Study on Enhancement of Sub-Cooled Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture

2002 ◽  
Author(s):  
Yasuo Koizumi ◽  
Tomoyuki Suzuki ◽  
Hiroyasu Ohtake
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Water Flow ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Water Flow Rate ◽  
Flow Region ◽  
High Water ◽  
Water Velocity ◽  
Rate Region

The influence of particle introduction into a subcooled water flow on boiling heat transfer and critical heat flux (CHF) was examined. When the water velocity was low, the particles crowded on the bottom wall of the flow channel and flowed just like sliding on the wall. When the water velocity was high, the particles were well dispersed in the water flow. In the non-boiling region, the heat transfer was augmented by the introduction of the particles into the water flow. As the introduction of the particles were increased, the augmentation was also increased in the high water flow rate region. However, it was independent upon the particle introduction rate in the low water flow rate region. The onset of boiling was delayed by the particle inclusion. The boiling heat transfer was enhanced by the particles. However, it was rather decreased in the high heat flux fully-developed-boiling region. The CHF was decreased by the particle inclusion in the low water flow region and was not affected in the high water flow region.

Heat Transfer Coefficient of a Graphite Mold Quenched by Water

2019 ◽  
Author(s):  
Yi Pan ◽  
Jeffrey Thomas ◽  
Chris Propes
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Water Flow ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Mold Surface ◽  
Graphite Mold

Abstract Metal matrix composites (MMCs) can be manufactured by infiltrating a melting matrix alloy into hard powders — such as silicon carbide and tungsten carbide — loaded in a graphite mold and quenched to achieve a specific quenching temperature profile for proper solidification. Water quench is a widely used quenching technique within the aluminum and steel industry. It is more common to apply numerical simulation to optimize process parameters and help improve product quality, which depends upon reliable boundary conditions (e.g., heat flux or heat transfer coefficient); however, heat transfer coefficient changes with surface temperature and water flow rate. Moreover, the heat transfer coefficient in the discussed manufacturing process was never quantified. A combined experimental and simulation method to investigate heat transfer coefficient of the external surface of the graphite mold associated with water quenching is proposed. Firstly, the heat flux from the graphite mold is measured, which varies with water flow rate, mold surface temperature, nozzle arrangement, and water flow pattern. Without modifying the hardware design, this study focuses on the effects of water flow rate and mold surface temperature on surface heat flux. Secondly, the temperature distribution within the mold is used to inversely determine the heat transfer coefficient by solving an inversed optimization problem.

Study on Boiling Heat Transfer and Critical Heat Flux in Mist Cooling: Effect of Droplet Size on Heat Transfer Characteristics

2004 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Tomoyasu Tanaki ◽  
Yasuo Koizumi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Droplet Size ◽  
Flow Rate ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Liquid Mass ◽  
Mist Cooling

Boiling heat transfer and critical heat flux—CHF—in mist cooling were investigated experimentally and analytically. Especially, the heat transfer in the mist cooling was examined focusing on the effects of droplet size and droplet velocity on the heat transfer characteristics. Steady state experiments of heat transfer were conducted using a pure copper cylinder and mist flow of water-air at room temperature. Liquid flow rate was 0.3, 0.9, 1.8, 4 and 8 l/hr, respectively; each air flow rate on normal condition was 0, 40, 75 and 120 lN/min. Furthermore, liquid mass flux on the heater surface for each experimental condition was measured by using a cylinder with a scale and the same diameter as the heater. Distribution of air velocity, average velocity of droplets and average diameter of droplets were measured by using a fine Pitot tube, laser doppler anemometry and immersion method, respectively. Three correlations of the mist cooling rate for non-boiling, evaporation of droplets and evaporation of the liquid film were developed by using the measured liquid mass flux, characteristic droplet velocity and wall superheat. A CHF model was presented by focusing on maximum evaporation rate of the liquid mass flux on a heater. A droplet evaporation model was proposed by using the transient heat conduction in a sphere. Finally, three dimensionless correlations for the mist cooling were presented.

