scholarly journals EXPERIMENTAL INVESTIGATION OF CRITICAL HEAT FLUX IN ANNULUS AT LOW PRESSURE AND LOW FLOW PARAMETERS

2020 ◽  
Vol 28 ◽  
pp. 50-58
Author(s):  
Daniel Vlček ◽  
Ladislav Suk ◽  
Kamil Števanka ◽  
Taron Petrosyan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Low Pressure ◽  
Low Flow ◽  
Inconel 625 ◽  
Outer Diameter ◽  
Flow Parameters ◽  
Low Mass ◽  
Vertically Aligned

Steady state flow boiling experiments were conducted on a technically smooth Inconel 625 tube with outer diameter 9.1 mm at inlet pressures 131, 220 and 323 kPa, inlet temperatures 62, 78 and 94 °C and approximately 400, 600 and 1000 kg/(m2.s) mass flow. Water of these parameters was entering into the vertically aligned annulus, where the uniformly heated tube was placed until the critical heat flux (CHF) appeared. The experimental data were compared to estimations of CHF by local PGT tube correlation and Groeneveld’s look-up tables for tubes. The results imply that in the region of low pressure and low mass flux, the differences between calculations and experiments are substantial (more than 50 % of CHF). The calculations further imply that look-up tables and tube correlations should be corrected to the annulus geometry. Here, the Doerffer’s approach was chosen and led to a substantial enhancement of CHF estimation. Yet, a new correlation for the region of low pressure and flow is needed.

scholarly journals Experimental Investigation of Critical Heat Flux on Different Surfaces at Low Pressure and Low Flow

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5205
Author(s):  
Ladislav Suk ◽  
Taron Petrosyan ◽  
Kamil Stevanka ◽  
Daniel Vlcek ◽  
Pavel Gejdos
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Surface Characteristic ◽  
Low Flow ◽  
Inconel 625 ◽  
Outer Diameter ◽  
Vertically Aligned ◽  
Experimental Runs ◽  
Effect Of Surface

Steady state flow boiling experiments were carried out on several heated tubes with outer diameter 9.14 mm at outlet pressures 120, 200 and 300 kPa, inlet temperatures 64, 78 and 91 °C and approximately 400, 500, 600 and 800 kg/(m2·s) mass flux entering the vertically aligned test annulus until critical heat flux (CHF) was reached. The tubes were made of Inconel 625 with a length of 400 mm. The Inconel tubes were tested in three different modifications as smooth, abraded with 150 grit sandpaper and bead blasted. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., wettability, roughness and oxide layer morphology) on the occurrence of CHF. Despite the changes in initial wettability, the CHF dependency was not clearly observed, however, the changes in roughness led to an increase in CHF. The total number of 115 experimental runs were collected and the results were also compared with other literature experimental data.

scholarly journals INVESTIGATION OF CRITICAL HEAT FLUX ON ABRADED INCONEL 625 TUBE

2020 ◽  
Vol 28 ◽  
pp. 15-22
Author(s):  
Ladislav Suk ◽  
Kamil Števanka ◽  
Taron Petrosyan ◽  
Daniel Vlček
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Flow Boiling ◽  
Glass Tube ◽  
Annular Channel ◽  
Low Flow ◽  
Inconel 625 ◽  
Confocal Laser ◽  
Outer Diameter ◽  
Flow Parameters

Aim of this work was to study flow boiling in an annular channel at low pressure and low flow on a tube with modified surface roughness. The tube with the outer diameter of 9.14 mm and the heated length of 380 mm was made of Inconel 625 and was manually modified using 150 grit sandpaper. The tube was placed in a glass tube with an inner diameter of 14.8 mm. Outlet pressure was set to 120, 200 and 300 kPa with varying mass flow from 400 to 600 kg/(m2.s). A high speed camera was used to record several experiments to fully understand ongoing phenomena. Surface roughness was analysed using a confocal laser microscope and the effects of different mass flux and pressure on the CHF value were observed. Above all, the optimization of the flow parameters was done from the collected data and from the observed behaviour of the experimental loop.

scholarly journals CRITICAL HEAT FLUX ENHANCEMENT IN FLOW BOILING OF Al2O3AND SiC NANOFLUIDS UNDER LOW PRESSURE AND LOW FLOW CONDITIONS

2012 ◽  
Vol 44 (4) ◽  
pp. 429-436 ◽  
Author(s):  
Seung-Won Lee ◽  
Seong-Dae Park ◽  
Sa-Rah Kang ◽  
Seong-Man Kim ◽  
Han Seo ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Low Pressure ◽  
Low Flow ◽  
Flow Conditions ◽  
Flux Enhancement

