Academic literature on the topic 'Condensation; Condensate film'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Condensation; Condensate film.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Condensation; Condensate film"
1
Dong, Jing Lan, Wei Ping Yan, and Chao Hui Zhang. "Convective Condensation of Oxy-Coal Combustion Flue Gas of Laminar Fow in a Vertical Pipe." Applied Mechanics and Materials 325-326 (June 2013): 389–97. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.389.
Full textAbstract:
The problem of the oxy-fuel combustion flue gas condensation is the condensation of vapor in the presence of high concentration non-condensable gas. The vapor condensing at dew point temperature releases heat and diffuses on to the surface of the pipe through a non-condensable gas film. Thus it is treated as combined heat and mass transfer problem governed by mass, momentum and energy balance equations for the vaporgas mixture and diffusion equation for the vapor species. The flow of the falling condensate film is governed by the momentum and energy balance equations. The temperature at the gas-to-liquid interface, at which the condensation takes place, is estimated with the help of the heat balance and mass balance equations at the interface. The local values of the condensation Nusselt number, condensate Reynolds number, gasliquid interface temperature and pressure drop are estimated from the numerical results for different values of the system parameters at inlet, such as vapor component, temperature of vaporgas mixture, gas phase Reynolds number and total pressure. The thermodynamic calculations were made and analyzed using numerical calculation method under different conditions.
2
Mitrovic, J. "Effects of Vapor Superheat and Condensate Subcooling on Laminar Film Condensation." Journal of Heat Transfer 122, no. 1 (August 9, 1999): 192–96. http://dx.doi.org/10.1115/1.521450.
Full textAbstract:
Nusselt’s model is employed to illustrate the effects of vapor superheat and condensate subcooling on laminar film condensation occurring under simultaneous actions of gravity and interfacial shear. The vapor superheat affects the condensation kinetics in cooperation with heat transfer in both phases. Under comparable conditions, the condensate film is thinner and the heat transfer coefficient larger for superheated than for saturated vapor. The heat flux on the cooling surface arising from the sensible heat of condensate increases as the critical point of the condensing substance is approached and, at this point, the Nusselt condensation model gives the single-phase boundary layer solutions. [S0022-1481(00)00701-5]
3
Mosaad, El-Sayed. "Heat transfer performance of film condensation created by forced flow." Thermal Science 23, no. 3 Part B (2019): 2001–11. http://dx.doi.org/10.2298/tsci171218134m.
Full textAbstract:
In this work, condensate film on a vertical wall cooled on the external side by forced flow is analysed as a conjugate heat transfer problem. The treated case is that the condensate film and forced flow boundary-layer are in a parallel-flow arrangement. The mass, momentum and energy boundary-layer equations of the condensate film and forced flow are set in a dimensionless form to generalize the model. The parameters affecting the thermal communication between the condensate film and the forced flow are defined from the analysis. These parameters explain the relative impact of the three involved thermal resistances of solid wall, forced convection and film condensation on the local and mean Nusselt number. The study shows that the Nusselt number predicted by the present conjugate model is different from that predicted by a Nusselt-type model.
4
Lin, Yan-Ting, and Sheng-An Yang. "Turbulent Film Condensation on a Nonisothermal Horizontal Tube." Journal of Mechanics 21, no. 4 (December 2005): 235–42. http://dx.doi.org/10.1017/s1727719100000678.
Full textAbstract:
AbstractA simple model has been developed for the study of turbulent film condensation from downward flowing vapors onto a horizontal circular tube with variable wall temperature. The interfacial shear at the vapor condensate film is evaluated with the help of Colburn analogy. The condensate film flow and local/or mean heat transfer characteristics from a horizontal tube with non-uniform temperature variation under the effect of Froude number, sub-cooling parameter and system pressure parameter has been conducted. Although the non-uniform wall temperature variation has an appreciable influence on the local film flow and heat transfer; however, the dependence of mean heat transfer on the non-uniform wall temperature variation is almost negligible.
