Theoretical Model for Nucleate Boiling Heat and Mass Transfer of Binary Mixtures

2003 ◽  
Vol 125 (6) ◽  
pp. 1106-1115 ◽  
Author(s):  
Ju¨rgen Kern ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Binary Mixtures ◽  
Phase Interface ◽  
Nucleate Boiling ◽  
Interfacial Thermal Resistance ◽  
Transfer Coefficients ◽  
Total Heat Flow ◽  
Heat Transfer Coefficients ◽  
Liquid Vapor

A model is presented to calculate nucleate boiling heat transfer coefficients of binary mixtures. The model includes the governing physical phenomena, such as the variation of the phase interface curvature, the adhesion pressure between wall and liquid, the interfacial thermal resistance as well as the local variation of composition and liquid-vapor equilibrium. Marangoni convection is considered, too. The theoretical background of these phenomena is described and their implementation is explained. The model is verified by comparing calculated heat transfer coefficients of hydrocarbon mixtures with experimental data. Computational and experimental data are in good agreement. In the examples a considerable amount of the total heat flow passes through a tiny thin film area, called micro region, where the liquid-vapor phase interface is attached to the wall. Very high spatial gradients of heat flux and mixture concentration occur interacting with overall heat transfer performance.

Nucleate Boiling in Thermally Developing and Fully Developed Laminar Falling Water Films

1988 ◽  
Vol 110 (1) ◽  
pp. 221-228 ◽  
Author(s):  
M. Cerza ◽  
V. Sernas
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nucleate Boiling ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Number Range ◽  
Flow Rates ◽  
Entry Length ◽  
Heat Transfer Coefficients ◽  
Water Films

This paper reports an experimental investigation of nucleate boiling in thin water films falling down the outside of a cylindrical heated tube. A mathematical model for the convective (nonboiling) heat transfer coefficient in the laminar thermal entry length was developed and used as a comparison to the experimental boiling heat transfer coefficients. A heat transfer correlation based on mechanistic arguments is presented and is shown to represent the experimental data fairly well. The experimental data were also compared with existing heat transfer data in the literature. The flow rates utilized in this study corresponded to a Reynolds number range from 670 and 4300 and the heat flux range was 6 to 70 kW/m2.

Heat Transfer Characteristics of Flow Boiling of R134a in Uniformly Heated Horizontal Circular Microtubes

2010 ◽  
Author(s):  
Saptarshi Basu ◽  
Sidy Ndao ◽  
Gregory J. Michna ◽  
Yoav Peles ◽  
Michael K. Jensen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Mass Flux ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Nucleate Boiling ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental study of two-phase heat transfer coefficients was carried out using R134a in uniformly heated horizontal circular microtubes with diameters of 0.50 mm and 1.60 mm. The effects of mass flux, heat flux, saturation pressure, and vapor quality on heat transfer coefficients were studied. The flow parameters investigated were as follows: exit pressures of 490, 670, 890, and 1160 kPa; mass fluxes of 300–1500 kg/m2s; heat fluxes of 0–350 kW/m2; inlet subcooling of 5, 20, and 40 °C; and exit qualities of 0 to 1.0. The parametric trends presented in the study are consistent with published literature. Heat transfer coefficients increased with increasing heat flux and saturation pressure while they were independent of variations in mass flux. Vapor quality had a negligible influence on heat transfer coefficients. For the conditions studied, the trends indicated that the dominant heat transfer mechanism was nucleate boiling. The experimental data was compared to three microchannel correlations — the Lazarek-Black, the Kandlikar, and the Tran Correlations. None of the correlations predicted the experimental data very well, although they all predicted the correct trend within limits of experimental error.

The Effects of Nucleate Boiling Versus Film Boiling on Heat Transfer in Power Boiler Tubes

1962 ◽  
Vol 84 (4) ◽  
pp. 365-371 ◽  
Author(s):  
H. S. Swenson ◽  
J. R. Carver ◽  
G. Szoeke
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Inside Surface ◽  
Film Boiling ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Steam Quality ◽  
Heat Transfer Coefficients

In large, subcritical pressure, once-through power boilers heat is transferred to steam and water mixtures ranging in steam quality from zero per cent at the bottom of the furnace to 100 per cent at the top. In order to provide design information for this type of boiler, heat-transfer coefficients for forced convection film boiling were determined for water at 3000 psia flowing upward in a vertical stainless-steel tube, AISI Type 304, having an inside diameter of 0.408 inches and a heated length of 6 feet. Heat fluxes ranged between 90,000 and 180,000 Btu/hr-sq ft and were obtained by electrical resistance heating of the tube. The operation of the experimental equipment was controlled so that nucleate boiling, transition boiling, and stable film boiling occurred simultaneously in different zones of the tube. The film boiling data were correlated with a modified form of the equation Nu = a a(Re)m(Pr)n using steam properties evaluated at inside surface temperature. Results of a second series of heat-transfer tests with tubes having a helical rib on the inside surface showed that nucleate boiling could be maintained to much higher steam qualities with that type of tube than with a smooth-bore tube.

