Parametric Effects of Heater Size, Contact Angle, and Surrounding Vessel Size On Pool Boiling Critical Heat Flux From Horizontal Surfaces

2021 ◽  
Author(s):  
Zhenyu She ◽  
Vijay K. Dhir
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Critical Heat Flux ◽  
Nucleate Boiling ◽  
Flat Plates ◽  
Vessel Size ◽  
Saturated Water ◽  
Nucleate Boiling Heat Transfer ◽  
Parametric Effects ◽  
Glass Tubes

Abstract Saturated water at one atmosphere pressure was boiled on horizontal copper discs of diameters 1.0,1.5 and 2.0 cm. respectively. The contact angle was varied from 10 to 80 degrees by controlling thermal oxidation of the discs, while the surrounding vessel size was changed by placing glass tubes of different inner diameters around the discs. Nucleate boiling heat transfer data were obtained up to critical heat flux (CHF), where vapor removal patterns were photographed. Dominant wavelengths at vapor jet interface and vapor jet diameters were measured from the photographs of the well wetted discs. For a well wetted surface, the magnitude of CHF increased when the heater size was reduced from 2.0 to 1.0 cm. Improving the wettability enhanced the CHF substantially, whereas the increased size of the liquid holding vessel had a smaller effect. The highest measured CHF is 233 W/cm2 or 2.11 times Zuber's CHF prediction for infinite horizontal flat plates. It was obtained on a 1.0 cm. disc of contact angle about 10 degrees surrounded by a large vessel. The CHF for this surface was increased from 201 to 233 W/cm2 when the ratio of heater size to surrounding vessel size was reduced from 1 to about 0.

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.

scholarly journals Determination of Pool Boiling Critical Heat Flux Enhancement in Nanofluids

2007 ◽  
Author(s):  
Bao H. Truong
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Porous Coating ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Sem Images ◽  
Heat Transfer Coefficients ◽  
Nucleate Boiling Heat Transfer

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed a CHF enhancement up to 68% and there seems to be a monotonic relationship between the nanoparticle concentration and the magnitude of enhancement. Alumina nanofluids had a CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. Scanning Electron Microscopy (SEM) images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater’s surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica.

Critical Heat Flux for Subcooled Water Flowing Normal to a Cylinder

1964 ◽  
Vol 86 (1) ◽  
pp. 68-74 ◽  
Author(s):  
G. C. Vliet ◽  
G. Leppert
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Atmospheric Pressure ◽  
Marked Effect ◽  
Fractional Power ◽  
Nucleate Boiling ◽  
Water Velocity ◽  
Critical Flux ◽  
Vapor Cavity ◽  
Saturated Water

Empirical data are presented which show the effects of diameter, water velocity, and subcooling on the critical heat flux from an electrically heated, cylindrical lube or wire. The maximum flux which can be accommodated in subcooled nucleate boiling is found to vary directly with the water velocity and subcooling and inversely with a fractional power of the heater diameter. The exponent which describes the diameter dependence is itself a function of both velocity and subcooling. Measurements of the critical flux are reported for water at atmospheric pressure over a range of subcooling from 3 to 100 deg F, velocity from 0.5 to 11 ft/sec, and heater diameter from 0.010 to 0.189 in. Visual and photographic observations indicate a marked effect of subcooling on the flow mechanism near the critical heat flux. High subcooling prevents the formation of the vapor cavity which was described in the previous paper [1] for nearly saturated water, although the failure of nucleate boiling still occurs at the rear of the cylinder and is accompanied by a concentration of vapor in that region.

