The partitioning of the heat flux supplied at the wall is one of the key issues that needs to be resolved if one is to model subcooled flow boiling accurately. The first step in studying wall heat flux partitioning is to account for the various heat transfer mechanisms involved and to know the location at which the onset of nucleate boiling (ONB) occurs. Active nucleation site density data is required to account for the energy carried away by the bubbles departing from the wall. Subcooled flow boiling experiments were conducted using a flat plate copper surface and a nine-rod (zircalloy-4) bundle. The location of ONB during the experiments was determined from visual observations as well as from the thermocouple output. From the data obtained it is found that the heat flux and wall superheat required for inception are dependent on flow rate, liquid subcooling, and contact angle. The existing correlations for ONB underpredict the wall superheat at ONB in most cases. A correlation for predicting the wall superheat and wall heat flux at ONB has been developed from the data obtained in this study and that reported in the literature. Experimental data are within ±30 percent of that predicted from the correlation. Active nucleation site density was determined by manually counting the individual sites in pictures obtained using a CCD camera. Correlations for nucleation site density, which are independent of flow rate and liquid subcooling, but dependent on contact angle have been developed for two ranges of wall superheat—one below 15°C and another above 15°C.
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Technical Papers
Onset of Nucleate Boiling and Active Nucleation Site Density During Subcooled Flow Boiling
Nilanjana Basu,
Nilanjana Basu
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
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Gopinath R. Warrier,
Gopinath R. Warrier
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
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Vijay K. Dhir
e-mail: vdhir@seas.ucla.edu
Vijay K. Dhir
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
Search for other works by this author on:
Nilanjana Basu
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
Gopinath R. Warrier
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
Vijay K. Dhir
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095-1597
e-mail: vdhir@seas.ucla.edu
Contributed by the Heat Transfer Division for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received by the Heat Transfer Division October 9, 2001; revision received February 1, 2002. Associate Editor: F. B. Cheung.
J. Heat Transfer. Aug 2002, 124(4): 717-728 (12 pages)
Published Online: July 16, 2002
Article history
Received:
October 9, 2001
Revised:
February 1, 2002
Online:
July 16, 2002
Citation
Basu , N., Warrier , G. R., and Dhir, V. K. (July 16, 2002). "Onset of Nucleate Boiling and Active Nucleation Site Density During Subcooled Flow Boiling ." ASME. J. Heat Transfer. August 2002; 124(4): 717–728. https://doi.org/10.1115/1.1471522
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