Thermal Analysis of the Heat Sink Performance using FEM

This introduction paper is based on the paper "Thermal Analysis of the Heat Sink Performance using FEM" published by "Journal of the Korea Academia-Industrial cooperation Society".

1. Overview:

Title: Thermal Analysis of the Heat Sink Performance using FEM
Author: Bong-Gu Lee¹, Min Lee²
Year of publication: 2014
Journal/academic society of publication: Journal of the Korea Academia-Industrial cooperation Society
Keywords: Heat sink, FEM, Peltier Module, Internal Structure, Natural Convection

2. Abstract:

This study examined the numerical analysis results with respect to the thermal behavior of a natural convection cooled pin-fin heat sink. The heat sink consisted of pin fins integrated with plate fins. The heat sinks were designed with two different types to fit the limited internal space. The two types of heat sinks designed were analyzed using the ANSYS software package, and the numerical analysis results were compared with the cooling performance of the two types of heat sinks. The results of the simulation were analyzed according to the temperature distribution and air flow characteristics, heat flux etc. This study examined the correlation of the cooling performance with the heat sink internal structure and fin shape. FEM (Finite Element Method) confirmed the cooling performance of heat sink type A under natural convection conditions as the best results. The results of the numerical simulation showed that the heat sink type A shape showed an approximately 70 percent better heat transfer rate with natural convection than that of type B.

3. Introduction:

With the recent advancements in electronic and mechanical component technology, electronic equipment is becoming higher in performance, smaller in size, and more multifunctional. This trend leads to increased heat generation within systems, which can degrade performance or cause malfunctions. Heat sinks are employed to manage the temperature of these heat-generating parts. Thermoelectric devices (TE) have been utilized for cooling purposes. TE devices, composed of P-type and N-type semiconductors, can be categorized into Thermoelectric coolers (Peltier effect) and Thermoelectric generators (Seebeck effect). Peltier coolers convert electricity into thermal energy, creating a cooling effect on one side and heating on the other (heat pumping). If the temperature of the heat-generating part of a Peltier device is not well controlled, heat can conduct back to the cooling part, drastically reducing efficiency. Heat sinks, typically featuring cooling fins attached to a base plate, are used for this temperature control. This study focuses on numerically analyzing the thermal performance of two types of heat sinks with internal tunnel structures using the ANSYS finite element program. The analysis was conducted under natural convection conditions to compare and evaluate the thermal performance based on cooling fin shape, heat transfer characteristics, and temperature distribution over time.

4. Summary of the study:

Background of the research topic:

The increasing power density and miniaturization of electronic devices lead to significant heat generation, which can impair device performance and reliability. Heat sinks are essential components for thermal management, dissipating heat to the surrounding environment. Peltier modules, a type of thermoelectric cooler, are often used but require efficient heat dissipation from their hot side to maintain cooling efficiency.

Status of previous research:

Previous research has extensively covered thermoelectric devices [1-3], including the Peltier effect for coolers [4-6] and the Seebeck effect for generators [7]. The heat pumping phenomenon in Peltier devices is well-documented [8]. Common heat sinks involve plate-fin designs [9,10], and various studies have explored different heat sink designs and their optimization through analysis and experiments [11-13]. Research on plate-type heat sinks using forced convection has been widely conducted [14,15], and the impact of pin-fin dimensions (height, diameter, spacing) on heat transfer has been investigated [16].

Purpose of the study:

The purpose of this study was to evaluate the thermal performance of two different types of heat sinks with internal tunnel structures using the finite element program ANSYS. The numerical analysis aimed to compare and analyze the cooling performance under natural convection conditions based on the cooling fin shape. Furthermore, the study aimed to predict the performance of the heat sinks based on the analysis results of heat transfer characteristics and temperature distribution over time.

Core study:

The core of this study involves the design and 3D modeling of two distinct heat sink types (Type A and Type B) featuring internal tunnel structures and pin fins. These designs were then subjected to transient thermal analysis using ANSYS software under natural convection conditions. The study focused on comparing their cooling performance by examining temperature distribution, heat flux, and overall heat transfer rates to determine the more effective design for the given constraints.

5. Research Methodology

Research Design:

Two types of heat sinks, designated Type A and Type B, with internal pin fin structures, were designed using Pro-E software. The material selected for the heat sinks was Aluminum (AL6061). The thermal performance of these designs was evaluated using transient thermal analysis within the ANSYS FEM software package, specifically under natural convection conditions.

