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Usage the transfer properties in heating and evaporable cooling of the fluid film during design stage of heat and mass exchangers

Tuz V.E., Dr. Sci. (Engin.), Professor, Lebed N.L., PhD (Engin.), Associate Professor
National Technical University of Ukraine "Kyiv Polytechnic Institute", pr. Peremohy, 37, Kyiv, 03056, Ukraine
Language: Ukrainian
Source: The Problems of General Energy, 2014, 4(39):42-45
Section: Study and optimization of the technological objects and systems of the energy sector
UDC: 532.529
Received: 01.12.2014
Published: 27.11.2014

Abstract:

In designing the heat-mass-exchange apparatuses of power units the changing characteristics of the heat exchange process along the length of the contact surface in order to improve the efficiency of equipment.
In contact of the gravitational film with moving gas-vapor mixture, in addition to hydrodynamic and thermal boundary layers the diffusion boundary layer is also formed. In this case, the heat and mass transfer coefficients depend on the direction and value of the cross-flow mass.
The solution of the combined differential equations describing heat and mass transfer processes in the system, is conducted with known values of middle surface heat and mass transfer coefficients. To obtain accurate result it is necessary to take into account the averaging of factor values at the initial area and the heat exchange area. To do this it is necessary to define the limits of the initial areas.
Experimental study of heat and mass transfer processes in evaporative liquid and gas cooling allowed to establish a non-linear change of heat transfer coefficients and heat and mass transfer along the length of the channel.
Based on the obtained results the dependencies were defined that allow to determine the length of the initial heat area depending on the operating conditions of the contacting phases and geometric channel characteristics.

Keywords: film of the liquid, gas flow, heat transfer rate, initial heat area.

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