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.

Microporous Coatings to Maximize Pool Boiling Heat Transfer of Saturated R-123 and Water

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Joo Han Kim ◽  
Ajay Gurung ◽  
Miguel Amaya ◽  
Sang Muk Kwark ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Microporous Coating ◽  
Plain Surface ◽  
Improved Performance

The present research is an experimental study for the enhancement of boiling heat transfer using microporous coatings. Two types of coatings are investigated: one that is bonded using epoxy and the other by soldering. Effects on pool boiling performance were investigated, of different metal particle sizes of the epoxy-based coating, on R-123 refrigerants, and on water. All boiling tests were performed with 1 cm × 1 cm test heaters in the horizontal, upward-facing orientation in saturated conditions at atmospheric pressure and under increasing heat flux. The surface enhanced by the epoxy-based microporous coatings significantly augmented both nucleate boiling heat transfer coefficients and critical heat flux (CHF) of R-123 relative to those of a plain surface. However, for water, with the same microporous coating, boiling performance did not improve as much, and thermal resistance of the epoxy component limited the maximum heat flux that could be applied. Therefore, for water, to seek improved performance, the solder-based microporous coating was applied. This thermally conductive microporous coating, TCMC, greatly enhanced the boiling performance of water relative to the plain surface, increasing the heat transfer coefficient up to ∼5.6 times, and doubling the CHF.

Critical Heat Flux of Steady Boiling for Water Jet Impingement in Flat Stagnation Zone on Superhydrophilic Surface

2005 ◽  
Vol 128 (7) ◽  
pp. 726-729 ◽  
Author(s):  
Zhenhua Liu ◽  
Yuhao Qiu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Stagnation Zone ◽  
Heat Transfer Characteristics ◽  
Nucleate Boiling Heat Transfer ◽  
The Common ◽  
Superhydrophilic Surface

The nucleate boiling heat transfer characteristics of a round water jet impingement in a flat stagnation zone on the superhydrophilic surface were experimentally investigated. The superhydrophilic heat transfer surface was formed by a TiO2 coating process. The experimental results were compared with those on the common metal surface. In particular, the quantificational effects of the flow conditions, heating conditions, and the coating methods on the critical heat flux (CHF) were systemically investigated. The experimental data showed that the nucleate boiling heat transfer characteristics on the superhydrophilic surface are significantly different from those on the common metal surface. The CHF of boiling on the superhydrophilic surface is greatly increased by decreasing of the solid-liquid contact angle.

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.

Transient Pool Boiling Heat Transfer—Part 2: Boiling Heat Transfer and Burnout

1977 ◽  
Vol 99 (4) ◽  
pp. 554-560 ◽  
Author(s):  
A. Sakurai ◽  
M. Shiotsu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Input ◽  
Boiling Heat Transfer ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Boiling Heat Transfer Coefficient ◽  
Transient Boiling

Transient boiling heat transfer for exponential heat input to a platinum wire supported horizontally in a pool of water was investigated. Transient boiling heat transfer coefficient, transient DNB heat flux, and transient maximum heat flux were obtained for exponential periods ranging from 5 ms to 10 s and for system pressures ranging from 0.1 to 2.1 MPa. Transient boiling heat transfer coefficient after the commencement of boiling becomes lower than the steady boiling heat transfer coefficient at the same heat flux. This was explained to be as a result of the time lag of the activation of originally flooded cavities for the increasing rate of the heat input. Initial heat flux was varied from zero to near the steady maximum heat flux. Effect of initial boiling condition on transient DNB and maximum heat fluxes was negligible. Mechanism of transient boiling heat transfer beyond steady DNB heat flux was suggested.

Experimental Study of Boiling Heat Transfer From a Sphere Embedded in a Liquid-Saturated Porous Medium

1990 ◽  
Vol 112 (3) ◽  
pp. 736-743 ◽  
Author(s):  
V. X. Tung ◽  
V. K. Dhir
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Particle Size ◽  
Porous Medium ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Maximum Heat ◽  
Maximum Heat Flux

Boiling heat transfer from a sphere embedded in a porous medium composed of nonheated glass particles was studied under steady-state and transient quenching conditions. In the experiments, the diameter of the nonheated glass particles forming the porous layers was varied parametrically. Freon-113 was used as the test liquid. Experimental results showed that the maximum heat flux increased monotonically with increasing glass particle diameter and approached an asymptotic value corresponding to the maximum heat flux obtained in a pool free of glass particles. It was also observed that the minimum heat flux was nearly insensitive to the particle size and the film boiling heat transfer coefficient increased slightly with decreasing particle size. In the nucleate boiling region, the heat transfer coefficient showed a much weaker dependence on wall superheat in the presence of particles. Transient data indicated that the surface temperature was not uniform during quenching. Therefore, different maximum heat fluxes were obtained depending on the location of the thermocouple whose temperature history was employed in recovering the transient boiling curve. However, for some applications, cooling rates predicted by imposing the steady-state boiling curve may not be in large error.

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.

Jet Impingement Boiling From a Circular Free-Surface Jet During Quenching: Part 1—Single-Phase Jet

2001 ◽  
Vol 123 (5) ◽  
pp. 901-910 ◽  
Author(s):  
David E. Hall ◽  
Frank P. Incropera ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Free Surface ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Transient Temperature ◽  
Spatial Distributions ◽  
Maximum Heat

This paper reports results from an experimental study of boiling heat transfer during quenching of a cylindrical copper disk by a subcooled, circular, free-surface water jet. The disk was heated to approximately 650°C, and as quenching occurred, transient temperature measurements were taken at discrete locations near the surface and applied as boundary conditions in a conduction model to deduce transient heat flux distributions at the surface. Results are presented in the form of heat flux distributions and boiling curves for radial locations varying from the stagnation point to ten nozzle diameters for jet velocities between 2.0 and 4.0 m/s 11,300⩽Red⩽22,600. Data for nucleate boiling in the stagnation region and spatial distributions of maximum heat flux are presented and are in good agreement with correlations developed from steady-state experiments. Spatial distributions of minimum film boiling temperatures and heat fluxes are also reported and reveal a fundamental dependence on jet deflection and streamwise location. A companion paper (Hall et al., 2001) describes single-phase and boiling heat transfer measurements from a two-phase (water-air), free-surface, circular jet produced by injecting air bubbles into the jet upstream of the nozzle exit.

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