纯水静态闪蒸起始阶段气泡群时空分布规律的实验研究
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摘要
设计搭建了静态闪蒸实验台,利用高速摄像对不同压降速率下纯水静态闪蒸起始阶段气泡群的时间和空间分布规律开展了实验研究。实验中液膜初始厚度为0.2 m,压降速率为0.27～0.64 MPa·s-1。实验结果表明:气泡群主要出现在压力陡降段。在时间分布上,压降速率越大,气泡群出现的时间越早,气泡数目增长越快,且气泡群数目达到最大值所需要的时间越短。在空间分布上,气泡数量随深度呈现了"缓增-陡增-缓增"的增长趋势;压降速率越小,气泡分布越集中;相同深度范围内,压降速率越大,气泡数量越多;至压力陡降段结束时刻,气泡群相对数量随液膜深度的增大有峰值存在。最后,根据实验结果拟合了气泡群时间和空间分布规律的实验关系式,其计算值与实验值吻合良好。
Experimental study on temporal and spatial distribution of bubbles during initial stage of static flash of pure water was carried out with depressurization rates varying between 0.27 MPa·s-1and 0.64 MPa·s-1, and the initial height of waterfilm at 0.2 m. The results indicated that bubbles appeared primarily within the stage of pressure's rapid decline. In terms of temporal distribution, the faster the pressure dropped, the earlier the bubbles turned up, and the faster the number of bubbles increased with time, and also the earlier the bubble number reachedits maximum value. In terms of spatial distribution, the number of bubbles grew in trend of "slow-quick-slow"with increasing depth. Small depressurization rate could narrow bubble distribution along depth. At the same depth,the faster the pressure dropped, the larger the bubble number was. At the end of pressure's fast decline, the relativebubble number had a peak value with increasing depth. Finally, above experiment results were fitted into a pair ofcorrelations for the temporal and spatial distribution of bubbles. Their calculation results matched well with experimental results.
Experimental study on temporal and spatial distribution of bubbles during initial stage of static flash of pure water was carried out with depressurization rates varying between 0.27 MPa·s-1and 0.64 MPa·s-1, and the initial height of waterfilm at 0.2 m. The results indicated that bubbles appeared primarily within the stage of pressure's rapid decline. In terms of temporal distribution, the faster the pressure dropped, the earlier the bubbles turned up, and the faster the number of bubbles increased with time, and also the earlier the bubble number reachedits maximum value. In terms of spatial distribution, the number of bubbles grew in trend of "slow-quick-slow"with increasing depth. Small depressurization rate could narrow bubble distribution along depth. At the same depth,the faster the pressure dropped, the larger the bubble number was. At the end of pressure's fast decline, the relativebubble number had a peak value with increasing depth. Finally, above experiment results were fitted into a pair ofcorrelations for the temporal and spatial distribution of bubbles. Their calculation results matched well with experimental results.
引文
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[26]王朝阳,张丹,杨庆忠,等. NaCl溶液静态闪蒸瞬态传热特性的实验研究[J].中国科学院大学学报, 2017, 34(2):166-171.Wang C Y, Zhang D, Yang Q Z, et al. Experimental study on heat transfer characteristics of aqueous NaCl solution in static flash evaporation[J]. Journal of University of Chinese Academy of Sciences, 2017, 34(2):166-171.
[27] Zhang D, Chong D T, Yan J J, et al. Study on steam carrying effect in static flash evaporation[J]. International Journal of Heat and Mass Transfer, 2012, 55(17/18):4487-4497.
[28]于龙文,张丹,赵凯,等.静态闪蒸过程中的单个气泡成长实验研究[J].工程热物理学报, 2015, 36(6):1274-1277.Yu W L, Zhang D, Zhao K, et al. Experimental study on bubble growth of sodium chloride aqueous solution in static flash evaporation[J]. Journal of Engineering Thermophysics, 2015, 36(6):1274-1277.
[29] Pinhasi G A, Ullmann A, Dayan A. 1D plane numerical model for boiling liquid expanding vapor explosion(BLEVE)[J].International Journal of Heat&Mass Transfer, 2007, 50(23):4780-4795.
[30] Moffat R J. Contribution to the theory of single-sample uncertainty analysis[J]. Journal of Fluid Engineering-Transactions of the ASME, 1982, 104:250-260.
[2] Zhou Z, Wu W, Chen B, et al. An experimental study on the spray and thermal characteristics of R134a two-phase flashing spray[J].International Journal of Heat and Mass Transfer, 2012, 55(15/16):4460-4468.
[3] Chen W L, Zhang W W, Chen H, et al. Spray cooling and flash evaporation cooling:the current development and application[J].Reneable and Sustainable Energy Reviews, 2016, 55:614-628.
[4] Monteiro R L, Bruno A M C, Laurindo J B. A microwave multiflash drying process for producing crispy bananas[J]. Journal of Food Engineering, 2016, 178:1-11.
[5] Zotrrelli M F, Porciuncula B D A, Laurindo J B. A convective multi-flash drying process for producing dehydrated crispy fruits[J]. Journal of Food Engineering, 2012, 108(4):523-531.
[6] Chantasiriwan S. Distribution of juice heater surface for optimum performance of evaporation process in raw sugar manufacturing[J].Journal of Food Engineering, 2017, 195:21-30.
