Subcooled Boiling of PF-5060 Dielectric Liquid on Microporous Surfaces

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Amir F. Ali
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Average Rate ◽  
Nucleate Boiling ◽  
Dielectric Liquid ◽  
Subcooled Boiling ◽  
Surface Layers ◽  
Electrochemically Deposited ◽  
Cu Substrates ◽  
Surface Saturation

Presented are the results of experiments that investigated nucleate boiling of PF-5060 on microporous Cu surface layers at saturation and 10 K, 20 K, and 30 K subcooling. The three microporous layers, electrochemically deposited on 10×10 mm2 Cu substrates and investigated herein, are ∼139 μm, 171 μm, and 220 μm thick. The critical heat flux increases linearly with increased subcooling, ΔTsub, at an average rate of 4.5%/K. For the 171 μm thick, Cu microporous surface, saturation boiling CHF of 27.8 W/cm2 increases to 63.25 W/cm2 at ΔTsub=30 K, while the saturation hMNB of 13.5 W/cm2 K decreases slightly to 12.7 W/cm2 K at ΔTsub=30 K. The values of the surface superheat, ΔTsat, at hMNB and CHF increase from 2.0 K and 2.16 K at saturation to 4.2 and 6.42 K at 30 K subcooling.

Saturation and Subcooled Boiling on Copper Nano-Dendrites Surfaces

2010 ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Amir F. Ali
Keyword(s):  
Nucleate Boiling ◽  
Subcooled Boiling ◽  
Structured Surfaces ◽  
Electrochemically Deposited ◽  
Cu Substrates

Nucleate boiling of PF-5060 liquid on nano-dendrites surfaces is investigated at saturation and ΔTsub = 10, 20 and 30 K. The electrochemically deposited surfaces layers on 10 × 10 mm Cu substrates are ∼ 139, 171 and 220 μm thick. CHF and hMNB are significantly higher and occur at lower ΔTsat than has been reported on plane, macro-, micro- and nano-structured surfaces. CHF increases linearly 4.5%/K, while hMNB, occurring at end of the fully developed nucleate boiling region, decreases and corresponding ΔTsat increases with increased subcooling. For the 171 μm-thick surface: CHFsat of 27.8 W/cm2 increases to 63.25 W/cm2 at ΔTsub = 30 K, while saturation hMNB of 13.5 W/cm2.K decreases to 12.7 W/cm2.K at 30 K subcooling. ΔTsat at hMNB and CHF increases from 2.0 K and 2.16 K at saturation to 4.2 and 6.42 K at 30 K subcooling.

Saturation Boiling Critical Heat Flux of PF-5060 Dielectric Liquid on Microporous Copper Surfaces

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Amir F. Ali
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Inclination Angle ◽  
Nucleate Boiling ◽  
Dielectric Liquid ◽  
Copper Surfaces ◽  
Inclination Angles ◽  
Surface Inclination ◽  
Effect Of Surface ◽  
Good Agreement

Pool boiling experiments are performed to investigate potential enhancement of critical heat flux (CHF) of PF-5060 dielectric liquid on microporous copper (MPC) surfaces and the effect of surface inclination angle. The morphology and microstructure of the MPC surfaces change with thickness. The experiments tested seven 10 × 10 mm MPC surfaces with thicknesses from 80 to 230 μm at inclination angles of 0 deg (upward facing), 60 deg, 90 deg (vertical), 120 deg, 150 deg, 160 deg, 170 deg, and 180 deg (downward facing). CHF increases as the thickness of the surface increases and/or the inclination angle decreases. The values in the upward facing orientation are 36–59% higher than on smooth Cu. For all surfaces, CHF values in the downward facing orientation are approximately 28% of those in the upward facing orientation. A developed CHF correlation, similar to those of Zuber and Kutateladze, accounts for the effects of inclination angle and thickness of the MPC surfaces. It is in good agreement with experimental data to within ±8%. Still photographs of nucleate boiling on the MPC surfaces at different inclinations help the interpretation of the experimental results.

