Pool boiling characteristics of silica/water nanofluid and variation of heater surface roughness in domain of time

2018 ◽  
Vol 95 ◽  
pp. 98-105 ◽  
Author(s):  
Faezeh Rostamian ◽  
Nasrin Etesami
Keyword(s):  
Surface Roughness ◽  
Pool Boiling ◽  
Heater Surface

Experimental Investigation on Surface Particle Interactions During Pool Boiling of Nanofluids

2011 ◽  
Author(s):  
Harish Ganapathy ◽  
V. Emlin ◽  
Anant Narendra Parikh ◽  
V. Sajith
Keyword(s):  
Surface Roughness ◽  
Interaction Parameter ◽  
Surface Characterization ◽  
Pool Boiling ◽  
Particle Interaction ◽  
Nucleate Boiling ◽  
Optical Measurements ◽  
Sorption Layer ◽  
Surface Particle ◽  
Enhanced Boiling

The pool boiling characteristics of nanofluids is affected by the interaction between the nanoparticles and the heater surface which forms a sorption layer and this layer increases the surface wettability and thereby enhances the CHF. While deteriorated nucleate boiling has been attributed to the decreased activation of cavities due to the increased wettability, it fails to explain the enhanced performance observed by several researchers, which can be explained only by an increase in surface roughness and hence a direct increase in the number of cavities, thereby compensating for the increase in wettability. Attempts to characterize the roughness of heater surfaces have been restricted to magnified visualizations and intrusive probing. No non-intrusive tests have been reported on flat heaters, which are ideal to conduct surface analyses. The present work is aimed at conducting a non-intrusive experimental study to analyse the surface roughness modification due to the sorption layer on flat plate heaters. Experiments have been carried out using electro-stabilized aluminium oxide water based nanofluids of different concentrations with heaters having varying values of surface roughness. The burn-out heat flux was measured and the effect of sedimentation time was studied. The surface-particle interaction parameter (Ra/dp) was varied to capture the phenomena of plugging as well as splitting of nucleation sites. An experiment having a high value of the interaction parameter shows enhanced boiling performance and that with a value close to 1 shows deteriorated performance. Further it was seen that this behaviour is dependent on the particle concentration. Detailed surface characterization has been done using an optical measurements setup and atomic force microscopy. Boiling on nano-coated heaters has been investigated and presented as an effective solution to counter the disadvantageous transient boiling behavior of nanofluids.

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.

A Method for Measuring Contact Angle and the Influence of Surface-Fluid Parameters on the Boiling Heat Transfer Performance

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Alex P. da Cunha ◽  
Taye S. Mogaji ◽  
Reinaldo R. de Souza ◽  
Elaine M. Cardoso
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Contact Angle ◽  
Heat Transfer Performance ◽  
Sessile Drop ◽  
Pool Boiling ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
Experimental Apparatus ◽  
Boiling Process

Abstract An experimental apparatus and a computational routine were developed and implemented in order to obtain the sessile drop images and the contact angle measurement for different fluids and surface conditions. Moreover, experimental results of heat transfer coefficients (HTCs) during pool boiling of de-ionized water (DI water), Al2O3-DI water- and Fe2O3-DI water-based nanofluids are presented in this paper. Based on these results, the effect of surface roughness and nanofluid concentration on the surface wettability, contact angle, and the heat transfer coefficient was analyzed. The experiments were performed on copper heating surfaces with different roughness values (corresponding to a smooth surface or a rough surface). The coated surfaces were produced by the nanofluid pool boiling process at two different volumetric concentrations. All surfaces were subjected to metallographic, wettability and roughness tests. For smooth surfaces, in comparison to DI water, heat transfer enhancement up to 60% is observed for both nanofluids at low concentrations. As the concentration of the nanofluid increases, the surface roughness increases and the contact angle decreases, characterizing a hydrophilic behavior. The analyses indicate that the boiling process of nanofluid leads to the deposition of a coating layer on the surface, which influences the heat transfer performance in two-phase systems.

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.

Sign in / Sign up

Export Citation Format

Share Document