EFFECT OF CONFINEMENT AND HEATER SURFACE INCLINATION ON POOL BOILING PERFORMANCE OF PATTERNED WETTABILITY SURFACES

2020 ◽  
Vol 27 (8) ◽  
pp. 711-727
Author(s):  
Ajinkya Sarode ◽  
Rishi Raj ◽  
Atul Bhargav
Keyword(s):  
Pool Boiling ◽  
Heater Surface ◽  
Surface Inclination

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

Pool Boiling of n-Pentane, CFC-113, and Water Under Reduced Gravity: Parabolic Flight Experiments With a Transparent Heater

1995 ◽  
Vol 117 (2) ◽  
pp. 408-417 ◽  
Author(s):  
T. Oka ◽  
Y. Abe ◽  
Y. H. Mori ◽  
A. Nagashima
Keyword(s):  
Heat Transfer ◽  
Parabolic Flight ◽  
Pool Boiling ◽  
Glass Plate ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Rear Side ◽  
Heater Surface ◽  
Reduced Gravity ◽  
Liquid Behavior

A series of pool boiling experiments have been conducted under reduced gravity condition (the order of 10−2 times the terrestrial gravity) available in an aircraft taking parabolic flight. A transparent resistant heater, a transparent indium oxide film plated on a glass plate, was employed so that the vapor/liquid behavior interacting with the heater surface could be observed from the rear side of the heater simultaneously with the side view of vapor bubbles above the heater surface. The experiments were performed for three different fluids—n-pentane, CFC-113, and water—under subcooled conditions. The critical heat fluxes for both n-pentane and CFC-113 under the reduced gravity were lowered to about 40 percent of the corresponding terrestrial values. Although the heat transfer characteristics in a low heat flux nucleate boiling regime for both n-pentane and CFC-113 showed no more than a slight change with the reduction in gravity, a significant heat transfer deterioration was noted with water in the reduced gravity boiling. The observation from the rear side of the heater suggested that this particular difference in the gravity dependency of heat transfer was ascribed to a considerable difference, between the organic fluids and water, in the behavior of attachment to the heater surface of the bubbles grown up, while the behavior of attachment must depend on the surface tension of each fluid and the wettability of the heater surface with the fluid.

Effect of Thermophysical Properties of the Heater Substrate on Critical Heat Flux in Pool Boiling

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Pruthvik A. Raghupathi ◽  
Satish G. Kandlikar
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Temperature Fluctuations ◽  
Operating Conditions ◽  
Force Balance ◽  
Heater Surface ◽  
Monel 400

While the role of the liquid properties, surface morphology, and operating conditions on critical heat flux (CHF) in pool boiling is well investigated, the effect of the properties of the heater material is not well understood. Previous studies indicate that the heater thickness plays an important role on the CHF phenomenon. However, beyond a certain thickness, called the asymptotic thickness, the local temperature fluctuations on the heater surface caused by the periodic bubble ebullition cycle are evened out, and the CHF is not influenced by further increasing the thickness. In the present work, data from literature and pool boiling experiments conducted in this study with seven substrates—aluminum, brass, copper, carbon steel, Monel 400, silver, and silicon—are used to determine the effect of the thermophysical property of the material on CHF for thick heaters that are used in industrial pool boiling applications. The results indicate that the product of density (ρ) and specific heat (cp) represents an important substrate property group that affects the CHF, and that the thermal conductivity is not an important parameter. A well-established force-balance-based CHF model (Kandlikar model) is modified to account for the thermal properties of the substrate. The predicted CHF values are within 15% of the experimental results.

scholarly journals Experimental Observation of the Dynamic Micro- and Macro-Layer During Pool Boiling

2008 ◽  
Author(s):  
Craig Gerardi ◽  
Jacopo Buongiorno ◽  
Lin-Wen Hu ◽  
Thomas McKrell
Keyword(s):  
Thin Films ◽  
Experimental Study ◽  
Experimental Observation ◽  
Bubble Growth ◽  
High Speed ◽  
Pool Boiling ◽  
Experimental Confirmation ◽  
Nucleate Pool Boiling ◽  
Heater Surface

This paper presents the results of an experimental study on nucleate pool boiling. Experiments were performed using vapor-deposited thin films which were electrically heated. High-speed infrared and visible cameras simultaneously observed bubble growth from the heater surface. Possible experimental confirmation of microlayer dynamics is presented.

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.

Surface Deposition of Nanoparticles During Pool Boiling of Nanofluids and Its Effects on CHF Enhancement Using Nanofluids

2007 ◽  
Author(s):  
Hyung Dae Kim ◽  
Moo Hwan Kim
Keyword(s):  
Tio2 Nanoparticles ◽  
Pool Boiling ◽  
Surface Wettability ◽  
Heater Surface ◽  
Surface Deposition ◽  
Nanoparticle Deposition ◽  
Water Based ◽  
Enhanced Surface ◽  
Capillary Wicking ◽  
Horizontal Wire

This paper is concerned about mechanism of outstanding CHF enhancement phenomena using nanofluids, a subject with academically and industrially remarkable interest. Pool boiling experiments using an electrically heated horizontal wire were carried out with various water-based nanofluids containing Ag, Al2O3, SiO2, and TiO2 nanoparticles. The results showed that nanoparticle deposition on the heater surface occurred during pool boiling of nanofluids, and that the effect of nanoparticle porous layer on CHF could explain enough the CHF enhancement of nanofluids. Then the porous surface was characterized using surface wettability and capillary wicking performance, which are the significant properties of boiling surface influencing CHF. Discussion of the results suggested that the outstandingly enhanced CHF performances of nanofluids under the nucleate pool boiling were associated with enhanced surface wettability and liquid suction effect due to capillary wicking on the nanoparticle-deposited surface.

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