DEVELOPMENT OF COLD THERMAL PLUMES INDUCED BY A ROTATING COLD SURFACE

1995 ◽  
Vol 2 (4) ◽  
pp. 335-342 ◽  
Author(s):  
Genshi Kawashima ◽  
Wen-Jei Yang ◽  
Hiroshi Ohue
Keyword(s):  
Cold Surface ◽  
Thermal Plumes

Effects of Gap Geometry and Gravity on Boiling Around a Constrained Bubble in 2-Propanol/Water Mixtures

2006 ◽  
Vol 129 (2) ◽  
pp. 114-123
Author(s):  
Chen-li Sun ◽  
Van P. Carey
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Molar Fraction ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Cold Surface ◽  
Boiling Regime ◽  
Wall Superheat ◽  
Boiling Process ◽  
Lower Heat

In this study, boiling experiments were conducted with 2-propanol/water mixtures in confined gap geometry under various levels of gravity. The temperature field created within the parallel plate gap resulted in evaporation over the portion of the vapor-liquid interface of the bubble near the heated surface, and condensation near the cold surface. Full boiling curves were obtained and two boiling regimes—nucleate boiling and pseudofilm boiling—and the transition condition, the critical heat flux (CHF), were identified. The observations indicated that the presence of the gap geometry pushed the nucleate boiling regime to a lower superheated temperature range, resulting in correspondingly lower heat flux. With further increases of wall superheat, the vapor generated by the boiling process was trapped in the gap to blanket the heated surface. This caused premature occurrence of CHF conditions and deterioration of heat transfer in the pseudo-film boiling regime. The influence of the confined space was particularly significant when greater Marangoni forces were present under reduced gravity conditions. The CHF value of x (molar fraction)=0.025, which corresponded to weaker Marangoni forces, was found to be greater than that of x=0.015 with a 6.4mm gap.

PIV methods for quantifying human thermal plumes in a cabin environment without ventilation

2016 ◽  
Vol 20 (3) ◽  
pp. 535-548 ◽  
Author(s):  
Jiayu Li ◽  
Junjie Liu ◽  
Congcong Wang ◽  
Nan Jiang ◽  
Xiaodong Cao
Keyword(s):  
Thermal Plumes ◽  
Cabin Environment

Addressing Paraffin Deposition Challenges Through New Technologies

2021 ◽  
Author(s):  
Saugata Gon ◽  
Christopher Russell ◽  
Kasper Koert Jan Baack ◽  
Heather Blackwood ◽  
Alfred Hase
Keyword(s):  
Temperature Gradient ◽  
Surface Temperature ◽  
New Technologies ◽  
Test Methods ◽  
Large Temperature ◽  
Mixing Condition ◽  
Cold Finger ◽  
Cold Surface ◽  
Bulk Oil ◽  
Conventional Test

Abstract Paraffin deposition is a common challenge for production facilities globally where production fluid/process surface temperature cools down and reach below the wax appearance temperature (WAT) of the oil. Although chemical treatment is used widely for suitable mitigation of wax deposition, conventional test methods like cold finger often fail to recommend the right product for the field. The current study will present development of two new technologies PARA-Window and Dynamic Paraffin Deposition Cell (DPDC)to address such limitations. Large temperature gradient between bulk oil and cold surface has been identified as a major limitation of cold finger. To address this, PARA-Window has been developed to capture the paraffin deposition at a more realistic temperature gradient (5°C) between the bulk oil and surface temperature using a NIR optical probe. Absence of brine and lack of shear has been identified as another limitation of cold finger technique. DPDC has been developed to study paraffin deposition and chemical effectiveness in presence of brine. Specially designed cells are placed horizontally inside a shaker bath to achieve good mixing between oil and water for DPDC application. A prior study by Russell et al., (2019) showed the effectiveness of PARA-Window in capturing deposition phenomena of higher molecular weight paraffin chains that resemble closely to field deposits under narrow temperature gradient around WAT. Conventional test methods fail to capture meaningful product differentiation in most oils under such conditions and hence can only recommend a crystal modifier type of paraffin chemistries. PARA-Window technique can expand product selection to other type of paraffin chemistries (paraffin crystal modifiers, dispersants and solvents) as shown earlier by Russell et al., (2021). The usage of DPDC allows us to create a dynamic mixing condition inside the test cells with both oil and water under a condition similar to production pipe systems. This allows DPDC to assess water effect on paraffin chemistries (crystal modifiers and dispersants). This study presents the usage of these two new technologies to screen performance of different types of paraffin chemistries on select oils and their advantages over cold finger. The results identify how mimicking field conditions using these new technologies can capture new insights into paraffin products.

Influence of Thermal Plume on Particle Inhalability of a Lying Mannequin in a Room

2021 ◽  
Author(s):  
Maryam Habibi ◽  
Mohsen Heidary ◽  
Mohammad Mehdi Tavakol ◽  
Goodarz Ahmadi
Keyword(s):  
Respiratory System ◽  
Spherical Particles ◽  
Thermal Plume ◽  
Ansys Fluent ◽  
Thermal Plumes ◽  
Micro Particles ◽  
Upward Direction ◽  
Fluent Software ◽  
Turbulence Dispersion ◽  
Aspiration Efficiency

Abstract In this study, the dispersion and deposition of particles in the respiratory system attached to a mannequin lying down inside a room were investigated numerically. The respiratory system model was prepared by processing the CT scan images of a volunteer and was attached to a mannequin lying in the middle of a room. The flow field around the mannequin and effects of the thermal plume on the particle aspiration by the mannequin model was simulated using the Ansys-Fluent software. The aspiration efficiency of spherical particles in the airway was studied with the Lagrangian particle trajectory analysis, including the turbulence dispersion effects. For validation of numerical simulations, the aspiration efficiency of the particles obtained from the numerical solution was compared with the case of a standing mannequin. The results are presented for two different modes with upward and downward thermal plumes. For the first mode, due to the strong effect of the thermal plume in the upward direction, the aspiration efficiency of midrange particles increases. However, the aspiration efficiency of large micro-particles decreases for the first mode. For the second mode, with the downward thermal plume, the aspiration efficiency of small micro-particles increases significantly.

Experimental Research on Steam Condensation on Cold Surface: Facility Design

2014 ◽  
Author(s):  
Li-Yong Han ◽  
Lin Yang ◽  
Shan Zhou ◽  
Shen Wang ◽  
Chun-Lai Tian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Cooling System ◽  
Theoretical Research ◽  
Test Facility ◽  
Measurement Technology ◽  
Ambient Conditions ◽  
Steam Condensation ◽  
Cold Surface ◽  
Process Gas

The passive containment cooling system (PCCS) of the 3rd generation APWR utilizes natural phenomena to transfer the heat released from the reactor to the environment during postulated designed basic accidents. Steam condensation on the inner surface of the containment shell is one of the most dominate mechanism to keep the ambient conditions within the design limits. Extensive experiment and theoretical research shows condensation is a complex process, gas pressure, film temperature and velocity of the gas have impact on the heat transfer coefficient. To span the expected range of conditions and provide proper model for evaluating the condensation heat transfer process, SCOPE test facility was designed by State Nuclear Power Technology Research & Development Centre (SNPTRD) in various conditions anticipated the operating range of CAP1400 in accident conditions. Pressurized test section with a rectangular flowing channel was used, with one of the walls cooled to maintain low temperature for condensing, supplying systems was designed for different pressures, gas temperatures, velocities and coolant water temperatures. Facility components, test section structure, supplying systems and measurement technology were described in this paper, also results of some pre-tests was introduce to show property of the facility.

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