A study of critical heat flux for low flow of water in vertical round tubes under low pressure

1991 ◽  
Vol 132 (2) ◽  
pp. 225-237 ◽  
Author(s):  
Soon Heung Chang ◽  
Won-Pil Baek ◽  
Tae Min Bae
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Low Pressure ◽  
Low Flow

Effect of Inlet Restriction on Flow Boiling Heat Transfer in a Horizontal Microtube

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
YanFeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Mass Fluxes ◽  
Flow Boiling Heat Transfer ◽  
Low Mass

Flow boiling heat transfer in a horizontal microtube with inlet restriction (orifice) under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two microtubes with smaller diameters are assembled at the inlet of main microtube to achieve the restriction ratios of 50% and 20%. The experimental measurement is carried out at mass fluxes ranging from 160 to 870 kg/m2·s, heat fluxes varying from 6 to 170 kW/m2, inlet temperatures of 23 and 35 °C, and saturation pressures of 10 and 45 kPa. The effects of the orifices on two-phase pressure drop, critical heat flux (CHF), and flow boiling heat transfer coefficient are studied. The results show that the pressure drop caused by the orifice takes a considerable portion in the total pressure drop at low mass fluxes. This ratio decreases as the vapor quality or mass flux increases. The difference of normal critical heat flux in the microtubes with different orifice sizes is negligible. In the aspect of flow boiling heat transfer, the orifice is able to enhance the heat transfer at low mass flux and high saturation pressure, which indicates the contribution of orifice in the nucleate boiling dominated regime. However, the effect of orifice on flow boiling heat transfer is negligible in the forced convective boiling dominated regime.

An Experimental Study on the Critical Heat Flux for Low Flow of Water in Bilaterally Heated Vertical Annuli Under Low Pressure Conditions

2014 ◽  
Author(s):  
Lei Zhou ◽  
Guangxu Liu ◽  
Yuanfeng Zan ◽  
Xiao Yan
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Nuclear Power ◽  
Low Pressure ◽  
Operating Conditions ◽  
Low Flow ◽  
Plant Design ◽  
Water Reactors ◽  
Vertical Annuli

Critical heat flux (CHF) has been widely studied in the past decades because of its importance for nuclear power plant design. But most of the studies are based on flow under normal operating conditions for light water reactors. CHF under low flow and low pressure is of significance when considering operating transients and accidents. In this study, experimental study has been carried out on CHF for low flow rate and low pressure water flow in vertical bilaterally heated annuli. Parameter trends on CHF is discussed and a new predictive correlation was fitted based on the CHF data points. This study is meaningful for concerned nuclear engineering and similar experiment design.

Critical heat flux in non-uniformly heated tube under low-pressure and low-mass-flux condition

2005 ◽  
Vol 35 (1) ◽  
pp. 47-60 ◽  
Author(s):  
Hisashi Umekawa ◽  
Tetsuo Kitajima ◽  
Mio Hirayama ◽  
Mamoru Ozawa ◽  
Kaichiro Mishima ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Low Pressure ◽  
Heated Tube ◽  
Flux Condition ◽  
Low Mass

Flow Instability and Critical Heat Flux for Flow Boiling of Water in a Vertical Annulus at Low Pressure

2011 ◽  
Author(s):  
Christoph Haas ◽  
Leonhard Meyer ◽  
Thomas Schulenberg
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Flow Instability ◽  
Flow Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Low Pressure ◽  
Vertical Annulus ◽  
Zircaloy Tube

We investigated the critical heat flux (CHF) for flow boiling of water in a vertical annulus. The coaxial annulus has a diameter ratio of 1.37 and the inner zircaloy tube is heated directly over a length of 325 mm. CHF can occur prematurely due to flow instabilities. Therefore, we analyzed the flow stability at different heat input conditions using two types of pumps, a rotary and a gear type pump. The unstable CHF occurred at 61% and 90% of the stable value for the rotary and the gear type pump, respectively. Consequently, the following CHF experiments were conducted at stable flow conditions. The outlet pressure was constant at 120 kPa, the mass flux varied from 250 to 1000 kg/(m2s) and the inlet subcooling was at 102, 167, and 250 kJ/kg. The CHF results increase with mass flux from 0.67 to 2.62 MW/m2 and show similar trends compared to literature data. However, the experimental data for flow boiling in annuli at low pressure are limited. Additionally, we measured the dynamic contact angle between the zircaloy tube surface and water using the Wilhelmy method.

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