Film Boiling in a Scaling Liquid

1976 ◽  
Vol 98 (2) ◽  
pp. 173-177 ◽  
Author(s):  
L. C. Farrar ◽  
E. Marschall
Keyword(s):  
Calcium Sulfate ◽  
Heating Surface ◽  
Sulfate Solution ◽  
High Heat ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Saturated Liquid ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Heating Surfaces

Film boiling experiments were carried out in an aqueous-calcium sulfate solution. The experimental results indicate that scale formation on heating surfaces during evaporation of a calcium sulfate solution can be avoided under carefully controlled conditions. Experimental heat transfer results for both distilled water and aqueous calcium solutions compare very well with analytical predictions. In addition, for high heat fluxes, contact between liquid and heating surface was found to exist during stable film boiling in a quiescent, saturated or almost saturated liquid.

Liquid-Solid Contact During Flow Film Boiling of Subcooled Freon-11

1990 ◽  
Vol 112 (2) ◽  
pp. 465-471 ◽  
Author(s):  
K. H. Chang ◽  
L. C. Witte
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Small Scale ◽  
Solid Contact ◽  
Heated Cylinder ◽  
Experimental Heat ◽  
Wall Superheat ◽  
Flow Film Boiling

Liquid-solid contacts were measured for flow film boiling of subcooled Freon-11 over an electrically heated cylinder equipped with a surface microthermocouple probe. No systematic variation of the extent of liquid-solid contact with wall superheat, liquid subcooling, or velocity was detected. Only random small-scale contacts that contribute negligibly to overall heat transfer were detected when the surface was above the homogeneous nucleation temperature of the Freon-11. When large-scale contacts were detected, they led to an unexpected intermediate transition from local film boiling to local transition boiling. An explanation is proposed for these unexpected transitions. A comparison of analytical results that used experimentally determined liquid-solid contact parameters to experimental heat fluxes did not show good agreement. It was concluded that the available model for heat transfer accounting for liquid-solid contact is not adequate for flow film boiling.

Effect of Velocity on Heat Transfer to Boiling Freon-113

1980 ◽  
Vol 102 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Salim Yilmaz ◽  
J. W. Westwater
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Atmospheric Pressure ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Forced Flow ◽  
Film Boiling ◽  
Square Root ◽  
Peak Heat Flux

Measurements were made of the heat transfer to Freon-113 at near atmospheric pressure, boiling outside a 6.5 mm dia horizontal steam-heated copper tube. Tests included pool boiling and also forced flow vertically upward at uelocities of 2.4, 4.0 and 6.8 m/s. The metal-to-liquid ΔT ranged from 13 to 125° C, resulting in nucleate, transition, and film boiling. The boiling curves for different velocities did not intersect or overlap, contrary to some prior investigators. The peak heat flux was proportional to the square root of velocity, agreeing with the Vliet-Leppert correlation, but disagreeing with the Lienhard-Eichhorn prediction of an exponent of 0.33. The forced-flow nucleate boiling data were well correlated by Rohsenow’s equation, except at high heat fluxes. Heat fluxes in film boiling were proportional to velocity to the exponent 0.56, close to the 0.50 value given by Bromley, LeRoy, and Robbers. Transition boiling was very sensitive to velocity; at a ΔT of 55° C the heat flux was 900 percent higher for a velocity of 2.4 m/s than for zero velocity.

scholarly journals Numerical prediction of nucleate pool boiling heat transfer coefficient under high heat fluxes

2016 ◽  
Vol 20 (suppl. 1) ◽  
pp. 113-123 ◽  
Author(s):  
Milada Pezo ◽  
Vladimir Stevanovic
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pool Boiling ◽  
Heating Surface ◽  
High Heat ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Two Phase ◽  
Boiling Heat Transfer Coefficient

This paper presents CFD (Computational Fluid Dynamics) approach to prediction of the heat transfer coefficient for nucleate pool boiling under high heat fluxes. Three-dimensional numerical simulations of the atmospheric saturated pool boiling are performed. Mathematical modelling of pool boiling requires a treatment of vapor-liquid two-phase mixture on the macro level, as well as on the micro level, such as bubble growth and departure from the heating surface. Two-phase flow is modelled by the two-fluid model, which consists of the mass, momentum and energy conservation equations for each phase. Interface transfer processes are calculated by the closure laws. Micro level phenomena on the heating surface are modelled with the bubble nucleation site density, the bubble resistance time on the heating wall and with the certain level of randomness in the location of bubble nucleation sites. The developed model was used to determine the heat transfer coefficient and results of numerical simulations are compared with available experimental results and several empirical correlations. A considerable scattering of the predictions of the pool boiling heat transfer coefficient by experimental correlations is observed, while the numerically predicted values are within the range of results calculated by well-known Kutateladze, Mostinski, Kruzhilin and Rohsenow correlations. The presented numerical modeling approach is original regarding both the application of the two-fluid two-phase model for the determination of heat transfer coefficient in pool boiling and the defined boundary conditions at the heated wall surface.

