Pool Boiling of R514A, R1224 yd(Z), and R1336mzz(E) on a Reentrant Cavity Surface

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
M. A. Kedzierski ◽  
L. Lin
Keyword(s):  
Heat Flux ◽  
Air Conditioning ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Heat Fluxes ◽  
Single Component ◽  
Cavity Surface ◽  
Average Heat

Abstract This paper quantifies the pool boiling performance of R514A, R1224 yd(Z), and R1336mzz(E) on a flattened, horizontal Turbo-ESP surface for air-conditioning applications for heat fluxes between roughly 10 kWm−2 and 100 kWm−2. R514A, R1224 yd(Z), and R1336mzz(E) are replacements for R123 and R245fa. All of these replacement refrigerants had measured boiling heat fluxes that were larger than that for R123 for most heat fluxes. For example, for heat fluxes between 10 kWm−2 and 80 kWm−2, R514A, R1224 yd(Z), and R1336mzz(E) exhibited average heat fluxes that were 30%, 57%, and 13% larger than that for R123 for a saturation temperature of 277.6 K. For the same comparison done at a saturation temperature of 298.2 K, the average heat flux for R514A was roughly 43% larger than that for R123. A pool boiling model, that was previously developed for pure and mixed refrigerants on the Turbo-ESP surface, was compared to the measured boiling performance. The model predicted the measured superheats of the mixed refrigerants and the single-component refrigerants to within ± 0.7 K and ± 0.45 K, respectively.

Effect of Acoustic Excitation on R134a/Al2O3 Nanolubricant Mixture Boiling on a Reentrant Cavity Surface

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
M. A. Kedzierski ◽  
S. E. Fick
Keyword(s):  
Heat Flux ◽  
Volume Fraction ◽  
Power Level ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Cavity Surface ◽  
Test Surface ◽  
Acoustic Excitation ◽  
Al2o3 Nanoparticles ◽  
Maximum Enhancement

This paper quantifies the influence of acoustic excitation of Al2O3 nanoparticles on the pool-boiling performance of R134a/polyolester mixtures on a commercial (Turbo-BII-HP) boiling surface. A nanolubricant with 10 nm diameter Al2O3 nanoparticles at a 5.1% volume fraction in the base polyolester lubricant was mixed with R134a at a 1% mass fraction. The study showed that high-frequency ultrasound at 1 MHz can improve R134a/nanolubricant boiling on a reentrant cavity surface by as much as 44%. This maximum enhancement occurred for an applied power level to the fluid of approximately 6 W and a heat flux of approximately 6.9 kW/m2. Applied power levels larger and smaller than 6 W resulted in smaller boiling heat transfer enhancements. In total, five different applied power levels were studied: 0 W, 4 W, 6 W, 8 W, and 12 W. The largest and smallest enhancement averaged over the tested heat flux range were approximately 12% and 2% for the applied power levels of 6 W and 4 W, respectively. In situ insonation at 1 MHz resulted in an improved dispersion of the nanolubricant on the test surface. An existing pool-boiling model for refrigerant/nanolubricant mixtures was modified to include the effect of acoustic excitation. For heat fluxes greater than 25 kW m−2, the model was within 4.5% of the measured heat flux ratios for mixtures, and the average agreement between measurements and predictions was approximately 1% for all power levels.

scholarly journals Pool Boiling of Low-Global Warming Potential Replacements for R134a on a Reentrant Cavity Surface

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
M. A. Kedzierski ◽  
L. Lin ◽  
D. Kang
Keyword(s):  
Mass Transfer ◽  
Heat Flux ◽  
Global Warming ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Cavity Surface ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
Viscosity Effects ◽  
Low Global Warming Potential

This paper quantifies the pool boiling performance of R134a, R1234yf, R513A, and R450A on a flattened, horizontal reentrant cavity surface. The study showed that the boiling performance of R134a on the Turbo-ESP exceeded that of the replacement refrigerants for heat fluxes greater than 20 kW m−2. On average, the heat flux for R1234yf and R513A was 16% and 19% less than that for R134a, respectively, for R134a heat fluxes between 20 kW m−2 and 110 kW m−2. The heat flux for R450A was on average 57% less than that of R134a for heat fluxes between 30 kW m−2 and 110 kW m−2. A model was developed to predict both single-component and multicomponent pool boiling of the test refrigerants on the Turbo-ESP surface. The model accounts for viscosity effects on bubble population and uses the Fritz equation to account for increased vapor production with increasing superheat. Both loss of available superheat and mass transfer resistance effects were modeled for the refrigerant mixtures. For most heat fluxes, the model predicted the measured superheat to within ±0.31 K.

