaporator channels exhibited comparable performance, with a maximum heat transfer coefficient of about 2.2 W/(cm(2)K) at a heat flux of 30-35 W/cm(2) and a critical heat flux of around 50 W/cm(2). Isolated bubbles characterized the flow regime at peak performance for the large diameter channels, while confined bubbles and chaotic churn flow typified the evaporators with small diameters. In line with previous pool boiling experiments, the nucleate boiling mechanism was significantly enhanced, tip to 4 times, by the nano- and micro-porous enhancement structure.
Place, publisher, year, edition, pages
NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2009. 327-334 p.
Thermosyphon, electronics cooling, enhanced boiling, nano- and micro-structures, porous networks, two-phase heat transfer, micro-channels, R134A, high speed visualization
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-30867DOI: 10.1115/HT2008-56471ISI: 000265637100037ScopusID: 2-s2.0-70349160840ISBN: 978-0-7918-4848-7OAI: oai:DiVA.org:kth-30867DiVA: diva2:401983
ASME Heat Transfer Summer Conference Jacksonville, FL, AUG 10-14, 2008
QC 201103042011-03-042011-03-042012-03-21Bibliographically approved