The Determination of Forced-Convection Surface-Boiling Heat Transfer

1964 ◽  
Vol 86 (3) ◽  
pp. 365-372 ◽  
Author(s):  
A. E. Bergles ◽  
W. M. Rohsenow
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Experimental Results ◽  
Boiling Curve ◽  
Wall Superheat ◽  
Good Agreement

The characteristics of the boiling curve for forced-convection surface boiling are examined in detail. In the region of low wall superheat, the heat transfer can be predicted by available correlations for forced convection. An analysis is presented for the inception of first significant boiling. Experimental results are in good agreement with analytical predictions. Pool-boiling data were taken under saturated and subcooled conditions for surfaces similar to those used in forced-convection surface boiling. These data indicate that the curves for forced-convection surface boiling cannot be based on data for saturated pool boiling but must rather be based on actual forced-convection data.

Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Muhamad Zuhairi Sulaiman ◽  
Masahiro Takamura ◽  
Kazuki Nakahashi ◽  
Tomio Okawa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Flux Enhancement ◽  
Optimum Configuration ◽  
Wall Superheat ◽  
Nucleate Boiling Heat Transfer

Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40, and 60 mins. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however; in contrast effect of enhancement for downward. Maximum enhancements of CHF for upward- and downward-facing heater are 2.1 and 1.9 times, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater's BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 min which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.

Pool Boiling Heat Transfer Characteristics on Twisted Tube Bundles in a Flooded Evaporator

2013 ◽  
Vol 416-417 ◽  
pp. 1049-1055
Author(s):  
Ji Cheng Zhou ◽  
Dong Sheng Zhu ◽  
Zheng Qi Huo ◽  
Jun Li ◽  
Yan Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Heat Transfer Characteristics ◽  
Pool Boiling Heat Transfer ◽  
Twisted Tube ◽  
Wall Superheat ◽  
Twisted Tubes

The objectives of this paper are to study the pool boiling heat transfer characteristics of twisted tubes in the flooded evaporator. The twisted tubes are processed from common circular evaporating tubes with an outer diameter of 15.88mm. The outer major axis diameter, minor axis diameter, wall thickness and length of the twisted tube are 19.50mm, 11.28mm, 1.09mm, and 3310mm, respectively. The outside tube pool boiling heat transfer coefficients, tube side Reynolds numbers, the wall superheat, the saturation temperature of refrigerant and the heat flux are considered as the key parameters. The results show that pool boiling heat transfer coefficient data increase with , and , respectively, and decrease as the wall superheat increases. It can be found in the case study that the overall heat transfer coefficient of twisted tube flooded evaporator (TFE) is about 1.15 times as high as the one of common flooded evaporator (FE) with a same heat capacity. It is proved that an application of the TFE in the water-cooled screw chiller can be feasible.

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

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.

Nucleate Boiling on Biotemplated Nanostructured Surfaces

2012 ◽  
Author(s):  
Md. Mahamudur Rahman ◽  
Stephen M. King ◽  
Emre Olceroglu ◽  
Matthew McCarthy
Keyword(s):  
Heat Transfer ◽  
Self Assembly ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Pool Boiling Heat Transfer ◽  
Nanostructured Surfaces ◽  
Transfer Capability ◽  
Good Agreement

The fabrication and characterization of biotemplated nanostructured surfaces for enhanced pool boiling heat transfer is reported. By introducing micro/nano-porosity and surface roughness at the liquid-vapor interface, significant enhancement in surface heat transfer capability can be achieved during nucleate boiling. This work uses the self-assembly and mineralization of the Tobacco mosaic virus (TMV) to create superhydrophilic (∼9°), superhydrophobic (∼163°), and mixed hydrophilic-hydrophobic (∼70°) surfaces to investigate the effects of surface wettability and heterogeneity on boiling heat transfer performance. Pool boiling results showing CHF and HTC values for nickel-coated TMV, Teflon-coated TMV, mixed nickel + Teflon coated TMV, flat silicon, and flat Teflon are reported. The mixed surfaces demonstrate a CHF enhancement of ∼ 70% compared to flat silicon and ∼140% compared to flat Teflon. The results are in good agreement with the literature and will guide the design of optimized surfaces for further enhancement. This work demonstrates the feasibility of enhancing pool boiling heat transfer using TMV based nanostructured coatings.

