Kansas State University
1.
Li, Nanxi.
High-pressure
pool boiling and physical insight of engineered
surfaces.
Degree: PhD, Department of Mechanical and
Nuclear Engineering, 2017, Kansas State University
URL: http://hdl.handle.net/2097/35561 
Boiling is a very effective way of heat transfer due
to the latent heat of vaporization. Large amount of heat can be
removed as bubbles form and leave the heated surface. Boiling heat
transfer has lots of applications both in our daily lives and in
the industry. The performance of boiling can be described with two
important parameters, i.e. the heat transfer coefficient (HTC) and
the critical heat flux (CHF). Enhancing the performance of boiling
will greatly increase the efficiency of thermal systems, decrease
the size of heat exchangers, and improve the safety of thermal
facilities. Boiling heat transfer is an extremely complex process.
After over a century of research, the mechanism for the HTC and CHF
enhancement is still elusive. Previous research has demonstrated
that fluid properties, system pressures, surface properties, and
heater properties etc. have huge impact on the performance of
boiling. Numerous methods, both active and passive, have been
developed to enhance boiling heat transfer. In this work, the
effect of pressure was investigated on a plain copper substrate
from atmospheric pressure to 45 psig. Boiling heat transfer
performance enhancement was then investigated on Teflon© coated
copper surfaces, and graphene oxide coated copper surfaces under
various system pressures. It was found that both HTC and CHF
increases with the system pressure on all three types of surfaces.
Enhancement of HTC on the Teflon© coated copper surface is
contributed by the decrease in wettability. It is also hypothesized
that the enhancement in both HTC and CHF on the graphene oxide
coated surface is due to pinning from micro and nanostructures in
the graphene oxide coating or non-homogeneous wettability.
Condensation and freezing experiments were conducted on engineered
surfaces in order to further characterize the pinning effect of
non-homogeneous wettability and micro/nano structure of the
surface.
Advisors/Committee Members: Amy R. Betz.Subjects/Keywords: Pool
boiling; High
pressure;
Wettability; Engineered
surfaces
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APA (6th Edition):
Li, N. (2017). High-pressure
pool boiling and physical insight of engineered
surfaces. (Doctoral Dissertation). Kansas State University. Retrieved from http://hdl.handle.net/2097/35561
Chicago Manual of Style (16th Edition):
Li, Nanxi. “High-pressure
pool boiling and physical insight of engineered
surfaces.” 2017. Doctoral Dissertation, Kansas State University. Accessed January 24, 2021.
http://hdl.handle.net/2097/35561.
MLA Handbook (7th Edition):
Li, Nanxi. “High-pressure
pool boiling and physical insight of engineered
surfaces.” 2017. Web. 24 Jan 2021.
Vancouver:
Li N. High-pressure
pool boiling and physical insight of engineered
surfaces. [Internet] [Doctoral dissertation]. Kansas State University; 2017. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/2097/35561.
Council of Science Editors:
Li N. High-pressure
pool boiling and physical insight of engineered
surfaces. [Doctoral Dissertation]. Kansas State University; 2017. Available from: http://hdl.handle.net/2097/35561
Kansas State University
2.
Dahariya, Smreeti.
High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces.
Degree: PhD, Department of Mechanical and
Nuclear Engineering, 2020, Kansas State University
URL: http://hdl.handle.net/2097/40311
Boiling has received considerable attention in the
technology advancement of electronics cooling for high-performance
computing applications. Two-phase cooling has an advantage over a
single-phase cooling in the high heat removal rate with a small
thermal gradient due to the latent heat of vaporization. Many
surface modifications have been done in the past including surface
roughness, mixed wettability and, porous wick copper play a crucial
role in the liquid-vapor phase change heat transfer. However, the
mechanisms of high-pressure pool-boiling heat transfer enhancement
due to surface modifications has not been well studied or
understood. The properties of water, such as the latent heat of
vaporization, surface tension, the difference in specific volume of
liquid and vapor, decrease at high-pressure. High-pressure
pool-boiling heat transfer enhancement is studied fundamentally on
various engineered surfaces. The boiling tests are performed at a
maximum pressure of 90 psig (620.5 kPa) and then compared to
results at 0 psig (0 kPa). The results indicate that the pressure
influences the boiling performance through changes in bubble
dynamics. The bubble departure diameter, bubble departure
frequency, and the active nucleation sites change with pressure.
The pool-boiling heat transfer enhancement of a Teflon© coated
surface is also experimentally tested, using water as the working
fluid. The boiling results are compared with a plain surface at two
different pressures, 30 and 45 psig. The maximum heat transfer
enhancement is found at the low heat fluxes. At high heat fluxes, a
negligible effect is observed in HTC. The primary reasons for the
HTC enhancement at low heat fluxes are active nucleation sites at
low wall superheat and bubble departure size. The Teflon© coated
surface promotes nucleation because of the lower surface energy
requirement.
