Pool Boiling Studies on Nano-Textured Surfaces: Impact of High Subcooling

2007 ◽  
Author(s):  
Vijaykumar Sathyamurthi ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Silicon Wafer ◽  
Pool Boiling ◽  
Chemical Vapor ◽  
Type A ◽  
Nucleate Boiling ◽  
Test Fluid ◽  
Type B ◽  
Textured Surfaces ◽  
Carbon Nano Tubes

The effect of surface nano-texturing using Multi-Walled Carbon Nano-Tubes (MWCNT) on pool boiling heat transfer is studied under high subcooling (∼30 °C). Three different substrates were used in this study: a bare silicon wafer (450 μm thick), and two similar silicon wafers coated with 9 μm (Type-A) and 25 μm tall (Type-B) MWCNT. The MWCNT are deposited by Chemical Vapor Deposition (CVD), have diameters ranging between 8–16 nanometers and a randomized center to center pitch ranging between 24–45 nm. PF-5060, a fluorocarbon is used as the test fluid. In the nucleate boiling regime the surface coated with Type-A MWCNT shows a significant enhancement in heat transfer in comparison to the bare silicon wafer and Type-B MWCNT coated wafer. Type-B MWCNT on the silicon substrate results in only a slightly higher heat transfer rate as compared to the bare silicon wafer. The presence of MWCNT seems to disrupt the formation of a stable vapor film thus delaying the onset of film boiling. Based on the experimental results, the following transport mechanisms have been identified for the observed enhancement of pool boiling heat flux on the MWCNT: the enhanced surface area (nano-fin effect), enhanced nucleation, disruption of the “microlayer” region in nucleate boiling, and the high thermal conductivity of MWCNT.

Subcooled Pool Boiling Studies on Nano-Textured Surfaces

2007 ◽  
Author(s):  
Vijaykumar Sathyamurthi ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Pool Boiling ◽  
Type A ◽  
Nucleate Boiling ◽  
Test Fluid ◽  
Type B ◽  
Textured Surfaces ◽  
Transfer Enhancement ◽  
Boiling Regime

Heat transfer in subcooled pool boiling on nano-textured surfaces is reported in this study. Silicon wafers coated with Multiwalled Carbon Nanotubes (MWCNT) forests 9 microns (Type-A), and 25 microns (Type-B) in height and 8–15 nm in diameter with a randomized pitch of 16–30 nm, form the test surfaces. The test fluid is a fluoroinert (PF-5060, Manufacturer: 3M Co.) with a boiling point of 56°C. The test rig is of the constant heat flux type. Heat transfer enhancement of approximately 1.3 to 32% is observed in the nucleate boiling regime for Type-A at subcooling levels of 20°C. Type-B CNT shows an enhancement of about 13–30% in the nucleate boiling regime for 20°C subcooling. Digital images acquired during the tests show increased nucleation occurring on surfaces coated with MWCNT. Potential factors that could explain the observed heat transfer enhancement are: the enhanced surface area (nano-fin effect), disruption of the “microlayer” region in nucleate boiling, an increase in the size of cold-spots and the high thermal conductivity of MWCNT.

Subcooled Pool Boiling Experiments on Horizontal Heaters Coated With Carbon Nanotubes

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
V. Sathyamurthi ◽  
H-S. Ahn ◽  
D. Banerjee ◽  
S. C. Lau
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Heat Flux ◽  
Pool Boiling ◽  
Type A ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Test Fluid ◽  
Type B ◽  
Coated Surfaces

Pool boiling experiments were conducted with three horizontal, flat, silicon surfaces, two of which were coated with vertically aligned multiwalled carbon nanotubes (MWCNTs). The two wafers were coated with MWCNT of two different thicknesses: 9 μm (Type-A) and 25 μm (Type-B). Experiments were conducted for the nucleate boiling and film boiling regimes for saturated and subcooled conditions with liquid subcooling of 0–30°C using a dielectric fluorocarbon liquid (PF-5060) as test fluid. The pool boiling heat flux data obtained from the bare silicon test surface were used as a base line for all heat transfer comparisons. Type-B MWCNT coatings enhanced the critical heat flux (CHF) in saturated nucleate boiling by 58%. The heat flux at the Leidenfrost point was enhanced by a maximum of ∼150% (i.e., 2.5 times) at 10°C subcooling. Type-A MWCNT enhanced the CHF in nucleate boiling by as much as 62%. Both Type-A MWCNT and bare silicon test surfaces showed similar heat transfer rates (within the bounds of experimental uncertainty) in film boiling. The Leidenfrost points on the boiling curve for Type-A MWCNT occurred at higher wall superheats. The percentage enhancements in the value of heat flux at the CHF condition decreased with an increase in liquid subcooling. However the enhancement in heat flux at the Leidenfrost points for the nanotube coated surfaces increased with liquid subcooling. Significantly higher bubble nucleation rates were observed for both nanotube coated surfaces.

