Falling-Film Absorption Around Microchannel Tube Banks

2011 ◽  
Author(s):  
Ananda Krishna Nagavarapu ◽  
Srinivas Garimella
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Water Solution ◽  
Small Diameter ◽  
Operating Conditions ◽  
Test Facility ◽  
Vapor Flow ◽  
Falling Film ◽  
Flow Rates ◽  
Wide Range

An experimental investigation of heat and mass transfer in a falling-film absorber with microchannel tube arrays was conducted. Liquid ammonia-water solution flows in a falling-film mode around an array of small diameter coolant tubes, while vapor flows upward through the tube array counter-current to the falling film. This absorber was installed in a test facility consisting of all components of a functional single-effect absorption chiller, including a desorber, rectifier, condenser, evaporator, solution heat exchanger, and refrigerant pre-cooler, to obtain realistic operating conditions at the absorber and to account for the influence of the other components in the system. Unlike studies in the literature on bench-top, single-component, single-pressure test stands, here the experiments were conducted on the absorber at vapor, solution, and coupling fluid conditions representative of space-conditioning systems in the heating and cooling modes. Absorption measurements were taken over a wide range of solution flow rates, concentrations, and coupling fluid temperatures, which simulated operation of thermally activated absorption systems at different cooling capacities and ambient conditions. These measurements are used to interpret the effects of solution and vapor flow rates, concentrations, and coupling fluid conditions on the respective heat and mass transfer coefficients.

Falling-Film Absorption Around Microchannel Tube Banks

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Ananda Krishna Nagavarapu ◽  
Srinivas Garimella
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Water Solution ◽  
Small Diameter ◽  
Operating Conditions ◽  
Test Facility ◽  
Vapor Flow ◽  
Falling Film ◽  
Flow Rates ◽  
Wide Range

An experimental investigation of heat and mass transfer in a falling-film absorber with microchannel tube arrays was conducted. Liquid ammonia–water solution flows in a falling-film mode around an array of small diameter coolant tubes, while vapor flows upward through the tube array counter-current to the falling film. This absorber was installed in a test facility consisting of all components of a functional single-effect absorption chiller, including a desorber, rectifier, condenser, evaporator, solution heat exchanger, and refrigerant precooler, to obtain realistic operating conditions at the absorber and to account for the influence of the other components in the system. Unlike studies in the literature on bench-top, single-component, single-pressure test stands, here the experiments were conducted on the absorber at vapor, solution, and coupling fluid conditions representative of space-conditioning systems in the heating and cooling modes. Absorption measurements were taken over a wide range of solution flow rates, concentrations, and coupling fluid temperatures, which simulated operation of thermally activated absorption systems at different cooling capacities and ambient conditions. These measurements are used to interpret the effects of solution and vapor flow rates, concentrations, and coupling fluid conditions on the respective heat and mass transfer coefficients.

scholarly journals Modeling of conjugated heat and mass transfer in the entrance region of falling liquid film at various values of the Froude number

2018 ◽  
Vol 194 ◽  
pp. 01007
Author(s):  
Maria V. Bartashevich
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Liquid Film ◽  
Froude Number ◽  
Heat And Mass Transfer ◽  
Water Solution ◽  
Lithium Bromide ◽  
Entrance Region ◽  
Falling Film ◽  
Falling Liquid Film

Mathematical model of conjugated heat and mass transfer in absorption on the entrance region of the semi-infinite liquid film of lithium bromide water solution is investigated for different values of Froude number. The calculations shown that larger values of Froude number corresponds to a smaller thickness of the falling film. It was demonstrated that for large values of the Froude number the heat transfer from the surface is greater than for smaller values.

scholarly journals The Correlation of Coupled Heat and Mass Transfer Experimental Data for Vertical Falling Film Absorption

1999 ◽  
Author(s):  
William A. Miller ◽  
Majid Keyhani
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Water Vapor ◽  
Heat And Mass Transfer ◽  
Mass Fraction ◽  
Operating Conditions ◽  
Falling Film ◽  
Design Data ◽  
Vertical Column ◽  
Absorption Chillers