5
Nozu, S., and H. Honda. "Condensation of Refrigerants in Horizontal, Spirally Grooved Microfin Tubes: Numerical Analysis of Heat Transfer in the Annular Flow Regime." Journal of Heat Transfer 122, no. 1 (August 1, 1999): 80–91. http://dx.doi.org/10.1115/1.521439.
Full textAbstract:
A method is presented for estimating the condensation heat transfer coefficient in a horizontal, spirally grooved microfin tube. Based on the flow observation study performed by the authors, a laminar film condensation model in the annular flow regime is proposed. The model assumes that all the condensate flow occurs through the grooves. The condensate film is segmented into thin and thick film regions. In the thin film region formed on the fin surface, the condensate is assumed to be drained by the combined surface tension and vapor shear forces. In the thick film region formed in the groove, on the other hand, the condensate is assumed to be driven by the vapor shear force. The present and previous local heat transfer data including four fluids (CFC11, HCFC22, HCFC123, and HFC134a) and three microfin tubes are found to agree with the present predictions to a mean absolute deviation of 15.1 percent. [S0022-1481(00)01501-2]
6
Galamba, D., and V. K. Dhir. "Transient Simultaneous Condensation and Melting of a Vertical Surface." Journal of Heat Transfer 107, no. 4 (November 1, 1985): 812–18. http://dx.doi.org/10.1115/1.3247508.
Full textAbstract:
Transient melting of a vertical wall as a result of condensation of saturated vapor is investigated analytically. Using a Nusselt-type analysis the equations governing the laminar melt and condensate films are solved by a combination of analytical and numerical finite-differencing techniques. The solutions in the axial distance-time plane fall into three regions: the piling region where the melt and condensate thicknesses are only functions of time, the Goursat region where the thicknesses are functions of both the axial distance and time, and the steady-state region where the film thicknesses are only functions of the axial distance. The time to achieve a steady-state condition is obtained analytically.
7
Webb, R. L., T. M. Rudy, and M. A. Kedzierski. "Prediction of the Condensation Coefficient on Horizontal Integral-Fin Tubes." Journal of Heat Transfer 107, no. 2 (May 1, 1985): 369–76. http://dx.doi.org/10.1115/1.3247424.
Full textAbstract:
A theoretical model is developed for prediction of the condensation coefficient on horizontal integral-fin tubes for both high and low surface tension fluids. The model includes the effects of surface tension on film drainage and on condensate retention between the fins. First, the fraction of the tube circumference that is flooded with condensate is calculated. Typically, the condensation coefficient in the flooded region is negligible compared to that of the unflooded region. Then the condensation coefficient on the unflooded portion is calculated, assuming that surface tension force drains the condensate from the fins. The model is used to predict the R-11 condensation coefficient on horizontal, integral-fin tubes having 748, 1024, and 1378 fpm. The predicted values are within ±20 percent of the experimental values.
8
Honda, H., S. Nozu, and Y. Takeda. "A Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes." Journal of Heat Transfer 111, no. 2 (May 1, 1989): 525–32. http://dx.doi.org/10.1115/1.3250709.
Full textAbstract:
The previous theoretical model of film condensation on a single horizontal low finned tube is extended to include the effect of condensate inundation. Based on the flow characteristics of condensate on a vertical column of horizontal low finned tubes, two major flow modes, the column mode and the sheet mode, are considered. In the column mode, the surface of the lower tubes is divided into the portion under the condensate column where the condensate flow is affected by the impinging condensate from the upper tubes, and the portion between the condensate columns where the condensate flow is not affected by the impinging condensate. In the sheet mode, the whole tube surface is assumed to be affected by the impinging condensate. Sample calculations for practical conditions show that the effects of the fin spacing and the number of vertical tube rows on the heat transfer performance is significant for R-12, while the effects are small for steam. The predicted value of the heat transfer coefficient for each tube row compares well with available experimental data, including four fluids and five tube bundles.
9
Wang, Hua Sheng, and John W. Rose. "A Theory of Film Condensation in Horizontal Noncircular Section Microchannels." Journal of Heat Transfer 127, no. 10 (June 16, 2005): 1096–105. http://dx.doi.org/10.1115/1.2033905.
