Effect of Nano-Scale Surface Conditions for Boiling Heat Transfer and Its Enhancement

2005 ◽  
Author(s):  
S. Chiba ◽  
K. Yuki ◽  
H. Hashizume ◽  
S. Toda
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Copper Substrate ◽  
Nucleate Boiling ◽  
Water Mist ◽  
Surface Conditions ◽  
Nano Scale ◽  
Mist Cooling ◽  
The One

In this paper, the Leidenfrost phenomena and water mist cooling are described from the viewpoint of surface conditions of heat transfer interfaces. The effect of nano-scale structures on boiling heat transfer phenomena is researched. It is clarified that the Leidenfrost phenomena on a substrate with adhered nanoscale carbons (nano carbons) are different from the one in case of a normal heat transfer interface. The photographs taken by a high-speed camera show that the boiling on a substrate with nano carbons takes the different form in comparison with the one on a normal interface. In case that the surface temperature of a copper substrate is about 140 degree C, a water droplet has a neck of water between itself and the substrate with nano carbons. On the other hand, the nucleate boiling is observed on a normal copper substrate. From the relation between evaporation time and initial surface temperature, heat transfer enhancement can be achieved under the nucleate boiling conditions. Also, the critical heat flux of water mist cooling could be enhanced by adhering nano carbons on heat-transfer interfaces. It is supposed that the wettability between water and copper is improved by the nano carbons.

Boiling Heat Transfer Characteristics of Staggered-array Water Impinging Jets on Hot Steel Plate

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Sang Gun Lee ◽  
Jin Sub Kim ◽  
Dong Hwan Shin ◽  
Jungho Lee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Steel Plate ◽  
Nucleate Boiling ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Maximum Heat ◽  
Maximum Heat Flux

The effect of staggered-array water impinging jets on boiling heat transfer was investigated by a simultaneous measurement between boiling visualization and heat transfer characteristics. The boiling phenomena of staggered-array impinging jets on hot steel plate were visualized by 4K UHD video camera. The surface temperature and heat flux on hot steel plate was determined by solving 2-D inverse heat conduction problem, which was measured by the flat-plate heat flux gauge. The experiment was made at jet Reynolds number of Re = 5,000 and the jet-to-jet distance of staggered-array jets of S/Dn = 10. Complex flow interaction of staggered-array impinging jets exhibited hexagonal flow pattern like as honey-comb. The calculated surface heat transfer profiles show a good agreement with the corresponding boiling visualization. The peak of heat flux accords with the location which nucleate boiling is occurred at. In early stage, the positions of maximum heat flux locate at the stagnation point of each jet as the relatively low surface temperature is shown at their positions. At the elapsed time of 10 s, the flat shape of heat flux profile is formed in the hexagonal area where the interacting flow uniformly cools down the wetted surface. After that, the wetted area continuously enlarges with time and the maximum heat flux is observed at its peripheral. These results point out that the flow interaction of staggered-array jets effectively cools down the closer area around jets and also show an expansion of nucleate boiling and suppression of film boiling during water jet cooling on hot steel plate. [This work was supported by the KETEP grant funded by the Ministry of Trade, Industry & Energy, Korea (Grant No. 20142010102910).]

Boiling Visualization of Two Adjacent Impinging Jets on Hot Steel Plate

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Jungho Lee ◽  
Sangho Sohn ◽  
Sang Gun Lee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Flat Plate ◽  
Boiling Heat Transfer ◽  
Steel Plate ◽  
Nucleate Boiling ◽  
Impinging Jets ◽  
High Heat Flux ◽  
Plate Heat

The simultaneous measurement between the boiling visualization and the boiling heat transfer characteristics by two adjacent impinging jets on hot steel plate was made by the experimental technique that has a function of high-temperature flat-plate heat flux gauge. The 22 K-type thermocouples were installed at 1 mm below the surface of flat-plate heat flux gauge. The 2-D inverse heat conduction was formulated to solve the surface temperature and heat flux. The boiling visualization was synchronized with a 4K video camera which was meaningful to understand complex boiling heat transfer phenomena. The heat flux gauge was uniformly heated up to 900°C by induction heating. The successive boiling images show where the nucleate boiling starts to occur on hot surface and the film boiling turns to be collapsed. The measured surface temperature and heat flux distribution agrees well with the corresponding boiling visualization: While heat transfer at the stagnation point shows a maximum heat flux, the interaction between two adjacent impinging jets exhibits a relative high heat flux and a steep temperature gradient until the end of boiling heat transfer at which single-phase convection occurs near 200°C.

