Laminar Film Condensation From a Steam-Air Mixture Undergoing Forced Flow Down a Vertical Surface

1971 ◽  
Vol 93 (3) ◽  
pp. 297-304 ◽  
Author(s):  
V. E. Denny ◽  
A. F. Mills ◽  
V. J. Jusionis
Keyword(s):  
Liquid Film ◽  
Numerical Solution ◽  
Finite Difference Methods ◽  
Vertical Surface ◽  
Forced Flow ◽  
Film Condensation ◽  
Two Phase ◽  
Noncondensable Gas ◽  
Laminar Film ◽  
Laminar Film Condensation

An analytical study of the effects of noncondensable gas on laminar film condensation of vapor under going forced flow along a vertical surface is presented. Due to the markedly nonsimilar character of the coupled two-phase-flow problem, the set of parabolic equations governing conservation of momentum, species, and energy in the vapor phase was solved by means of finite-difference methods using a forward marching technique. Interfacial boundary conditions for the numerical solution were extracted from a locally valid Nusselt-type analysis of the liquid-film behavior. Locally variable properties in the liquid were treated by means of the reference-temperature concept, while those in the vapor were treated exactly. Closure of the numerical solution at each step was effected by satisfying overall mass and energy balances on the liquid film. A general computer program for solving the problem has been developed and is applied here to condensation from water-vapor–air mixtures. Heat-transfer results, in the form q/qNu versus x, are reported for vapor velocities in the range 0.1 to 10.0 fps with the mass fraction of air ranging from 0.001 to 0.1. The temperature in the free stream is in the range 100–212 deg F, with overall temperature differences ranging from 5 to 40 deg F. The influence of noncondensable gas is most marked for low vapor velocities and large gas concentrations. The nonsimilar character of the problem is especially evident near x = 0, where the connective behavior of the vapor boundary layer is highly position-dependent.

Paper 6: Effect of Vapour Drag on Laminar Film Condensation on a Vertical Surface

1965 ◽  
Vol 180 (10) ◽  
pp. 280-287 ◽  
Author(s):  
Y. R. Mayhew ◽  
D. J. Griffiths ◽  
J. W. Phillips
Keyword(s):  
Reynolds Number ◽  
Liquid Film ◽  
Atmospheric Pressure ◽  
Vertical Surface ◽  
Simple Theory ◽  
Experimental Results ◽  
Film Condensation ◽  
Laminar Film ◽  
Laminar Film Condensation

A simple theory is presented for laminar film condensation of a pure vapour on a vertical surface which takes account of the drag induced on the liquid film by the flow of the condensing vapour. Experiments were carried out with steam at atmospheric pressure condensing inside a vertical 1.824 in diameter tube 8 in high. The downward vapour velocity was varied from 5 to 150 ft/s, the corresponding range of the film Reynolds number at the bottom of the tube being 200-500. Experimental results agreed well with the theory.

The Effect of Noncondensable Gas on Laminar Film Condensation of Liquid Metals

1973 ◽  
Vol 95 (1) ◽  
pp. 6-11 ◽  
Author(s):  
R. H. Turner ◽  
A. F. Mills ◽  
V. E. Denny
Keyword(s):  
Liquid Metals ◽  
Dominant Role ◽  
Boundary Layer Separation ◽  
Vertical Surface ◽  
Film Condensation ◽  
Vapor Flow ◽  
Interfacial Resistance ◽  
Noncondensable Gas ◽  
Laminar Film ◽  
Laminar Film Condensation

The effect of noncondensable gas on laminar film condensation of a liquid metal on an isothermal vertical surface with forced vapor flow is analyzed. Where necessary the interfacial resistance due to thermodynamic nonequilibrium is included for a condensation coefficient σ = 1. A computer program has been developed to solve a finite-difference analog of the governing partial differential equations and is applied here to the mercury–air and sodium–argon systems. Heat-transfer results are presented for vapor velocities in the range 1 to 100 fps with mass fraction of gas varying from 10−5 to 3 × 10−2. The overall temperature difference ranged from 0.1 to 30 deg F while the temperature levels were 1200 and 900 deg R for mercury–air and 2000 and 1500 deg R for sodium–argon. The effect of noncondensable gas is most marked for low vapor velocities and high gas concentrations. At the lower pressure levels the inter facial resistance plays a dominant role, causing maxima in the curves of q/qNu versus x. For the mercury–air system the adverse buoyancy force causes vapor boundary-layer separation when the free-stream vapor velocity is low.

Laminar Film Condensation on a Nanosphere

2012 ◽  
Vol 3 (1) ◽  
Author(s):  
J. A. Esfahani ◽  
S. Koohi-Fayegh
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Temperature Jump ◽  
Velocity Slip ◽  
Liquid Film Thickness ◽  
Film Condensation ◽  
Runge Kutta Method ◽  
Laminar Film ◽  
Laminar Film Condensation ◽  
Liquid Mass Flow Rate

The present work investigates an analytical study on the problem of laminar film condensation on a nanosphere. Due to the microscale interaction, the problem is analyzed by taking into account the effects of slip in velocity and jump in temperature. A relation is derived for the liquid film thickness in the form of a nonlinear differential equation which is solved numerically using the fourth order Runge–Kutta method. Finally, the effect of velocity slip and temperature jump on different condensation parameters including the liquid film thickness, velocity and temperature profiles, Nusselt number, and liquid mass flow rate is discussed. It is found that the increase in the velocity slip and temperature jump results in a thinner liquid film and therefore increases the heat transfer coefficient.

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