Prediction of Heat Transfer Coefficients Under Sub-Cooled Boiling Conditions

2000 ◽  
Author(s):  
Edward V. McAssey ◽  
Jinfeng Wu ◽  
Thomas Dougherty ◽  
Bao Wen Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sharp Increase ◽  
Nucleate Boiling ◽  
Prediction Methods ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract Data are presented for sub-cooled boiling of water in the range of two to four atmospheres. The results show that the sharp increase in heat transfer coefficient associated with nucleate boiling occurs at wall superheats of 20 °C to 30 °C. Comparisons between experimental and predicted heat transfer coefficients are also presented. The two prediction methods examined are the Chen correlation and the Kandlikar correlation.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Bulk Liquid ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

Calibration of External Heat Transfer Coefficients During Cooling of a Partially-Filled Water Tank Using Measured Temperature-Time Data

2018 ◽  
Author(s):  
Vishal Ramesh ◽  
Sandip Mazumder ◽  
Gurpreet Matharu ◽  
Dhaval Vaishnav ◽  
Syed Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Measured Temperature ◽  
Water Tank ◽  
Time Data ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature Time

A combined Computational Fluid Dynamics (CFD) and experimental approach is presented to determine (calibrate) the external convective heat transfer coefficients (h) around a partially-filled water tank cooled in a climactic chamber. A CFD analysis that includes natural convection in both phases (water and air) was performed using a 2D-axisymmetric tank model with three prescribed average heat transfer coefficients for the top, side and bottom walls of the tank. The commercial CFD code ANSYS-Fluent™, along with User-Defined Functions (UDFs), were utilized to compute and extract temperature vs. time curves at five different thermocouple locations within the tank. The prescribed h values were then altered to match experimentally obtained temperature-time data at the same locations. The calibration was deemed successful when results from the simulations exhibited match with experimental data within ±2°C for all thermocouples. The calibrated h values were finally used in full-scale 3D simulations and compared to the experimental data to test their accuracy. Predicted 3D results were found to agree with experimental results within the error of the calibration, thereby lending credibility to the overall approach.

Heat transfer coefficients for quenching process simulation

2004 ◽  
Vol 120 ◽  
pp. 269-276
Author(s):  
M. Maniruzzaman ◽  
R. D. Sisson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Quenching Process

Quenching heat treatment in a liquid medium is a very complex heat transfer process. Heat extraction from the part surface occurs through several different heat transfer mechanisms in distinct temperature ranges, namely, film boiling, partial film boiling (i.e. transition), nucleate boiling and convection. The maximum heat transfer occurs during the nucleate boiling stage. Experimental study shows that, the effective surface heat transfer coefficient varies more than two orders of magnitude with the temperature during the quenching. For quenching process simulation, accurate prediction of the time-temperature history and microstructure evolution within the part largely depends on the accuracy of the boundary condition supplied. The heat transfer coefficient is the most important boundary condition for process simulation. This study focuses on creating a database of heat transfer coefficients for various liquid quenchant-metallic alloy combinations through experimentation using three different quench probes. This database is a web-based tool for use in quench process simulation. It provides at-a-glance information for quick and easy analysis and sets the stage for a Decision Support System (DSS) and Data Mining for heat-treating process.

1987 Max Jakob Memorial Award Lecture: Dynamics and Stability of Thin Heated Liquid Films

1990 ◽  
Vol 112 (3) ◽  
pp. 538-546 ◽  
Author(s):  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Molecular Forces ◽  
Memorial Award ◽  
Film Heat Transfer

This review covers the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface. Very large heat transfer coefficients can be obtained. The applications include various boiling heat transfer and film cooling devices. A relatively new area for study is heat transfer through ultrathin films, which are less than 100 nm in thickness, and hence subject to van der Waals and other long-range molecular forces. Some recent work employing lubrication theory to obtain an evolution equation for the growth of a surface wave is described. Earlier phenomenological work is briefly discussed, as well as the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer.

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