Microchannel Heat Sink Experiment: Testing Convective Coefficients

Instructor: Dr. Ralph BudwigFall 2006

Nicholas Tebbe

Victor Ponce

James Dorrell

December 7, 2006

Background and Motivation

Playstation 3

Nvidia GeForce 7950

Objectives

• Determine the convective coefficient

• 80% certainty

• Reynolds numbers between 500-1500

Lee, Poh-Seng; Garimella, Suresh V.; Liu, Dong “Investigation of heat transfer in rectangular microchannels.” International Journal of Heat and Mass Transfer 48, 2005, 1688-1704.

Prototype: Microchannel

Photos

Photos

Prototype: Manifold

Setup

Number Component

1 Water Reservoir

3 Pump

5 Manifold

6 Microchannel Substrate

7 Nichrome Heater

9 Thermocouple

10 Graduated Cylinder

To and Ti

TcΔV

Δt

• Energy Balance

• Newton’s Law of Cooling

q m Cp ΔT=

q h A ΔT=

Data Reduction

RSS Analysis

Max UncertaintyRe: 8.8%h: 13.54%

Experiment Design

Convective Coefficient vs Reynolds Number

0

5000

10000

15000

20000

25000

30000

35000

400 600 800 1000 1200 1400

Reynolds Number

Co

nve

ctiv

e C

oef

fici

ent

(W/m

2 -K)

Minimizing UncertaintyPercent Contribution

• Reynold’s Number– Viscosity of Water: 70%– Velocity calculation: 25%

• Convection Coefficient– Water Outlet Temperature: 60%– Copper Temperature: 10%

ResultsConvective Coefficient vs Reynolds Number

Comparison With Correlations

0

5000

10000

15000

20000

25000

30000

400 600 800 1000 1200 1400

Reynolds Number

Co

nve

ctiv

e C

oef

fici

ent

(W/m

2K)

Dittus-BoelterTurbulent

StephanLaminar

Sieder-TateLaminar

IncroperaDeWitt Laminar

PetukhovTurbulent

Choi Laminar

Wu and LittleLaminar

RegressionBest Fit Line

Comparison

Conclusions

• Max Uncertainty = 13.54%

• Temperature contributed 60% of error

• Rough channels cause turbulence

• Dittus-Boelter Correlation recommended

Questions

?