Abstract
In this study, thermal resistances of horizontal cylinders with triangular fins were measured in regard to fin numbers, fins heights, and temperature differences. Thereafter, an empirical correlation was proposed and validated for predicting the Nusselt numbers under the following conditions: Rayleigh number, 200,000–1,000,000; fin aspect ratio, 1.6–5.0; and fin number, 9–72. Finally, with the proposed correlation, the effects of fin numbers, fins heights, and fin thicknesses on the thermal resistances of the horizontal cylinders with triangular fins were investigated. It was shown that the thermal resistance generally increases as the fin number, fin height, and fin thickness increase. It is expected that horizontal cylinders for various cooling devices with triangular fins can be designed based on the findings of the present study.
Highlights
Because of the demands for more powerful and compact energy systems, current energy systems are experiencing a rapid increase in their heat loads [1,2]
The results of the measured temperature differences between the cylinder surface and ambient air for various heat inputs are shown in Figure 5 and Table 3
The Nusselt numbers were calculated from the thermal resistances using Equation (2) below, which is the relationship between the thermal resistance and the Nusselt number
Summary
Because of the demands for more powerful and compact energy systems, current energy systems are experiencing a rapid increase in their heat loads [1,2]. As a result, cooling devices for energy systems have become essential, because system temperatures can become excessively high if heat is not dissipated through proper cooling devices. High temperatures are detrimental to the performance and reliability of these systems. In the case of light emitting diode (LED) lightings, the light outputs decrease with increasing diode temperatures, the light colors change undesirably at high temperatures, and diodes can deteriorate irreversibly at high temperatures [3,4,5,6,7]. Various cooling devices have been proposed, among which, extended surfaces under natural convection have been widely used [8,9]
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