Full textAbstract:
The paper presents a theoretical model to predict film condensation heat transfer from a vapor flowing in horizontal square and equilateral triangular section minichannels or microchannels. The model is based on fundamental analysis which assumes laminar condensate flow on the channel walls and takes account of surface tension, interfacial shear stress, and gravity. Results are given for channel sizes (side of square or triangle) in the range of 0.5–5 mm and for refrigerants R134a, R22, and R410A. The cases considered here are where the channel wall temperature is uniform and the vapor is saturated at the inlet. The general behavior of the condensate flow pattern (spanwise and streamwise profiles of the condensate film), as well as streamwise variation of local mean (over section perimeter) heat-transfer coefficient and vapor mass quality, are qualitatively in accord with expectations on physical grounds. The magnitudes of the calculated heat-transfer coefficients are in general agreement with experimental data for similar, but nonidentical, channel geometry and flow parameters.
10
Kazeminejad, H. "Effect of Vapour Drag on Laminar Film Condensation on a Vertical Rectangular Fin." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 207, no. 1 (January 1993): 63–69. http://dx.doi.org/10.1243/pime_proc_1993_207_099_02.
Full textAbstract:
A simple theory is presented for laminar film condensation of a pure vapour on a vertical rectangular fin which takes account of drag induced on the liquid film by the flow of the condensing vapour. Under these conditions, the governing conjugate differential equations for the fin and condensate flow are solved numerically to determine the fin temperature and condensate film thickness distributions. For the range of parameters investigated, it was found that the reduction in condensate thermal resistance due to vapour shear significantly enhances the heat-transfer rate to the fin and decreases the fin efficiency. The model also provides a clear picture of the relative effect of the gravity force, friction drag and momentum drag on the performance of the fin.
Dissertations / Theses on the topic "Condensation; Condensate film"
1
Bartleman, Alan. "The condensation of hydrocarbons in a vertical reflux condenser tube." Thesis, University of Strathclyde, 2001. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21409.
Full textAbstract:
A new test facility, with a vertical reflux condenser of 1500mm overall length and 45mm internal diameter, has been commissioned and tested and methods developed for measuring key process parameters. An experimental study of reflux condensation in a single tube using n-pentane and iso-octane and binary mixtures of these single component hydrocarbons has been undertaken. Using water as the cooling medium, a correlation was developed for determining the coolant-side heat transfer coefficient in the reflux condenser based on the Wilson plot method. The composition of binary liquid mixture samples from the test facility was determined using an empirical correlation developed using density measurements from a vibrating u-tube densitometer. The single components were condensed in the range 32.0-48.4°C and 0.106-1.515bara by adjusting the test condenser heat load for fixed conditions on the coolant side to investigate how the condensate-film heat transfer coefficient varied with the condensate film Reynolds number. The results show good agreement with the method recommended by HTFS for correcting the Nusselt theory for the effects of waves. A further small correction was made to improve the fit to the data. The binary hydrocarbon mixtures were condensed across the range 65.9-90.1°C and 0.729-1.531bara by conducting similar experiments where the feed vapour contained 50% and 70% n-pentane. Composition measurements of the condensate and vapour leaving the test condenser were made to examine the separation of components during partial reflux condensation. The results suggest that this separation is influenced by heat flux and that it would be improved if the test condenser were operated at a lower heat flux. Further experimental work is needed to verify this, and to investigate how this influences the number of thermodynamic stages, which was found to be less than one with the conditions reported here. Analysis of the heat transfer resistances on the vapour side showed that the standard procedure of using a dry-gas heat transfer coefficient, with or without a mass transfer correction term based on the film theory, poorly predicted the experimental values. These predictions were improved by the use of an enhancement factor, which may be more relevant in counter-current than co-current condensing situations. The results indicate that use of a dry-gas heat transfer coefficient with the film theory correction factor, over-predicts the mass transfer resistance. Comparison was made between the data and predictions based on the integral condensation curve, as might be used in Silver's method for condenser thermal design. It was shown that this method poorly predicted the surface area and the separation achieved in the test condenser. The results indicate that the heat and mass transfer coefficients obtained in a plain tube are significantly higher than those based on using a dry-gas heat transfer coefficient corrected by film theory. Implications for the design of reflux condensers have been presented.
