Modelling of dropwise condensation on a cylindrical surface including the sweeping effect

Özler, Talip Emrah
The purpose of this study was to analyze the dropwise condensation on a cylindrical surface including the sweeping effect theoretically. For this purpose, first the problem of the equilibrium shape and departure size of drops on the outer surface of a cylinder was formulated. The equations of the surface of the drop were obtained by minimizing (for a given volume) the total energy of the drop which consists of surface and gravitational energy by using the techniques of variational calculus. The departure size of the droplets on a surface at varies angle of inclinations were also determined experimentally. Drop departure size is observed to decrease up to as the surface inclination was decreased up to 90 degree and then it increased up to 180 degree. Mean base heat flux, drop departure rate, sweeping frequency, fraction of covered area, sweeping period, local heat flux and average heat flux for the dropwise condensation on a cylindrical surface including the sweeping effect is formulated and the resulting integral equation was solved by using the finite difference techniques. The results show that drop departure rate and sweeping frequency was strongly affected by the angular position and reached asymptotic value at large angular positions. Comparing the results of the average heat flux values at different diameters show that at larger diameters the average heat flux becomes larger. This is due to the increased sweeping effect at larger diameters.


Theoretical investigation of conjugate condensation heat transfer inside vertical tubes
Köse, Serhat; Yeşin, Ahmet Orhan; Department of Mechanical Engineering (2010)
Based on the well-known theoretical studies related to the film condensation inside vertical tubes, a known temperature distribution is prescribed as boundary condition at the inner surface of the tube wall. But, in reality, there is a thermal interaction between the condensate fluid and conduction through the wall where the temperature variation along the inner surface of the tube wall is unknown and this unknown temperature profile should be determined by taking account of this interaction. In other words...
Modeling of fluid -vapor interface in the condensation zone of a grooved heat pipe
Alipour, Mobin; Dursunkaya, Zafer; Department of Mechanical Engineering (2017)
Condensation in grooved heat pipes involves several simultaneous phenomena including vapor-liquid boundaries whose shapes are unknown a priori, fluid flow due to capillary and dispersion pressure gradients and condensation over ultra thin films. In grooved heat pipes, the majority of condensation occurs on fin tops due to the thinner liquid film, having a lower thermal resistance, compared to inside the groove where the fluid is substantially thicker. Majority of the studies in the literature assume an appr...
Optimum spacing between vertical, parallel heat generating boards cooled by natural convection in a fixed volume
Saygan, Samet; Yüncü, Hafit; Department of Mechanical Engineering (2014)
In this study, the effect of distance between vertical and parallel heat generating plates which are fixed in a given volume on the natural convection to the air between plates is investigated both numerically and experimentally. The conservation equations which represent the constant property air flow in fixed and rectangular cross section channel are solved by the FloEFD software which used the Finite Volume Method and the SIMPLE algorithm. The maximum temperatures of plates are compared with the experime...
Akkus, Yigit; ÇETİN, BARBAROS; Dursunkaya, Zafer (2017-08-30)
In this study, a computational model for the evaporation from a sessile liquid droplet fed from the center to keep the diameter of the droplet constant is presented. The continuity, momentum and energy equations are solved with temperature dependent thenno-physical properties using COMSOL Multi-physics. At the surface of the droplet, convective heat and evaporative mass fluxes are assigned. Since the flow field is affected by evaporative flux, an iterative scheme is built and the computation is automated us...
Assessment of SLW-1 model in the presence of gray and non-gray particles
Özen, Guzide; ATEŞ, CİHAN; Selçuk, Nevin; Külah, Görkem (2019-02-01)
In this study, predictive accuracy of Gray Gas and SLW-1 approximations is benchmarked against Spectral Line-Based Weighted Sum of Grey Gases Model (SLW) in multidimensional enclosures involving gray/non-gray absorbing, emitting and scattering particles. Input data required for the radiation code and its validation are provided from two combustion tests previously carried out in a 300 kWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) test rig burning low calorific value Turkish lignite with high vola...
Citation Formats
T. E. Özler, “Modelling of dropwise condensation on a cylindrical surface including the sweeping effect,” M.S. - Master of Science, Middle East Technical University, 2007.