Heat Transfer and Fragmentation During Molten-Metal/Water Interactions

1973 ◽  
Vol 95 (4) ◽  
pp. 521-527 ◽  
Author(s):  
L. C. Witte ◽  
T. J. Vyas ◽  
A. A. Gelabert
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Liquid Nitrogen ◽  
Molten Metal ◽  
High Speed ◽  
Vapor Film ◽  
Molten Metals ◽  
Lead Zinc ◽  
Insight Into ◽  
Rapid Transfer

Molten metals, (mercury, lead, zinc, bismuth, tin, and aluminum) were quenched in water and liquid nitrogen. High-speed photographs provide insight into the fragmentation phenomenon. The key to the vapor explosion is the very rapid transfer of heat which requires substantial surface area: fragmentation provides this necessary surface area. Prior fragmentation theories are examined in light of these experiments and are found to be inadequate. This study indicates strongly that fragmentation occurs when a sample is molten and fragmentation is a response to an external stimulus. Alternate causes of fragmentation are proposed and are predicated upon the initial collapse of a vapor film around the molten metal. The data also show that energy required to form new surface area and to displace water during the fragmentation phenomenon is not significant when compared to the energy available in a molten sample.

Flow and Heat Transfer Characteristics of Liquid Nitrogen in Mini/Micro-Channels

2011 ◽  
Author(s):  
P. Zhang
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Liquid Nitrogen ◽  
High Speed ◽  
Flow Boiling ◽  
Flow State ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Micro Channels

Flow and heat transfer characteristics of liquid nitrogen in mini/micro-channels own many particular aspects and are very important for applications. In the present study, the investigation of flow and heat transfer characteristics of liquid nitrogen in mini/micro-channels is presented. It is found that small viscosity enables the flow state in mini/micro-channels to be turbulent state, which proves that the classical theory for pressure drop is still valid if the surface roughness of the passage is properly taken into consideration. Experiments of flow boiling of liquid nitrogen are conducted under both adiabatic and diabatic conditions. It is shown that confinement number Co = 0.5 can be applicable in classifying the heat transfer characteristics of liquid nitrogen in macro- and micro-channels. Flow visualization in micro-channels at low temperatures poses big challenges in image magnification and illumination. These two problems have been subtly overcome in the investigation and clear images have been obtained. The flow patterns and flow regimes of two-phase flow of liquid nitrogen indicate different features from the room-temperature fluidss. Furthermore, a very simple but effective method for 3D flow visualization by one high-speed camera is proposed and implemented. Finally, numerical analysis of the flow boiling of liquid nitrogen in mini/micro-channel is carried out to deepen the understanding of mechanism.

scholarly journals Зависимость нагрева стабилизированных нержавеющей сталью токоограничивающих элементов на основе ВТСП-лент второго поколения от воздействия тока и параметров теплоотвода на границе с жидким азотом

2020 ◽  
Vol 46 (1) ◽  
pp. 28
Author(s):  
С.В. Самойленков ◽  
В.И. Щербаков ◽  
Д.Р. Кумаров ◽  
Д.А. Горбунова
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Stainless Steel ◽  
Surface Area ◽  
Liquid Nitrogen ◽  
Fault Current ◽  
Current Limiting

Fault current heating of the current limiting modules made of 2G HTS tapes and stabilized with stainless steel was studied. It is demonstrated that the speed of current limiting element heating hardly depends on the degree of the stainless steel stabilization. The ways to improve the heat transfer with the help of the increase of the elements’ surface area were demonstrated with the use of a mathematical model taking into account parameters of heat transfer to liquid nitrogen.

scholarly journals Heat-Up Performance of Catalyst Carriers—A Parameter Study and Thermodynamic Analysis

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 964
Author(s):  
Thomas Steiner ◽  
Daniel Neurauter ◽  
Peer Moewius ◽  
Christoph Pfeifer ◽  
Verena Schallhart ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Area ◽  
Internal Surface ◽  
Installation Space ◽  
Parameter Study ◽  
Thin Wall ◽  
Primary Role ◽  
Internal Surface Area

This study investigates geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on heat-up behavior. Parameters considered to have a significant impact on the thermal economy of a monolith are: internal surface area, heat transfer coefficient, and mass of the converter, as well as its heat capacity. During simulation experiments, it could be determined that the primary role is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient only has a secondary role. Furthermore, an optimization loop was implemented, whereby the internal surface area of a commonly used substrate was chosen as a reference. The lengths of the thin wall and high cell density monoliths investigated were adapted consecutively to obtain the reference internal surface area. The results obtained by this optimization process contribute to improving the heat-up performance while simultaneously reducing the valuable installation space required.

Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

2021 ◽  
pp. 146808742110072
Author(s):  
Karri Keskinen ◽  
Walter Vera-Tudela ◽  
Yuri M Wright ◽  
Konstantinos Boulouchos
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
High Temperature ◽  
High Speed ◽  
Transfer Problem ◽  
Wall Heat Transfer ◽  
Gas Temperature ◽  
Reference Case ◽  
High Pressure High Temperature

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

scholarly journals Precise regulation of the relative rates of surface area and volume synthesis in bacterial cells growing in dynamic environments

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Handuo Shi ◽  
Yan Hu ◽  
Pascal D. Odermatt ◽  
Carlos G. Gonzalez ◽  
Lichao Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Time Delay ◽  
Surface Area ◽  
Environmental Changes ◽  
Volume Ratio ◽  
Dynamic Environments ◽  
Bacterial Cells ◽  
Bacterial Growth Rate ◽  
State Size ◽  
Insight Into

AbstractThe steady-state size of bacterial cells correlates with nutrient-determined growth rate. Here, we explore how rod-shaped bacterial cells regulate their morphology during rapid environmental changes. We quantify cellular dimensions throughout passage cycles of stationary-phase cells diluted into fresh medium and grown back to saturation. We find that cells exhibit characteristic dynamics in surface area to volume ratio (SA/V), which are conserved across genetic and chemical perturbations as well as across species and growth temperatures. A mathematical model with a single fitting parameter (the time delay between surface and volume synthesis) is quantitatively consistent with our SA/V experimental observations. The model supports that this time delay is due to differential expression of volume and surface-related genes, and that the first division after dilution occurs at a tightly controlled SA/V. Our minimal model thus provides insight into the connections between bacterial growth rate and cell shape in dynamic environments.

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