Enhanced Boiling Heat Transfer From Micro-Porous Cylindrical Surfaces in Saturated FC-87 and R-123

1997 ◽  
Vol 119 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J. Y. Chang ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bulk Liquid ◽  
High Heat Flux ◽  
High Flux ◽  
Boiling Enhancement ◽  
Nucleate Boiling Heat Transfer ◽  
Enhanced Boiling

The present research is an experimental study of pool boiling heat transfer from cylindrical heater surfaces immersed in saturated FC-87 and R-123. The baseline heater surfaces tested are plain, integral-fin with 709 fins/m, and commercial enhanced (High-Flux and Turbo-B). In addition, a highly effective micro-scale enhancement coating is applied to the plain and integral-fin surfaces to augment nucleate boiling heat transfer. Experiments are performed to understand the effects of surface micro- and macro-geometries on boiling heat transfer. The boiling performance of the micro-porous enhanced plain and integral-fin surfaces are compared with the High-Flux and the Turbo-B surfaces. At high heat flux conditions, the break down of the bulk liquid feed mechanism reduces boiling enhancement from the cylindrical surfaces.

scholarly journals Boiling Heat Transfer Performance of Parallel Porous Microchannels

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2970
Author(s):  
Donghui Zhang ◽  
Haiyang Xu ◽  
Yi Chen ◽  
Leiqing Wang ◽  
Jian Qu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Boiling Process

Flow boiling in microporous layers has attracted a great deal of attention in the enhanced heat transfer field due to its high heat dissipation potential. In this study, flow boiling experiments were performed on both porous microchannels and a copper-based microchannel, using water as the coolant. As the heat flux was less than 80 W/cm2, the porous microchannels presented significantly higher boiling heat transfer coefficients than the copper-based microchannel. This was closely associated with the promotion of the nucleation site density of the porous coating. With the further increase in heat flux, the heat transfer coefficients of the porous microchannels were close to those of the copper-based sample. The boiling process in the porous microchannel was found to be dominated by the nucleate boiling mechanism from low to moderate heat flux (<80 W/cm2).This switched to the convection boiling mode at high heat flux. The porous samples were able to mitigate flow instability greatly. A visual observation revealed that porous microchannels could suppress the flow fluctuation due to the establishment of a stable nucleate boiling process. Porous microchannels showed no advantage over the copper-based sample in the critical heat flux. The optimal thickness-to-particle-size ratio (δ/d) for the porous microchannel was confirmed to be between 2–5. In this range, the maximum enhanced effect on boiling heat transfer could be achieved.

Effects of Pore Diameters and System Pressure on Saturated Pool Nucleate Boiling Heat Transfer From Porous Surfaces

1982 ◽  
Vol 104 (2) ◽  
pp. 286-291 ◽  
Author(s):  
W. Nakayama ◽  
T. Daikoku ◽  
T. Nakajima
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Formation ◽  
Nucleate Boiling ◽  
High Heat ◽  
Porous Surface ◽  
Operational Parameters ◽  
High Heat Transfer ◽  
System Pressure ◽  
Nucleate Boiling Heat Transfer

The porous surface structure was manufactured with precision for the experimental study of nucleate boiling heat transfer in R-11. Boiling curves and the data of bubble formation were obtained with a variety of geometrical and operational parameters; the pore diameters were of 50, 100, 150 μm, there was a combination of pores of different sizes; and the system pressures were of 0.04, 0.1, 0.23 MPa. The boiling curves exhibit certain trends effected by the diameter and population density of pores. A combination of high system pressure and pore sizes of 100 or 150 μm dia enables boiling to persist even when the wall superheat is reduced to an extremely low level of 0.1 K. A noteworthy feature of porous surface boiling is that intense bubble formation does not necessarily yield a high heat-transfer performance. Examination of the data indicates that liquid suction and evaporation inside the cavities are a proable mechanism of boiling with small temperature differences.

