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.

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 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.

Effect of Heat Flux on Pool Boiling Heat Transfer Enhancement (Numerical Investigation Approach)

2020 ◽  
Author(s):  
T. S. Mogaji ◽  
O. A. Sogbesan ◽  
Tien-Chien Jen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Numerical Investigation ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Enhancement

Abstract This study presents numerical investigation results of heat flux effect on pool boiling heat transfer enhancement during nucleate boiling heat transfer of water. The simulation was performed for five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum using ANSYS simulation software at 1 atmospheric pressure. The samples were heated in a domain developed for bubble growth during nucleate boiling process under the same operational condition of applied heat flux ranged from 100 to 1000 kW/m2 and their corresponding heat transfer coefficient was obtained numerically. Obtained experimental data of other authors from the open literature result is in close agreement with the simulated data, thus confirming the validity of the CFD simulation method used in this study. It is found that heat transfer coefficient increases with increasing heat flux. The results revealed that in comparison to other materials tested, better heat transfer performance up to 38.5% and 7.11% is observed for aluminum and brass at lower superheated temperature difference conditions of 6.96K and 14.01K respectively. This behavior indicates better bubble development and detachment capability of these heating surface materials and could be used in improving the performance of thermal devices toward producing compact and miniaturized equipment.

Analysis of the Polarity Influence on Nucleate Pool Boiling Under a DC Electric Field

1999 ◽  
Vol 121 (4) ◽  
pp. 856-864 ◽  
Author(s):  
M. C. Zaghdoudi ◽  
M. Lallemand
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Enhancement ◽  
Field Polarity ◽  
The One

An experimental study of the action of an intense electric field on the pool boiling of n-pentane is presented. By the application of a 25 kV/cm electric field strength, a threefold heat transfer enhancement is obtained. The effect of the electric field polarity has been researched. In nucleate boiling, the negative polarity allows to obtain a heat transfer enhancement, which is better than the one obtained in positive polarity. However, in natural convection and near the critical heat flux, the polarity of the electric field has a low influence on the heat transfer. The interpretations of the observed results are based on the action of the electric field on the boiling phenomenon and more particularly on the analysis of the electric field distribution between the electrodes. The influence of the space charge injection and the effect of the temperature on the electric field distribution have been investigated. The results obtained in the two cases of polarity are discussed in terms of effects of electrical and thermal phenomena on the distribution of the electric field between the electrodes.

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%.

Sign in / Sign up

Export Citation Format

Share Document