2
Pinkas, Jan. "Kondenzační výměník za kotel na tuhá paliva 200 kW." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443194.
Full textAbstract:
The point of this thesis is a waste gas condensator for 200kW woodchips burning boiler. In the first part of the thesis types of heat exchangers are introduced. Condensation is introduced. Further all necessary equations and relations for vertical shall and tube heat exchanger are specified. Following those relations waste gas condensator is designed. Situation under different input conditions is talked over in the end.
3
Whitlock, Shannon. "Bose-Einstein condensates on a magnetic film atom chip." Australasian Digital Thesis Program, 2007. http://adt.lib.swin.edu.au/public/adt-VSWT20070613.172308/index.html.
Full textAbstract:
Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Atom Optics and Ultrafast Spectroscopy, 2007.A thesis submitted for the degree of Doctor of Philosophy, Centre for Atom Optics and Ultrafast Spectroscopy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 107-118.
4
Whitlock, Shannon, and n/a. "Bose-Einstein condensates on a magnetic film atom chip." Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070613.172308.
Full textAbstract:
Atom chips are devices used to magnetically trap and manipulate ultracold atoms
and Bose-Einstein condensates near a surface. In particular, permanent magnetic film
atom chips can allow very tight confinement and intricate magnetic field designs while
circumventing technical current noise. Research described in this thesis is focused
on the development of a magnetic film atom chip, the production of Bose-Einstein
condensates near the film surface, the characterisation of the associated magnetic
potentials using rf spectroscopy of ultracold atoms and the realisation of a precision
sensor based on splitting Bose-Einstein condensates in a double-well potential.
The atom chip itself combines the edge of a perpendicularly magnetised GdTbFeCo
film with a machined silver wire structure. A mirror magneto-optical trap collects
up to 5 x 108 87Rb atoms beneath the chip surface. The current-carrying wires
are then used to transfer the cloud of atoms to the magnetic film microtrap and
radio frequency evaporative cooling is applied to produce Bose-Einstein condensates
consisting of 1 x 105 atoms.
We have identified small spatial magnetic field variations near the film surface that
fragment the ultracold atom cloud. These variations originate from inhomogeneity in
the film magnetisation and are characterised using a novel technique based on spatially
resolved radio frequency spectroscopy of the atoms to map the magnetic field landscape
over a large area. The observations agree with an analytic model for the spatial decay
of random magnetic fields from the film surface.
Bose-Einstein condensates in our unique potential landscape have been used as a
precision sensor for potential gradients. We transfer the atoms to the central region
of the chip which produces a double-well potential. A single BEC is formed far from
the surface and is then dynamically split in two by moving the trap closer to the
surface. After splitting, the population of atoms in each well is extremely sensitive to
the asymmetry of the potential and can be used to sense tiny magnetic field gradients
or changes in gravity on a small spatial scale.
5
Swartz, Matthew M. "Experimental Study of Turbulent Natural Convective Condensation In the Presence of Non-Condensable Gas on Vertical and Inclined Surfaces." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/918.
Full textAbstract:
Pressurized water reactor nuclear plants, currently under construction, have been designed with passive containment cooling systems. Turbulent, natural-convective condensation, with high non-condensable mass fraction, on the walls of the containment vessel is a primary heat transfer mechanism in these new plant designs. A number of studies have been completed over the past two decades to justify use of the heat and mass transfer analogy for this scenario. A majority of these studies are founded upon natural-convective heat transfer correlations and apply a diffusion layer model to couple heat and mass transfer. Reasonable success in predicting experimental trends for vertical surfaces has been achieved when correction factors are applied. The corrections are attributed to mass transfer suction, film waviness or mist formation, even though little experimental evidence exists to justify these claims. This work examines the influence of film waves and mass transfer suction on the turbulent, natural-convective condensing flow with non-condensable gas present. Testing was conducted using 0.457 m x 2.13 m and a 0.914 m x 2.13 m condensing surfaces suspended in a large pressure vessel. The test surfaces could be rotated from vertical to horizontal to examine the inclination angle effect. The test facility implements relatively high accuracy calorimetric and condensate mass flow measurements to validate the measured heat and mass transfer rates. Test results show that application of the Bayley (1955) and Al-Arabi and Sakr (1988) heat transfer correlations using the heat and mass transfer analogy is appropriate for conditions in which the liquid film remains laminar. For transitional and wavy film flows, a clear augmentation in heat transfer was observed due to disruption of the gas layer by film waves. This result has implications for the scalability of existing correlations. A new correlation is proposed and results compared to several other datasets.