Dynamic Model of Enhanced Boiling Heat Transfer on Porous Surfaces—Part I: Experimental Investigation

1980 ◽  
Vol 102 (3) ◽  
pp. 445-450 ◽  
Author(s):  
W. Nakayama ◽  
T. Daikoku ◽  
H. Kuwahara ◽  
T. Nakajima
Keyword(s):  
Heat Transfer ◽  
Dynamic Model ◽  
Boiling Heat Transfer ◽  
Bubble Formation ◽  
Nucleate Boiling ◽  
Vital Role ◽  
Structured Surfaces ◽  
Wall Superheat ◽  
Nucleate Boiling Heat Transfer ◽  
Enhanced Boiling

Enhancement of nucleate boiling heat transfer has been studied with the structured surfaces composed of interconnected internal cavities in the form of tunnels and small pores connecting the pool liquid and the tunnels. The boiling curves of R-11, water and nitrogen show 80 to 90 percent reduction of wall superheat required to transfer the same heat flux as that on plain surfaces, when the pore diameter is set around 0.1 mm. The experimental data on bubble formation showed a significant contribution of latent heat transport to the enhancement. A visualization study made with a transparent structured model suggested that the liquid suction into the tunnel is triggered by the bubble growth at active pores and subsequent evaporation inside the tunnel plays a vital role in driving the bubble formation cycle. This observation led to a conception of the dynamic model expounded in Part II.

An Investigation of Local Degassing Effects on Heat Transfer During Gas-Saturated Boiling From a Small Cylinder

1999 ◽  
Author(s):  
Y. S. Hong ◽  
C. N. Ammerman ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Gas Content ◽  
Working Fluid ◽  
Dissolved Gas ◽  
System Pressure ◽  
Boiling Enhancement ◽  
Nucleate Boiling Heat Transfer ◽  
Saturated Boiling

Abstract Boiling heat transfer from a 50-μm-diameter wire immersed in FC-72 is examined. Effects of pressure, subcooling, and dissolved gas concentration on nucleate boiling heat transfer and critical heat flux (CHF) are investigated. The current study is an ongoing effort to systematically quantify dissolved gas content effects on boiling heat transfer. The present investigators previously determined that gas-saturated boiling efficiency is affected by local degassing of the working fluid near the heater surface. This local degassing effect is further investigated in the present study using helium, air, and carbon dioxide as dissolved gases. In addition, the limits of gas-saturated boiling enhancement are determined by varying system pressure.

Study of Boiling Heat Transfer on Heterogeneous Wetting Surface With MD Simulation

2021 ◽  
Author(s):  
Zeyu Liu ◽  
Runkeng Liu ◽  
Peng Li ◽  
Anyi Xu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Evaporation Rate ◽  
Heat Transfer Performance ◽  
Nucleate Boiling ◽  
High Heat ◽  
Area Fraction ◽  
High Heat Flux ◽  
Transfer Performance ◽  
Hydrophobic Region

Abstract Wettability has been proved as an important issue to the thermal transport at solid-liquid interface at different scales, however, its enhancement mechanism has not been clearly understood till now. In this study, the nucleate boiling behavior of argon fluid on heterogeneous wetting surfaces were examined with the non-equilibrium molecular dynamics (MD) method, the ring-patterned and stripe-patterned schemes were designed and analyzed, respectively. By comparing the boiling inception time and evaporation rate of liquid argon atoms, it is found that the ring-patterned surface shows an advantage in the nucleate boiling heat transfer compared with the stripe-patterned one. The differences in heat transfer characteristics for different surfaces can be explained through the qualitative analysis of fluid density distribution and solid-fluid interaction energy. Furthermore, the boiling phenomena on ring-patterned surfaces with alternated hydrophilic and hydrophobic intervals were simulated to study the influence of area fraction of hydrophilic region on the heat transfer performance. It is observed that bubble nucleus firstly appears over the hydrophobic region of the substrate. The substrate with more hydrophilic area will have a better heat transfer performance. It is also demonstrated that there is an optimal area fraction, which can make the evaporation rate of fluid reach the highest value. The findings in this work can contribute to the design and fabrication of nanocoating surface to enhance its heat transfer performance under high heat flux condition.

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