Pool Boiling Heat Transfer with Nanotube Arrays Surface on Titanium

2012 ◽  
Vol 550-553 ◽  
pp. 2913-2916 ◽  
Author(s):  
Jin Liang Tao ◽  
Xin Liang Wang ◽  
Pei Hua Shi ◽  
Xiao Ping Shi
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Test Fluid ◽  
Porous Coating ◽  
Pool Boiling Heat Transfer ◽  
Nucleate Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

In this paper, a new porous coating was formed directly on the surface of titanium metal via anodic oxidation. And by the SEM, the morphology of the coating, which is composed of well-ordered perpendicular nanotubes, was characterized. Moreover, taking deionized water as the test fluid, a visualization study of the coating on its pool boiling heat transfer performance was made. The results demonstrated that compared with the smooth surface, the nucleate boiling heat transfer coefficient can increase 3 times while the nucleate boiling super heat was reduced 30%.

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.

Inverse Determination of the Local Heat Transfer Coefficients for Nucleate Boiling on a Horizontal Cylinder

2003 ◽  
Vol 125 (6) ◽  
pp. 1087-1095 ◽  
Author(s):  
H. Louahlia-Gualous ◽  
P. K. Panday ◽  
E. A. Artioukhine
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pool Boiling ◽  
Gradient Methods ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Iterative Regularization

This article treats the local heat transfer for nucleate pool boiling around the cylinder using the inverse heat conduction analysis. The physical model considers a half section of a cylinder with unknown surface temperature and heat flux density. The iterative regularization and the conjugate gradient methods are used for solving the inverse analysis. The local Nusselt number profiles for nucleate pool boiling are presented and analyzed for different electric heat. The mean Nusselt number estimated by IHCP is closed with the measured values. The results of IHCP are compared to those of Cornewell and Houston (1994), Stephan and Abdelsalam (1980) and Memory et al. (1995). The influence of the error of the measured temperatures and the error in placement of the thermocouples are studied.

Pool Boiling Heat Transfer From Plain and Microporous, Square Pin Finned Surfaces in Saturated FC-72

1999 ◽  
Author(s):  
K. N. Rainey ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Large Scale ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Small Scale ◽  
Surface Microstructure ◽  
Transfer Coefficients ◽  
Microporous Coating ◽  
Nucleate Boiling Heat Transfer

Abstract The present research is an experimental study of “double enhancement” behavior in pool boiling from heater surfaces simulating microelectronic devices immersed in saturated FC-72 at atmospheric pressure. The term “double enhancement” refers to the combination of two different enhancement techniques: a large-scale area enhancement (square pin fin array) and a small-scale surface enhancement (microporous coating). Fin lengths were varied from 0 (flat surface) to 8 mm. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (fins are vertical) are investigated. Results showed significant increases in nucleate boiling heat transfer coefficients with the application of the microporous coating to the heater surfaces. CHF was found to be relatively insensitive to surface microstructure for the finned surfaces except in the case of the surface with 8 mm long fins. The nucleate boiling and CHF behavior has been found to be the result of multiple, counteracting mechanisms: surface area enhancement, fin efficiency, surface microstructure (active nucleation site density), vapor bubble departure resistance, and re-wetting liquid flow resistance.

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.

Comparison of Droplet Evaporation and Nucleate Boiling Mechanisms on Nanoporous Superhydrophilic Surfaces

2019 ◽  
Author(s):  
Samuel Cabrera ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Droplet Evaporation ◽  
Transfer Performance ◽  
Nanostructured Surface ◽  
Nanostructured Surfaces ◽  
Droplet Vaporization

Abstract Recent studies have indicated that at slightly superheated surface temperatures, droplet evaporation on a nanoporous superhydrophilic surface exhibits onset of nucleation and nucleate boiling effects similar to pool boiling processes. This paper discusses water droplet evaporation experiments and pool boiling experiments conducted on nanostructured surfaces of a 45° downward facing pyramid copper and aluminum substrate. The nanostructured surfaces were used to conduct both droplet evaporation experiments and pool boiling experiments and thus allow direct comparison of the underlying heat transfer performance and mechanisms for these two different processes. The four surfaces tested were the following: bare copper surface, nanostructured surface on copper, bare aluminum surface, and nanostructured surface on aluminum. Mean heat flux values at varying superheats were obtained through temperature and time measurements. To better understand the heat performance of each surface, the wetting and wicking characteristics of each surface were also tested. Experimental results indicate that many of the mechanisms associated with pool boiling may also play a role in droplet vaporization, and their presence can produce levels of heat transfer performance comparable to, or even higher than, that observed in pool boiling at a comparable wall superheat. The results demonstrate that the nanostructured surface affects onset of nucleate boiling and maximum heat flux in both droplet vaporization and nucleate boiling on these surfaces. The implications of these results for strategies to enhance spray cooling and pool boiling are also discussed.

Experimental Study of Surfactant Effects on Pool Boiling Heat Transfer

1990 ◽  
Vol 112 (1) ◽  
pp. 207-212 ◽  
Author(s):  
Ying Liang Tzan ◽  
Yu Min Yang
Keyword(s):  
Heat Transfer ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Sodium Lauryl Sulfate ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Additive Concentration ◽  
Lauryl Sulfate ◽  
Diffusion Effect ◽  
Nucleate Boiling Heat Transfer

In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.

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