Experimental data generalization on heat transfer in cooling system with axial sectional finning in conditions of free convection

Aeronautical and Space-Rocket Engineering

Design, construction and manufacturing of flying vehicles


Аuthors

Lopatin A. A.*, Nikolaeva D. V.**, Gabdullina R. A.***

Institute of Aviation, Land Transport and Energy, KNRTU-KAI, 10, K. Marx str., Kazan, 420111, Russia

*e-mail: aalopatin@kai.ru
**e-mail: Dashulkakuku@mail.ru
***e-mail: rozzy94@mail.ru

Abstract

At present, power electronic components with high heat release have been widely applied in various fields of modern industry. The main problem the developers of the element base are facing consists in creating cooling and thermal stabilization systems capable of removing heat fluxes of high density, while working in a wide range of ambient temperatures. When creating such systems, it is necessary, alongside with the thermal ones, to account for the mass-size characteristics of the device as a whole. Thus, much depends on the heat transfer intensification method selection.

Quite enough attention is paid in modern literature to the issues of radio electronic equipment thermally loaded elements, as evidenced by a significant number of articles and monographs on this topic. Heat release is one of the main causes of the unstable operation of radio electronic equipment. Among the basic factors exerting maximum destructive effect, the increased temperature of the elements is one of the main ones. Thus, the devices operation in the field of the radio electronic equipment is closely associated with heat removal from the thermally loaded components. Depending on the structure and shape of the cooled components, various solutions are employed for organizing continuous heat removal.

Certain problems of large heat fluxes removing in the elements of industrial electronic equipment were considered in [1-3]. The correct choice of the cooling system type ensures trouble-free operation of all cooled components of the device.

A considerable amount of publications in modern scientific publications, both in Russia and abroad, attest to the considerable interest in the issues related to the heat transfer intensification for surfaces of various shapes and sizes as applied to cooling systems for electronic equipment. The issues of heat transfer intensification are set forth in [4-10]. In particular, the criterion equations of various authors for the Nusselt number computing for natural convection are presented in [2, 9]. Experimental studies of the convective heat transfer intensification in rectangular dissected channels and in channels with discrete turbulators were described in [1, 10]. In the studied dissected channels, a process of rational convective heat transfer intensification was implemented, reliably controlled by changing the values of the basic dimensionless geometric parameters. The generalizing dependences for discrete-rough channels were obtained in [7] for free convection conditions, and flow modes and mechanisms of intensification were studied. In [11-14], the authors experimentally studied one of the parameters characterizing the cooling systems both qualitatively and quantitatively, namely, the thermal resistance.

The fins application as a method of heat transfer intensifying leads to the increase in the heat transfer coefficient value by a factor of tens. This method of intensification implies a wide variety of vatious types of fins, such as: longitudinal, transverse, rolling, spiral and many others [15,16]. In [15] the analysis of the expediency of employing different types of fins from the viewpoint of the coolant aggregate state is presented. The optimal edges number selection is presented in [16]. The heat transfer intensification of the systems with a cut-off fin is also considered in [17-20].

The purpose of this work consists in studying the efficiency of the split finning under conditions of natural convection. A test bench was developed for performing the experiment on the study of heat transfer. While the experiments on heat transfer near the cut edge under conditions of natural convection, criterion dependencies were obtained.

Relying on the analysis of literature sources and accounting for the results obtained while experimental studies, the authors established that from the viewpoint of the of axial split finning practical applicability, there are a number of specifics, associated primarily with the fact that the “petals”, obtained as a result of dissection of the heat exchange surface, can be considered as independent ribs. The studies of heat transfer intensification under conditions of natural convection with the cut ribs application were conducted and presented as a result of the work. While the experiment, the effectiveness of the use of split finning is demonstrated, and the most optimal geometric parameters of the working area were revealed. The process of heat transfer was visualized. The boundary layer thickness near the cut edge was computed. Criterion dependencies for heat transfer computing of the systems with axial cut fins were obtained. The prospect of this study is of experimental data verification by numerical modeling programs.

Keywords:

cooling systems, split fins, heat exchange, heat exchange intensification, heat flow, boundary layer thickness computing

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