Analysis of Triangular Microchannel Under Forced Convection Heat Transfer Condition for Laminar Flow Condition

2013 ◽  
Author(s):  
D. A. Kamble ◽  
B. S. Gawali
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Water Flow ◽  
Flow Rate ◽  
Heat Input ◽  
Water Flow Rate ◽  
Temperature Drop ◽  
Experimental Result ◽  
Rate Condition ◽  
Wide Range

Micro-convection is a strategic area in transport phenomena, since it is the basis for a wide range of miniaturized high-performance heat transfer applications. Surface area is one of the important parameter for high flux heat transfer in microchannel performance. This experimental study deals with heat transfer using triangular microchannel having hydraulic diameters of 321μm and 289μm. Experimentation is carried out for triangular microchannel set for different heat input and flow rate condition. Triangular microchannel are manufactured with EDM technology. Testing of microchannel under laminar flow is considered with different tip angle, spacing, and length of microchannels. The different microchannels made up of copper material with 29 microchannel each having three different sets of length of 50 mm, 70 mm and 90 mm respectively. Tip angles for triangular microchannel is varied 50 ° and 60 ° with width of 30 mm each respectively are analyzed numerically. Spacing between triangular microchannels is also varied and 300μm and 400μm are considered for the analysis. Water flow rate is considered laminar flow. The flow rate of water is varied from 0.0167 kg/sec to 0.167 kg/sce to carry away heat. It is observed that as hydraulic diameters increase the heat transfer coefficient decreases. As the heat input to microchannel increases from 10 Watt to 100 Watt the temperature drop across varies from 2° C to 22°C as water flow rate increases. The numerical analysis is done using computer C programming. Experimental result differ from theoretical for temperature drop with variation of 2°C to 5°C. It is also observed that in all triangular microchannels its geometry i.e. tip angle and hydraulic diameter are dominant parameters which influences on rate of heat transfer. With increasing channel depth, increases flow passage area therefore enhances heat transfer sufficiently. From experimentation a Nu number correlation is proposed with considering tip angle, length, spacing of microchannel and other related parameters.

Experimental Study on Boiling Heat Transfer in Cylinder Head Jacket

2012 ◽  
Vol 433-440 ◽  
pp. 18-23
Author(s):  
Xiao Liu ◽  
Yuan Fu Cao ◽  
Ti En Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Flux ◽  
Diesel Engine ◽  
Flow Rate ◽  
Cylinder Head ◽  
Boiling Heat Transfer ◽  
Practical Application ◽  
Inlet Velocity ◽  
Inlet Flow Rate

Experiments of the valve bridge are carried out and the boiling states are investigated, to study the boiling heat transfer in cylinder head jacket. The effects of inlet flow rate and temperature on boiling heat flux are analyzed, as well as the thickness of fire deck. The results show that the inlet velocity has little effect on the velocity in valve bridge zone, even the velocity in the valve bridge zone can strongly affect on boiling heat transfer. The results can offer references to practical application in power-enhanced diesel engine.

scholarly journals Experimental Study on the Heat Transfer Characteristics of the Enhanced Fin-Tube Heat Exchanger Applied a Coiled Turbulator

2017 ◽  
Author(s):  
Sun-Joon Byun ◽  
Sang-Jae Lee ◽  
Jae-Min Cha ◽  
Zhen-Huan Wang ◽  
Young-Chul Kwon
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Water Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Water Flow Rate ◽  
Transfer Performance ◽  
Tube Heat Exchanger ◽  
Fin Tube

This study presents the comparison of heat transfer capacity and pressure drop characteristics between a basic fin-tube heat exchanger and a modified heat exchanger with the structural change of branch tubes and coiled turbulators. All experiments were carried out using an air-enthalpy type calorimeter based on the method described in ASHRAE standards, under heat exchanger experimental conditions. 14 different kinds of heat exchangers were used for the experiment. Cooling and heating capacities of the turbulator heat exchanger were excellent, compared to the basic one. As the insertion ratio of the coiled turbulator and the number of row increased, the heat transfer performance increased. However, the capacity per unit area was more effective in 4 rows than 6 rows, and the cooling performance of the 6 row turbulator heat exchanger (100% turbulator insert ratio) was down to about 6% than that of 4 row one. As the water flow rate and the turbulator insertion ratio increased, the pressure drop of the water side increased. This trend was more pronounced in 6 rows. In the cooling condition, the pressure drop on the air side was slightly increased due to the generation of condensed water, but was insignificant under the heating condition. The power consumption of the pump was more affected by the water flow rate than the coiled turbulator. The equivalent hydraulic diameter of a tube by the turbulator was reduced and then the heat transfer performance was improved. Thus, the tube diameter was smaller, the heat flux was better.

