On the occurrence of burnout downstream of a flow obstacle in boiling two-phase upward flow within a vertical annular channel

Shoji Mori, Akira Tominaga, Tohru Fukano

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

If a flow obstacle, such as a spacer is placed in a boiling two-phase flow within a channel, the temperature on the surface of the heating tube is severely affected by the existence of the spacer. Under certain conditions, a spacer has a cooling effect, and under other conditions, the spacer causes dryout of the cooling water film on the heating surface. The burnout mechanism, which always occurs upstream of a spacer, however, remains unclear. In a previous paper [Fukano, T., Mori, S., Akamatsu, S., Baba, A., 2002. Relation between temperature fluctuation of a heating surface and generation of drypatch caused by a cylindrical spacer in a vertical boiling two-phase upward flow in a narrow annular channel. Nucl. Eng. Des. 217, 81-90], we reported that the disturbance wave has a significant effect on dryout and burnout occurrence and that a spacer greatly affects the behavior of the liquid film downstream of the spacer. In the present study, we examined in detail the influences of a spacer on the heat transfer and film thickness characteristics downstream of the spacer by considering the result in steam-water and air-water systems. The main results are summarized as follows:(1)The spacer averages the liquid film in the disturbance wave flow. As a result, dryout tends not to occur downstream of the spacer. This means that large temperature increases do not occur there. However, traces of disturbance waves remain, even if the disturbance waves are averaged by the spacer.(2)There is a high probability that the location at which burnout occurs is upstream of the downstream spacer, irrespective of the spacer spacing.(3)The newly proposed burnout occurrence model can explain the phenomena that burnout does occur upstream of the downstream spacer, even if the liquid film thickness tF m is approximately the same before and behind the spacer.

Original languageEnglish
Pages (from-to)2240-2249
Number of pages10
JournalNuclear Engineering and Design
Volume237
Issue number23
DOIs
Publication statusPublished - Dec 1 2007
Externally publishedYes

Fingerprint

burnout
two phase flow
Two phase flow
boiling
spacers
Boiling liquids
Liquid films
occurrences
disturbance
Heating
Film thickness
heating
liquid
Water
Steam
Cooling water
Temperature
cooling water
temperature
disturbances

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering
  • Safety, Risk, Reliability and Quality
  • Waste Management and Disposal
  • Mechanical Engineering

Cite this

On the occurrence of burnout downstream of a flow obstacle in boiling two-phase upward flow within a vertical annular channel. / Mori, Shoji; Tominaga, Akira; Fukano, Tohru.

In: Nuclear Engineering and Design, Vol. 237, No. 23, 01.12.2007, p. 2240-2249.

Research output: Contribution to journalArticle

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