Coupled heat and mass transfer analysis of NH3-H2O falling film absorption on inner tube surface with low solution flow rates
Tóm tắt
NH3-H2O falling film absorption usually takes place with low solution flow rate in real absorption refrigeration system. An experimental study of inner vertical absorption is carried out for the consideration of air-cooling absorber. Variable working conditions are tested to evaluate the heat and mass transfer performances. The traditional evaluation method based on log-mean-temperature (concentration) difference is criticized for its lack of theoretical basis while simultaneous heat and mass transfer process occurs. A new method proposed by Kim and Infante Ferreira is modified to evaluate the experimental results with reasonable assumptions. The method is based on the derivation of coupled heat and mass transfer differential equations of NH3-H2O absorption process. The analysis of the same experimental data shows that the new method realizes better consistency with smaller error, especially in heat transfer aspect. Heat and mass transfer performance is enhanced with the increase of solution Reynolds number. Sub-cooling of inlet weak solution also has positive influence on the absorption process, which should be evaluated by the new method correctly. Two correlations are developed to evaluate both Nusselt and Sherwood numbers for the design of air-cooling absorber.
Tài liệu tham khảo
WANG R Z, GE T S, CHEN C J, et al. Solar sorption cooling systems for residential applications: Options and guidelines [J]. International Journal of Refrigeration, 2009, 32: 638–660.
FERNANDEZ-SEARA J, UHIA F J, SIERES J. Analysis of an air cooled ammonia-water vertical tubular absorber [J]. International Journal of Thermal Science, 2007, 46: 93–103.
KILLON J D, GARIMELLA S. A critical review of models of coupled heat and mass transfer in falling-film absorption [J]. International Journal of Refrigeration, 2001, 24: 755–797.
KANG Y T, AKISAWA A, KASHIWAGI T. Experimental correlation of combined heat and mass transfer for NH3-H2O falling film absorption [J]. International Journal of Refrigeration, 1999, 22: 250–262.
KANG Y T, NAGANO T, KASHIWAGI T. Mass transfer correlation of NH3-H2O bubble absorption [J]. International Journal of Refrigeration, 2002: 25: 878–886.
KIMH Y, SAHA B B, KOYAMA S. Development of a slug flow absorber working with ammonia-water mixture. Part I. Flow characterization and experimental investigation [J]. International Journal of Refrigeration, 2003, 26: 508–515.
KIMH Y, SAHA B B, KOYAMA S. Development of a slug flow absorber working with ammonia-water mixture. Part II. Data reduction model for local heat and mass transfer characterization [J]. International Journal of Refrigeration, 2003, 26: 698–706.
KWON K, JEONG S. Effect of vapor flow on the falling-film heat and mass transfer of the ammonia/water absorber [J]. International Journal of Refrigeration, 2004, 27: 955–964.
CEREZO J, BOUROUIS M, VALLES M, et al. Experimental study of an ammonia-water bubble absorber using a plate heat exchanger for absorption refrigeration machines [J]. Applied Thermal Engineering, 2009, 29: 1005–1011.
NIU X F, DU K, HU Z H, et al. Experimental analysis on the effect of magnetic field on ammoniawater falling-film absorption [J]. Journal of Engineering Thermophysics, 2008, 29(6): 919–922 (in Chinese).
SHENG W, WU W D, ZHANG H, et al. Enhancing influence of Al2O3 nano-particles on ammonia bubble absorption process [J]. Journal of Chemical Industry and Engineering, 2008, 59(11): 2762–2767 (in Chinese).
GOEL N, GOSWAMI D Y. Experimental verification of a new heat and mass transfer enhancement concept in a microchannel falling film absorber [J]. Journal of Heat Transfer, 2007, 129: 154–161.
ZHAO R, CHENG W L, JIANG S L, et al. Experimental study of ammonia bubble absorption: Effect of flow rate and orifice diameter [J]. Fluid Machinery, 2006, 34(3): 58–61 (in Chinese).
FUJITA I, HIHARA E. Heat and mass transfer coefficients of falling-film absorption process [J]. International Journal of Heat and Mass Transfer, 2005, 48(13): 2779–2786.
ISLAM M R, WIJEYSUNDERA N E, HO J C. Evaluation of heat and mass transfer coefficients for fallingfilms on tubular absorbers [J]. International Journal of Refrigeration, 2003, 26: 197–204.
ISLAM M R, WIJEYSUNDERA N E, HO J C. Simplified models for coupled heat and mass transfer in falling-film absorbers [J]. International Journal of Heat and Mass Transfer, 2004, 47: 395–406.
ISLAM M R, WIJEYSUNDERA N E, HO J C. Heat and mass transfer effectiveness and correlations for counter-flow absorbers [J]. International Journal of Heat and Mass Transfer, 2006, 49: 4171–4182.
KIM D S, INFANTE FERREIRA C A. Analytic modeling of a falling film absorber and experimental determination of transfer coefficients [J]. International Journal of Heat and Mass Transfer, 2009, 52: 4757–4765.
KIM D S, INFANTE FERREIRA C A. Flow patterns and heat and mass transfer coefficients of low Reynolds number falling film flows on vertical plates: Effect of a wire screen and an additive [J]. International Journal of Refrigeration, 2008, 32: 138–149.
KIM D S, INFANTE FERREIRA C A. Effectiveness of non-volatile falling film absorbers with solution and coolant in counter-flow [J]. International Journal of Refrigeration, 2010, 33(1): 79–87.
CONDE M. Thermodynamic properties of {NH3+H2O} mixtures for the industrial design of absorption refrigeration equipment [R]. Zurich, Switzerland: M. Conde Engineering, 2006.
MEDRANO M, BOUROUIS M, CORONAS A. Absorption of water vapour in the falling film of waterlithium bromide inside a vertical tube at air-cooling thermal conditions [J]. International Journal of Thermal Science, 2002, 41: 891–898.
HIHARA E, SAITO T. Effect of surfactant on falling film absorption [J]. International Journal of Refrigeration, 1993, 16(5): 339–346.
CHENYM, SUNCY. Experimental study on the heat and mass transfer of a combined absorber-evaporator exchanger [J]. International Journal of Heat and Mass Transfer, 1997, 40(4): 961–971.
LEWIS W K, WHITMAN W G. Principles of gas absorption [J]. Industrial & Engineering Chemistry, 1924, 16(12): 1215–1220.
LIN P. Theoretical and experimental investigation of NH3-H2O falling film absorption and its application in two-stage air-cooling absorption refrigeration [D]. Shanghai: School of Mechanical Engineering, Shanghai Jiao Tong University, 2011 (in Chinese).
FERNANDEZ-SEARA J F, SIERES J, RODRiGUEZ C, et al. Ammonia-water absorption in vertical tubular absorbers [J]. International Journal of Thermal Science, 2005, 44: 277–288.
GOEL N, GOSWAMI D Y. Analysis of a countercurrent vapor flow absorber [J]. International Journal of Heat and Mass Transfer, 2005, 48: 1283–1292.
LIN P, WANG R Z, XIA Z Z. Numerical investigation of a two-stage air-cooling absorption refrigeration system for solar cooling: Cycle analysis and absorption cooling performance [J]. Renewable Energy, 2011, 36: 1401–1412.
SIEDER E N, TATE G E. Heat transfer and pressure drop of liquids in tubes [J]. Industrial & Engineering Chemistry, 1936, 28(12): 1429–1435.