Film Boiling Heat Transfer Enhancement via Electrostatic Leidenfrost State Suppression

2015 ◽  
Author(s):  
Arjang Shahriari ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heat Dissipation ◽  
Nuclear Reactor ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Vapor Layer ◽  
Steam Generation ◽  
Boiling Regime ◽  
Enhanced Boiling

Boiling heat transfer has enormous impact on the effectiveness of various industrial processes like steam generation, desalination, and nuclear reactor operations. Heat transfer in the film boiling regime is significantly reduced as compared to the nucleate boiling regime due to the existence of a vapor layer at the solid-liquid interface (Leidenfrost effect). This vapor layer degrades heat transfer by up to two orders of magnitude and causes dryout, which can result in severe temperature excursions. This work maps out the heat transfer benefits of electrostatic suppression of the Leidenfrost state. Electrical suppression of the Leidenfrost state is observed for a variety of liquids, including organic solvents, water and electrically conducting salt solutions. Successful Leidenfrost state suppression is observed with moderate voltages even at ultrahigh temperatures exceeding 550 °C. Elimination of the vapor layer increases heat dissipation capacity of film boiling by more than one order of magnitude; up to 45X enhancement was measured in this work. This work also introduces the concept of tunable film boiling heat transfer. Overall, electrically-enhanced boiling can enable a new class of technologies for active control and enhancement of boiling heat transfer, with various applications in energy systems.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2001 ◽  
Vol 1 (1) ◽  
pp. 32
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2002 ◽  
Vol 1 (1) ◽  
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

An Experimental Study of Transition and Film Boiling Heat Transfer in Liquid-Saturated Porous Bed

1986 ◽  
Vol 108 (1) ◽  
pp. 117-124 ◽  
Author(s):  
S. Fukusako ◽  
T. Komoriya ◽  
N. Seki
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Circular Cylinder ◽  
Boiling Heat Transfer ◽  
Heating Surface ◽  
Local Maximum ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Experimental Investigations ◽  
Porous Bed

Experimental investigations of transition and film boiling in a liquid-saturated porous bed are reported. The porous bed contained in a vertical circular cylinder is made up of packed spherical beads whose diameters range from 1.0 to 16.5 mm, while the depth of the bed overlying the heating surface varies from 10 to 300 mm. Water and fluorocarbon refrigerants R-11 and R-113 are adopted as testing liquids. Special attention is focused on the effect of the diameter of spherical beads on boiling heat transfer in the transition boiling region. It is found that for the small bead diameters the steady boiling heat transfer rises monotonically with temperature from nucleate boiling through the film boiling region, without going through a local maximum.

scholarly journals Boiling Heat Transfer With Cryogenic Fluids at Standard, Fractional, and Near-Zero Gravity

1964 ◽  
Vol 86 (3) ◽  
pp. 351-358 ◽  
Author(s):  
H. Merte ◽  
J. A. Clark
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Test Time ◽  
Zero Gravity ◽  
Saturated Liquid ◽  
Cryogenic Fluids ◽  
Short Test ◽  
Minimum Heat

A study is reported of boiling heat transfer with saturated liquid nitrogen under atmospheric pressure at standard, fractional, and near-zero gravity. A drop-tower technique is used to achieve the reduced gravities. Because of the short test time available a transient technique using a sphere as a transient calorimeter is employed to obtain the heat-transfer data. This technique permits the ready acquisition of data in all boiling regimes from the film boiling region through nucleate boiling. Comparison is made with correlations for film boiling and for maximum and minimum heat flux and their corresponding Δtsat.

Enhanced Boiling Heat Transfer From Micro-Porous Cylindrical Surfaces in Saturated FC-87 and R-123

1997 ◽  
Vol 119 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J. Y. Chang ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bulk Liquid ◽  
High Heat Flux ◽  
High Flux ◽  
Boiling Enhancement ◽  
Nucleate Boiling Heat Transfer ◽  
Enhanced Boiling

The present research is an experimental study of pool boiling heat transfer from cylindrical heater surfaces immersed in saturated FC-87 and R-123. The baseline heater surfaces tested are plain, integral-fin with 709 fins/m, and commercial enhanced (High-Flux and Turbo-B). In addition, a highly effective micro-scale enhancement coating is applied to the plain and integral-fin surfaces to augment nucleate boiling heat transfer. Experiments are performed to understand the effects of surface micro- and macro-geometries on boiling heat transfer. The boiling performance of the micro-porous enhanced plain and integral-fin surfaces are compared with the High-Flux and the Turbo-B surfaces. At high heat flux conditions, the break down of the bulk liquid feed mechanism reduces boiling enhancement from the cylindrical surfaces.

