The Experts below are selected from a list of 26592 Experts worldwide ranked by ideXlab platform
Shengqiang Shen - One of the best experts on this subject based on the ideXlab platform.
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Numerical investigation on characteristics of falling film in horizontal-tube falling film evaporator
Desalination and Water Treatment, 2014Co-Authors: Wei-guo Jiang, Shengqiang Shen, Xingsen MuAbstract:AbstractHorizontal-tube falling film technology is widely used in multi-effect desalination plant. The film characteristics of falling water film outside the tubes in horizontal-tube falling film evaporator were simulated. The numerical result was compared with the experimental result and they were proven with good agreement. The film thickness distribution at different Reynolds number and different circular angle had been investigated. Also, the effects of liquid flow rate and tube diameter on the film thickness distribution were discussed in detail. Numerical simulation result shows that, with the increase in Reynolds number, the falling film thickness at a certain circumferential angle increases with almost linear growth rate, and the thinnest film at the surface of the tube appears at the angle of about 120°. The result also indicates that the local dry out spot on the surface of the tube would occur when the fluid flow rate decreases to a certain value. In addition, the film thickness decreases with ...
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experimental study of falling film evaporation heat transfer coefficient on horizontal tube
Desalination and Water Treatment, 2012Co-Authors: Xingsen Mu, Shengqiang Shen, Yong YangAbstract:Abstract The horizontal-tube falling film evaporation is a widely adopted technique in multiple-effect distillation desalination plant. It has a high heat transfer coefficient under quite small temperature difference. In this paper, an experimental equipment for horizontal-tube falling film evaporation was set up. Experiments were carried out to show how the heat transfer coefficient is affected by different parameters including heat flux, circumference direction of tubes, spray density, evaporation temperature, and experimental fluid. Results indicate that the heat transfer coefficient decreases after a little increase with growth of spray density. The heat transfer coefficient decreases along the tube circumference, but at the bottom of the tube, it shows increasing trend. In addition, a simple comparison between seawater and fresh water in heat transfer coefficient is also provided.
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experimental study of falling film evaporation heat transfer outside horizontal tubes
Desalination, 2008Co-Authors: Luopeng Yang, Shengqiang ShenAbstract:Abstract The heat transfer process of falling film horizontal evaporation includes evaporation outside tubes and condensation inside tubes, the heat transfer coefficient of the former is about 50% of that of the latter. So the overall heat transfer coefficient is influenced mainly by the falling film evaporation outside tubes. An experimental study of falling film heat transfer outside horizontal tubes was carried out in order to show how the heat transfer coefficient is affected by different parameters such as flow density evaporation temperatures, temperature difference between wall and saturation water, and mass concentration of the seawater. Experiments were conducted using 14 mm outer diameter Al-brass tubes heated by internal electric heaters so that a uniform heat flux was generated on the outside surface of tubes. The results show that when flow density Γ varies between 0.013 kg/ms
Luopeng Yang - One of the best experts on this subject based on the ideXlab platform.
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experimental study of falling film evaporation heat transfer outside horizontal tubes
Desalination, 2008Co-Authors: Luopeng Yang, Shengqiang ShenAbstract:Abstract The heat transfer process of falling film horizontal evaporation includes evaporation outside tubes and condensation inside tubes, the heat transfer coefficient of the former is about 50% of that of the latter. So the overall heat transfer coefficient is influenced mainly by the falling film evaporation outside tubes. An experimental study of falling film heat transfer outside horizontal tubes was carried out in order to show how the heat transfer coefficient is affected by different parameters such as flow density evaporation temperatures, temperature difference between wall and saturation water, and mass concentration of the seawater. Experiments were conducted using 14 mm outer diameter Al-brass tubes heated by internal electric heaters so that a uniform heat flux was generated on the outside surface of tubes. The results show that when flow density Γ varies between 0.013 kg/ms
Marcel Christians - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer and Visualization of Falling Film Evaporation on a Tube Bundle
2020Co-Authors: Marcel ChristiansAbstract:Horizontal falling film evaporators have the potential of displacing flooded evaporators in industry, due to advantages such as lower required refrigerant charge and lower pressure drop. However, there is a need to improve the understanding of falling film evaporation mechanisms to provide accurate thermal design methods. In this work, the existing LTCM falling film facility was utilized to perform falling film evaporation measurements on a single tube, a vertical row of horizontal tubes and a small tube bundle. Two enhanced boiling tubes, namely the Wolverine Turbo-B5 and the Wieland Gewa-B5, were tested using R-134a and R-236fa. The tests were carried out at a constant saturation temperature of Tsat = 5°C, liquid film Reynolds numbers ranging from 0 to 3000, and heat fluxes between 15 and 90 kW/m2 in pool boiling and falling film configurations. A visualization study was performed under adiabatic and diabatic conditions (in both single-array and bundle configurations) to study the flow. The physical phenomena governing the falling film evaporation process have been studied, and insight into their effects on the performance of tube bundles has been gained. Measurements of the local heat transfer coefficient were obtained and utilized to generate new prediction methods, including a method for predicting the onset-of-dryout film flow rate during falling film evaporation, local pool boiling and falling film heat transfer prediction methods and a falling film multiplier prediction method.
