scholarly journals Mathematical modelling of steam-water cycle with auxiliary empirical functions application

2010 ◽  
Vol 31 (3) ◽  
pp. 165-183 ◽  
Author(s):  
Grzegorz Szapajko ◽  
Henryk Rusinowski
Keyword(s):  
Heat Transfer ◽  
Mathematical Modelling ◽  
Water Cycle ◽  
Empirical Modelling ◽  
Flow Capacity ◽  
Energy Processes ◽  
Semiempirical Models ◽  
Energy Balances ◽  
Modelling Methods ◽  
Mass And Energy Balances

Mathematical modelling of steam-water cycle with auxiliary empirical functions applicationResearch oriented on identification of operating states variations with the application of mathematical models of thermal processes has been developed in the field of energy processes diagnostics. Simple models, characterised by short calculation time, are necessary for thermal diagnostics needs. Such models can be obtained using empirical modelling methods. Good results brings the construction of analytical model with auxiliary empirical built-in functions. The paper presents a mathematical model of a steam-water cycle containing mass and energy balances and semiempirical models of steam expansion line in turbine as well as heat transfer in exchangers. A model of steam expansion line in a turbine is worked out with the application of a steam flow capacity equation and an internal efficiency of process equation for each group of stages for the analysed turbine. A model of a heat exchanger contains energy balance and the relation describing heat transfer in an exchanger, proposed by Beckman. Estimation of empirical equations coefficients was realised with the application of special and reliable measurements. Estimation criterion was a weighted relative sum of the remainder squares. There are exemplary calculations results presented in the final part of paper.

scholarly journals Antifreeze life cycle assessment, II: Mathematical modeling

2005 ◽  
Vol 11 (2) ◽  
pp. 85-92
Author(s):  
Jelena Kesic ◽  
Dejan Skala
Keyword(s):  
Mathematical Modeling ◽  
Life Cycle Assessment ◽  
Life Cycle ◽  
Satisfactory Solution ◽  
Different Types ◽  
Two Parameters ◽  
Energy Processes ◽  
Energy Balances ◽  
Mass And Energy Balances

A mathematical model based on the mass and energy balances of all the processes included in antifreeze life cycle assessment (LCA) was defined in the first part of this study [1]. The part of energy that can be transformed into some other kind of energy is called exergy in all energy processes. The concept of exergy considers the quality of different types of energy and materials. It is also a connection between energy and mass transformations where the physical meaning of exergy loss is the loss of material and energy that must be used in the process. The results of the LCA calculation are very useful for analyzing the obtained products and used processes and for determining the conditions under which this analysis was conducted. The result of this study indicated that recycling is the most satisfactory solution for the treatment of used antifreeze taking into account two parameters: material and energy consumption. The reuse of antifreeze should not be neglected as a solution of this analysis.

Innovative energy and mass balance of a continuous evaporating crystallizer

2019 ◽  
pp. 646-654
Author(s):  
Jan Iciek ◽  
Kornel Hulak ◽  
Radosław Gruska
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Working Conditions ◽  
Crystallization Process ◽  
Heat Losses ◽  
Inert Gas ◽  
Gas Removal ◽  
Energy Balances ◽  
Heat Released ◽  
Mass And Energy Balances

The article presents the mass and energy balances of the sucrose crystallization process in a continuous evaporating crystallizer. The developed algorithm allows to assess the working conditions of the continuous evaporating crystallizers and the technological and energy parameters. The energy balance algorithm takes into account the heat released during the crystallization of sucrose, which was analyzed in this study, heat losses to the environment and heat losses due the vapor used for inert gas removal.

