The characteristics of premature and stable critical heat flux for downward flow boiling at low pressure in a narrow rectangular channel

Cited 8 time in webofscience Cited 13 time in scopus
  • Hit : 925
  • Download : 0
Flow instability and critical heat flux (CHF) especially for downward flow of water in a vertical narrow rectangular channel heated from both sides were experimentally investigated. The gap, width, heated width, and heated length of the channel were 2.35, 40, 30, and 350 mm, respectively. The flow boiling was developed as the wall heat flux was increased for the imposed mass flux of 500 and 1000 kg m(-2) - s(-1) for high inlet subcooling (52-74 K) conditions under atmospheric pressure. In this paper, the unstable boiling flow was investigated by monitoring the channel pressure drop and high speed visualization for side view of boiling (HSV-SVB) with the back-lighting method. The results showed that an irremovable pressure drop fluctuation was involved in the flow boiling after the distinct initiating point called as the onset of pressure drop fluctuation (OPDF). We determined that coalescence of bubble (or vapor) layers on opposing heated surfaces triggered the OPDF, since an abrupt increase of pressure drop was occurred as the expansion of the liquid-vapor interface became bounded by the other layer on the opposite side. The fluctuation was amplified as the exit quality was increased and the flow regime passed through the unstable slug or churn flow. For a low inlet throttling condition, premature CHF was induced at the maximum fluctuation during those flow regimes. On the other hand, stable CHF was obtained in the re-stabilized flow regime as the annular flow was developed only for large inlet throttling conditions with an additional pressure drop across the valve of more than 0.4 bar for our experimental configuration.
Publisher
ELSEVIER SCIENCE INC
Issue Date
2015-12
Language
English
Article Type
Article
Keywords

2-PHASE FLOW; MICROCHANNEL; INSTABILITY; WATER; PREDICTION; TRANSITION; SINKS; DROP

Citation

EXPERIMENTAL THERMAL AND FLUID SCIENCE, v.69, pp.86 - 98

ISSN
0894-1777
DOI
10.1016/j.expthermflusci.2015.07.015
URI
http://hdl.handle.net/10203/203665
Appears in Collection
NE-Journal Papers(저널논문)
Files in This Item
There are no files associated with this item.
This item is cited by other documents in WoS
⊙ Detail Information in WoSⓡ Click to see webofscience_button
⊙ Cited 8 items in WoS Click to see citing articles in records_button

qr_code

  • mendeley

    citeulike


rss_1.0 rss_2.0 atom_1.0