Heat Transfer Measurements to Examine Surface Roughness and Blowing Effects in Hypersonic Flows

The experimental investigations were carried out of a pressurized water nuclear reactor (PWR) with enhanced surface using different concentration (0.5 and 2.0 vol%) of ZnO/DI-water based nanofluids as a coolant. The experimental setup consisted of a flow loop with a nuclear fuel rod section that was heated by electrical current. The fuel rod surfaces were termed as two-dimensional surface roughness (square transverse ribbed surface) and three-dimensional surface roughness (diamond shaped blocks). The variation in temperature of nuclear fuel rod was measured along the length of a specified section. Heat transfer coefficient was calculated by measuring heat flux and temperature differences between surface and bulk fluid. The experimental results of nanofluids were compared with the coolant as a DI-water data. The maximum heat transfer coefficient enhancement was achieved 33% at Re = 1.15 × 105 for fuel rod with three-dimensional surface roughness using 2.0 vol% nanofluids compared to DI-water.

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A novel scheme for simulating the effect of microstructure surface roughness on the heat transfer characteristics of subcooled flow boiling

Case Studies in Thermal Engineering ◽

10.1016/j.csite.2020.100829 ◽

2020 ◽

pp. 100829

Author(s):

Hasan Alimoradi ◽

Mehrzad Shams ◽

Nasser Ashgriz ◽

Ali Bozorgnezhad

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Flow Boiling ◽

Heat Transfer Characteristics ◽

Subcooled Flow Boiling ◽

Transfer Characteristics ◽

Subcooled Flow ◽

Effect Of Microstructure

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Effect of Surface Roughness on Pool Boiling Heat Transfer of Water on a Superhydrophilic Aluminum Surface

Journal of Heat Transfer ◽

10.1115/1.4036599 ◽

2017 ◽

Vol 139 (10) ◽

Cited By ~ 25

Author(s):

Jinsub Kim ◽

Seongchul Jun ◽

Jungho Lee ◽

Juan Godinez ◽

Seung M. You

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Boiling Heat Transfer ◽

Aluminum Surface ◽

Transfer Coefficients ◽

Copper Surfaces ◽

Heat Transfer Coefficients ◽

Superhydrophilic Surface ◽

Aluminum Surfaces ◽

Effect Of Surface

The effect of surface roughness on the pool boiling heat transfer of water was investigated on superhydrophilic aluminum surfaces. The formation of nanoscale protrusions on the aluminum surface was confirmed after immersing it in boiling water, which modified surface wettability to form a superhydrophilic surface. The effect of surface roughness was examined at different average roughness (Ra) values ranging from 0.11 to 2.93 μm. The boiling heat transfer coefficients increased with an increase in roughness owing to the increased number of cavities. However, the superhydrophilic aluminum surfaces exhibited degradation of the heat transfer coefficients when compared with copper surfaces owing to the flooding of promising cavities. The superhydrophilic aluminum surfaces exhibited a higher critical heat flux (CHF) than the copper surfaces. The CHF was 1650 kW/m2 for Ra = 0.11 μm, and it increased to 2150 kW/m2 for Ra = 0.35 μm. Surface roughness is considered to affect CHF as it improves the capillary wicking on the superhydrophilic surface. However, further increase in surface roughness above 0.35 μm did not augment the CHF, even at Ra = 2.93 μm. This upper limit of the CHF appears to result from the hydrodynamic limit on the superhydrophilic surface, because the roughest surface with Ra = 2.93 μm still showed a faster liquid spreading speed.

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