Study on Nucleate Boiling Heat Transfer by Measuring Spatially Instantaneous Local Surface Temperature and Observing Instantaneous Bubble/Liquid Fluid Behavior

2013 ◽  
Author(s):  
Yasuo Koizumi ◽  
Kenta Hayashi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Heat Transfer Surface ◽  
Bubble Generation ◽  
Three Phase ◽  
Nucleate Boiling Heat Transfer

Pool nucleate boiling heat transfer experiments were performed for water at 0.101 MPa to examine the elementary process of the nucleate boiling. Heat transfer surface was made from a copper printed circuit board. Direct current was supplied to heat it up. The Bakelite plate of the backside of a copper layer was taken off at the center portion of the heat transfer surface. The instantaneous variation of the backside temperature of the heat transfer surface was measured with an infrared radiation camera. Bubble behavior was recorded with a high speed video camera. In the isolated bubble region, surface temperature was uniform during waiting time. When boiling bubble generation started, a large dip in the surface temperature was formed under the bubble. After the bubble left from the heat transfer surface, the surface temperature returned to former uniform temperature distribution. Surface temperature was not affected by the bubble generation beyond 1.6 mm from the center of the bubble. In the isolated bubble region, a convection term was approximately 80 % in total heat transfer rate. The importance of the three-phase interface line in the heat transfer should be checked carefully. In the intermediate and high heat flux region, the variation of surface temperature and heat flux were small. Rather those were close to their average values even at critical heat flux condition. It seemed that the large part of the heat transfer surface was covered with water even at the critical heat flux condition. The heat flux at the area that appeared to be the three-phase contact line was not so high and close to the average heat flux.

Nucleate Pool Boiling of Nitrogen With Different Surface Conditions

1968 ◽  
Vol 90 (4) ◽  
pp. 437-444 ◽  
Author(s):  
P. J. Marto ◽  
J. A. Moulson ◽  
M. D. Maynard
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Past History ◽  
Pool Boiling ◽  
Testing Procedure ◽  
Nucleate Boiling ◽  
Test Surface ◽  
Surface Conditions ◽  
Boiling Heat Transfer Coefficient ◽  
Teflon Coating

Pool-boiling heat transfer of liquid nitrogen from circular, 1-in.-dia horizontal disks was studied. Surface conditions included copper and nickel mirror finishes, and copper surfaces which were roughened, grease-coated, and Teflon-coated. Artificial cavities were manufactured, including mechanically drilled cylindrical holes of diameter 0.0043 and 0.015 in., and also a 0.022-in.-dia spark cut conical hole. Results indicate that a systematic testing procedure is necessary to obtain reproducible nucleate-boiling data. Surface roughness and surface material alter the nucleate-boiling curve. A grease coating significantly decreases the nucleate-boiling heat-transfer coefficient. A Teflon coating has very little effect. Past history of the test surface, including the length of time spent while boiling, can change boiling results. The effect of artificial cavities on both natural convection and nucleate-boiling was determined.

Spray Cooling Enhancement by Addition of a Surfactant

1998 ◽  
Vol 120 (1) ◽  
pp. 92-98 ◽  
Author(s):  
Y. M. Qiao ◽  
S. Chandra
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Bubble Nucleation ◽  
Spray Droplets ◽  
Cooling Enhancement

An experimental study was done on the effect of dissolving a surfactant in water sprays used to cool a hot surface. A copper surface was heated to an initial temperature of 240°C and then rapidly cooled using a spray of either pure water or an aqueous solution containing 100 ppm by weight of sodium dodecyl sulfate. The variation of surface temperature was measured during cooling, and spray impact was photographed. Addition of the surfactant was found to enhance nucleate boiling heat flux by up to 300 percent. The surface temperature required to initiate vapor bubble nucleation was reduced from 118°C to 103°C. These effects were attributed to the surfactant promoting bubble nucleation and foaming in spray droplets. Nucleate boiling heat transfer enhancement was observed at all liquid mass fluxes and droplet velocities in the range of our experiments. The surfactant slightly reduced transition boiling heat transfer, and also reduced the temperature at which spray droplets started to wet the surface. Changing the orientation of the surface with respect to gravity had no effect on heat transfer.

scholarly journals Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3189 ◽  
Author(s):  
Shoukat Khan ◽  
Muataz Atieh ◽  
Muammer Koç
Keyword(s):  
Heat Transfer ◽  
Surface Coating ◽  
Boiling Heat Transfer ◽  
Waste Heat ◽  
Material Selection ◽  
Nucleate Boiling ◽  
Surface Geometry ◽  
Nano Scale ◽  
Wide Range ◽  
Nucleate Boiling Heat Transfer

