An Experimental Investigation of Flow Boiling Characteristics in a Single Transparent Heated Microtube

2009 ◽  
Author(s):  
Osamu Kawanami ◽  
Shih-Che Huang ◽  
Kazunari Kawakami ◽  
Itsuro Honda ◽  
Yousuke Kawashima ◽  
...  
Keyword(s):  
Heat Flux ◽  
Wall Temperature ◽  
Mass Velocity ◽  
Tube Wall ◽  
Flow Boiling ◽  
High Mass ◽  
Test Fluid ◽  
High Heat Flux ◽  
Gold Plating ◽  
Heated Tube

In the present study, flow boiling in a transparent heated microtube having a diameter of 1 mm was investigated in detail. The transparent heated tube was manufactured by the electroless gold plating method. The enclosed gas-liquid interface could be clearly recognized through the tube wall, and the inner wall temperature measurement and direct heating of the film were simultaneously conducted by using the tube. Deaerated and deionized water that was subcooled temperature of 15 K was used as a test fluid, and constant and stable mass velocities of 50, 100, and 200 kg/m2s were provided by using a twin plunger pump. Among our experimental results, a vapor bubble grew up in a direction opposite the flow at a low heat flux and low mass velocities; however, this flow pattern was not observed at a high mass velocity of 200 kg/m2s. Under the conditions of G = 50 kg/m2s and high heat flux, the liquid film surrounding an elongated bubble near the heated tube wall occasionally thickened partially. The inner wall temperature exhibited large random oscillations in this regime; however, the visual observation revealed that dry-patches did not occur. The mass velocity had a negligible effect on the boiling heat transfer except in the counter-growth bubble flow regime.

Single-Side Heated Monoblock, High Heat Flux Removal Using Water Subcooled Flow Boiling

2003 ◽  
Author(s):  
Ronald D. Boyd ◽  
Ali Ekhlassi ◽  
Penrose Cofie ◽  
Richard Martin ◽  
Hongtao Zhang
Keyword(s):  
Heat Flux ◽  
Wall Temperature ◽  
Test Section ◽  
Flow Boiling ◽  
Three Dimensional ◽  
High Heat ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Single Side

Plasma-facing components for fusion reactors and other high heat flux heat sinks are usually subjected to a peripherally non-uniform heat flux. The configuration under study is related to these applications and consists of a single-side heated monoblock cross-section test section with a circular coolant channel bored through the center. The monoblock test section has a heated length of 180.0 mm and has 10.0 mm and 30.0 mm inside diameter and outside square sides, respectively. It was subjected to a constant heat flux on one side only, and the remaining portion of the outside surfaces is not exposed to a heat flux. The inlet channel water temperature was held near at 26.0°C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59 Mg/m2s. The results consist of three-dimensional monoblock test section wall temperature distributions and a clear display of both critical heat flux and post-critical heat flux for this single-side heated configuration. These results are very encouraging in that they are among the first full set of truly three-dimensional monoblock test section wall temperature measurements for a one-side heated monoblock flow channel which contains the effects of conjugate heat transfer for turbulent, subcooled flow boiling. Comparisons are made between these results for the monoblock test section and those for a single-side heated circular test section.

Single-Side Heated Monoblock, High Heat Flux Removal Using Water Subcooled Turbulent Flow Boiling

2004 ◽  
Vol 126 (1) ◽  
pp. 17-21
Author(s):  
Ronald D. Boyd ◽  
Penrose Cofie ◽  
Hongtao Zhang ◽  
Ali Ekhlassi
Keyword(s):  
Heat Flux ◽  
Wall Temperature ◽  
Test Section ◽  
Flow Boiling ◽  
Three Dimensional ◽  
High Heat ◽  
Constant Heat Flux ◽  
Phase Region ◽  
High Heat Flux ◽  
Single Side

Plasma-facing components for fusion reactors and other high heat flux heat sinks are subjected to a peripherally nonuniform heat flux. The monoblock test section under study is a single-side heated square cross-section heat sink with a circular coolant channel bored through the center. The heated length of the test section is 180 mm. The inside diameter and outside square sides are 10 mm and 30 mm, respectively. It was subjected to a constant heat flux on one side of the outside surfaces, and the remaining portion was not heated. The exit water subcooling varied from 55 to 101°C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59Mg/m2s. The results consist of three-dimensional wall temperature distributions and a display of two-dimensional quasi-boiling curves. These results are among the first full set of three-dimensional wall temperature measurements for a single-side heated monoblock flow channel which contains the effects of conjugate heat transfer for turbulent, subcooled flow boiling. In the single-phase region, good predictability resulted when the thermal hydraulic diameter was used.

Flow Boiling in Transparent Heated Microtube

2008 ◽  
Author(s):  
Osamu Kawanami ◽  
Shih-Che Huang ◽  
Kazunari Kawakami ◽  
Itsuro Honda ◽  
Yousuke Kawashima ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Flow Boiling ◽  
Flow Behavior ◽  
High Heat Flux ◽  
Experimental Conditions ◽  
The Heat Transfer Coefficient

In the present study, a detailed investigation of flow boiling in a transparent heated microtube was performed. The transparent heated tube was made by electroless gold plating method. The enclosed gas-liquid interface could be clearly recognized through the tube wall, and the inner wall temperature measurement and direct heating of the film were simultaneously conducted by using the tube. The experimental conditions were: tube diameter 1 mm, mass velocity 100 kg/m2s, inlet liquid sub-cooling 20 K and heat flux up to 384 kW/m2 in the open system. Flow fluctuation was minimized by employing a twin plunger pump. Among our experimental results, we observed a high-frequency fluctuation of the inner wall temperature and a sharp peak for the heat transfer coefficient with high heat flux conditions, which have not been reported in previous experiments. This abrupt increase in the heat transfer coefficient coincided with a slight rapid axial growth of an elongated bubble found in the observation of the flow behavior. Hence, in low heat flux conditions, the fluctuations of temperature and heat transfer coefficient are strongly suppressed except for the instances when there is no bubble in the tube.

