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 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 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

scholarly journals Predicting Critical Heat Flux With Multiphase CFD: 4 Years in the Making

2017 ◽  
Author(s):  
Emilio Baglietto ◽  
Etienne Demarly ◽  
Ravikishore Kommajosyula
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Heated Surface ◽  
Force Balance ◽  
Modeling Framework ◽  
Lift Off ◽  
Limiting Condition

Advancement in the experimental techniques have brought new insights into the microscale boiling phenomena, and provide the base for a new physical interpretation of flow boiling heat transfer. A new modeling framework in Computational Fluid Dynamics has been assembled at MIT, and aims at introducing all necessary mechanisms, and explicitly tracks: (1) the size and dynamics of the bubbles on the surface; (2) the amount of microlayer and dry area under each bubble; (3) the amount of surface area influenced by sliding bubbles; (4) the quenching of the boiling surface following a bubble departure and (5) the statistical bubble interaction on the surface. The preliminary assessment of the new framework is used to further extend the portability of the model through an improved formulation of the force balance models for bubble departure and lift-off. Starting from this improved representation at the wall, the work concentrates on the bubble dynamics and dry spot quantification on the heated surface, which governs the Critical Heat Flux (CHF) limit. A new proposition is brought forward, where Critical Heat Flux is a natural limiting condition for the heat flux partitioning on the boiling surface. The first principle based CHF is qualitatively demonstrated, and has the potential to deliver a radically new simulation technique to support the design of advanced heat transfer systems.

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