Enhancement of Saturation Boiling of PF-5060 on Microporous Copper Dendrite Surfaces

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Amir F. Ali
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Central Processor ◽  
Surface Layers ◽  
Reliable Operation ◽  
Electrochemically Deposited ◽  
Nucleate Boiling Heat Transfer ◽  
Cu Substrates ◽  
Boiling Heat Transfer Coefficient

Experiments are performed to investigate saturation boiling of degassed PF-5060 dielectric liquid on microporous copper dendrite surface layers deposited on 10×10 mm2 Cu substrates. The electrochemically deposited surface layers are of different thicknesses (145.6 μm, 46.3 μm, and 33.1 μm). The thickest layer gives the best results: the saturation CHF of 25.27 W/cm2 occurs at a surface superheat of only 2.9 K and the maximum nucleate boiling heat transfer coefficient, hMNB, near the end of the fully developed nucleate boiling region, is 8.76 W/cm2 K. In addition, nucleate boiling ensues at a surface temperature slightly above saturation (<0.5 K), with no temperature excursion. The temperature excursions before initiating boiling on the 46.3 μm and 33.1 μm thick Cu nanodendrite surface layers are small (3.7 K and 6 K), corresponding to surface temperatures of ∼55.1°C and 57.4°C, respectively. These temperatures are much lower than recommended (85°C) for reliable operation of most silicon electronics and central processor units.

Saturation Boiling of PF-5060 Dielectric Liquids on Micro-Porous Copper Dendrites Surfaces

2009 ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Amir F. Ali
Keyword(s):  
Average Pore Size ◽  
Nucleate Boiling ◽  
Surface Layers ◽  
Average Pore ◽  
Porous Copper ◽  
Volume Porosity ◽  
Electrochemically Deposited ◽  
Nucleate Boiling Heat Transfer ◽  
Cu Substrates ◽  
Boiling Heat Transfer Coefficient

Experiments are performed to investigate saturation boiling of degassed PF-5060 dielectric liquid on micro-porous copper dendrites surface layers deposited on 10 × 10 mm Cu substrates. The electrochemically deposited surface layers are of different thickness (50, 70, and 220 μm), average pore size (15, 30 and 80 μm) and volume porosity (96, 94.3, and 93.6%). The thickest layer, deposited using 3.0 A/cm2 for 25s, gives the best results: the saturation CHF of 25.27 W/cm2 occurs at a surface superheat of only 2.9 K and the maximum nucleate boiling heat transfer coefficient, hMNB, near the end of the fully developed nucleate boiling region is 8.76 W/cm2.K. In addition, nucleate boiling begins at surface temperature slightly above saturation (&lt; 0.5 K) with no temperature excursion. The temperature excursions before initiating boiling on the 70 μm and 50 μm thick Cu nano-dendrites surface layers are small (3.7 K and 6 K), corresponding to surface temperatures of ∼ 55.1 °C and 57.4 °C, respectively. These temperatures are much lower than recommended (85 °C) for reliable operation of most silicon electronics and CPUs.

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.

Study on Subcooled-Forced Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture

1999 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Manabu Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Liquid Layer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Superheated Liquid ◽  
Flow Boiling Heat Transfer

Abstract The effect of solid particle introduction on subcooled-forced flow boiling heat transfer and a critical heat flux was examined experimentally. In the experiment, glass beads of 0.6 mm diameter were mixed in subcooled water. Experiments were conducted in a range of the subcooling of 40 K, a velocity of 0.17–6.7 m/s, a volumetric particle ratio of 0–17%. When particles were introduced, the growth of a superheated liquid layer near a heat trasnsfer surface seemed to be suppressed and the onset of nucleate boiling was delayed. The particles promoted the condensation of bubbles on the heat transfer surface, which shifted the initiation of a net vapor generation to a high heat flux region. Boiling heat trasnfer was augmented by the particle introduction. The suppression of the growth of the superheated liquid layer and the promotion of bubble condensation and dissipation by the particles seemed to contribute that heat transfer augmentation. The wall superheat at the critical heat flux was elevated by the particle introduction and the critical heat flux itself was also enhanced. However, the degree of the critical heat flux improvement was not drastic.

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