ASME Heat Sink Design Competition

Background: This document is meant to provide students with pertinent details forthe AY2020 ASME Heat Sink Design Competition. For this competition, students willdesign, analyze and optimize an additively manufactured heat sink to cool a constantheat flux power electronics module subject to forced convection. The student teamsthat are evaluated as having the most effective, unique designs will have anopportunity to test their designs using the additive manufacturing facilities at GE andstate-of-the-art test equipment at Oregon State University. These student groups willalso present their work at the 2020 ITherm Conference.

Design Constraints

The full design constraints are partially based on the individual constraints of the testequipment, show in Fig. 1 below:

Fig. 1: Test facility for evaluating the performance of additively manufactured heat sinks

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ASME Heat Sink Design Competition

Several pertinent details of the measurement can be found in Table 2 and Fig. 2.

Measurement Details

Component Type Operating Condition

Wind Tunnel Aerolab Educational Wind Tunnel

75 MPH

Cartridge Heater McMaster-Caarr(P/N:3618K712 )

Qty 4 generating 50.8 W of total heat

In-LineThermocouples

K-Type Grainger P/N: 3AAA2

0.02°C – Accuracy1 Hz Sampling Rate

Base Thermocouple Omega Engineering P/N: KMQXL-040G-55

0.02°C – Accuracy1 Hz Sampling Rate

0.040” Probe Diameter

Thermal Interface Material (TIM)

Schlegel Electronic Materials

(P/N: OP-9700)

Thermal Conductivity10 W/(m·K)

Thickness – 40 mil

A schematic of the emulated electronics stack is shown in Fig. 2 (a). Each CAD fileMUST begin with the attachment base shown in Figure 2. One thermocouple will beinserted into the heat sink’s base as shown below.

Table 2: Test facility component details and operating conditions.

Fig. 2: Measurement illustration and attachment base requirements.

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ASME Heat Sink Design Competition

Design Objectives and Scoring

The design objectives for the final competition are provided in the list below:1. Cost-based Figure of Merit.2. Best use of additive manufacturing.3. Presentation Skills

The heat sink will be manufactured with Aluminum A357. Heat treatedconventionally manufactured A357 has a thermal conductivity of 170 W/m·K, and itis expected that as printed the effective thermal conductivity is ~110 W/m·K. Formodelling, it can be assumed that the surface roughness is 35 microns. Othermanufacturing constraints including minimum feature sizes and tolerances will bediscussed by GE Additive in a teleconference to be scheduled with participatingteams.

Additive Manufacturing Constraints

Overall scoring will be assessed according to the details provided in Table 5, below:

Metric Assigned Point Value

Cost-based Figure of Merit 40

Presentation Skills 30

Best use of AM 30

Table 5: Scoring metrics for final competition.

The design objectives for the white paper are provided in the list below:1. Highest Cost-based Figure of Merit (FOM) achieved with a fan operating

at a volume flow rate of 100 CFM (see attached fan specs).2. Best use of additive manufacturing.3. Writing style/formatting/clarity.

Metric Assigned Point Value

Cost-based FOM Estimate and Analytical Technique

50

Best use of AM 30

Writing Style/Formatting 20

Table 4: Scoring metrics for white paper.

ASME Heat Sink Design Competition

The groups should submit a cost-based Figure of Merit (FOM). This FOM can becalculated according to the following Eqns.:

Cost-based Figure of Merit

𝐹𝑂𝑀 = ൗ1 (𝑇𝑜𝑡𝑎𝑙 𝐶𝑜𝑠𝑡 · 𝑇𝑇𝐶 − 𝑇𝑎𝑚𝑏 )(1)

$𝑝𝑢𝑚𝑝𝑒𝑑_𝑎𝑖𝑟 = 𝑃 ∙ 𝑡 ∙$

𝑘𝑊ℎ

(2)𝑇𝑜𝑡𝑎𝑙 𝐶𝑜𝑠𝑡 = $ℎ𝑒𝑎𝑡 𝑠𝑖𝑛𝑘 + $𝑝𝑢𝑚𝑝𝑒𝑑_𝑎𝑖𝑟

(3)

In Eqns. 1 – 4, TTC is the temperature at the thermocouple placed in the base of theheat sink as shown in Figure 2, $heat sink is the cost of the heat sink ($60/kg),$pumped_air is the cost to supply air flow across the fins, P is the pumping/fan power, tis the total operating time (assume 20,000 hrs.), p is the pressure drop across the

heat sink (measured upstream and downstream of the heat sink chamber), ሶ𝑉 is thevolumetric flow rate of air (assume 70 MPH inside the entire chamber plenum), and$/kWh is the average cost of electricity in the U.S.

While each team is encouraged to model and predict their own FOM, the officialvalue will be determined by a validated CFD model. This analysis will be completedconcurrent to the white paper review process. Guidelines for successful metalprinting still apply to your submission, but the minimum feature size must be kept to500 microns for insertion into the CFD model developed by the competitioncommittee. The .stl file for the team’s heat sink must be submitted with the whitepaper in order to move forward in the competition.

Please be aware that any submissions for this competition (data contained in thewhite paper, .stl file, analytical techniques, etc.) will all be open to the public. Nopropriety information/models can be considered for this competition.

𝑃 = ሶ𝑉 · Δ𝑝 (4)

ASME Heat Sink Design Competition

Measured Data for Model Validation

Below is a plot and table of thermal resistance data with respect to Reynolds numberfor flow over a flat plate (the attachment base only) made with additivemanufacturing. The characteristic length in the Reynolds number was taken as thedepth of the plate (2.00”). A total power of 50.8 W was applied to the four cartridgeheaters embedded in the base of the copper rod (see Figure 2). Heat losses withrespect to wind tunnel air speed is also given below.

Wind Speed (m/sec) Percentage Heat Loss

31.69 29.1

27.17 30.1

22.64 31.2

18.11 31.9

13.58 33.6

9.06 35.5

Reynolds Resistance (K/W)

62500 2.97

94852 2.47

125735 2.15

157353 1.94

187500 1.75

219853 1.49

ASME Heat Sink Design Competition

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This is a completely subjective assessment of the overall design aesthetic and use ofAM for minimizing pressure drop, thermal resistance, etc. Creativity is rewarded inthis category along with the formation of structures that would otherwise not bepossible with conventional manufacturing methods.

Best Use of Additive Manufacturing

Conventional

ManufacturingWhat’s Possible

with AM

Be Creative!