scholarly journals Heat Transfer Characteristics of High-Temperature Dusty Flue Gas from Industrial Furnaces in a Granular Bed with Buried Tubes

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3589
Author(s):  
Shaowu Yin ◽  
Feiyang Xue ◽  
Xu Wang ◽  
Lige Tong ◽  
Li Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Flow ◽  
Flow Rate ◽  
Waste Heat ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Granular Bed ◽  
Cooling Water Flow Rate

Experimental heat transfer equipment with a buried tube granular bed was set up for waste heat recovery of flue gas. The effects of flue gas inlet temperature (1096.65–1286.45 K) and cooling water flow rate (2.6–5.1 m3/h) were studied through experiment and computational fluid dynamics’ (CFD) method. On the basis of logarithmic mean temperature difference method, the total heat transfer coefficient of the granular bed was used to characterize its heat transfer performance. Experimental results showed that the waste heat recovery rate of the equipment exceeded 72%. An increase in the cooling water flow rate and inlet gas temperature was beneficial to recovering waste heat. The cooling water flow rate increases from 2.6 m3/h to 5.1 m3/h and the recovery rate of waste heat increases by 1.9%. Moreover, the heat transfer coefficient of the granular bed increased by 4.4% and the inlet gas temperature increased from 1096.65 K to 1286.45 K. The recovery rate of waste heat increased by 1.7% and the heat transfer coefficient of the granular bed rose by 26.6%. Therefore, experimental correlations between the total heat transfer coefficient of a granular bed and the cooling water flow rate and inlet temperature of dusty gas were proposed. The CFD method was used to simulate the heat transfer in the granular bed, and the effect of gas temperature on the heat transfer coefficient of granular bed was studied. Results showed that the relative error was less than 2%.

Experimental Study on Al2O3/H2O Nanofluid Flow Boiling Heat Transfer Under Different Pressures

2016 ◽  
Author(s):  
Y. Wang ◽  
K. H. Deng ◽  
B. Liu ◽  
J. M. Wu ◽  
G. H. Su
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Volume Concentration ◽  
Flow Boiling ◽  
Heating Surface ◽  
Nanofluid Flow ◽  
Flow Boiling Heat Transfer ◽  
Heat Transfer Capacity

In present work, Al2O3/H2O nanofluid was prepared by ultrasonic oscillation. Furthermore, nanofluid flow boiling heat transfer in a vertical cube is experimentally studied, with 0.1% and 0.5% volume concentration and 20nm diameter. Some factors are under consideration, including heat flux on the heating surface (48∼289kW·m−2), pressure (0.2∼0.8MPa) and mass flow rate (400∼1100 kgm−2s−1). The results confirm that the flow boiling heat transfer of Al2O3/H2O nanofluid is improved mostly about 86% compared with pure water. And the average Nusselt number enhancement rate of nanofluid compared with deionized water is 35% in the range of this work. Moreover, the heat transfer capacity of nanofluid increase with the heat flux on the heating surface, pressure and the volume concentration of nanoparticle. It is proved that nanoparticle deposited on the heating surface by SEM observations, and TEM observations for nanoparticle confirm that nanoparticle have not obviously changed after boiling. In addition, the enhancement rate of nanofluid flow boiling heat transfer capacity increase with the pressure, and the influence of mass flow rate is negligible. In conclusion, this work is a supplement for nanofluid flow boiling heating transfer, especially for the influence of pressure.

Osmotic destruction of Saccharomyces cerevisiae is not related to a high water flow rate across the membrane

2001 ◽  
Vol 9 (3) ◽  
pp. 205-210 ◽  
Author(s):  
Laurent Beney ◽  
Iñigo Martı́nez de Marañón ◽  
Pierre-André Marechal ◽  
Sylvie Moundanga ◽  
Patrick Gervais
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Water Flow ◽  
Flow Rate ◽  
Water Flow Rate ◽  
High Water
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