Study on Nucleate Boiling Heat Transfer by Measuring Spatially Instantaneous Local Surface Temperature and Observing Instantaneous Bubble/Liquid Fluid Behavior

2013 ◽  
Author(s):  
Yasuo Koizumi ◽  
Kenta Hayashi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Heat Transfer Surface ◽  
Bubble Generation ◽  
Three Phase ◽  
Nucleate Boiling Heat Transfer

Pool nucleate boiling heat transfer experiments were performed for water at 0.101 MPa to examine the elementary process of the nucleate boiling. Heat transfer surface was made from a copper printed circuit board. Direct current was supplied to heat it up. The Bakelite plate of the backside of a copper layer was taken off at the center portion of the heat transfer surface. The instantaneous variation of the backside temperature of the heat transfer surface was measured with an infrared radiation camera. Bubble behavior was recorded with a high speed video camera. In the isolated bubble region, surface temperature was uniform during waiting time. When boiling bubble generation started, a large dip in the surface temperature was formed under the bubble. After the bubble left from the heat transfer surface, the surface temperature returned to former uniform temperature distribution. Surface temperature was not affected by the bubble generation beyond 1.6 mm from the center of the bubble. In the isolated bubble region, a convection term was approximately 80 % in total heat transfer rate. The importance of the three-phase interface line in the heat transfer should be checked carefully. In the intermediate and high heat flux region, the variation of surface temperature and heat flux were small. Rather those were close to their average values even at critical heat flux condition. It seemed that the large part of the heat transfer surface was covered with water even at the critical heat flux condition. The heat flux at the area that appeared to be the three-phase contact line was not so high and close to the average heat flux.

Pool Boiling of Benzene, Diphenyl, and Benzene-Diphenyl Mixtures Under Pressure

1963 ◽  
Vol 85 (3) ◽  
pp. 215-220 ◽  
Author(s):  
D. A. Huber ◽  
J. C. Hoehne
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Physical Property ◽  
Horizontal Tube ◽  
Nucleate Boiling ◽  
Volatile Components ◽  
Pure Fluids ◽  
Nucleate Boiling Heat Transfer ◽  
Physical Property Data

Experimental measurements are presented for the nucleate boiling of benzene, diphenyl, and benzene-diphenyl mixtures on a 3/8-in. od horizontal tube. The data were obtained in a pool boiling apparatus at pressures ranging from 13.5 to 488.5 psia. For the pure fluids, the nucleate boiling heat-transfer data were best correlated by the Rohsenow [12], Gilmour [8], and Levy [10] equations. Critical heat flux data reported for these fluids are correlated with those in the literature. The critical heat flux values for the pure fluids were best correlated by the Bernath relationship [1]; however, none of the literature expressions adequately predicted the large increases in critical heat flux that were obtained when small percentages of benzene were added to diphenyl. Similar increases in critical heat flux, when small amounts of volatile components are added, have been noted before, but no generalized correlations have been advanced. Some of the discrepancy may be due to inadequate knowledge of physical property data for the mixtures and failure to account for the mass transfer which occurs in bubble growth of multicomponent mixtures.

Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids

2012 ◽  
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 minutes. 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 CHF for upward- and downward-facing heater are 2.1 and 1.9, 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 minute 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.

Lattice Boltzmann Simulations of Macro/Microscale Effects on Saturated Pool Boiling Curves for Heated Horizontal Surfaces

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Ping Cheng ◽  
Chaoyang Zhang ◽  
Shuai Gong
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Lattice Boltzmann ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Correlation Equation ◽  
Nucleate Boiling ◽  
Nucleate Boiling Heat Transfer

Results of lattice Boltzmann (LB) simulations of macroscale effects (heating modes, heater size, and saturation temperature) as well as microscale effects (wettability and roughness) on saturated pool boiling from superheated horizontal surfaces are summarized in this paper. These effects on pool boiling curves from natural convection through nucleate boiling to critical heat flux (CHF) and from transition boiling to film boiling are illustrated. It is found that macroscale effects have negligible influence on nucleate boiling heat transfer, and Rohsenow's correlation equation fits well with the simulated nucleate boiling heat transfer on smooth hydrophilic and hydrophobic horizontal surfaces. Both macroscale and microscale effects have important influence on critical heat flux and transition boiling heat transfer.

Sign in / Sign up

Export Citation Format

Share Document