6
Glushchuk, Andrey. "Film condensation on curvilinear fin: preparation of SAFIR and EMERALD experiments aboard International Space Station." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210060.
Full textAbstract:
In 21 century finned surfaces are used in almost all condensers to enhance their heat transfer capabilities. A lot of different models are presented in the literature: on horizontal and vertical finned tubes, inside finned tubes. The validation method of the theoretical models is based on comparison between measurement of average heat transfer coefficient and one calculated by the model. But in this case it is impossible to validate all approaches made in the theory.\
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
7
Pavlovic, Goran. "Exciton-polaritons in low dimensional structures." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00632151.
Full textAbstract:
Some special features of polaritons, quasi-particles being normal modes of system of excitons interacting with photons in so called strong coupling regime, are theoretically and numerically analyze in low dimensional systems. In Chapter 1 is given a brief overview of 0D, 1D and 2D semiconductor structures with a general introduction to the polariton field. Chapter 2 is devoted to micro / nano wires. The so called whispering gallery modes are studied in the general case of an anisotropic systems as well as polariton formation in ZnO wires. Theoretical model is compared with an experiment. In the Chapter 3 Josephson type dynamics with Bose-Einstein condensates of polaritons is analyzed taking into account pseudospin degree of freedom. Chapter 4 start with an introduction to Aharonov-Bohm effect, as the best known represent of geometrical phases. An another geometrical phase - Berry phase, occurring for a wide class of systems performing adiabatic motion on a closed ring, is main subject of this section. We considered one proposition for an exciton polariton ring interferometer based on Berry phase effect. Chapter 5 concerns one 0D system : strongly coupled quantum dot exciton to cavity photon. We have discussed possibility of obtaining entangled states from a quantum dot embedded in a photonic crystal in polariton regime.
8
Guille, Claire. "Etude de la formation par epitaxie par jets moleculaires des interfaces entre inas et gaas." Paris 6, 1987. http://www.theses.fr/1987PA066415.
Full textAbstract:
Malgre le fort desaccord parametrique existant entre gaas et inas (7,2%), il est possible de realiser des couches pseudomorphes de l'un des materiaux sur l'autre, en se limitant a des couches d'epaisseurs inferieures a une dizaine d'a. Dans ces conditions,l'interface inas/gaas est plane et chimiquement abrupte, a la demi-couche pres. L'interface inverse est diffuse et rugueuse a l'echelle atomique. Au cours de la formulation de cette heterojonction, il y a segregation d'in en surface et formation d'un compose ternaire. Ce type de phenomene de segregation d'in se produit egalement dans les composes ternaires ingaas et peut etre a l'origine de leur rugosite superficielle. Etude comparative avec d'autres systemes iii-as
9
Bassani, Franck. "Dopage indium d'hétérostructures CdTe/CdZnTe en épitaxie par jets moléculaires." Grenoble 1, 1993. http://www.theses.fr/1993GRE10043.
