scholarly journals Discussion: “Mass-Transfer Model in Subcooled Nucleate Boiling” (Snyder, N. W., and Robin, T. T., 1969, ASME J. Heat Transfer, 91, pp. 404–411)

1969 ◽  
Vol 91 (3) ◽  
pp. 412-412
Author(s):  
M. G. Cooper
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Nucleate Boiling ◽  
Transfer Model ◽  
Mass Transfer Model

Mass-Transfer Model in Subcooled Nucleate Boiling

1969 ◽  
Vol 91 (3) ◽  
pp. 404-411 ◽  
Author(s):  
N. W. Snyder ◽  
T. T. Robin
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Energy Transport ◽  
Heated Surface ◽  
Thin Liquid Film ◽  
Nucleate Boiling ◽  
Transfer Mechanism ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Mass Transfer Mechanism

The mass-transfer model of subcooled boiling, conceived in 1952 by N. W. Snyder, is reviewed. Described is an experiment in which a water-vapor bubble was studied from its growth on a heated surface, through a thermal layer, and into a turbulent stream of subcooled water flowing parallel to the heated surface. The effectiveness of the turbulent subcooled stream in removing heat deposited by condensation on the surface of the bubble was determined. The results show that the thermal-energy transport associated with the mass-transfer mechanism in boiling heat transfer can be absorbed effectively at the top of the bubble. Also given are the results of a theoretical investigation in which two models of bubble dynamics were derived. The first model describes the artificial bubble produced in the experiment just noted. The second model describes the dynamics of a bubble growing on a heated surface, into a subcooled liquid, and with an evaporating thin liquid film below the bubble on the heated surface. The results show that the importance of the mass-transfer mechanism has been underestimated in the past and that this mechanism is responsible for a substantial portion, or almost all, of the heat transfer in subcooled nucleate boiling in forced convection.

Numerical Simulation of Flow Boiling of Binary Mixtures Using Multi-Fluid Modeling Approach

2011 ◽  
Author(s):  
Vedanth Srinivasan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Interfacial Area ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Number Density ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper, the development of a new mass transfer model to simulate the thermal and phase change characteristics encountered by binary mixtures during flow boiling process is discussed. A new boiling mass transfer model based on detailed bubble dynamic effects, inclusive of local bubble shear, drag and buoyancy dynamics, has been developed and full implemented within the commercial CFD code AVL FIRE v2010. In the present study the phasic mass, momentum and energy equations are solved in a segregated fashion in conjunction with an interfacial area transport and a number density equation to study the heat and mass transfer characteristics of binary flow boiling inside a rectangular duct. Turbulence in the fluidic system and those generated by the bubbly flow are treated using an advanced k-ζ-f model. The simulation results comprising of flow variables such as volume fraction, fluidic velocities and temperature and the resultant heat flux generated on the heated wall section clearly monitors the suppression in heat transfer coefficients with enhancement in flow convection. Competing mechanisms such as phase change process and turbulent convection are identified to influence the heat transfer characteristics. In particular, the varying influence of the mass transfer effects on the heat flux characteristics with alteration in wall temperature is well demonstrated. Comparisons of the predicted heat transfer coefficients for varying wall superheat and varying fluidic velocity indicates a very good agreement with experimental data, wherever available. Description of the flow field inclusive of interfacial area and number density distribution is provided. The current model can be easily extended to simulate multiphase flow in complex systems such as a cooling water jacket for automotive applications.

scholarly journals Understanding the mass, momentum, and energy transfer in the frozen soil with three levels of model complexities

2020 ◽  
Vol 24 (10) ◽  
pp. 4813-4830 ◽  
Author(s):  
Lianyu Yu ◽  
Yijian Zeng ◽  
Zhongbo Su
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Energy Transfer ◽  
Frozen Soil ◽  
Transfer Model ◽  
Vapor Flow ◽  
Mass Transfer Model ◽  
Simultaneous Transfer ◽  
Explicit Consideration

Abstract. Frozen ground covers a vast area of the Earth's surface and it has important ecohydrological implications for cold regions under changing climate. However, it is challenging to characterize the simultaneous transfer of mass and energy in frozen soils. Within the modeling framework of Simultaneous Transfer of Mass, Momentum, and Energy in Unsaturated Soil (STEMMUS), the complexity of the soil heat and mass transfer model varies from the basic coupled model (termed BCM) to the advanced coupled heat and mass transfer model (ACM), and, furthermore, to the explicit consideration of airflow (ACM–AIR). The impact of different model complexities on understanding the mass, momentum, and energy transfer in frozen soil was investigated. The model performance in simulating water and heat transfer and surface latent heat flux was evaluated over a typical Tibetan plateau meadow site. Results indicate that the ACM considerably improved the simulation of soil moisture, temperature, and latent heat flux. The analysis of the heat budget reveals that the improvement of soil temperature simulations by ACM is attributed to its physical consideration of vapor flow and the thermal effect on water flow, with the former mainly functioning above the evaporative front and the latter dominating below the evaporative front. The contribution of airflow-induced water and heat transport (driven by the air pressure gradient) to the total mass and energy fluxes is negligible. Nevertheless, given the explicit consideration of airflow, vapor flow and its effects on heat transfer were enhanced during the freezing–thawing transition period.

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