Effects of different concentrations of Al2O3 nanoparticles and base fluid types on pool boiling heat transfer in copper foam with bottom condensed reflux

Experimental investigations were performed to understand the fundamentals of pool boiling heat transfer in nanofluids. The pool boiling curves of water and nanofluids at the pressure of 2.89 psia (Tsat = 60°C) were obtained and compared using a flat square (1 × 1 cm) heater. The tested nanofluids contain aluminum oxide (Al2O3) nanoparticles dispersed in distilled-deionized water. The concentrations of nanofluids range from 0 gram/liter to 0.05 gram/liter. The results show that the boiling heat transfer coefficient is independent of concentrations of nanofluids. Remarkable enhancement (~200%) of CHF was achieved for low concentrations of nanofluids (above 0.01 gram/liter). The boiling parameters, such as bubble size and departure frequency, were measured and analyzed using a 390-μm-diameter platinum wire. The measurement reveals that the size of bubbles increases and the bubble frequency decreases significantly in saturated nanofluids as compared to those in pure saturated water. The surface orientation effects on boiling heat transfer in nanofluids are also investigated. The results show that CHF enhancement of nanofluids is more effective as the boiling surface faces downward.

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Characterization and Pool Boiling Heat Transfer Studies of Nanofluids

Journal of Heat Transfer ◽

10.1115/1.3111260 ◽

2009 ◽

Vol 131 (8) ◽

Cited By ~ 36

Author(s):

R. Kathiravan ◽

Ravi Kumar ◽

Akhilesh Gupta ◽

Ramesh Chandra

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Copper Nanoparticles ◽

Boiling Heat Transfer ◽

Base Fluid ◽

Pool Boiling ◽

Outer Diameter ◽

Distilled Water ◽

Pool Boiling Heat Transfer

Copper nanoparticles with an average size of 10 nm are prepared by the sputtering method and are characterized using different techniques, viz., X-ray diffraction spectrum, atomic force microscopy, and transmission electron microscopy. The pool boiling heat transfer characteristics of 0.25%, 0.5%, and 1.0% by weight concentrations of copper nanoparticles dispersed in distilled water and in distilled water with 9.0 wt % of sodium dodecyl sulfate (SDS) are studied. Also the data for the boiling of pure distilled water and water with SDS are acquired. The above data are obtained using commercial seamless stainless steel tube heater with an outer diameter of 9.0 mm and an average surface roughness of 1.09 μm. The experimental results concluded that (i) critical heat flux (CHF) obtained in water with surfactant nanofluids gives nearly one-third of the CHF obtained by copper-water nanofluids, (ii) pool boiling heat transfer coefficient decreases with the increase in the concentration of nanoparticles in water base fluids, and (iii) heat transfer coefficient increases with the addition of 9.0% surfactant in water. Further addition of nanoparticles in this mixture reduces the heat transfer coefficient. (iv) CHF increases nearly 50% with an increase in concentration of nanoparticles in the water as base fluid and nearly 60% in the water with surfactant as base fluid.

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Pool Boiling Amelioration by Aqueous Dispersion of Silica Nanoparticles

Nanomaterials ◽

10.3390/nano11082138 ◽

2021 ◽

Vol 11 (8) ◽

pp. 2138

Author(s):

Sayantan Mukherjee ◽

Naser Ali ◽

Nawaf F. Aljuwayhel ◽

Purna C. Mishra ◽

Swarnendu Sen ◽

...

Keyword(s):

Heat Transfer ◽

Contact Angle ◽

Boiling Heat Transfer ◽

Base Fluid ◽

Bubble Diameter ◽

Pool Boiling ◽

Nucleate Boiling ◽

Surface Wettability ◽

Bulk Fluid ◽

Pool Boiling Heat Transfer

Non-metallic oxide nanofluids have recently attracted interest in pool boiling heat transfer (PBHT) studies. Research work on carbon and silica-based nanofluids is now being reported frequently by scholars. The majority of these research studies showed improvement in PBHT performance. The present study reports an investigation on the PBHT characteristics and performance of water-based silica nanofluids in the nucleate boiling region. Sonication-aided stable silica nanofluids with 0.0001, 0.001, 0.01, and 0.1 particle concentrations were prepared. The stability of nanofluids was detected and confirmed via visible light absorbance and zeta potential analyses. The PBHT performance of nanofluids was examined in a customized boiling pool with a flat heating surface. The boiling characteristics, pool boiling heat transfer coefficient (PBHTC), and critical heat flux (CHF) were analyzed. The effects of surface wettability, contact angle, and surface roughness on heat transfer performance were investigated. Bubble diameter and bubble departure frequency were estimated using experimental results. PBHTC and CHF of water have shown an increase due to the nanoparticle inclusion, where they have reached a maximum improvement of ≈1.33 times over that of the base fluid. The surface wettability of nanofluids was also enhanced due to a decrease in boiling surface contact angle from 74.1° to 48.5°. The roughness of the boiling surface was reduced up to 1.5 times compared to the base fluid, which was due to the nanoparticle deposition on the boiling surface. Such deposition reduces the active nucleation sites and increases the thermal resistance between the boiling surface and bulk fluid layer. The presence of the dispersed nanoparticles caused a lower bubble departure frequency by 2.17% and an increase in bubble diameter by 4.48%, which vigorously affects the pool boiling performance.

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