Full textAbstract:
Ce travail concerne le dopage indium des couches minces de cdte et des heterostructures cdte/cdznte elaborees par la technique d'epitaxie par jets moleculaires selon les orientations (001), (111) et (211). Nous avons mis en evidence l'importance des conditions stchiometriques de surface durant la croissance: un flux excedentaire de cd controle ainsi qu'une temperature d'elaboration basse (220c) sont necessaires. Pour une gamme de concentration d'indium comprise entre 10#1#6 et 10#1#8 cm##3, l'analyse des proprietes electrique et optique des couches minces de cdte(001) uniformement dopees montre une activite electrique proche de l'unite et l'absence de centres profonds. Le dopage planaire des heterostructures cdte/cdznte a ete realise avec succes: l'optimisation des conditions de spectrometrie de masse des ions secondaires permet de deduire que le dopant in est tres bien localise spatialement (<15 a); une etude spectroscopique de la variation de l'energie de localisation de l'exciton sur le donneur en fonction du confinement quantique a ete entreprise. Nous presentons egalement les resultats de dopage selon les orientations (111) et (211). L'utilisation de substrats (111) legerement desorientes et orientes (211) permet de s'affranchir des macles. En particulier, l'orientation (211) permet d'elaborer des couches d'excellente qualite cristalline dont les proprietes electriques et optiques sont voisines de celles des couches de cdte(001). Nous avons mis en evidence l'ecrantage du champ piezoelectrique pour une heterostructure cdte/cdznte(211) a dopage module
10
Fontaine, Christophe. "Hétéroépitaxie par jets moléculaires de semiconducteurs II-VI." Grenoble 1, 1986. http://www.theses.fr/1986GRE10062.
Full textAbstract:
Etude de l'heteroepitaxie de cdte, cd::(1-x)zn::(x)te et cd::(x)hg::(1-x)te sur cdznte, insb et gaas (001) et (111) et des differents parametres qui gouvernent la qualite cristalline. Il s'avere que la croissance (001) est meilleure que la croissance (111). L'interet d'une interface graduelle est demontre a fort desaccord de maille. A faible desaccord de mailles les contraintes dans les couches epitaxiques ont ete mesurees. Dans ces conditions experimentales, la relaxatioon des couches est gouvernee par un mecanisme de generation de dislocations et non par l'activation thermique des dislocations presentes. Les modeles existants ne permettent pas de decrire la relaxation dans les couches cdte. Presentation d'un modele qui rend compte des observations
Book chapters on the topic "Condensation; Condensate film"
1
Fujii, Tetsu. "Representative Physical Properties for the Condensate Film and the Vapor Boundary Layer." In Theory of Laminar Film Condensation, 153–72. New York, NY: Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4612-3152-3_9.
Full text
2
Charef, Adil, M’barek Feddaoui, Abderrahman Nait Alla, and Monssif Najim. "Computational Study of Liquid Film Condensation with the Presence of Non-Condensable Gas in a Vertical Tube." In Desalination and Water Treatment. InTech, 2018. http://dx.doi.org/10.5772/intechopen.76753.
Full textConference papers on the topic "Condensation; Condensate film"
1
Utaka, Yoshio, and Tetsuji Nishikawa. "Unsteady Measurement of Condensate Film Thickness for Solutal Marangoni Condensation." In International Heat Transfer Conference 12. Connecticut: Begellhouse, 2002. http://dx.doi.org/10.1615/ihtc12.600.
Full text
2
Wang, Huasheng, and John W. Rose. "Film Condensation in Horizontal Triangular Section Microchannels: A Theoretical Model." In ASME 2004 2nd International Conference on Microchannels and Minichannels. ASMEDC, 2004. http://dx.doi.org/10.1115/icmm2004-2395.
Full textAbstract:
The paper presents a theoretical model to predict film condensation heat transfer from a vapor flowing in a horizontal tube with equilateral triangular section minichannels or microchannels. The model is based on fundamental analysis which assumes laminar condensate flow on the channel walls and takes account of surface tension, vapor shear stress and gravity. The case considered here is where the channel wall temperature is uniform and the vapor is saturated at inlet. Sample numerical results are given for the channel size (side of triangle) of 1.0 mm and for refrigerant R134a. The general behaviour of the condensate flow pattern (spanwise and streamwise profiles of the condensate film), as well as streamwise variation in quality and local mean (over section perimeter) heat-transfer coefficient, are qualitatively in accord with expectations on physical grounds.
