Heat transfer between liquid and air on surface with different shape of dimples

Dubrovskyi V.V., Cand. Sci. (Eng.), Senior Researcher
Institute of General Energy of the National Academy of Sciences of Ukraine, 172 Antonovycha St., Kyiv, 03680, Ukraine
Language: Ukrainian
Source: Problemy zahal`noi enerhetyky - The Problems of General Energy, 2016, 1(44):41-47
Section: Study and optimization of the technological objects and systems of the energy sector
UDC: 536.24
Received: 10.02.2016
Published: 13.04.2016
Abstract: Profiling of the surface of sprinklers of film-type cooling towers in the form of dimples leads to a significant increase in heat transfer between the liquid and surrounding air as compared with a smooth surface. The shape of dimples on the surface of the flow affects the degree of flow turbulization and heat transfer intensification. The search for the geometric shapes of dimples on the sprinklers surface leading to an increase in the efficiency of the operation of cooling towers is a topical technical problem.
The aim of this work is to investigate experimentally the influence of dimples shape on the surface of sprinklers on the heat transfer from flowing water film to ambient air and determine the best profiled surface of sprinklers.
Our experiments were carried out with dimples of spherical, cylindrical, rhombic, and square shapes on the surfaces of sprinklers. These investigations were performed on different modes of interaction between the water and air phases under conditions of cross flow of water film by air of different velocity as well as under conditions of quiescent air environment.
We have obtained empirical dependencies that allow one to calculate the coefficients of heat transfer on the surfaces with spherical, cylindrical, rhombic, and square dimples. We have established that, from the view point of heat transfer, surfaces with spherical dimples are the best, and we recommend them for the implementation at film-type cooling towers.
Keywords: film-type cooling tower, the shape of dimples on the surface of sprinklers, heat transfer, degree of cooling.
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