Heat transfer during film condensation inside horizontal tubes in stratified phase flow
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ORIGINAL
Heat transfer during film condensation inside horizontal tubes in stratified phase flow Volodymyr Sereda 1
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Volodymyr Rifert 1 & Vadim Gorin 1 & Oleksandr Baraniuk 1 & Peter Barabash 1
Received: 29 January 2020 / Accepted: 11 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper, the experimental study of heat transfer during condensation of freons R22 and R407С in a plain smooth tube with 17 mm inner diameter was carried out at saturated condensing temperature 40 °C, while mass velocity ranged between 6 and 57 kg/(m2s) and vapour quality changed from 0.23 to 0.95. The unique measurements of circumferential heat fluxes and heat transfer coefficients were performed with the thick wall method during the stratified flow of the phases. The authors performed numerical simulation of heat transfer from condensing vapour to cooling water through the thick-walled cylindrical wall. The CFD model was validated by conducting the physical experiment, which indicated the results coincidence with an error from 7 to 20%. The obtained results allowed improving prediction of effective heat transfer coefficients for vapour condensation, which takes into account the influence of condensate flow in the bottom part of the tube on the heat transfer. This method generalizes with sufficient accuracy (error ± 30%) the experimental data on condensation of freons R22, R134a, R123, R125, R32, R410a, propane, isobutene, propylene, dimethyl ether, carbon dioxide and methane under the stratified flow conditions. Using this method for designing heat exchangers, which utilize such types of fluids, will increase the efficiency of thermal energy systems. Keywords CFD model . Condensate stream . Film condensation . Heat transfer . Heat exchanger . Plain tube . Stratified flow
Nomenclature Al Ald Av Avd cp d e fi Frl G g Ga h hl
– tube area that is flooded with condensate, [m2] – dimensionless tube area that is flooded with condensate – tube area that is occupied by vapour, [m2] – dimensionless tube area that is occupied by vapour – liquid specific heat, [J/(kgK)] – inner diameter of the tube, [m] – deviation, [%] – interfacial roughness factor Þ2 – liquid Froude number (¼ ½Gρð1−x ) 2 gd l – mass velocity, [kg/(m2s)] – gravitational acceleration, [m/s2] – Galileo number (¼ ρl ðρl −ρv Þgd3 =μ2l ) – heat transfer coefficient, [W/(m2K)]; enthalpy, [J/kg] – liquid height, [m]
* Volodymyr Sereda [email protected] 1
National Technical University of Ukraine“Igor Sikorsky Kyiv Polytechnic Institute”, Politehnichna 6, Kyiv 03056, Ukraine
hld hlv hv Jal k Kw l ℒ Nu p Pl Pr pr q Rv Ref Rel Relo Rev Revo
– dimensionless liquid height – latent heat, [J/kg] – heat transfer coefficient assuming total mass flowing 0:33 as a vapour (¼ 0:023Re0:8 v Prv k v =d ) – liquid Jakob number (¼ ρl ðρl −ρv Þgd3 =μ2l ) – thermal conductivity, [W/(mK)] – correction factor – length of the tube, [m] 1=3 – characteristic length, (¼ μ2l = ρ2l g ) – Nusselt number (=hd/λl) – pressure, [Pa] – wetted perimeter, [
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