Nucleate boiling is a phase change heat transfer process with a wide range of applications i.e., steam power plants, thermal desalination, heat pipes, domestic heating and cooling, refrigeration and air-conditioning, electronic cooling, cooling of turbo-machinery, waste heat recovery and much more. Due to its quite broad range of applications, any improvement in this area leads to significant economic, environmental and energy efficiency outcomes. This paper presents a comprehensive review and critical analysis on the recent developments in the area of micro-nano scale coating technologies, materials, and their applications for modification of surface geometry and chemistry, which play an important role in the enhancement of nucleate boiling heat transfer. In many industrial applications boiling is a surface phenomenon, which depends upon its variables such as surface area, thermal conductivity, wettability, porosity, and roughness. Compared to subtractive methods, the surface coating is more versatile in material selection, simple, quick, robust in implementation and is quite functional to apply to already installed systems. The present status of these techniques for boiling heat transfer enhancement, along with their future challenges, enhancement potentials, limitations, and their possible industrial implementation are also discussed in this paper.

Pool Nucleate Boiling on Heat Transfer Surface With Deposited Sea Salts

2016 ◽  
Author(s):  
Shinichiro Uesawa ◽  
Yasuo Koizumi ◽  
Mitsuhiko Shibata ◽  
Hiroyuki Yoshida
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Heat Transfer Surface ◽  
Artificial Seawater ◽  
Distilled Water ◽  
Nacl Solution ◽  
Nucleate Boiling Heat Transfer

Pool nucleate boiling heat transfer experiments of the 3.5 - 10wt% NaCl solution, the real seawater and the 3.5 - 10wt% artificial seawater solution as well as distilled water for the basis of comparison were performed to examine the effect of salts on boiling heat transfer. Seawater was injected into the reactor cores in the accident at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. This study intended to provide base data to consider reactor core cooling by seawater. Boiling curves of the 3.5 - 10wt% NaCl solution, the real seawater and the 3.5 - 10wt% artificial seawater solutions as well as distilled water were well predicted with the Rohsenow pool nucleate boiling heat transfer correlation although the curves were a little shifted to the higher wall superheat region. The formation of secondary coalescent large bubble was suppressed in the experiments of the NaCl solutions, real seawater and the artificial seawater solutions, and small primary bubbles detached directly from the heat transfer surface. Sea salt deposition was observed only in the experiments of the 7.0wt% and 10wt% artificial seawater solutions. The deposited salt was calcium sulfate. Slow heat transfer surface temperature excursion occurred in the experiments of the 7.0wt% and 10wt% artificial seawater solutions after the heat flux was raised to 600 kW/m2 and 120 kW/m2, respectively. The critical heat flux of the 7.0wt% and 10wt% artificial seawater solutions were 600 kW/m2 and 120 kW/m2, respectively if the occurrence of the slow heat transfer surface temperature excursion was defined as the critical heat flux condition. The heat transfer surface temperature excursion might be caused by the growth of the deposited salt layer.

Nucleate Boiling Heat Transfer Under Liquid Jet Impingement

2007 ◽  
Author(s):  
Ahmed M. T. Omar ◽  
M. S. Hamed ◽  
M. Shoukri
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Coolant Temperature ◽  
Liquid Jet ◽  
Planar Jet ◽  
Nucleate Boiling Heat Transfer

Liquid jet impingement is a very effective way of cooling of simple and complicated geometry objects. The attainable cooling rate is radically enhanced when using liquids as coolant due to the possibility of having boiling to occur during the impingement process. Bubble activity on the surface and the resulted mixing with the fluid bulk produces an additional factor of enhancement which at some levels of surface temperature dominates other convective mechanism due to the coolant flow perpendicular or parallel to the surface. The efficient nucleate boiling heat transfer regime can be divided into: partial nucleate boiling and fully developed nucleate boiling. The heat transfer capacity of each and the range of surface temperature over which each of these two boiling regimes up to the critical heat flux (CHF) are experimentally investigated in this research for different coolant temperature and velocity. For this purpose, single planar jet is used to provide the cooling medium of a flat surface that is being heated steadily. The boiling surface temperature was thus controlled by a feed back computer program to allow for steady state operation. So, at each level of boiling surface temperature observation of boiling mode and heat transfer mechanisms was elongated and verified. The experiments were conducted using degassed water jet velocity range between 0.75 and 1.7 m/s and degree of sub-cooling range from 10 to 28 °C at atmospheric pressure. The variation of the heat flux with those factors at different surface superheat up to the CHF point is presented. A physical interpretation is introduced to explain the effects of the input parameters on the heat transfer changes in these regimes.

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