Influences of various parameters such as liquid inlet flow, feeding height, inlet aperture, diameter of tube and inclined angle on the wetting ability of liquid film were studied. Image processing method was adopted to measure wetting length of liquid film on the plain tube with different parameters. The experimental results showed that with the increase of the flow rate, the wetting ability of the liquid film stays the same after reaching the peak. When the feeding height is investigated, the flow pattern needs to be considered. The effect of feeding height on wetting ability is negligible with the flow pattern of columnar flow. Wetting ability decreases firstly then remains unchanged with increasing feeding height under columnar-sheet flow regime. Shortly after sheet flow, wetting ability reaches saturation. As for increasing the inlet aperture, the flow pattern needs to be considered. Wetting ability increases first and then decreases under columnar flow, but the variation is relatively small. When flow pattern is transformed into columnar-sheet flow or sheet flow, liquid wetting ability will fall. Under the condition of a certain flow rate, the larger the diameter is, the larger the wetting area of the liquid film is, but the worse the wetting ability is. When the experimental tube is not horizontally placed, the change regulation of wetting length is no longer symmetrical with the liquid inlet column, but the lower part is stronger and the upper part is weaker.
Shi LIN Zheng ZHANG Kunyu ZHUANG Xi LIU Zhoutian GE Junhan CHEN Xuelai LI
. Experimental Study on the Wetting Ability of Falling Film[J]. The Chinese Journal of Process Engineering, 2018
, 18(1)
: 49
-56
.
DOI: 10.12034/j.issn.1009-606X.217203
[1] 何茂刚，王小飞，张颖．制冷用水平管降膜蒸发器的研究进展及新技术[J]．化工学报，2008，59(S2)：23-28．
HE M G，WANG X F，ZHANG Y．Review of prior research and new technology for horizontal-tube falling-film evaporator used in refrigeration[J]．CIESC Journal，2008，59(S2)：23-28．
[2] HONDA H，NOZU S，UCHIMA B．A prediction method for heat transfer during film condensation on horizontal low integral-fin tubes[J]．Nihon Kikai Gakkai Ronbunshu B Hentransactions of the Japan Society of Mechanical Engineers Part B，1986，53(109)：218-225．
[3] ARMBRUSTER R，MITROVIC J．Patterns of falling film flow over horizontal smooth tubes[J]．Begel House Inc，1994，3：275-280．
[4] HU X，JACOBI A M．The intertube falling film：part 1—flow characteristics，mode transitions，and hysteresis[J]．Journal of Heat Transfer，1996，118(3)：616-625．
[5] HU X，JACOBI A M．The intertube falling film：part 2—Mode effects on sensible heat transfer to a falling liquid film[J]．Journal of Heat Transfer，1996，118(3)：626-633．
[6] HU X，JACOBI A M．Departure-site spacing for liquid droplets and jets falling between horizontal circular tubes[J]．Experimental Thermal & Fluid Science，1998，16(4)：322-331．
[7] HAN-SHIK C，WUSIMAN K，SEONG-SOO K，et al．Liquid film falling behaviour on horizontal circular cylinder[J]．Journal of Central South University，2012，19(5)：1353-1358．
[8] WANG X F, JACOBI A M. A thermodynamic basis for predicting falling-film mode transitions[J]. International Journal of Refrigeration, 2014, 43(4):123-132．
[9] MITROVIC J．Flow structures of a liquid film falling on horizontal tubes[J]．Chemical Engineering & Technology，2005，28(6)：684-694．
[10] NUSSELT W．Die oberflachen kondensation des wasser damfes[J]．Z．Ver．Dtsch．Ing，1916(60)：541-546．
[11] ROGERS J T．Laminar falling film flow and heat transfer characteristics on horizontal tubes[J]．Canadian Journal of Chemical Engineering，1981，59(2)：213-222．
[12] ROGERS J T，Goindi S S．Experimental laminar falling film heat transfer coefficients on a large diameter horizontal tube[J]．Canadian Journal of Chemical Engineering，1989，67(4)：560-568．
[13] HOU H，BI Q， MA H，et al．Distribution characteristics of falling film thickness around a horizontal tube[J]．Desalination，2012， 285(3)：393-398．
[14] 许莉，王世昌，王宇新，等．水平管外壁液膜流动状态及其对传热的影响[J]．化工学报，2002，53(6)：555-559．
XU L，WANG S C，WANG Y X，et al．Flowing state of liquid films over horizontal tubes and its influences on heat-transfer characteristic[J]．CIESC Journal，2002，53(6)：555-559．
[15] XU L，WANG S，WANG Y，et al．Flowing state in liquid films over horizontal tubes[J]．Desalination，2013，156(1-3)：101-107．
[16] GSTOEHL D，ROQUES J F，CRISINEL P，et al．Measurement of falling film thickness around a horizontal tube using a laser measurement technique[J]．Heat Transfer Engineering，2004，25(8)：28-34．
[17] WANG X F，HE M G，FAN H L，et al．Measurement of falling film thickness around a horizontal tube using laser-induced fluorescence technique[J]．Journal of Physics：Conference Series，2009，147(1)：175-180．
[18] 郭斌，李会雄，郭笃鹏． 水平管外降膜流动液膜厚度的测量及分析[J]．工程热物理学报，2011，32(1)：71-74．
GUO B，LI H X，GUO D P．Measurement and analysis of the thickness distribution of falling liquid films around horizontal tubes[J]．Journal of Engineering Thermophysics，2011，32(1)：71-74．
[19] 吕凯，王小飞，张颖，等．水平蒸发管管间相邻液柱分离间距测量[J]．化工学报，2012，63(3)：740-745．
LV K，WANG X F，ZHANG Y，et al．Departure-site spacing for liquid columns falling between horizontal circular tubes[J]．CIESC Journal，2012，63(3)：740-745．
[20] CHEN X，SHEN S Q，WANG Y X，et al．Measurement on falling film thickness distribution around horizontal tube with laser-induced fluorescence technology[J]．International Journal of Heat & Mass Transfer，2015，89：707-713．
[21] LAZCANO-VéLIZ Y，SIQUEIROS J，JUáREZ-ROMERO D，et al．Analysis of effective wetting area of a horizontal generator for an absorption heat transformer[J]．Applied Thermal Engineering，2014，62(2)：845-849．
[22] Yoon J I，Phan T T，Moon C G，et al．Heat and mass transfer characteristics of a horizontal tube falling film absorber with small diameter tubes[J]．Heat and Mass Transfer，2008，44(4)：437-444．