[7] Rahimi B, Lieb K R, Chua H T, et al. A novel flash boosted evaporation process for alumina refineries[J]. Applied Thermal Engineering, 2016, 94:375-384.
[8] Jin Z J, Ye H, Wang H, et al. Thermodynamic analysis of siphon flash evaporation desalination system using ocean thermal energy[J]. Energy Convers. Manage, 2017, 136:66-77.
[9] Ikegami Y, Sasaki H, Gouda T, et al. Experimental study on a spray flash desalination(influence of the direction of injection)[J].Desalination, 2006, 194(1/2/3):81-89.
[10]王开安,孙静茹,黄仲漩.闪蒸沉积装置:105088139A[P]. 2015.Wang K A, Sun J R, Huang Z X. Flash deposition device:105088139A[P]. 2015.
[11] Polanco G, Holdo A E, Munday G. General review of flashing jet studies[J]. Journal of Hazardous Materials, 2010, 173(1):2-18.
[12] Roshani B, Flugel A, Schmitz I, et al. Simultaneous measurements of fuel vapor concentration and temperature in a flash-boiling propane jet using laser-induced gratings[J]. Journal of Raman Spectroscopy, 2013, 44(10):1356-1362.
[13] Li S Y, Zhang Y Y, Xu B. Correlation analysis of superheated liquid jet breakup to bubble formation in a transparent slit nozzle[J]. Experimental Thermal and Fluid Science, 2015, 68:452-458.
[14] Kim W, Yu T, Yoon W. Atomization characteristics of emulsified fuel oil by instant emulsification[J]. Journal of Mechanical Science&Technology, 2012, 26(6):1781-1791.
[15] Miyatake O, Murakami K, Kawata Y, et al. Fundamental experiments with flash evaporation[J]. Heat Transfer-Japanese Research, 1973, 2(4):89-100.
[16] Miyatake O, Fujii T, Tanaka T, et al. Flash evaporation phenomena of pool water[J]. Heat Transfer-Japanese Research,1977, 6(2):13-24.
[17] Saury D, Harmand S, Siroux M. Experimental study of flash evaporation of a water film[J]. International Journal of Heat and Mass Transfer, 2002, 45(16):3446-3457.
[18] Saury D, Harmand S, Siroux M. Flash evaporation from a water pool:influence of the liquid height and of the depressurization rate[J]. International Journal of Thermal Sciences, 2005, 44(10):953-965.
[19] Gopalakrishna S, Purushothaman V, Lior N. An experimental study of flash evaporation from liquid pools[J]. Desalination, 1987,65(11):139-151.
[20] Chen H, Cheng W L, Zhang W W, et al. Energy saving evaluation of a novel energy system based on spray cooling for surpercomputer center[J]. Energy, 2017, 141:304-315.
[21] Chen H, Cheng W L, Zhang W W, et al. Experimental study on optimal spray parameters of piezoelectric atomizer based spray cooling[J]. International Journal of Heat and Mass Transfer, 2016,103:57-65.
[22] Jin W, Low S, Yu S. Some experimental observations on the single and multi-phase flow patterns in a model flash evaporation chamber[J]. International Communications in Heat and Mass Transfer, 1999, 26(6):839-848.
[23] Jin W, Low S. Investigation of single flow patterns in a model flash evaporation chamber using PIV measurement and numerical simulation[J]. Desalination, 2002, 150(1):51-63.
[24] Mikic B B, Rohsenow W M, Griffith P. Bubble growth rates[J].International Journal of Heat and Mass Transfer, 1970, 13:657-666.
[25] Zhang D, Chong D T, Yan J J, et al. Experimental study on static flash evaporation of aqueous NaCl solution at different flash speed:heat transfer characteristics[J]. International Journal of Heat and Mass Transfer, 2013, 65(7):584-591.
[26]王朝阳,张丹,杨庆忠,等. NaCl溶液静态闪蒸瞬态传热特性的实验研究[J].中国科学院大学学报, 2017, 34(2):166-171.Wang C Y, Zhang D, Yang Q Z, et al. Experimental study on heat transfer characteristics of aqueous NaCl solution in static flash evaporation[J]. Journal of University of Chinese Academy of Sciences, 2017, 34(2):166-171.
[27] Zhang D, Chong D T, Yan J J, et al. Study on steam carrying effect in static flash evaporation[J]. International Journal of Heat and Mass Transfer, 2012, 55(17/18):4487-4497.
[28]于龙文,张丹,赵凯,等.静态闪蒸过程中的单个气泡成长实验研究[J].工程热物理学报, 2015, 36(6):1274-1277.Yu W L, Zhang D, Zhao K, et al. Experimental study on bubble growth of sodium chloride aqueous solution in static flash evaporation[J]. Journal of Engineering Thermophysics, 2015, 36(6):1274-1277.
[29] Pinhasi G A, Ullmann A, Dayan A. 1D plane numerical model for boiling liquid expanding vapor explosion(BLEVE)[J].International Journal of Heat&Mass Transfer, 2007, 50(23):4780-4795.
[30] Moffat R J. Contribution to the theory of single-sample uncertainty analysis[J]. Journal of Fluid Engineering-Transactions of the ASME, 1982, 104:250-260.