Experimental Study of Helix-Finned Surface for Nucleate Pool Boiling

2016 ◽  
Author(s):  
Kailun Chen ◽  
Changqi Yan ◽  
Cable Kurwitz ◽  
Kun Cheng ◽  
Haozhi Bian
Keyword(s):  
Heat Transfer ◽  
3D Printing ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Heat Dissipation ◽  
Nucleate Boiling ◽  
Experimental Investigations ◽  
Printing Technique ◽  
Finned Surface ◽  
3D Printing Technique

This research presents results from experimental investigations on helix-finned surface fabricated by a 3D printing technique to evaluate boiling heat transfer performance. The experiments were conducted in saturated water at atmospheric pressure. To the author’s knowledge, this is the first attempt that helical pin fins are employed in thermal management. The boiling curve of the enhanced surface was characterized by a much lower wall superheat at the same heat flux compared with plain surfaces. High-speed visualization was used to display instantaneous bubble behaviors such as the bubble departure frequency, which was obtained from analyzed images. It was observed that the helix-finned surface had higher bubble departure frequencies compared to plain surfaces and an earlier onset of nucleate boiling was noticed. It is concluded that the surface roughness and micron level cavities produced by the 3D printing technique on the helix surface are key factors to enhance boiling heat transfer. With the experience gained, dimension optimization of helical structure should be studied further to meet the needs of increased heat dissipation rate.

Electrical Suppression of Film Boiling During Quenching

2016 ◽  
Author(s):  
Arjang Shahriari ◽  
Mark Hermes ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Cooling Curve ◽  
Vapor Layer ◽  
Steam Generation ◽  
Voltage Dependent ◽  
Order Of Magnitude ◽  
Leidenfrost Effect ◽  
Solid Liquid Interface

Boiling heat transfer impacts the performance of various industrial processes like quenching, desalination and steam generation. At high temperatures, boiling heat transfer is limited by the formation of a vapor layer at the solid-liquid interface (Leidenfrost effect), where the low thermal conductivity of the vapor layer inhibits heat transfer. Interfacial electrowetting (EW) fields can disrupt this vapor layer to promote liquid-surface wetting. This concept works for a variety of quenching media including water and organic solvents. We experimentally analyze EW-induced disruption of the vapor layer, and measure the resulting enhanced cooling during quenching. Imaging is employed to visualize the fluid-surface interactions and understand boiling patterns in the presence of an electrical voltage. It is seen that EW fundamentally changes the boiling pattern, wherein, a stable vapor layer is replaced by intermittent wetting of the surface. This switch in the heat transfer mode substantially reduces the cool down time. An order of magnitude increase in the cooling rate is observed. An analytical model is developed to extract instantaneous voltage dependent heat transfer rates from the cooling curve. The results show that electric fields can alter and tune the traditional cooling curve. Overall, this study presents a new concept to control the mechanical properties and metallurgy, by electrical control of the quench rate.

Modeling the Influence of Marangoni Flows on the Leidenfrost State on Solid and Liquid Substrates

2018 ◽  
Author(s):  
Arjang Shahriari ◽  
Palash V. Acharya ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Layer Thickness ◽  
Nucleate Boiling ◽  
Vapor Layer ◽  
Boiling Regime ◽  
First Order ◽  
Leidenfrost Effect ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Marangoni Flows

Boiling heat transfer affects various processes related to energy, water and manufacturing. In the film boiling regime, heat transfer is substantially lower than in the nucleate boiling regime, due to the formation of a vapor layer at the solid-liquid interface (Leidenfrost effect). In this work, we present analytical modeling of the Leidenfrost state of droplets on solid and liquid substrates. A key aspect of this study is the focus on surface tension gradients on the surface of a liquid (Leidenfrost droplet or liquid substrate), which actuate thermo-capillary driven Marangoni flows. It is noted that this work develops a first-order simplified model, which assumes a uniform vapor layer thickness. The presence of Marangoni flows has non-trivial implications on the resulting thickness of the Leidenfrost vapor layer. Our analysis shows that the pumping effect generated in the vapor layer due to Marangoni flows can significantly reduce the Leidenfrost vapor layer thickness.

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