The Mechanism of and Stability Criterion for Nucleate Pool Boiling of Sodium

1969 ◽  
Vol 91 (3) ◽  
pp. 315-328 ◽  
Author(s):  
I. Shai ◽  
W. M. Rohsenow
Keyword(s):  
Heat Flux ◽  
Liquid Metals ◽  
Bubble Formation ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Nucleate Pool Boiling ◽  
Thermal Layer ◽  
Minimum Heat ◽  
Bubble Growth And Departure ◽  
Recorded Temperature

Experimental data for sodium boiling on horizontal surfaces containing artificial cavities at heat fluxes of 20,000 to 300,000 Btu/ft2 hr and pressures between 40 to 106 mm Hg were obtained. Observations are made for stable boiling, unstable boiling and “bumping.” Some recorded temperature variations in the solid close to the nucleating cavity are presented. It is suggested that for liquid metals the time for bubble growth and departure is a very small fraction of the total bubble cycle, hence the delay time during which a thermal layer grows is the most significant part of the process. On this basis the transient conduction heat transfer is solved for a periodic process, and the period time is found to be a function of the degree of superheat, the heat flux and the liquid thermal properties. A simplified model for stability of nucleate pool boiling of liquid metals is postulated from which the minimum heat flux for stable boiling can be found as a function of liquid-solid properties, liquid pressure, the degree of superheat, and the cavity radius and depth. At relatively low heat fluxes, convection currents have significant effects on the period time of bubble formation. An empirical correlation is proposed, which takes into account the convection effects, to match the experimental results.

Pool Boiling Using Thin Enhanced Structures Under Top-Confined Conditions

2006 ◽  
Vol 128 (12) ◽  
pp. 1302-1311 ◽  
Author(s):  
Camil-Daniel Ghiu ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Pool Boiling ◽  
Single Layer ◽  
Temperature Limit ◽  
Heat Fluxes ◽  
The Other ◽  
Vapor Flow ◽  
Maximum Heat ◽  
Maximum Heat Flux

An experimental study of pool boiling using enhanced structures under top-confined conditions was conducted with a dielectric fluorocarbon liquid (PF 5060). The single layer enhanced structures studied were fabricated in copper and quartz, had an overall size of 10×10mm2, and were 1mm thick. The parameters investigated in this study were the heat flux (0.8-34W∕cm2) and the top space S(0-13mm). High-speed visualizations were performed to elucidate the liquid/vapor flow in the space above the structure. The enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. On the other hand, the maximum heat flux for a prescribed 85°C surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime.

Nucleate Pool Boiling Heat Transfer of R134a and R134a-PVE Lubricant Mixtures on Smooth and Five Enhanced Tubes

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Wen-Tao Ji ◽  
Ding-Cai Zhang ◽  
Nan Feng ◽  
Jian-Fei Guo ◽  
Mitsuharu Numata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Enhanced Tubes ◽  
Mass Fractions

Pool boiling heat transfer coefficients of R134a with different lubricant mass fractions for one smooth tube and five enhanced tubes were tested at a saturation temperature of 6°C. The lubricant used was polyvinyl ether. The lubrication mass fractions were 0.25%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 7.0%, and 10.0%, respectively. Within the tested heat flux range, from 9000 W/m2 to 90,000 W/m2, the lubricant generally has a different influence on pool boiling heat transfer of these six tubes.

Rewetting Velocity of High-Temperature Vertical-Narrow-Annular Flow Passages Under Counter-Current Flow Condition

2003 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Masanori Tsukudo ◽  
Naoki Sakamoto
Keyword(s):  
Heat Flux ◽  
Annular Flow ◽  
Pool Boiling ◽  
Outer Wall ◽  
Heat Fluxes ◽  
Annular Gap ◽  
Wall Superheat ◽  
Peak Heat Flux ◽  
Inner Diameter ◽  
Counter Current

Quenching of a thin gap annular flow passage by gravitational liquid penetration was examined experimentally by using R-113. The outer wall was made of copper. The inner wall was made of copper or glass. The inner diameter of the outer wall of the annular flow passages was 40 or 41 mm and the annular gap clearance δ was 0.5, 1.0, 2.0 and 5.0 mm. The outer wall was heated initially up to 250 °C and also the inner wall was heated when the copper inner wall was used. The quenching was observed in δ ≥ 1.0 mm. When δ = 0.5 mm, the wall was just gradually cooled down. The relation between the wall superheat and the heat flux during quenching process was similar to the boiling curve of pool boiling. However, the peak heat flux as well as the heat flux in the film and the transition boiling was lower than those in the pool boiling. These heat fluxes became lower as the gap clearance became narrow. The rewetting velocity became slow as the gap clearance became narrow. The rewetting velocity seemed to have a unique relation for the Peclet number Pe = (ρSCSδSU/λS) and the Biot number Bi = hδs/λs ; Pe ∝ Bi which was the same as that of the Yamanouchi correlation. A decrease in the heat flux (the heat transfer coefficient) in the rewetting front region, which corresponds to the peak heat flux, results in a decrease in the rewetting velocity as the gap clearance becomes narrow.