scholarly journals Thermal efficiency of metal foams on pool boiling

2021 ◽  
Vol 2116 (1) ◽  
pp. 012005
Author(s):  
L L Manetti ◽  
A S Moita ◽  
E M Cardoso
Keyword(s):  
Nickel Foam ◽  
Pool Boiling ◽  
Heating Surface ◽  
High Heat ◽  
Heat Fluxes ◽  
Vapor Flow ◽  
Maximum Enhancement ◽  
Fin Efficiency ◽  
Nickel Foams ◽  
Similar Area

Abstract This paper presents an experimental work on pool boiling using HFE-7100 at saturated conditions, under atmospheric pressure, and copper and nickel foams as the heating surface with four different thicknesses varying between 0.5 mm and 3 mm, followed by an analysis of the effect of foam fin-efficiency based on Ghosh model. All foams showed a better heat transfer coefficient (HTC) than the plain surface; however, as the heat flux increased, the HTC from the thicker nickel foams decreased due to the bubble vapor flow inside the foam. On the other hand, the thinner nickel foam showed better HTC at high heat fluxes with a maximum enhancement of 120%. The foam efficiency presented a similar tendency with the HTC, i.e., as the thickness decreases the efficiency increases; however, as compared with copper foams with a similar area but different porous diameter, the copper foams are 40% more efficient than the nickel ones due to the foam material, which has a thermal conductivity 4.5 times higher.

Dynamics of Pool Boiling on Plain and Nanotube Coated Silicon Surfaces

2010 ◽  
Author(s):  
Vijaykumar Sathyamurthi ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Chaotic Dynamics ◽  
Pool Boiling ◽  
Deterministic Chaos ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Test Fluid

Saturated pool boiling experiments are conducted over silicon substrates with and without Multi-walled Carbon Nanotubes (MWCNT) with PF-5060 as the test fluid. Micro-fabricated thin film thermocouples located on the substrate acquire surface temperature fluctuation data at 1 kHz frequency. The high frequency surface temperature data is analyzed for the presence of chaotic dynamics. The shareware code, TISEAN© is used in analysis of the temperature time-series. Results show the presence of low-dimensional deterministic chaos, near Critical Heat Flux (CHF) and in some parts of the Fully Developed Nucleate Boiling (FDNB) regime. Some evidence of chaotic dynamics is also obtained for the film boiling regimes. Singular value decomposition is employed to generate pseudo-phase plots of the attractor. In contrast to previous studies involving multiple nucleation sites, the pseudo-phase plots show the presence of multi-fractal structure at high heat fluxes and in the film boiling regime. An estimate of invariant quantities such as correlation dimensions and Lyapunov exponents reveals the change in attractor geometry with heat flux levels. No significant impact of surface texturing is visible in terms of the invariant quantities.

Ultrasonic augmentation in pool boiling heat transfer over external surfaces: A review

2020 ◽  
pp. 095440622095035
Author(s):  
Abhishek Swarnkar ◽  
Vikas J Lakhera
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat ◽  
Ultrasonic Field ◽  
Ultrasonic Waves ◽  
Heat Fluxes ◽  
Surface Topology

Boiling heat transfer is known for high heat fluxes at relatively small temperature differences. However, over the decades, technological innovations have demanded further augmentation in heat fluxes associated with boiling. Among the various active and passive methods, use of ultrasonic waves in boiling liquid has emerged as a proven technique for the required heat transfer improvement as demonstrated by a number of researchers. The present article reviews the application of ultrasonic waves in enhancing the heat transfer in various regimes of pool boiling. It has been found that the use of ultrasonic field is more promising in case of sub-cooled boiling as compared to saturated condition. Along with ultrasonic field of lower frequency and higher power, the usage of various passive techniques of surface improvement such as micro channel, surface topology, nano coatings etc. leads to further augmentation of heat transfer. Also, the relative placement of heating surface in ultrasonic wave field must be considered inevitably while designing an ultrasonic field assisted pool boiling system. It requires further investigations to conduct more parametric studies such as effect of pressure along with the usage of ultrasonic waves during sub- cooled boiling. Also during ultrasonic assisted pool boiling, various nano fluids can be tested for improving the heat transfer characteristics particularly in the saturated nucleate boiling regime.

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