Numerical Study of Heat Transfer Enhancement in Microchannels

Jason Lam

z3252911

Supervisors:

Dr Victoria Timchenko

A/Prof. Guan Heng Yeoh

Problem Definition• Microchannels

• Operating frequency increases with

technological advancement

• Heat generation rates hamper

advancement

Problem Definition• Microchannels

• Applications

• Micro-channel

Heat Exchanger

• Features/Limitations

Features of microchannelsParameter Shell and tube heat

exchanger

Compact heat

exchanger

Micro-channel heat

exchanger

Surface area per unit

volume (m2· m-3)

50 – 100 850 – 1000 >1500

Heat transfer coefficient

(liquid) (W•m-2•K-1)

~ 5000

(tube side)

3000 – 7000 >7000

Heat transfer coefficient

(gas) (W•m-2•K-1)

20 – 100 50 – 300 400 – 2000

Approach Temperature (°C) ~ 20°C ~ 10°C <10°C

Limitations of microchannelsParameter

Shell and tube

heat exchanger

Compact heat

exchanger

Micro-channel heat

exchanger

Flow Regime

Turbulent Turbulent Laminar

 

Features of microchannels

Synthetic Jet Displacement

AnalysisNumerical Experimental

Institution University of New South WalesThe Institute of Thermomechanics

ASCR

Person Jason Lam Zdeněk Trávníček

Transport

phenomenaHeat Transfer (Temperature) Mass Transfer (Concentration)

Geometry

Geometry

• 2 Cavities

• 4 Orifices

CFX Mesh

CFX Mesh

Special Thermal/Mass Boundary Condition

Numerical Experimental

Source Ts = 25°C Naphthalene Sample

Location Partially applied at the bottom of the channel

Synthetic Jet Displacement

𝑌=𝑌𝑚𝑎𝑥 sin (2𝜋 𝑓𝑡 )

Results – Steady State Heat Transfer

Results – Steady State Heat Transfer

Results – Steady State Heat Transfer

Results – Transient Heat Transfer

Results – Heat Transfer (Comparison)

Results –Heat Transfer (Comparison)

Results – Fluid Flow (Comparison)

Results – Fluid Flow (Comparison)

Results – Fluid Flow (Comparison)

Conclusions

• Numerical data has been validated with the experiment with

fair agreement

• The synthetic jet is a feasible method for promoting mixing

and enhancing heat transfer

• Most appropriate method for cooling microchips.

Questions?