The boiling results are also obtained for wick
surfaces. The wick surfaces are fabricated using a sintering
process. The boiling results are compared with a plain surface. The
reasons for enhancements in the pool-boiling performance are
primarily due to increased bubble generation, higher bubble release
frequency, reduced thermal-hydraulic length modulation, and
enhanced thermal conductivity due to the sintered wick layer. The
analysis suggests that the Rayleigh-critical wavelength decreases
by 4.67 % of varying pressure, which may cause the bubble pinning
between the gaps of sintered particles and avoids the bubble
coalescence. Changes in the pitch distance indicate that a
liquid-vapor phase separation happens at the solid/liquid
interface, which impacts the heat-transfer performance
significantly.
Similarly, the role of the high-pressure over the
wicking layer is further analyzed and studied. It is found that the
critical flow length, λu reduces by three times with 200 μm
particles. The results suggest that the porous wick layer provides
a capillary-assist to liquid flow effect, and delays the surface
dry out. The surface modification and the pressure amplify the
boiling heat…
Advisors/Committee Members: Amy R. Betz.Subjects/Keywords: Critical
Heat Flux; Heat
Transfer Coefficient;
Thermal-Hydraulic;
Rayleigh-Critical Wavelength; Pinning
Mechanism; Capillary
Pressure
Record Details
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Record Details
Similar Records
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dahariya, S. (2020). High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces. (Doctoral Dissertation). Kansas State University. Retrieved from http://hdl.handle.net/2097/40311
Chicago Manual of Style (16th Edition):
Dahariya, Smreeti. “High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces.” 2020. Doctoral Dissertation, Kansas State University. Accessed January 24, 2021.
http://hdl.handle.net/2097/40311.
MLA Handbook (7th Edition):
Dahariya, Smreeti. “High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces.” 2020. Web. 24 Jan 2021.
Vancouver:
Dahariya S. High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces. [Internet] [Doctoral dissertation]. Kansas State University; 2020. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/2097/40311.
Council of Science Editors:
Dahariya S. High-pressure
pool-boiling heat transfer enhancement and mechanism on engineered
surfaces. [Doctoral Dissertation]. Kansas State University; 2020. Available from: http://hdl.handle.net/2097/40311
3.
Van Dyke, Alexander Scott.
Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces.
Degree: MS, Department of Mechanical and
Nuclear Engineering, 2015, Kansas State University
URL: http://hdl.handle.net/2097/19105
The purpose of this research was to test if biphilic
surfaces mitigate frost and ice formation. Frost, which forms when
humid air comes into contact with a surface that is below the dew
point and freezing temperature of water, hinders engineering
systems such as aeronautics, refrigeration systems, and wind
turbines. Most previous research has investigated increasingly
superhydrophobic materials to delay frost formation; however, these
materials are dependent on fluctuating operating conditions and
surface roughness. Therefore, the hypothesis for this research was
that a biphilic surface would slow the frost formation process and
create a less dense frost layer, and water vapor would
preferentially condense on hydrophilic areas, thus controlling
where nucleation initially occurs. Preferential nucleation can
control the size, shape, and location of frost nucleation. To
fabricate biphilic surfaces, a hydrophobic material was coated on a
silicon wafer, and a pattern of hydrophobic material was removed
using photolithography to reveal hydrophilic silicon-oxide. Circles
were patterned at various pitches and diameters. The heat sink was
comprised of two parts: a solid bottom half and a finned upper
half. Half of the heat sink was placed inside a polyethylene base
for insulation. Tests were conducted in quiescent air at room
temperature, 22 °C, and two relative humidities, 30% and 60%.
Substrate temperatures were held constant throughout all tests. All
tests showed a trend that biphilic surfaces suppress freezing
temperature more effectively than plain hydrophilic or hydrophobic
surfaces; however, no difference between pattern orientation or
size was noticed for maximum freezing temperature. However, the
biphilic patterns did affect other aspects such as time to freezing
and volume of water on the surface. These effects are from the
patterns altering the nucleation and coalescence behavior of
condensation.
Advisors/Committee Members: Amy R. Betz.Subjects/Keywords: Frost
formation;
Biphilic;
Nucleation; Phase
change heat transfer; Surface
enhancement; Mechanical Engineering (0548)
…at Kansas State University,
Manhattan, KS, was used to fabricate the mixed surfaces. A… …Kansas State University, where they were made biphilic. The silicon wafers
were placed in a…
Record Details
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Share »
Record Details
Similar Records
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Van Dyke, A. S. (2015). Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces. (Masters Thesis). Kansas State University. Retrieved from http://hdl.handle.net/2097/19105
Chicago Manual of Style (16th Edition):
Van Dyke, Alexander Scott. “Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces.” 2015. Masters Thesis, Kansas State University. Accessed January 24, 2021.
http://hdl.handle.net/2097/19105.
MLA Handbook (7th Edition):
Van Dyke, Alexander Scott. “Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces.” 2015. Web. 24 Jan 2021.
Vancouver:
Van Dyke AS. Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces. [Internet] [Masters thesis]. Kansas State University; 2015. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/2097/19105.
Council of Science Editors:
Van Dyke AS. Frost
nucleation and growth on hydrophilic, hydrophobic, and biphilic
surfaces. [Masters Thesis]. Kansas State University; 2015. Available from: http://hdl.handle.net/2097/19105
Open Access Theses and Dissertations