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falling film evaporation on enhanced tubes part 1 experimental results for pool boiling onset of dryout and falling film evaporation
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Marcel Christians, John R. ThomeAbstract:Horizontal falling film evaporators have the potential of displacing flooded evaporators as the standard in the refrigeration industry due to compelling advantages, such as smaller refrigerant charge and lower pressure drop. However, there is a need to improve the understanding of falling film evaporation mechanisms to provide accurate thermal design methods. In this work, falling film evaporation measurements on a single tube, a vertical row of ten horizontal tubes and a small tube bundle with three rows of 10 tubes each are presented. Two enhanced boiling tubes, the Wolverine Turbo-B5 and the Wieland Gewa-B5, were tested using R-134a and R-236fa. The tests were carried out at a saturation temperature of T-sat = 5 degrees C, film Reynolds numbers ranging from 0 to 3000, and heat fluxes between 15 and 90 kW m(-2) in pool boiling and falling film configurations. A visualization study was performed under diabatic conditions to study the flow. (C) 2011 Elsevier Ltd and IIR. All rights reserved.
A Oliva - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental investigation of a vertical libr falling film absorber considering wave regimes and in presence of mist flow
International Journal of Thermal Sciences, 2016Co-Authors: E Garciarivera, J Castro, J Farnos, A OlivaAbstract:Abstract The absorber represents the most critical component in absorption systems and one of the key issues. In this component complex heat and mass transfer phenomena during the absorption process takes place simultaneously. For this reason the development of mathematical models validated against experimental data always constitutes useful tools for the design and improvement of falling film absorbers. A testing device has been designed and built to reproduce absorption phenomena in vertical LiBr−H2O falling film absorbers with the primary objective to obtain experimental data. On the other hand, a mathematical model of falling film absorption of H2O vapour in LiBr aqueous solutions has been implemented. Wave regime is considered by including and solving the Free Surface Deflection Equation. The numerical results are validated using the experimental data. During the development of this work, the authors have paid careful attention to the verification of experimental data. Such verification consists of performing energy and mass balances in the fluid film side. Important discrepancies were found in our experimental data. Therefore, an extensive study was carried out in order to find the source of such errors. The conclusion is that there is a drag of LiBr solution in the water vapour which increases with the Re number. This mist flow cannot be measured experimentally, but can be evaluated in an indirect way. The mathematical models have been adapted in order to consider the influence of mist flow. On the other hand, in the literature there are not many experimental works related to falling film absorbers which expose enough information to verify the reliability of their experimental data.
N E Wijeysundera - One of the best experts on this subject based on the ideXlab platform.
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mass transfer across the falling film simulations and experiments
Chemical Engineering Science, 2008Co-Authors: Z F Xu, B C Khoo, N E WijeysunderaAbstract:Abstract Mass transfer across the thin falling film gas–liquid interface is a very important process as in chemical engineering and other fields, and yet there is still a lack of general predictability of the transfer quantity based on basic hydrodynamic parameters and independent of the geometrical setup. In this work, a numerical simulation is carried out for a vertical falling film arrangement. The wave dynamics and the associated mass transfer phenomena are discussed and compared with previous experimental empirical relationships. Based on the validity of the simulated results for wave parameters, numerical experiments for mass transfer were carried out with the aim of comparing to the empirical relation based on a single hydrodynamic parameter β (the gradient of the vertical fluctuating velocity at the interface) established previously by Law and Khoo [2002. Transport across a turbulent gas–liquid interface. A.I.Ch.E. Journal 48(9), 1856–1868.] and Xu et al. [2006. Mass transfer across the turbulence gas–water interface. A.I.Ch.E. Journal 52, 3363–3374] with various non-falling film experiments. Separately, experiments in an inclined plate thin falling film apparatus were carried out to determine the β distribution and associated mass transfer. It is found that there is reasonable concurrence with the mentioned empirical relation, hence suggesting the general applicability of β characterizing the scalar transport across the gas–liquid interface independent of the means of turbulence generation.