An Analysis of Burnout Conditions for Flow of Boiling Water in Vertical Round Ducts

Abstract

A method of predicting the burnout conditions for flow of boiling water in vertical round ducts is presented. The analysis predicts that the burnout conditions are independent of the L/d-ratio and the inlet temperature, and that the burnout steam quality decreases with increasing surface heat flux and increasing mass velocity. It was also found that the burnout steam quality at low pressures increases with the pressure and reaches a maximum at approximately 70 kg/cm2, and thereafter decreases with a further increase of the pressure. The theoretical result compares very well with experimental data from different sources.

Discussion: “Measurements of Burnout Conditions for Flow of Boiling Water in a Vertical Annulus” (Becker, K. M., and Hernborg, G., 1964, ASME J. Heat Transfer, 86, pp. 393–404)

“…Petrick's remarks about the method are quite interesting. We agree that the computed burnout quality ratio depends upon the round duct correlation employed, and that in the present case we used our own correlation [21]. Concerning the Westingliouse 9-rod cluster data, the value of 0.53 for the quality ratio is unfortunately wrong.…”

“…XRD was computed from the round duct burnout correlation in reference [21], t]i(q/A) was introduced in accordance with the suggestion in the present paper that the round duct data had to be reduced by a factor which is a function of the 77-value and the heat flux. In equation (9) this factor was put equal to r]-rji(q/A).…”

Discussion: “An Analysis of Burnout Conditions for Flow of Boiling Water in Vertical Round Ducts” (Becker, K. M., and Persson, P., 1964, ASME J. Heat Transfer, 86, pp. 515–524)

“…The question raised here is if the authors have really proved the noneffect of Nsc and L/D ratio by utilizing the proposed model by Isbin, et al The appearance of L/D ratio and Nsc in equations (5), (6), and (7) comes about merely from a substitution of a si mule heat balance of the following form: By eliminating L/D ratio from equations (5) and (G) and setting A'" equal to zero, the authors now obtain a set of equations which say that the burnout is strictly a local phenomenon. Then it is pointed out that the obtained solutions must be checked in order to avoid a violation of the heat balance discussed above.…”

“…Obtaining these quantities would then serve to unify the burnout problem with other two-phase flow problems. 6 Numbers in brackets designate Additional References at end of discussion.…”

Closure to “Discussions of ‘An Analysis of Burnout Conditions for Flow of Boiling Water in Vertical Round Ducts’” (1964, ASME J. Heat Transfer, 86, pp. 524–528)

“…The question raised here is if the authors have really proved the noneffect of Nsc and L/D ratio by utilizing the proposed model by Isbin, et al The appearance of L/D ratio and Nsc in equations (5), (6), and (7) comes about merely from a substitution of a si mule heat balance of the following form:…”