Open AccessTWO-PHASE MODELLING OF THERMAL DISSIPATION IN A NATURAL BASIN
Author(s) -
Pranas Baltrėnas,
Petras Vaitiekûnas,
Vladislovas Katinas,
Antanas Markevičius
Publication year - 2004
Publication title -
journal of environmental engineering and landscape management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.514
H-Index - 28
eISSN - 1822-4199
pISSN - 1648-6897
DOI - 10.3846/16486897.2004.9636827
Subject(s) - wind speed , mechanics , heat transfer , heat transfer coefficient , turbulence modeling , thermodynamics , environmental science , meteorology , thermal conduction , boundary layer , atmospheric sciences , geology , physics , turbulence
The state of two‐phase flow ‘liquid‐gas’ has been modeled numerically by the three‐dimensional method of complex research of heat and mass transfer. This allows examining the interaction of some transfer processes in a natural cooling basin (the Drūkšiai lake): the wind power and direction, variable water density, the coefficient of heat conduction and heat transfer of the water‐air interface. Combined effect of these natural actions determines the heat amount that the basin is able to dissipate to the surrounding atmospheric media in thermal equilibrium (without changes in the mean water temperature).This paper presents a number of the most widely used expressions for the coefficients of vertical and horizontal heat transfer. On the basis of stream velocity and mean temperature profiles measured in the cooling pond as well as on that of their time variations suggestions are made that the mixing rate at the water surface is caused by natural space ‐ time variation of the wind, and can be described by the value of eddy viscosity coefficient ‐ 1 m2/s (numerical modeling with 0,9–1,3 m2/s). The wind influences the surface of the lake according to the experimental data, i e 1–3 % of the mean wind velocity. The model applies to the weakly wind, approximately 1–5 m/s of the mean wind velocity.Comparison of experimental and numerical results showed a qualitative agreement. For a better quantitative approximation, it is necessary to have more boundary conditions variable with time and to solve unsteady set equations for transfer processes.