Optimum design of a radial heat sink under natural convection

doi:10.1016/j.ijheatmasstransfer.2011.02.012

International Journal of Heat and Mass Transfer

Volume 54, Issues 11–12, May 2011, Pages 2499-2505

https://doi.org/10.1016/j.ijheatmasstransfer.2011.02.012 Get rights and content

Abstract

We investigated natural convection heat transfer around a radial heat sink adapted for dissipating heat on a circular LED (light emitting diode) light and optimized heat sink. The numerical results were validated with experimental results and it showed a good agreement. To select the optimum reference model, three types of heat sinks (L, LM and LMS model) were compared. Parametric studies were performed to compare the effects of the number of fins, long fin length, middle fin length and heat flux on the thermal resistance and average heat transfer coefficient. Finally, multi-objective optimizations considering thermal performance and mass simultaneously were performed and Pareto front were conducted with various weighting factors. It was found that it was impossible to optimize both thermal performance and heat sink mass at the same time, and there existed an upper limit to the ratio of weighting factors (ω₁/ω₂).

Introduction

The light-emitting diode (LED) market has grown recently, thanks to enhancements in LED luminous efficiency. Nevertheless, about 70% of the total energy consumed by an LED light is emitted as heat, creating a thermal problem. Without properly dissipating this heat, the performance and life of an LED light is impaired. Thus, to commercialize LED lights, the problem of heat dissipation must be solved first. Natural convection heat sinks are appropriate for LED lights, in view of their overall advantages.

There have been numerous experimental [1], [2], [3], [4], [5] and numerical [6], [7] studies of natural convection heat transfer in rectangular-fin or pin-fin heat sinks. Harahap and Setio [1] performed experiments to obtain the average heat transfer coefficients for five different rectangular heat sinks, and proposed a correlation to predict the average heat transfer coefficient. Huang et al. [2] conducted an experimental study of seven types of pin-fin heat sinks (both vertically and horizontally oriented), and the optimum shape of a pin-fin heat sink was suggested for each orientation. Bar-Cohen et al. [6] optimized a rectangular heat sink by employing existing correlations; they considered the mass of the heat sink, as well as the thermal performance. Dialameh et al. [7] carried out a numerical study to predict natural convection from arrays of aluminum horizontal rectangular thick fins with short lengths. They compared the effects of various fin geometries and temperature differences on the convection heat transfer of heat sinks, and proposed a non-dimensional correlation. However, most of these studies were concerned with heat sinks with rectangular bases, which might be not straightforward for cooling circular LED lights.

In this study, natural convection heat transfer around a radial heat sink is investigated, experimentally and numerically. The numerical model is validated by the experimental results. To determine the optimum reference model, we numerically compare the L model (long fin), the LM model (long and middle fins) and the LMS model (long, middle and short fins). Parametric studies are performed to compare the effects of the number of fins, long fin length, ratio of middle to long fin length, and heat flux on the thermal resistance and average heat transfer coefficient. Finally, optimal designs of radial heat sinks with various heat fluxes are suggested.

Section snippets

Mathematical modeling

Fig. 1 illustrates a radial heat sink, composed of a circular base and rectangular fins. The fins are assumed to be radially arranged at regular intervals. The heat sink base is horizontal, while the fins are vertical. The material of the heat sink is aluminum. Table 1 lists the properties of aluminum and air.

Experiments and validation

The numerical model is verified with experimental data, by comparing the differences between ambient and heat sink temperatures. The heat sink is made of aluminum (Al2014), with no additional surface treatment. As Fig. 3(a) shows, the experimental setup consisted of a film heater (Kapton-coated stainless steel, 25 μm), a heat sink, an insulator, type-T thermocouples (gauge 36), a data acquisition device (NI cDAQ-9172, NI9211), a power supply, a wattmeter, and a personal computer. The film heater

Results and discussion

To choose the optimum reference model, we compare the L model (long fin), the LM model (long and middle fins) and the LMS model (long, middle and short fins). Parametric studies and design optimization are carried out for the model exhibiting the best performance.

Conclusions

Numerical analyses were conducted to optimize a radial heat sink adapted to a circular LED light. Experiments were performed to validate the numerical model, and the agreement was good. To determine the optimum model, three types of heat sink (L, LM and LMS models) were compared and the LM model exhibited superior thermal performance. Parametric studies were performed to compare the effects of three geometric parameters (number of long fins, long fin length and middle fin length) and an

Acknowledgment

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2010-0008537).

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Optimum design of a radial heat sink under natural convection

Abstract

Introduction

Section snippets

Mathematical modeling

Experiments and validation

Results and discussion

Conclusions

Acknowledgment

Int. J. Heat Mass Transfer

Int. J. Heat Mass Transfer

Appl. Therm. Eng.

Int. J. Heat Mass Transfer

Int. J. Heat Mass Transfer

Int. J. Heat Mass Transfer

Correlation for heat dissipation and natural convection heat-transfer from horizontally based, vertically-finned arrays

Appl. Energy