3
Wang, Hua Sheng, and John W. Rose. "Film Condensation in Microchannels: Effect of Tube Inclination." In ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2006. http://dx.doi.org/10.1115/icnmm2006-96049.
Full textAbstract:
A recent model for condensation in microchannels by the authors has been modified to investigate the effect of channel inclination. Provisional results are obtained for the case studied earlier for horizontal channels i.e. for R134a with saturated vapour at inlet and prescribed uniform wall temperature. Calculations give distributions around the channel perimeter of condensate film thickness and heat flux from which the mean (around the channel perimeter) heat flux and heat-transfer coefficient are found. Results are presented for square channels with side 0.5, 1.0 and 3.0 mm.
4
Gu, Hongfang, Qiwei Guo, Changsong Li, and Qing Zhou. "Phenomenon of Fog Formation and Flow Characteristics of Droplet-Vapor-Gas Mixture in a Cooler-Condenser." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10260.
Full textAbstract:
Abstract Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers.
5
Arnas, A. O¨zer, Daisie D. Boettner, Michael J. Benson, and Bret P. Van Poppel. "On the Teaching of Condensation Heat Transfer." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59277.
Full textAbstract:
The topic of condensation heat transfer is usually included in a chapter on Boiling and Condensation in most Heat Transfer textbooks. The assumptions made are those of laminar liquid film with constant thermo-physical properties, uniform vapor temperature equal to the saturation temperature of the vapor, negligible shear at the liquid-vapor interface, and negligible momentum and energy transfer by advection in the condensate film. The results presented are normally for the film thickness, the local convective heat transfer coefficient, and the Nusselt number. However, no means are presented to the student to determine if all of these simplifying assumptions are actually satisfied for a given problem. This investigation clarifies these points to improve teaching of the material and understanding by the student at the undergraduate and graduate level.
6
Koca, Aliihsan, Sevket Ozgur Atayilmaz, and Ozden Agra. "Free Convection Film Condensation of Steam in the Presence of Non-Condensing Gases Using CFD Based Approach in a Room Filled With Humid Air." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37273.
Full textAbstract:
In this paper, transient natural convection combined heat and mass transfer in enclosures filled with humid air, including condensation to the walls, which are subjected to time varying prescribed temperatures, was studied numerically. Ansys Fluent CFD code implemented to the model for wall condensation from a vapor and non-condensable gas mixture. User-Defined Function (UDF) has been used to predict the condensation rate for a mixture of air and water vapor flowing past a cooled surface. The effect of the condensation process on the flow and species distribution in the vapor phase is incorporated into the flow calculations through a customized source term applied in wall-adjacent cells. The condensation phenomenon is modeled from first principles as sink terms for the mass, momentum, species and energy conservation equations. The condensation rate is obtained by requiring the condensate–gas interface to be impermeable to the non-condensable gas. The Computational Fluid Dynamics (CFD) program was used to calculate the value of condensation rates, latent and sensible heat transfer rates as well as the relative humidity rates and mass fractions of species. In the study, the effects of different initial relative humidity ratios and the characteristic lengths of the condensation plate on the condensation mass fluxes were studied. The results indicated that the new system could reduce the risk of condensation on the cooling panels and provide a more comfortable indoor environment. The new system has a great potential for use in hot and humid climate regions with radiant cooling systems.
7
Gu, Hongfang, Qi Chen, Zhe Zhang, and Haiyang Guo. "Study of Condensation Flow Patterns and Heat Transfer Characteristic on a Horizontal Tube Bundle." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67459.