Data Collection and Analysis Methods:

The analysis was based on fundamental heat transfer principles, including Fourier's law of conduction (Eq. 1, 2 from the paper), Newton's law of cooling (Eq. 3), and fin effectiveness (Eq. 4).
The numerical simulation (FEM) was performed using ANSYS.
Boundary conditions for the simulation included:

A Peltier device providing a cooling temperature of -14°C (assuming a 13V input).
Natural convection boundary conditions on the heat sink surfaces, with an ambient temperature of 22°C.
Data analysis focused on temperature distribution across the heat sinks over a 30-second period and the resulting heat flux.

Research Topics and Scope:

The research scope encompassed:

The design and 3D modeling of two heat sink types (Type A and Type B) made from AL6061.
Comparison of their thermal performance under natural convection.
Investigation of the influence of the internal structure and fin shape on cooling capabilities.
Analysis of temperature distribution and heat flux to predict heat sink performance.
Meshing of the models for FEM analysis, with specific node and element counts for each type (Table 4).

6. Key Results:

Key Results:

The surface area of Heat Sink Type A (146,624 mm²) was approximately 25% larger than that of Type B (108,759 mm²) ([Table 3]).
Temperature Distribution ([Fig. 3], [Table 5]): After 30 seconds of operation under natural convection, Heat Sink Type A exhibited a minimum temperature of -11.44°C and a maximum of -11.19°C. Heat Sink Type B showed a minimum temperature of -12.05°C and a maximum of -11.92°C. The paper states that Type A has superior cooling performance due to its larger surface area, which enhances heat transfer efficiency.
Heat Flux ([Fig. 4]):
- Type A Heat Sink: Minimum heat flux of 2.34 W/m² (paper states 2.34W/m², Fig. 4 indicates 6.90e-6 W/mm² which is 6.9 W/m² if units are consistent with the text's interpretation for Type B), maximum heat flux of 2246.3 W/m² (paper states 2246.3W/m², Fig. 4a shows max in W/mm² - interpretation needed or take text value). The paper's text indicates 2246.3 W/m² as max. Using text values for clarity: Max 2246.3 W/m².
- Type B Heat Sink: Minimum heat flux of 6.9 W/m², maximum heat flux of 870.9 W/m².
Heat Transfer Rate: The heat transfer rate for Type A was highest at 14.9 kW, while Type B had a lower heat transfer rate of 8.7 kW.
Overall Performance: The numerical simulation results indicated that Heat Sink Type A demonstrated an approximately 70% better heat transfer rate under natural convection compared to Type B. This was attributed to faster air flow velocity over Type A's surfaces and a lower temperature distribution towards the fin tips, leading to increased heat flux and, due to its larger surface area, a higher overall heat transfer rate.

[Fig. 2] Elements of heat sink (a) type A (b) type B

[Fig. 3] Temperature distribution of heat sink (a) type A (b) type B

Figure Name List:

[Fig. 1] Heat conduction through a large plane wall
[Fig. 2] Type of heat sink with internal structure (a) type A (b) type B
[Fig. 3] Temperature distribution of heat sink (a) type A (b) type B
[Fig. 4] Heat flux of heat sink (a) type A (b) type B
[Table 1] Thermal properties of AL6061
[Table 2] Minimum thickness of the die casting products[16]
[Table 3] Type of surface area
[Table 4] Number of nodes and elements of heat sink
[Table 5] Temperature of heat sink

7. Conclusion:

This study confirmed the thermal performance of pin-fin and plate-fin heat sinks with internal tunnel structures under natural convection conditions through transient thermal analysis using FEM. The numerical analysis compared the cooling performance based on cooling fin shape.
The results showed that Heat Sink Type A exhibited an approximately 70% improvement in heat transfer rate under natural convection compared to Heat Sink Type B. This enhancement was attributed to the larger contact surface area of Type A with the air, which improved air flow and consequently, the heat transfer rate. Furthermore, the temperature distribution analysis over time revealed that Type A maintained lower temperatures towards the center of its fins.
Overall, Heat Sink Type A demonstrated superior results in terms of temperature distribution and heat flux. While increasing fin height and length can improve cooling performance by increasing the heat transfer area, the overall system size and specific application constraints (like in special molds) must be considered to select an appropriate fin height, length, and internal structure. The findings of this research suggest that when designing natural convection cooling devices, considering the internal shape and structure of the heat sink can lead to significantly improved thermal management.

8. References:

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9. Copyright:

This material is a paper by "Bong-Gu Lee, Min Lee". Based on "Thermal Analysis of the Heat Sink Performance using FEM".
Source of the paper: http://dx.doi.org/10.5762/KAIS.2014.15.9.5467

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