Heat transfer in films

Chang, Y. P., 1959, Wave Theory of Heat Transfer in Film Boiling, Trans. ASME, J. Heat Transfer 81 1. (2)... 

The treatments of Anderson et al. (A4, A5), Charvonia (C4), Calvert (Cl, C2), and others differ mainly in the manner in which the gas stream pressure drop is taken into account for various cases of gas flow. Labuntsov (L2) has carried out an analysis using two forms of the velocity profile which do not involve the assumption of sharply differentiated zones in the boundary layer this analysis is mainly concerned with heat transfer in films. 

Brauer (B15), 1957 Application of results on flow of films (B14) to case of heat transfer in film condensation. 

Labuntsov, D.A., Heat Transfer in Film Condensation of Pure Steam on Vertical Surfaces and Horizontal Tubes, Teploenergetika, Vol. 4, p. 72, 1957. 

Wilhelm Nusselt (1882-1957) was nominated Professor of Theoretical Mechanical Engineering at the Technische Hochschule, Karlsruhe in 1920. Between 1925 and 1952 he taught at the Technische Hochschule, Munich. In 1915 he published his fundamental work The Fundamental Laws of Heat Transfer , in which he introduced dimensionless groups for the first time. Further important investigations included heat transfer in film condensation, cross current heat transfer and the analogy between heat and mass transfer in evaporation. 

Fig. 4. 7 Influence of temperature dependent material properties on heat transfer in film condensation [4.9]...

Voskresenskij, K.D. Heat transfer in film condensation with temperature dependent properties of the condensate (russ.). Izv. Akad. Nauk USSR (1948) 1023-1028... 

Labunzov, D.A. Heat transfer in film condensation of pure vapours on vertical plates and horizontal tubes (russ.). Teploenergetika 7 (1957) 72-79... 

COEFFICIENTS FOR FILM-TYPE CONDENSATION. The basic equations for the rate of heat transfer in film-type condensation were first derived by Nusselt. " The Nusselt equations are based on the assumption that the vapor and liquid at the outside boundary of the liquid layer are in thermodynamic equilibrium, so that the only resistance to the flow of heat is that offered by the layer of condensate flowing downward in laminar flow under the action of gravity. It is also assumed that the velocity of the liquid at the wall is zero, that the velocity of the liquid at the outside of the film is not influenced by the velocity of the vapor, and that the temperatures of the wall and the vapor are constant. Superheat in the vapor is neglected, the condensate is assumed to leave the tube at the condensing temperature, and the physical properties of the liquid are taken at the mean film temperature. 

D. A. DiCicco and R. J. Schoenhals, Heat Transfer in Film Boiling With Pulsating Pressures, J. Heat Transfer (86) 457-461,1964. 

G. Gimbutis, Heat Transfer in Film Heat Exchangers, in Proc. I4th Int. Congress of Refrigeration, Moscow, vol. 2, pp. 1-7,1975. 

The heat-transfer quaUties of titanium are characterized by the coefficient of thermal conductivity. Even though the coefficient is low, heat transfer in service approaches that of admiralty brass (thermal conductivity seven times greater) because titanium s greater strength permits thinner-walled equipment, relative absence of corrosion scale, erosion—corrosion resistance that allows higher operating velocities, and the inherently passive film. 

Heat Transfer In general, the fluid mechanics of the film on the mixer side of the heat transfer surface is a function of what happens at that surface rather than the fluid mechanics going on around the impeller zone. The impeller largely provides flow across and adjacent to the heat-transfer surface and that is the major consideration of the heat-transfer result obtained. Many of the correlations are in terms of traditional dimensionless groups in heat transfer, while the impeller performance is often expressed as the impeller Reynolds number. 

Additionally, the surfactant properties of filmers reduce the potential for stagnant, heat-transfer-resisting films, which typically develop in a filmwise condensation process, by promoting the formation of condensate drops (dropwise condensation process) that reach critical mass and fall away to leave a bare metal surface (see Figure 11.2). This function, together with the well-known scouring effect on unwanted deposits keeps internal surfaces clean and thus improves heat-transfer efficiencies (often by 5-10%). 

C9. Coulson, J. M., and McNelly, M. J., Heat transfer in a climbing film evaporator, Trans. Inst. Chem. Engrs. (London) 34, 247 (1956). 

HEAT TRANSFER IN THE CONDENSATION OF VAPOURS 9.6.1. Film coefficients for vertical and inclined surfaces... 

Two-phase heat transfer in micro-channel heat sink was associated with different mechanisms for low, medium, and high-quality flows. Bubble flow and nucleate boiling occur only at low qualities (Xe < 0.05) corresponding to very low heat fluxes. High fluxes produce medium-quality (Xe = 0.05—0.55) or high-quality (Xe = 0.55—1.0) flows depending on the flow rate, where heat transfer is dominated by annular film evaporation. Due to the large differences in heat transfer mechan-... 

The equation given by Bromley (1950) can be used to estimate the heat-transfer coefficient for film boiling on tubes. Heat transfer in the film-boiling region will be controlled by conduction through the film of vapour, and Bromley s equation is similar to the Nusselt equation for condensation, where conduction is occurring through the film of condensate. 

Bromley, L. A. (1950) Chem. Eng. Prog. 46, 221. Heat transfer in stable film boding. 

Film Boiling and Heat Transfer in Liquid-Deficient Regions 274... 

FILM BOILING AND HEAT TRANSFER IN LIQUID-DEFICIENT REGIONS... 

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