Abstract Absorption chillers are gaining global acceptance as quality comfort cooling systems. These machines are the central chilling plants and the supply for comfort cooling for many large commercial buildings. Virtually all absorption chillers use lithium bromide (LiBr) and water as the absorption fluids. Water is the refrigerant. Research has shown LiBr to be one of the best absorption working fluids because it has a high affinity for water, releases water vapor at relatively low temperatures, and has a boiling point much higher than that of water. The heart of the chiller is the absorber, where a process of simultaneous heat and mass transfer occurs as the refrigerant water vapor is absorbed into a falling film of aqueous LiBr. The more water vapor absorbed into the falling film, the larger the chiller’s capacity for supporting comfort cooling. Improving the performance of the absorber leads directly to efficiency gains for the chiller. The design of an absorber is very empirical and requires experimental data. Yet design data and correlations are sparse in the open literature. The experimental data available to date have been derived at LiBr concentrations ranging from 0.30 to 0.60 mass fraction. No literature data are readily available for the design operating conditions of 0.62 and 0.64 mass fraction of LiBr and absorber pressures of 0.7 and 1.0 kPa. Experiments were conducted on an internally cooled smooth tube 0.01905 m in outside diameter and 1.53 m in length. Tests were conducted with no heat and mass transfer additive. The data, for testing at 0.62 and 0.64 mass fraction of LiBr, were scaled and correlated into both Nusselt (Nu) and Sherwood (Sh) formulations. The average absolute error in the Nusselt correlation is about ±3.5% of the Nu number reduced from the experimental data. The Sherwood correlation is about ±5% of the reduced Sh data. Data from the open literature were reduced to the authors’ Nu and Sh formulations and were within 5% of the correlations developed in the present study. Hence, this study provides correlations for the complex heat and mass transfer process that is validated against extensive experimental data. The study therefore contains useful information for the design of a vertical column absorber operating with no heat and mass transfer additive.

Heat and mass transfer characteristics of a horizontal tube falling film absorber with small diameter tubes

2007 ◽  
Vol 44 (4) ◽  
pp. 437-444 ◽  
Author(s):  
Jung-In Yoon ◽  
Thanh Tong Phan ◽  
Choon-Geun Moon ◽  
Ho-Saeng Lee ◽  
Seok-Kwon Jeong
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Small Diameter ◽  
Horizontal Tube ◽  
Falling Film ◽  
Transfer Characteristics

An Analytical Study of Heat and Mass Transfer Within an Oil Sand Bed

1987 ◽  
Vol 109 (2) ◽  
pp. 66-70
Author(s):  
M. A. Abdrabboh ◽  
G. A. Karim
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Oil Sands ◽  
Operating Conditions ◽  
Oil Sand ◽  
Mass Transfer Processes ◽  
Wide Range ◽  
Gaseous Stream ◽  
Fluid Concentration ◽  
Experimental Values

The physical processes that occur typically within an oil sand bed are considered when the bed is subjected to a hot gaseous stream. In this study, the extent of fluid volatilization was obtained from a consideration of the simultaneous heat and mass transfer processes within the oil sands. The resulting system of equations together with the boundary conditions were solved numerically using an implicit finite difference method. The transient fluid concentration and temperature distributions within the oil sand bed were then obtained under a wide range of operating conditions. The resulting theoretical rates of volatilization and temperatures show generally good agreement with corresponding experimental values that were obtained for the purpose.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

COMPARISON OF HEAT AND MASS TRANSFER IN FALLING FILM AND BUBBLE ABSORBERS OF AMMONIA-WATER

2002 ◽  
Vol 15 (3) ◽  
pp. 191-205 ◽  
Author(s):  
Ki Bong Lee ◽  
Byung Hee Chun ◽  
Jae Cheol Lee ◽  
Jae Chun Hyun ◽  
Sung Hyun Kim
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Falling Film ◽  
Ammonia Water

Effect of Nanoparticles on H2O/LiBr Falling Film Absorption Process

2016 ◽  
Author(s):  
L. Y. Zhang ◽  
Y. Li ◽  
Y. Wang ◽  
L. X. Cao ◽  
X. Z. Meng
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Fe3o4 Nanoparticles ◽  
Falling Film ◽  
Absorption Process ◽  
Nanoparticle Concentration ◽  
Water Vapor Absorption ◽  
Libr Solution ◽  
Falling Film Absorption ◽  
Film Absorption

Absorber is an important component in absorption refrigerating system. Its performance plays a significant role on the overall efficiency of absorption refrigerating system. The nanofluids which can enhance the heat and mass transfer will be utilized to absorber for enhancing the water vapor absorption process and improving the absorber efficiency. The software CFD-FLUENT is used to analyze the falling film absorption process of the nanofluids, which consists of H2O/LiBr solution with Fe3O4 nanoparticles in this paper. The results indicate that the enhancing heat and mass transfer of nanofluids is related to the nanoparticle concentration and size. The stronger the nanoparticle concentration, the greater enhancement of heat and mass transfer of falling film; while the smaller the nanoparticle size, the greater enhancement of heat and mass transfer of falling film. It is also found that the enhancement ratio of heat and mass transfer flux reach 1.48 and 1.37, respectively, as the Fe3O4 nanoparticles mass concentration of 0.01wt% and the size of 50nm.

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