Development of a Mini Heat Sink Model With Homogeneous Heat Transfer Capability

A model of mini heat sink with microchannels was developed to obtain homogeneous heat transfer capability. The channels are constructed in the form of eight triangular arrays based on a square substrate. Air is sucked from the periphery to the center of the substrate by a vacuum pump and heat transferred from the bottom surface of substrate can be removed by air flowing through channels. Corresponding to the given heat transfer power and the target temperature of substrate, the relationship among length, width and depth of channel was analytically established. By numerical simulation, local pressure drops at the joint of channels and air duct are first obtained and then the dimensions of each channel in a triangular array can be determined one by one. The investigation reveals that the widths of channels will vary with their depths, lengths and pressure differences between two ends. Since all channels are required for the same cooling power, the homogeneous heat transfer of heat sink can be realized. By assembling a certain number of heat sink units, the area of dissipation of heat sink can be enlarged and contoured to fit close to heating surface.

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Metallic Nanoemulsion for Microchannel Heat-Sink

ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2016-8010 ◽

2016 ◽

Author(s):

Yoshikazu Hayashi ◽

Gordon Yip ◽

Yoon Jo Kim ◽

Jong-Hoon Kim

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Specific Heat ◽

Heat Sink ◽

Effective Medium Theory ◽

Working Fluid ◽

Microchannel Heat Sink ◽

Viscosity Change ◽

Transfer Capability ◽

Heat Transfer Capability

Galinstan is a eutectic alloy of gallium, indium, and tin, of which thermal conductivity is ∼27 times higher than that of water, while the dynamic viscosity is only twice. Thus, heat transfer coefficient can be remarkably enhanced with a small penalty of pumping power. However, the direct use of galinstan can suffer from practical issues such as oxidation and low specific heat. Therefore, galinstan is mixed with a coolant as an additive to form a colloidal fluid; i.e., dispersion of nanoscale galinstan droplets in a coolant to enhance the thermal conductivity. It is expected that this “metallic nanoemulsion” can contribute to substantial improvement in heat transfer capability. Also, the common issues with colloidal fluids such as rapid sedimentation, erosion, and clogging, can be minimized by the “fluidity” of the liquid metal. It was shown that ultrasonic emulsification can yield few hundreds scale nanodroplets. However, the long exposure of galinstan to oxygen in water inevitably results in severe oxidation of the droplets. Theoretical analysis was also conducted to examine the feasibility of the metallic nanoemulsion as a microchannel heat-sink working fluid. Effective medium theory was used to evaluate the thermal conductivity of the mixture. The viscosity change was also predicted considering both the viscosity of dispersed phase and interaction between the droplets. Under one-dimensional laminar flow assumption, mass, momentum, and energy conservation equations were analytically solved. The effect of high thermal conductivity of galinstan was evident; the convection heat transfer capability was greatly enhanced, while the viscosity increase due to the nanoscale blending and the low specific heat of galinstan counteracts and reduce the flow rate and thus increase the caloric thermal resistance.

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Heat Sinks With Enhanced Heat Transfer Capability for Electronic Cooling Applications

Journal of Electronic Packaging ◽

10.1115/1.2229230 ◽

2005 ◽

Vol 128 (3) ◽

pp. 285-290 ◽

Cited By ~ 15

Author(s):

Evan Small ◽

Sadegh M. Sadeghipour ◽

Mehdi Asheghi

Keyword(s):

Heat Transfer ◽

Thermal Performance ◽

Heat Sink ◽

Engineering Students ◽

Electronic Cooling ◽

Heat Sinks ◽

Optimum Number ◽

Transfer Capability ◽

Improve Heat Transfer ◽

Heat Transfer Capability

In a competition at Carnegie Mellon University, the mechanical engineering students designed and manufactured 27 heat sinks. The heat sinks were then tested for thermal performance in cooling a mock processor. A heat sink with three rows of 9, 8, and 9 dimpled rectangular fins in staggered configuration performed the best, while having the least total volume (about 25% less than the set value). Validation of the observed thermal performance of this heat sink by experimentation and numerical simulations has motivated the present investigation. Thermal performance of the heat sinks with and without dimples have been evaluated and compared. Results of both the measurements and simulations indicate that dimples do in fact improve heat transfer capability of the heat sinks. However, dimples cause more pressure drop in the air flow. Keeping the total volume of the heat sink and the height of the fins constant and changing the number of the fins and their arrangement show that there is an optimum number of fins for the best performance of the heat sink. The optimum fin numbers are different for inline and staggered arrangements.

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