Pool Boiling in Saturated and Subcooled FC-72 Dielectric Fluid From a Porous Graphite Surface

2004 ◽  
Author(s):  
Mohamed S. El-Genk ◽  
Jack L. Parker
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Porous Coating ◽  
Dielectric Fluid ◽  
Subcooled Boiling ◽  
Porous Graphite ◽  
Rate Of Increase ◽  
Boiling Incipience

Experiments are conducted that investigated pool boiling of FC-72 liquid at saturation and 10, 20, and 30 K subcooling on porous graphite and smooth copper surfaces measuring 10 × 10 mm. The nucleate boiling heat flux, Critical Heat Flux (CHF), and surface superheats at boiling incipience are compared. Theses heat fluxes are also compared with those of other investigators for smooth copper and silicon, etched SiO2, surfaces and micro-porous coating. No temperature excursion at boiling incipience on the porous graphite that occurred at a surface superheats of < 1.0 K. Conversely, the temperature excursions of 24.0 K and 12.4–17.8 K are measured at incipient boiling in saturation and subcooled boiling on copper. Nucleate boiling heat fluxes on porous graphite are significantly higher and corresponding surface superheats are much smaller than on copper. CHF on porous graphite (27.3, 39.6, 49.0, and 57.1 W/cm2 in saturation and 10 K, 20 K, and 30 K subcooled boiling, respectively) are 61.5%–207% higher than those on copper (16.9, 19.5, 23.6, and 28.0 W/cm2, respectively). The surface superheats at CHF on the porous graphite of 11.5 K in saturation and 17–20 K in subcooled boiling are significantly lower that those on copper (25 K and 26–28 K, respectively). In addition, the rate of increase of CHF on porous graphite with increased subcooling is ~ 125% higher than that on copper.

Visualization of pool boiling and occurring critical heat flux on coiled wire

2020 ◽  
pp. 095440892094211
Author(s):  
Kianoush DolatiAsl ◽  
Younes Bakhshan ◽  
Ehsan Abedini
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Variable Temperature ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Sudden Increase ◽  
Fluid Temperature ◽  
Liquid Temperature ◽  
The Wire

Pool boiling is used in various industries and play a significant role in heat transfer. So far, multiple studies have been carried out on investigating boiling and applying heat flux on the wire. In the present paper, the boiling of the coiled wire under atmospheric pressure conditions has been investigated. The fluid temperature inside the pool is considered under both constant (equal to saturation temperature) and variable temperature conditions. The value of the ring density in the coiled wire is considered to be variable. Based on the results, changing the pool liquid temperature changes bubble departure diameter and frequency. Also, increasing the density of the coil ring increases the diameter of bubbles. It has been observed that the bubbles are usually formed inside the coil, and after moving to the two ends of the coil, they leave the coil. However, by increasing the amount of heat flux and the pool liquid temperature, the size of bubbles will be larger; therefore, the bubbles must leave the coil from the empty spaces between the rings. By increasing the amount of applied heat flux, the coil was enclosed in a layer of vapor, which results in a decrease in the amount of heat transfer coefficient, and finally, a sudden increase in temperature on the wire will occur, which indicates the critical heat flux. Also, it has been observed that the critical heat flux always arises in the coil region of wire and not in the straight part of the wire.

Peak Pool Boiling Heat-Flux Measurements on Finite Horizontal Flat Plates

1973 ◽  
Vol 95 (4) ◽  
pp. 477-482 ◽  
Author(s):  
J. H. Lienhard ◽  
V. K. Dhir ◽  
D. M. Riherd
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flat Plate ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Hydrodynamic Theory ◽  
Organic Liquids ◽  
Flat Plates ◽  
Peak Heat Flux ◽  
Flux Measurements

Experimental data obtained at both earth-normal and elevated gravity, in a variety of organic liquids and water, are used to verify the hydrodynamic theory for the peak pool boiling heat flux on flat plates. A modification of Zuber’s formula, which gives a 14 percent higher peak heat flux, is verified as long as the flat plate is more than three Taylor wavelengths across. For smaller heaters, the hydrodynamic theory requires a wide variation in heat flux owing to discontinuities in the number of escaping jets. Data for smaller plates bear out this predicted variation with heat fluxes that range between 40 percent and 235 percent of Zuber’s predicted value. Finally, a method is suggested for augmenting the peak heat flux on large heaters, and shown experimentally to be viable.

Investigation of the Dynamics of Nucleate Boiling in Subcooled Falling Liquid Films

2014 ◽  
Vol 9 (2) ◽  
pp. 145-155
Author(s):  
Vladimir Serdyukov ◽  
Anton Surtaev ◽  
Oleg Volodin
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Strong Dependence ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Heat Fluxes ◽  
Nucleation Frequency ◽  
Water Films ◽  
Falling Liquid Films

This paper deals with the features of nucleation dynamics at boiling in falling water films at different subcooling, Reynolds number and heat fluxes. With the use of high-speed infrared and digital video the local parameters of nucleate boiling in falling liquid films such as: bubbles’ diameter before condensation, frequency of nucleation and temperature of onset of bubble appearance were received. Analysis of the experimental data showed that bubbles’ diameter before condensation has strong dependence on initial temperature and increases with the rise of heat flux. The main influence on nucleation frequency has the variation of heat flux density. At the same time the experimental data on nucleation frequency in falling water films are close to the frequency of nucleation at pool boiling. To identify the main features the comparison of received data on the local characteristics at boiling in subcooled falling liquid film with existing models for pool boiling was made

Sign in / Sign up

Export Citation Format

Share Document