Development of Cooling System for a Large Area at High Heat Flux by Using Flow Boiling in Narrow Channels

2009 ◽  
Author(s):  
Shinichi Miura ◽  
Yukihiro Inada ◽  
Yasuhisa Shinmoto ◽  
Haruhiko Ohta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Mass Velocity ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
High Heat ◽  
High Heat Flux ◽  
Gap Size ◽  
Heated Channel

Advance of an electronic technology has caused the increase of heat generation density for semiconductors densely integrated. Thermal management becomes more important, and a cooling system for high heat flux is required. It is extremely effective to such a demand using flow boiling heat transfer because of its high heat removal ability. To develop the cooling system for a large area at high heat flux, the cold plate structure of narrow channels with auxiliary unheated channel for additional liquid supply was devised and confirmed its validity by experiments. A large surface of 150mm in heated length and 30mm in width with grooves of an apex angle of 90 deg, 0.5mm depth and 1mm in pitch was employed. A structure of narrow rectangular heated channel between parallel plates with an unheated auxiliary channel was employed and the heat transfer characteristics were examined by using water for different combinations of gap sizes and volumetric flow rates. Five different liquid distribution modes were tested and their data were compared. The values of CHF larger than 1.9×106W/m2 for gap size of 2mm under mass velocity based on total volumetric flow rate and on the cross section area of main heated channel 720kg/m2s or 1.7×106W/m2 for gap size of 5mm under 290kg/m2s were obtained under total volumetric flow rate 4.5×10−5m3/s regardless of the liquid distribution modes. Under several conditions, the extensions of dry-patches were observed at the upstream location of the main heated channel resulting burnout not at the downstream but at the upstream. High values of CHF larger than 2×106W/m2 were obtained only for gap size of 2mm. The result indicates that higher mass velocity in the main heated channel is more effective for the increase in CHF. It was clarified that there is optimum flow rate distribution to obtain the highest values of CHF. For gap size of 2mm, high heat transfer coefficient as much as 7.4×104W/m2K were obtained at heat flux 1.5×106W/m2 under mass velocity 720kg/m2s based on total volumetric flow rate and on the cross section area of main heated channel. Also to obtain high heat transfer coefficient, it is more useful to supply the cooling liquid from the auxiliary unheated channel for additional liquid supply in the transverse direction perpendicular to the flow in the main heated channel.

Review on high heat flux flow boiling of refrigerants and water for electronics cooling

2021 ◽  
Vol 180 ◽  
pp. 121787
Author(s):  
Behnam Parizad Benam ◽  
Abdolali Khalili Sadaghiani ◽  
Vedat Yağcı ◽  
Murat Parlak ◽  
Khellil Sefiane ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Flux Flow

Study on onset of nucleate boiling with screw tube for fusion reactor application

2021 ◽  
Author(s):  
Ji Hwan Lim ◽  
Minkyu Park
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Transfer Mechanism ◽  
High Heat Flux ◽  
Heat Transfer Mechanism ◽  
System Parameters ◽  
Smooth Tubes

Abstract The onset of nucleate boiling (ONB) is the point at which the heat transfer mechanism in fluids changes and is one of the thermo-hydraulic factors that must be considered when establishing a cooling system operation strategy. Because the high heat flux of several MW/m2, which is loaded within a tokamak, is applied under a one-side heating condition, it is necessary to determine a correlative relation that can predict ONB under special heating conditions. In this study, the ONB of a one-side-heated screw tube was experimentally analyzed via a subcooled flow boiling experiment. The helical nut structure of the screw tube flow path wall allows for improved heat transfer performance relative to smooth tubes, providing a screw tube with a 53.98% higher ONB than a smooth tube. The effects of the system parameters on the ONB heat flux were analyzed based on the changes in the heat transfer mechanism, with the results indicating that the flow rate and degree of subcooling are proportional to the ONB heat flux because increasing these factors improves the forced convection heat transfer and increases the condensation rate, respectively. However, it was observed that the liquid surface tension and latent heat decrease as the pressure increases, leading to a decrease in the ONB heat flux. An evaluation of the predictive performance of existing ONB correlations revealed that most have high error rates because they were developed based on ONB experiments on micro-channels or smooth tubes and not under one-side high heat load conditions. To address this, we used dimensional analysis based on Python code to develop new ONB correlations that reflect the influence of system parameters.

Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes

2018 ◽  
Author(s):  
Jensen Hoke ◽  
Todd Bandhauer ◽  
Jack Kotovsky ◽  
Julie Hamilton ◽  
Paul Fontejon
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Flow Boiling ◽  
Laser Diodes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Average Maximum

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.

A theoretical and experimental study on subcooled flow boiling at high heat flux

1994 ◽  
Vol 29 (5) ◽  
pp. 319-327 ◽  
Author(s):  
K. W. Lin ◽  
C. H. Lee ◽  
L. W. Hourng ◽  
J. C. Hsu
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow
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