scholarly journals Effect of Uniformly and Nonuniformly Coated Al2O3 Nanoparticles over Glass Tube Heater on Pool Boiling

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Nitin Doifode ◽  
Sameer Gajghate ◽  
Abdul Najim ◽  
Anil Acharya ◽  
Ashok Pise
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Pool Boiling ◽  
Glass Tube ◽  
Al2o3 Nanoparticles ◽  
High Speed Camera ◽  
Coated Nanoparticles ◽  
Nucleation Sites ◽  
Coated Surface

Effect of uniformly and nonuniformly coated Al2O3 nanoparticles over plain glass tube heater on pool boiling heat transfer was studied experimentally. A borosilicate glass tube coated with Al2O3 nanoparticle was used as test heater. The boiling behaviour was studied by using high speed camera. Result obtained for pool boiling shows enhancement in heat transfer for nanoparticle coated surface heater and compared with plain glass tube heater. Also heat transfer coefficient for nonuniformly coated nanoparticles was studied and compared with uniformly coated and plain glass tube. Coating effect of nanoparticles over glass tube increases its surface roughness and thereby creates more nucleation sites.

Experimental Study of Enhanced Pool Boiling Heat Transfer Using Graphite Foam Inserts

2011 ◽  
Vol 312-315 ◽  
pp. 352-357 ◽  
Author(s):  
K.C. Leong ◽  
L.W. Jin ◽  
I. Pranoto ◽  
H.Y Li ◽  
J.C. Chai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Bubble Formation ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Copper Block ◽  
Different Types ◽  
Graphite Foam

This paper presents the results of an experimental study of heat transfer in a pool boiling evaporator with porous insert. Different types of graphite foams were tested with the phase change coolant FC-72 in a designed thermosyphon. Comparisons between the graphite foams and a solid copper block show that the porous structure enhances pool boiling significantly. The boiling thermal resistance of the tested graphite foams was found to be about 2 times lower than that of the copper block. The bubble formation recorded by a high speed camera indicates that boiling from a graphite foam is more vigorous than from a copper block. The designed thermosyphon with graphite foam insert can remove heat fluxes of up to 112 W/cm2 with the maximum heater temperature maintained below 100°C.

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.

Pool Boiling Heat Transfer of Alumina-Water, Zinc Oxide-Water and Alumina-Water+Ethylene Glycol Nanofluids

2005 ◽  
Author(s):  
Gilbert Moreno ◽  
Steven J. Oldenburg ◽  
Seung M. You ◽  
Joo H. Kim
Keyword(s):  
Heat Transfer ◽  
Zinc Oxide ◽  
Ethylene Glycol ◽  
Aluminum Oxide ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Average Particle ◽  
Al2o3 Nanoparticles ◽  
Significant Difference

This investigation conducts pool boiling experiments under saturated conditions (Tsat = 60 °C) using nanofluids as the coolants. Three different nanofluids were tested including zinc oxide (ZnO)-water, aluminum oxide (Al2O3)-water and aluminum oxide (Al2O3)-water+ethylene glycol (ethylene glycol solution). At saturation (Tsat = 60°C), the pool boiling performance of the two pure water based nanofluids were similar. The maximum CHF enhancement as compared to the predicted Zuber’s [1] CHF evaluated at an equivalent saturation temperature is ∼180% for Al2O3-water nanofluids and ∼240% for ZnO-water nanofluids. In both cases, no degradation in the boiling heat transfer rate was observed for lower nanoparticle concentrations. However, higher nanoparticle concentrations demonstrate nucleate boiling heat transfer degradation at high heat fluxes. The dispersion of Al2O3 nanoparticles in various ethylene glycol solutions is also found to enhance CHF by as much as ∼130%. A significant difference in the diameter of individual grains/particles (27 ± 16.3 nm) and the volume weighted average diameter of particles in solution (155 ± 80 nm) indicates that the Al2O3-water nanofluids consist primarily of nanoparticle agglomerates. Gravimetric fractionation of the nanofluid produced nanofluids with particle/particle aggregate average diameters that ranged from 69–346 nm. Over the size range tested, there was no significant CHF dependence on the average particle diameter.

Pool Boiling Heat Transfer in Saturated Nanofluids

2004 ◽  
Author(s):  
J. H. Kim ◽  
K. H. Kim ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Experimental Investigations ◽  
Al2o3 Nanoparticles ◽  
Bubble Frequency ◽  
Pool Boiling Heat Transfer ◽  
Saturated Water ◽  
Low Concentrations ◽  
Boiling Heat Transfer Coefficient

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.

Effect of Al2O3 Nanolubricant on a Turbo-BII R134a Pool Boiling Surface

2012 ◽  
Author(s):  
M. A. Kedzierski
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Al2o3 Nanoparticles ◽  
Surface Wetting ◽  
Mass Fractions ◽  
Heat Transfer Degradation

This paper quantifies the influence of Al2O3 nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a Turbo-BII-HP boiling surface. An Al2O3 nanolubricant (a lubricant containing dispersed nano-size particles) was made by suspending nominally 10 nm diameter Al2O3 particles in a synthetic polyolester to roughly a 1.0% volume fraction. The nanoparticles caused, on average, a 12% degradation in the boiling heat transfer relative to that for R134a/polyolester mixtures without nanoparticles for the three lubricant mass fractions that were tested. The degradation was nearly constant for heat fluxes between 20 kW/m2 and 120 kW/m2. It was speculated that the boiling heat transfer degradation was primarily due to a combination of (1) film boiling in the reentrant cavity rendering the nucleate boiling enhancement mechanism of the nanoparticles ineffective and (2) a reduction in bubble frequency due to the increased surface wetting as caused by the nanoparticles. In addition, these degradation factors might be mitigated with increased nanoparticle loading.

scholarly journals Study of pool boiling heat transfer with FC-72 on open microchannel surfaces

2019 ◽  
Vol 213 ◽  
pp. 02038
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko ◽  
Milena Bedla-Pawlusek ◽  
Łukasz Nowakowski
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Fold Increase ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Nucleation Sites ◽  
Open Microchannel ◽  
Parallel Microchannels

The paper presents investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated FC-72 at atmospheric pressure. Parallel microchannels fabricated by machining were about 0.2 to 0.4 mm wide and 0.2 to 0.5 mm deep. Analyzed surfaces with microchannels allowed to obtain heat transfer coefficients within the range of 6.1 – 9.8 kW/m2K, which in relation to the flat surface gives a 3 – 5 - fold increase in HTC. One of the reasons for the increase in the heat transfer coefficient when increasing the heat flux was the growing number of active nucleation sites at the bottom of microchannels and its side surfaces.

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