Abstract
Heat transfer data are reported for the condensation of pure organic vapors and their eutectic mixtures with water on both horizontal one inch diameter copper and polytetrafluoroethylene-coated copper tubes at atmospheric pressure.
With the pure vapors heat transfer is reduced by the coating, this reduction being enhanced when condensing cyclohexane, attributable to an absorption effect. For the eutectic mixtures, except for carbon tetrachloride, heat transfer is not reduced by the coating and is substantially increased for the cyclohexane-water system.
An explanation is afforded in terms of buoyancy-surface force interaction.
Zusammenfassung
Es werden Versuchsergebnisse zum Wärmeübergang bei der Kondensation von reinen organischen Dämpfen und ihren eutektischen Mischungen mit Wasser an horizontalen Kupferrohren von 25 mm Durchmesser mitgeteilt, wobei die Rohre blank oder mit Polytetrafluoräthylen beschichtet waren.
Bei reinen Dämpfen verringerte die Beschichtung den Wärmeübergang, besonders bei Cyclohexan infolge Absorptionseffektes. Bei eutektischen Mischungen, außer Tetrachlorkohlenstoff, verringerte die Beschichtung nicht den Wärmeübergang, bei dem System Cyclohexan — Wasser stieg er sogar beträchtlich an. Zur Erklärung wird die Wechselwirkung zwischen Auftriebs- und Oberflächenkräften herangezogen.
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Abbreviations
- Cp :
-
specific heat based on the weight of water and organic present in the condensate, B.t.u./(lb.) (°F.)
- D:
-
outside diameter of the condenser tube, ft.
- g:
-
acceleration of gravity, ft./hr.2
- he :
-
heat transfer coefficient for eutectic mixture, B.t.u./(hr.) (ft.2) (°F.)
- hNu :
-
heat transfer coefficient for filmwise condensation from Nusselt's equation for pure organic vapor condensing on horizontal surfaces, B.t.u./(hr.) (ft.2) (°F.)
- h1 :
-
heat transfer coefficient for filmwise condensation from Nusselt's equation for pure water, B.t.u./(hr.) (ft.2) (°F.)
- h2 :
-
heat transfer coefficient for filmwise condensation from Nusselt's equation for pure organic, B.t.u./(hr.) (ft.2) (°F.)
- H:
-
ratio of eutectic to pure component heat transfer coefficient
- K:
-
thermal conductivity based on the weight of waterand organic present in the condensate, B.t.u./(hr.) (ft.2) (°F./ft.)
- Kav :
-
thermal conductivity based on the volume of water and organic present in the condensate, B.t.u./(hr.) (ft.2) (°F./ft.)
- K1 :
-
thermal conductivity of water, B.t.u./(hr.) (ft.2) (°F./ft.)
- K2 :
-
thermal conductivity of organic, B.t.u./(hr.) (ft.2) (°F./ft.)
- M1 :
-
molecular weight of water
- M2 :
-
molecular weight of organic
- \(N_{OH_2 }\) :
-
Ohnesorge number of organic,μ 2 /(ρ g D σ){1/2
- \(N_{pr_1 }\) :
-
Prandtl number of water
- \(N_{pr_2 }\) :
-
Prandtl number of organic
- σ1 :
-
surface tension of water, lb./ft.
- σ2 :
-
surface tension of organic, lb./ft.
- Q:
-
heat transfer rate, B.t.u./(hr.)
- Q1 :
-
heat given up by condensing steam, B.t.u./(hr.)
- Q2 :
-
heat given up by condensing organic vapor, B.t.u./(hr.)
- v1 :
-
volume fraction of water in condensate
- v2 :
-
volume fraction of organic in condensate
- WS/L :
-
work of adhesion between a liquid and a solid, ergs/cm.2
- x1 :
-
weight fraction of water in condensate
- x2 :
-
weight fraction of organic in condensate
- γ L/A:
-
interfacial free energy between liquid and air
- ΔT:
-
difference between the saturation and the inside copper surface temperatures, °F.
- ΔTf :
-
film temperature difference, °F.
- Δρ :
-
density difference, lb./ft.3
- Δ σ:
-
surface tension difference, lb./ft.
- θ :
-
intrinsic contact angle
- λ :
-
latent heat of vaporization based on weight of water and organic in the condensate, B.t.u./(lb.)
- λ1 :
-
latent heat of vaporization of water, B.t.u./lb.
- λ2 :
-
latent heat of vaporization of organic, B.t.u./lb.
- μ :
-
viscosity based on weight of water and organic in condensate, lb./(hr.) (ft.)
- μ 1 :
-
viscosity of water, lb.(hr.) (ft.)
- μ 2 :
-
viscosity of organic, lb./(hr.) (ft.)
- ρ :
-
density based on weight of water and organic in condensate, lb./ft.3
- ρ 1 :
-
density of water, lb./ft.3
- ρ 2 :
-
density of organic, lb./ft.3
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Ponter, A.B., Diah, I.G. Condensation of vapors of immiscible binary liquids on horizontal copper and polytetrafluoroethylene-coated copper tubes. Wäarme- und Stoffübertragung 7, 94–106 (1974). https://doi.org/10.1007/BF01369517
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DOI: https://doi.org/10.1007/BF01369517