Full textAbstract:
The numerous studies on condensation flow patterns and heat transfer were focused on the horizontal inside single tube. A number of heat and mass transfer correlations are used for design of shellside condensers based on tubeside condensation flow regimes. Due to a complex geometry and measurement difficulty in a tube bundle, there are few publications reported on shellside condensation flow regime and heat transfer characteristics. To investigate the condensation flow patterns and heat and mass transfer mechanism at the different flow regimes, a horizontal shellside condenser was tested from a multipurpose condensation rig recently. The horizontal test bundle is made of 36 tubes with the staggered tube layout. The tube OD is 19 mm and the tube length is 1.0 m using stainless steel. Four visualization windows were placed on the front and back sides on the shell for photographing condensation flow patterns. Steam and steam/air mixture were used as the test fluids. The condensation flow patterns, condensate film thickness and droplets distribution were recorded using a high-speed digital camera at a wide range of condensation process conditions. The experimental data show that the condensation flow regime changes from the shear-controlled flow to gravity-controlled flow depending on the vapor and condensate loads, bundle location and the concentration of the non-condensable gas. These experimental data provide a fundamental approach for developing the heat and mass transfer correlateons at different shellside condensation patterns. This paper presents the experimental result on shellside condensation patterns associated with heat transfer characteristics.
8
Peng, Baohong, and Li Yang. "The Enhancement of Marangoni Condensation Heat Transfer by Addition of Additives." In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52024.
Full textAbstract:
This paper investigated the heat transfer process that the condensing occurred on the tube and the vapor has been added with effective additives. The effective additives trigger interfacial convection that leads to loss of hydrodynamic stability at the liquid/vapor interface and produce a spontaneous disturbance in the condensate liquid. As a result, condensation heat transfer is significantly increased. Both physical models included the condensate liquid film and mathematical model based on the boundary layer equation were given and then transformed to a non-dimensional form by applying the similarity theory. The main concept of developing the model is to understand the basic mechanism of surface tension effect on the process of steam condensation.
9
Aili, Abulimiti, Qiaoyu Ge, and TieJun Zhang. "Condensation of Low-Surface-Tension Fluids on Microstructured Surfaces at Low Temperature." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71675.
Full textAbstract:
Filmwise condensation of a low surface tension fluid (i.e. refrigerant) on microstructured aluminum surfaces is studied to investigate the effect of the structures on condensation heat transfer at low temperature. The hypothesis is that the structures may cause thinning of the condensate film at micro-scales, thus resulting in an enhancement of condensation heat transfer. However, the structures may also decrease the mobility of the condensate near the surface due to increased friction, thus potentially leading to performance deterioration. The aim of this work is to investigate which of the two counteracting mechanisms dominate during filmwise condensation. Condensation experiments are carried out in a low-temperature vacuum chamber. Compared with the Nusselt model of condensation, the microstructured surfaces, either coated or uncoated, show similar performance, with potentially slight enhancement at low subcooling degree and slight deterioration at high subcooling degree. When the microstructured and silane-coated surface is infused with a non-volatile and very low-surface-tension lubricant oil, the lubricant is displaced by the condensate and there is almost no change in the condensation performance. Our results show that, unlike the case of dropwise condensation of high-surface tension fluids, microstructured and coated surfaces with/without infusing oil is not exciting to enhanced filmwise condensation of low-surface-tension fluids.
10
Ohtake, Hiroyasu, Yasuo Koizumi, and Soichiro Miyake. "Study on Condensation Heat Transfer of Micro Structured Surfaces." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82111.
Full textAbstract:
Condensation heat transfer experiments for steam were performed by using mirror-finished copper surfaces, mirror-finished silicon surfaces and silicon surfaces with micro grooves or micro pins on it. The micro-grooves and the micro-pins were created by the MEMS technology. The film- and also the drop-wise condensation were observed on the copper surface. The film-wise condensation heat flux was in good agreement with the values of the Nusselt equation. It was approximately one-tenth of the drop-wise condensation heat flux. The condensation on the mirror-finished silicon surface was the drop-wise condensation. The heat flux was approximately one-tenth of the drop-wise condensation heat flux on the copper surface. The condensation on the micro-grooved and the micro-pin silicon surfaces was film-wise. The condensation heat fluxes were approximately one-tenth of the copper surface film-wise condensation heat flux. When the contact angle was smaller than 70 degree, the condensation was film-wise and when larger than the value, drop-wise. It seemed that the hollow parts of the micro-grooved or the micro-pin surface were filled with condensate first after the condensation was initiated. It made the surface hydrophilic and the condensation film-wise.