A Fractal Model for Nucleate Pool Boiling Heat Transfer

In this paper, a fractal model for nucleate pool boiling heat transfer is developed based on the fractal distribution of sites (areas) of nucleation sites on boiling surfaces. Algebraic expressions for the fractal dimension and area fraction of nucleation sites are derived, which are shown to be a strong function of wall superheat. The predicted fractal dimension is shown in good agreement with those determined by the box-counting method. The fractal model for nucleate boiling heat transfer is found to be a function of wall superheat, the contact angle of the fluid and the heater material, and physical properties of the fluid with a minimum number of empirical constants. The predicted total heat flux from a boiling surface based on the present fractal model is compared with existing experimental data. An excellent agreement between the model predictions and experimental data is found, which verifies the validity of the present fractal model.

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A FRACTAL ANALYSIS OF SUBCOOLED NUCLEATE POOL BOILING

Fractals ◽

10.1142/s0218348x0800382x ◽

2008 ◽

Vol 16 (01) ◽

pp. 1-9 ◽

Cited By ~ 7

Author(s):

BOQI XIAO ◽

ZONGCHI WANG ◽

BOMING YU

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Boiling Heat Transfer ◽

Pool Boiling ◽

Fractal Model ◽

Nucleate Pool Boiling ◽

Empirical Constant ◽

Pool Boiling Heat Transfer ◽

Model Predictions ◽

Conventional Models

A fractal model for the subcooled nucleate pool boiling heat transfer is proposed in this paper. The analytical expressions for the subcooled nucleate pool boiling heat transfer are derived based on the fractal distribution of nucleation sites on boiling surfaces. The proposed fractal model for the subcooled nucleate pool boiling heat transfer is found to be a function of wall superheat, liquid subcooling, fractal dimension, the minimum and maximum active cavity size, the contact angle and physical properties of fluid. No additional/new empirical constant is introduced, and the proposed model contains less empirical constants than the conventional models. The model predictions are compared with the existing experimental data, and fair agreement between the model predictions and experimental data is found for different liquid subcoolings.

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Experiment of Enhanced Pool Boiling Heat Transfer on Coupling Effects of Nano-Structure and Synergistic Micro-Channel

ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2019-4215 ◽

2019 ◽

Author(s):

Linsong Gao ◽

Jizu Lv ◽

Minli Bai ◽

Chengzhi Hu ◽

Liqun Du ◽

...

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Capillary Flow ◽

Pool Boiling ◽

Micro Channel ◽

Nano Structure ◽

Pool Boiling Heat Transfer ◽

Wall Superheat ◽

Nucleation Sites ◽

The Heat Transfer Coefficient

Abstract The manipulation of micro- or nano-structure is a promising method to improve pool boiling heat transfer performance. However, most studies just focus on the micro- or nano-structure without considering the combination micro- and nano-structure. In this paper, we fabricated synergistic microchannel, nano-structure, and micro-nano structure surface on the nickel by different technologies. Pool boiling of DI water under saturated condition was experimentally investigated. Result shows at the wall superheat of 18 K, the heat transfer coefficient of micro-nano structure, nano-structure and synergistic micro-channel surface are 16400, 13050, and 13400 W/m2 K higher 89%, 50%, and 54% than that of smooth surface, respectively. The improved heat transfer is attributed to active nucleation sites and capillary flow.

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