Heat Transfer and Flow Phenomena in a Swirl Chamber Simulating Turbine Blade Internal Cooling

1998 ◽  
Author(s):  
C. R. Hedlund ◽  
P. M. Ligrani ◽  
H.-K. Moon ◽  
B. Glezer
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Internal Cooling ◽  
Vortex Pairs ◽  
Nusselt Numbers ◽  
Swirl Chamber ◽  
Flow Phenomena ◽  
Energy Balances

Heat transfer and fluid mechanics results are given for a swirl chamber whose geometry models an internal passage used to cool the leading edge of a turbine blade. The Reynolds numbers investigated, based on inlet duct characteristics, include values which are the same as in the application (18000–19400). The ratio of absolute air temperature between the inlet and wall of the swirl chamber ranges from 0.62 to 0.86 for the heat transfer measurements. Spatial variations of surface Nusselt numbers along swirl chamber surfaces are measured using infrared thermography in conjunction with thermocouples, energy balances, digital image processing, and in situ calibration procedures. The structure and streamwise development of arrays of Görtler vortex pairs, which develop along concave surfaces, are apparent from flow visualizations. Overall swirl chamber structure is also described from time-averaged surveys of the circumferential component of velocity, total pressure, static pressure, and the circumferential component of vorticity. Important variations of surface Nusselt numbers and time-averaged flow characteristics are present due to arrays of Görtler vortex pairs, especially near each of the two inlets, where Nusselt numbers are highest. Nusselt numbers then decrease and become more spatially uniform along the interior surface of the chamber as the flows advect away from each inlet.

Mathematical Modelling of Deciduous Tree Ignition by Ground Lightning Discharge Taking into Account Localization of Reactive Wood

2011 ◽  
Vol 6 (4) ◽  
pp. 95-106
Author(s):  
Nikolay Baranovskiy ◽  
Geniy Kuznetsov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Mathematical Modelling ◽  
Lightning Discharge ◽  
Deciduous Tree ◽  
Tree Trunk ◽  
Mathematical Statement ◽  
Cylindrical System ◽  
Typical Range

Physical and mathematical statement and results of the numerical simulation of a problem about deciduous tree (birch) ignition by ground lightning discharge are presented. The problem is considered in flat statement in cylindrical system of coordinates. Heat transfer features taking into account localization of reactive wood are considered. The parametrical analysis is carried out and conditions of tree trunk ignition in a typical range of parameters of influence of positive discharges are obtained

Mass and energy balances of an autothermal pilot carbonization unit

2019 ◽  
Vol 120 ◽  
pp. 144-155 ◽  
Author(s):  
Andrea Maria Rizzo ◽  
Marco Pettorali ◽  
Renato Nistri ◽  
David Chiaramonti
Keyword(s):  
Energy Balances ◽  
Mass And Energy Balances

scholarly journals A continuum model for meltwater flow through compacting snow

2017 ◽  
Vol 11 (6) ◽  
pp. 2799-2813 ◽  
Author(s):  
Colin R. Meyer ◽  
Ian J. Hewitt
Keyword(s):  
Continuum Model ◽  
Pore Space ◽  
Water Storage ◽  
Greenland Ice Sheet ◽  
Percolation Process ◽  
Surface Mass ◽  
Run Off ◽  
Flow Through ◽  
Energy Balances ◽  
Mass And Energy Balances

Abstract. Meltwater is produced on the surface of glaciers and ice sheets when the seasonal energy forcing warms the snow to its melting temperature. This meltwater percolates into the snow and subsequently runs off laterally in streams, is stored as liquid water, or refreezes, thus warming the subsurface through the release of latent heat. We present a continuum model for the percolation process that includes heat conduction, meltwater percolation and refreezing, as well as mechanical compaction. The model is forced by surface mass and energy balances, and the percolation process is described using Darcy's law, allowing for both partially and fully saturated pore space. Water is allowed to run off from the surface if the snow is fully saturated. The model outputs include the temperature, density, and water-content profiles and the surface runoff and water storage. We compare the propagation of freezing fronts that occur in the model to observations from the Greenland Ice Sheet. We show that the model applies to both accumulation and ablation areas and allows for a transition between the two as the surface energy forcing varies. The largest average firn temperatures occur at intermediate values of the surface forcing when perennial water storage is predicted.

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