Boiling Heat Transfer in a Shallow Fluidized Particulate Bed

1987 ◽  
Vol 109 (1) ◽  
pp. 196-203 ◽  
Author(s):  
Y. K. Chuah ◽  
V. P. Carey
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Thin Layers ◽  
Surface Nucleation ◽  
Particle Layer ◽  
Wall Superheat ◽  
Flux Level

Experimental data are presented which indicate the effects of a thin layer of unconfined particles on saturated pool boiling heat transfer from a horizontal surface. Results are presented for two different types of particles: (1) 0.275 and 0.475-mm-dia glass spheres which have low density and thermal conductivity, and (2) 0.100 and 0.200-mm-dia copper spheres which have high density and thermal conductivity. These two particle types are the extremes of particles found as corrosion products or contaminants in boiling systems. To ensure that the surface nucleation characteristics were well defined, polished chrome surfaces with a finite number of artificial nucleation sites were used. Experimental results are reported for heat fluxes between 20 kW/m2 and 100kW/m2 using water at 1 atm as a coolant. For both particle types, vapor was observed to move upward through chimneys in the particle layer, tending to fluidize the layer. Compared with ordinary pool boiling at the same surface heat flux level, the experiments indicate that addition of light, low-conductivity particles significantly increases the wall superheat, whereas addition of heavier, high-conductivity particles decreases wall superheat. Heat transfer coefficients measured in the experiments with a layer of copper particles were found to be as much as a factor of two larger than those measured for ordinary pool boiling at the same heat flux level. The results further indicate that at least for thin layers, the boiling curve is insensitive to layer thickness. These results are shown to be consistent with the expected effects of the particles on nucleation, fluid motion, and effective conductivity in the pool at or near the surface. The effect of surface nucleation site density on heat transfer with a particle layer present is also discussed.

Transient Characteristics of Pool Boiling Heat Transfer in Nanofluids

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Sang M. Kwark ◽  
Ratan Kumar ◽  
Gilberto Moreno ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Base Fluid ◽  
Pool Boiling ◽  
Thermal Characteristics ◽  
Boiling Curve ◽  
Heater Surface ◽  
Cooling Fluid ◽  
Transient Characteristics ◽  
Conductivity Enhancement

This study shows the transient characteristics of the pool boiling curves using nanofluid as the boiling fluid. This time-dependency is in sharp contrast to a unique steady-state pool boiling curve that is typically obtained for a pure fluid. Past nanofluids research has provided interesting information about the thermal characteristics for this potentially promising cooling fluid. Results from these studies have shown some extraordinary critical heat flux (CHF) values and thermal conductivity enhancement that is yet to be explained by existing theories and correlations. The nature of the pool boiling curve for a nanofluid is dependent on the nanoparticle concentration in the base fluid. Higher concentration nanofluids show a perceptible degradation in the boiling heat transfer (BHT) coefficient but have exhibited an enhanced CHF value (up to ∼80%) when compared to the CHF value of the base fluid (water). Another key observation has been in the significant deposition of nanoparticles on the heater surface. This fouling of the heater surface by nanoparticles is widely viewed as a main contributor that modifies the pool boiling curve of the base liquid. The deposition of the nanoparticles on the heater surface is dynamic and this in turn makes the nanofluid pool boiling curve exhibit transient characteristics.

Effect of Particle Morphology on Pool Boiling From Surfaces Coated With Sintered Particles

2015 ◽  
Author(s):  
Suchismita Sarangi ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Particle Morphology ◽  
Wall Superheat

Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings with different constituent particle sizes and total layer thicknesses have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux during pool boiling. However, the role of the particle morphology on pool boiling has not been explicitly investigated. Since the morphology of the particles affects the pore shape, permeability, surface roughness, effective conductivity and diffusivity of the sintered coating, it will impact the heat transfer coefficient and critical heat flux during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular, dendritic and spherical morphologies. In order to isolate the effect of particle morphology, particles with the same effective diameter (90–106 μm) are sintered under controlled conditions that yield the same porosity (∼60%) and coating thickness (∼6 particle diameters) for all samples tested. The effects of particle morphology on the incipient wall superheat, nucleate boiling heat transfer coefficient, and critical heat flux are analyzed. The morphology of the pore structure in the coating formed by sintering is observed with SEM images; bubble nucleation and departure characteristics affecting the heat transfer performance of the coatings are qualitatively assessed with the aid of high-speed flow visualizations to corroborate the trends observed in the boiling curves. The irregular particles are observed to show the highest heat transfer coefficient, followed by dendritic and then spherical particles. The critical heat flux is found to be independent of the particle morphology.

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