Analysis on Effect of Surfactant Concentration on Saturated Flow Boiling and Pool & Flow Boiling In Narrow Gaps

Suresh  Pittala

Analysis on Effect of Surfactant Concentration on Saturated Flow Boiling and Pool & Flow Boiling In Narrow Gaps

Comparative Study of Surfactant Solutions in Saturated Flow Boiling

by Suresh Pittala*,

- Published in Journal of Advances in Science and Technology, E-ISSN: 2230-9659

Volume 7, Issue No. 14, Aug 2014, Pages 0 - 0 (0)

Published by: Ignited Minds Journals

ABSTRACT

This paper presents the effects of superheat based onheat transfer models in a narrow gap. At low superheat conditions, heat flux ina narrow gap is higher than heat flux in .33/0 8 pool nucleate boiling due tothe restricted flow area and a high disturbance, approaches the nucleateboiling heat flux as superheat increasing, and reaches a critical value due toCCFL (counter-current flow limiting). Saturated flow boiling of environmentallyacceptable nonionic surfactant solutions of Alkyl (8–16) was compared to thatof pure water. The concentration of surfactant solutions was in the range of100–1000 ppm. The liquid flowed in an annular gap of 2.5 and 4.4 mm between twovertical tubes.

KEYWORD

surfactant concentration, saturated flow boiling, pool boiling, narrow gaps, superheat, heat flux, heat transfer models, nucleate boiling, restricted flow area, CCFL

INTRODUCTION

In course of the TMI-2 accident [1], high temperature core debris drained into the RPV lower plenum and the lower plenum wall was heated to about 1400 K. At this time, the lower plenum wall cooled down rapidly and the vessel integrity was preserved. At a severe accident in a LWR such as the TMI-2 accident, heat transfer models in a narrow annular gap between the overheated core debris and the RPV wall are important to evaluate integrity of the RPV and emergency procedures. Many experiments on gap cooling have been performed [2-7] and heat transfer models were proposed as gap cooling CHF. However, these experiments were performed at low superheat conditions and the CHF correlation did not include effects of superheat because CHF greatly depends on counter-current flow limiting (CCFL) at the top end of the narrow gap. Ohtake et al. [8] measured heat fluxes vs. superheat without CCFL conditions (large gap), and Henry & Hammersley [9] measured temperature trends under CCFL conditions at high superheat in quenching tests at high surface temperature. In these studies, however, local heat transfer and CHF correlations were not derived.

REVIEW OF LITERATURE:

Heat transfer studies of single miniature channels, as well as the analysis and inverse calculation of IR images of a heated microgap channel wall, are used to identify the existence of a characteristic M-shaped heat transfer coefficient variation with quality (or superficial velocity), with inflection points corresponding to transitions in the two-phase cooling modalities. For the high-quality, Annular flow conditions, the venerable Chen correlation is shown to yield predictive agreement for microgap channels that is comparable to that attained for macro channels and to provide a mechanistic context for the thermal transport rates attained in microgap channels. Results obtained from infrared imaging, revealing previously undetected, large surface temperature variations in annular flow, are also reviewed and related to the termination of the favorable thin-film evaporation mode in such channels.

Consequences of surfactant attentiveness on saturated flow boiling:

Kaminaga et al. (2000) [11] conducted an experiment on boiling heat transfer in small tubes of 1.45 and 2.8 mm with water under natural circulation condition. They observed that when the tube diameter was less than the Laplace constant the heat transfer coefficient was much higher than the conventional pool boiling. Sumith et al. (2003) [12]studied the characteristics of flow boiling heat transfer in a vertical tube of 1.45 mm diameter, which is less than the Laplace constant. Heat transfer coefficients were measured in the range of mass fluxes from 23.4 to 152.7 kg/m2 s, heat fluxes from 10 to 715 kW/m2. Large heat transfer enhancement was observed. The dominant flow pattern in the tube was a slug-annular or an annular flow, and then liquid film evaporation was found to dominate the heat transfer. Jacobi and Thome (2002) demonstrate that transient evaporation of the thin not nucleate boiling. Thome et al. (2004) [13] cited the following classification of the transition from macro scale to micro scale based on the hydraulic diameter: microchannels (1–100 lm), mesochannels (100 lm–1 mm), macro channels (1–6 mm) and conventional channels (>6 mm). They noted that such transition criteria do not reflect the influence of channel size on the physical heat transfer mechanism. Therefore the authors suggest that the best threshold criterion is that the bubble growth is confined by the channel, such the bubbles grow in length rather than in diameter.

Resemblance and dissimilarity flanked by flow Boiling in Micro channels and Pool Boiling: The heat transfer mechanism in the two processes has much similarity through transient conduction, micro convection, and micro layer evaporation playing similar roles in both. The necessary difference between the two processes appears from the presence of strong inactivity forces in the bulk flow and the large shear stress present at the wall. These forces affect the nucleation and other flow distinctiveness directly. Heat transfer processes are also affected [15].

CONCLUSION:

In this paper we found that saturated water flow boiling the mass flux did not affect the behavior of the boiling curve. Addition of small amount of surfactant to water changes the boiling curve drastically. At the same value of heat flux the temperature difference (Tw TS) for boiling of surfactant solution is significantly smaller than that for pure water while pool boiling has been widely investigated in nuclear power plants for potential application to the design of new passive heat removal systems employed in Advanced Light Water Reactors (ALWRs) designs [14]

REFERENCES:

1. Wolf, J. R., et al., NUREG/CR-6197, TMI V (93) EG10 (1993). 2. Chang, Y. and Yao, S. C, Trans, of ASME, Vol. 105, pp.192-195 (1983). 3. Fujita, Y, et al., Int. J. Heat Mass Transfer, Vol.31, No.2, pp.229-239 (1988). 4. Jeong, J. H., et al., SARJ-97 Workshop, JAERI-Conf. 98-009 (1997). 5. Schmidt, H., et al., 1st European-Japanese Two-Phase Flow Group Meeting (1998). 6. Koizumi, Y, et al, 36th Japanese Heat Transfer Conference, D221 (1999). 8. Ohtake, H., et al., JSME, Vol.64, No.624, Paper No.97-1435 (1998).

9. Henry, R. E. and Hammersley, R. J., 5th Int. Conf. on Simulation Methods in Nuclear Engineering (1996).

10. M. murase, T. kohriyama, Y. kawabe, Y. yoshidaand Y. okano, heat transfer models in narrow gap, Proceedings of ICONE 9 9 th International Conference on Nuclear Engineering April 8-12, 2001, Nice, France 11. Kaminaga, F., Chowdhury, F., Baduge, S., Matsumura, K., 2000. In: Proc. Boiling 2000: Phenom. Emerging Applicat. pp. 272–288 12. Sumith, B., Kaminaga, F., Matsumura, K., 2003. Saturated flow boiling of water in a vertical small diameter tube. Exp. Therm. Fluid Sci. 27, 789–801. 13. Thome, J.R., Dupont, V., Jacobi, A.M., 2004. Heat transfer model for evaporation in microchannels. Part I: presentation of model. Int. J. Heat Mass Transfer 47, 3375–3385. 14. Myeong-gie Kang, pool boiling heat transfer in a vertical annulus with a narrower upside gap, September 4, 2009 online available at http://www.kns.org/jknsfile/v41/JK0411285.pdf 15. Satish G. Kandlikar, Similarities and Differences Between Flow Boiling in Micro channels and Pool Boiling, Heat Transfer Engineering, 31(3):159–167, 2010, SSN: 0145-7632 print / 1521-0537