Falling-film evaporation on horizontal tubes—a critical review

Ribatski, Gherhardt; Jacobi, Anthony M.

doi:10.1016/j.ijrefrig.2004.12.002

Cited by 300 publications

(86 citation statements)

References 49 publications

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“…In principle, the algebraic equation (17) maybesolvedforq in terms of h − z, which may then be integrated with respect to z subject to (14) to obtain u as a function of y and z. The volume flux of fluid down the rivulet Q is then given by…”

Section: A General Formulationmentioning

confidence: 99%

“…If the viscosity function is of the form μ = μ(q), then, rather than solving (17) and integrating u z = q to obtain u as a function of y and z, we can make more progress analytically by eliminating z in favor of q via (17), so that dz =−{d[μ(q)q]/dq} dq, to obtain u in terms of q [50]:…”

Section: B Viscosity Function Of the Form µ = µ(Q)mentioning

confidence: 99%

“…In summary, when μ = μ(q) is prescribed, h and p are given by (16), u is given parametrically (with parameter q)by (17) and (23), and Q is given by (27). In Sec.…”

Section: B Viscosity Function Of the Form µ = µ(Q)mentioning

confidence: 99%

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Rivulet flow of generalized Newtonian fluids

2018

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Steady unidirectional gravity-driven flow of a uniform thin rivulet (i.e., a rivulet with small transverse aspect ratio) of a generalized Newtonian fluid down a vertical planar substrate is considered. The parametric solution for any generalized Newtonian fluid whose viscosity can be expressed as a function of the shear rate and the explicit solution for any generalized Newtonian fluid whose viscosity can be expressed as a function of the extra stress are obtained. These general solutions are used to describe rivulet flow of Carreau and Ellis fluids, highlighting the similarities and differences between the behavior of these two fluids. In addition, the general behavior of rivulets of nearly Newtonian fluids and of rivulets with small or large prescribed flux as well as the behavior of rivulets of strongly shear-thinning Carreau and Ellis fluids are also described. It is found that whereas the monotonic dependence of the viscosity of a Carreau fluid on its three nondimensional parameters and of an Ellis fluid on two of its three nondimensional parameters leads to the expected dependence of the behavior of the rivulet on these parameters (namely, that increasing the viscosity of the fluid leads to a larger rivulet), the nonmonotonic dependence of the viscosity of an Ellis fluid on the nondimensional parameter that measures the degree of shear thinning leads to a more complicated dependence of the behavior of the rivulet on this parameter. In particular, it is also found that when the maximum extra stress in the rivulet is sufficiently large a rivulet of an Ellis fluid in the strongly shear-thinning limit in which this parameter becomes large comprises two regions with different viscosities. In the general case of nonzero viscosity in the limit of large extra stress the two regions have different constant viscosities, whereas in the special case of zero viscosity in the limit of large extra stress one region has constant viscosity and the other has a nonconstant power-law viscosity, leading to a pluglike velocity profile with large magnitude in the narrow central region of the rivulet.

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Section: A General Formulationmentioning

confidence: 99%

Section: B Viscosity Function Of the Form µ = µ(Q)mentioning

confidence: 99%

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Rivulet flow of generalized Newtonian fluids

2018

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“…A study performed by Ribatski and Jacobi [8] summarized the existing literature on horizontal type falling filmtype evaporators. That study also examined a single smooth tube, enhanced surfaces, and the flow model that affects heat transfer on tube bundles and experimental parameters.…”

Section: Advances In Mechanical Engineeringmentioning

confidence: 99%

CFD and Experimental Analysis of a Falling Film outside Smooth and Helically Grooved Tubes

Onan

Özkan

Erdem

2014

Advances in Mechanical Engineering

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Simultaneous heat and mass transfer are investigated in a falling film outside grooved and smooth tubes. A numerical analysis of the helically trapezoidal-grooved and reference smooth tube was performed in the computational fluid dynamics program "Ansys Fluent 14. " The three-dimensional model drawings in the x, y, and z coordinates are used, and the effects of the falling film outside the helically grooved tube on the surface temperature and surface heat transfer coefficient are determined. The average surface temperature, heat transfer coefficient, and Nu values are determined experimentally for a constant heat flux. An uncertainty analysis and Nu correlation for the grooved tube are also provided in this study. The Reynolds number varied between 50 and 350 for the falling film and between 1500 and 3500 for air. Using a computational fluid dynamics (CFD) analysis for the reference smooth tube, the experimental results are validated within 2-12% difference. The experimental results are also within 6-13% of the grooved tubes.

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“…and also by changing the shape of the tube. Enhancing the tube can provide better heat transfer coefficient mainly because of increase in the number of nucleation sites, increase in the total surface area and the presence of turbulence [13]. A number of experimental studies [2,6,7,11] have been reported in the literature about the enhancement techniques.…”

Section: Introductionmentioning

confidence: 99%

Falling film evaporation on a thermal spray metal coated vertical corrugated plate conduits

Ebanesar

Mani

2017

Science and Technology for the Built Environment

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In falling film evaporation process, the heat is transferred from the condensing fluid to the liquid flowing over it. Tube geometry and tube size have an important role on the performance of the falling film evaporators. This paper presents a two dimensional CFD study of water falling film evaporation on a thermal spray metal coated vertical corrugated conduits. Two-phase flow simulation is done by using a finite volume method based commercial software, using k-ω equations with shear stress transport (SST). Sinusoidal corrugations with different porosity have been selected for the study. Evaporation and heat transfer during falling film evaporation are included through user defined functions (UDFs). Effect of Reynolds number, wall superheat and surface roughness on heat transfer coefficient is presented. Numerical results are compared with the results of horizontal circular tube falling film evaporation from literature. An enhancement of film heat transfer coefficient of at least 15% is observed for the vertical corrugated plate conduits.

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Falling-film evaporation on horizontal tubes—a critical review

Cited by 300 publications

References 49 publications

Rivulet flow of generalized Newtonian fluids

Rivulet flow of generalized Newtonian fluids

CFD and Experimental Analysis of a Falling Film outside Smooth and Helically Grooved Tubes

Falling film evaporation on a thermal spray metal coated vertical corrugated plate conduits

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