### Abstract

The objectives of this study are to investigate the effects of the power transient on critical heat flux (CHF), and to develop CHF and maximum heat flux (MHF) correlations in transient boiling systems with a countercurrent flow between the liquid and vapor flow. The test section consists of narrow, vertical, rectangular channels between parallel plates. Rate of change of wall temperature at the CHF point, (dT_{w}/dt)_{CHF}, and a nondimensional transient parameter, τ_{o}, = (L^{2}α_{f}T_{sat})|(dT_{w}/dt)|_{CHF} are introduced to evaluate the effects of power transients on CHF and MHF. Experimental ranges were 738.0-1,968.0 kg/m^{2}s for mass flux, 7.0-17.5 °C for inlet subcooling, and 3.0-8.0 mm for channel gap distance. The system pressure was kept constant at 1.0 atm. The experimental results show that CHF and MHF values increase with an increasing rate of change of wall temperature, and the increasing rate of CHF is higher in a wider channel gap distance. CHF and MHF increase linearly with increasing mass flux at the top of the test section, and the linearity decreases at the bottom of the test section. The effect of the inlet subcooling is significant at the top of the test section, therefore the test location close to liquid inlet has a higher CHF value than the location immediately below it. It was also found that the wider the channel gap distance, tim higher was the CHF value obtained for a given rate of change of wall temperature. New CHF and MHF correlations are developed for countercurrent flow in transient boiling systems. The CHF and MHF correlations are in good agreement with the experimental data within ±25% error bands, respectively.

Original language | English |
---|---|

Pages (from-to) | 27-37 |

Number of pages | 11 |

Journal | Heat Transfer Engineering |

Volume | 20 |

Issue number | 4 |

Publication status | Published - 1999 Dec 1 |

Externally published | Yes |

### Fingerprint

### ASJC Scopus subject areas

- Chemical Engineering(all)
- Fluid Flow and Transfer Processes
- Physical and Theoretical Chemistry
- Energy Engineering and Power Technology
- Fuel Technology

### Cite this

**Experimental investigation of CHF during countercurrent flow in transient boiling systems.** / Kang, Yong Tae.

Research output: Contribution to journal › Article

*Heat Transfer Engineering*, vol. 20, no. 4, pp. 27-37.

}

TY - JOUR

T1 - Experimental investigation of CHF during countercurrent flow in transient boiling systems

AU - Kang, Yong Tae

PY - 1999/12/1

Y1 - 1999/12/1

N2 - The objectives of this study are to investigate the effects of the power transient on critical heat flux (CHF), and to develop CHF and maximum heat flux (MHF) correlations in transient boiling systems with a countercurrent flow between the liquid and vapor flow. The test section consists of narrow, vertical, rectangular channels between parallel plates. Rate of change of wall temperature at the CHF point, (dTw/dt)CHF, and a nondimensional transient parameter, τo, = (L2αfTsat)|(dTw/dt)|CHF are introduced to evaluate the effects of power transients on CHF and MHF. Experimental ranges were 738.0-1,968.0 kg/m2s for mass flux, 7.0-17.5 °C for inlet subcooling, and 3.0-8.0 mm for channel gap distance. The system pressure was kept constant at 1.0 atm. The experimental results show that CHF and MHF values increase with an increasing rate of change of wall temperature, and the increasing rate of CHF is higher in a wider channel gap distance. CHF and MHF increase linearly with increasing mass flux at the top of the test section, and the linearity decreases at the bottom of the test section. The effect of the inlet subcooling is significant at the top of the test section, therefore the test location close to liquid inlet has a higher CHF value than the location immediately below it. It was also found that the wider the channel gap distance, tim higher was the CHF value obtained for a given rate of change of wall temperature. New CHF and MHF correlations are developed for countercurrent flow in transient boiling systems. The CHF and MHF correlations are in good agreement with the experimental data within ±25% error bands, respectively.

AB - The objectives of this study are to investigate the effects of the power transient on critical heat flux (CHF), and to develop CHF and maximum heat flux (MHF) correlations in transient boiling systems with a countercurrent flow between the liquid and vapor flow. The test section consists of narrow, vertical, rectangular channels between parallel plates. Rate of change of wall temperature at the CHF point, (dTw/dt)CHF, and a nondimensional transient parameter, τo, = (L2αfTsat)|(dTw/dt)|CHF are introduced to evaluate the effects of power transients on CHF and MHF. Experimental ranges were 738.0-1,968.0 kg/m2s for mass flux, 7.0-17.5 °C for inlet subcooling, and 3.0-8.0 mm for channel gap distance. The system pressure was kept constant at 1.0 atm. The experimental results show that CHF and MHF values increase with an increasing rate of change of wall temperature, and the increasing rate of CHF is higher in a wider channel gap distance. CHF and MHF increase linearly with increasing mass flux at the top of the test section, and the linearity decreases at the bottom of the test section. The effect of the inlet subcooling is significant at the top of the test section, therefore the test location close to liquid inlet has a higher CHF value than the location immediately below it. It was also found that the wider the channel gap distance, tim higher was the CHF value obtained for a given rate of change of wall temperature. New CHF and MHF correlations are developed for countercurrent flow in transient boiling systems. The CHF and MHF correlations are in good agreement with the experimental data within ±25% error bands, respectively.

UR - http://www.scopus.com/inward/record.url?scp=0033327710&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033327710&partnerID=8YFLogxK

M3 - Article

VL - 20

SP - 27

EP - 37

JO - Heat Transfer Engineering

JF - Heat Transfer Engineering

SN - 0145-7632

IS - 4

ER -