Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology applications The first major contribution was the development and advances of new heat pipes, such as loop heat pipes (LHPs), micro and miniature heat pipes, and pulsating heat pipes (PHPs) In addition, there are now many commercial applications that have helped contribute to the recent interest in heat pipes For example, several million heat pipes are manufactured each month for applications in CPU cooling and laptop computers Numerical modeling, analysis, and experimental simulation of heat pipes have significantly progressed due to a much greater understanding of various physical phenomena in heat pipes as well as advances in computational and experimental methodologies A review is presented hereafter concerning the types of heat pipes, heat pipe analysis, and simulations

Review and Advances in Heat Pipe Science and Technology

Two-phase forced convective flow in microchannels is promising for the cooling of integrated circuits. There has been limited research on boiling flow in channels with dimensions below 100 /spl mu/m, in which bubble formation and flow regimes can differ from those in larger channels. This work develops single and multi-channel experimental structures using plasma-etched silicon with pyrex glass cover, which allow uniform heating and spatially-resolved thermometry and provide optical access for visualization of boiling regimes. Boiling was observed with less than 5/spl deg/C of super-heating in rectangular channels with hydraulic diameters between 25 and 60 /spl mu/m. The channel wall widths are below 350 /spl mu/m, which minimizes solid conduction and reduces variations in the heat flux boundary condition. Pressure drop and wall temperature distribution data are consistent with predictions accounting for solid conduction and homogeneous two-phase convection.

http://microfluidics.stanford.edu/Publications/Micropumps_Cooling/Zhang%20Meas%20in%20Two%20Phase%20Microchannel%20JMEMS.pdf

Measurements and modeling of two-phase flow in microchannels with nearly constant heat flux boundary conditions

A detailed overview of heat pipes is presented in this paper, including a historical perspective, principles of operations, types of heat pipes, heat pipe performance characteristics, heat pipe limitations, heat pipe frozen startup and shutdown, heat pipe analysis and simulations, and various applications of heat pipes. Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology . The first major contribution was the development and advances of new heat pipes, such as loop heat pipes, micro and miniature heat pipes, and pulsating heat pipes. In addition, there are now many new commercial applications that have helped contribute to the recent interest in heat pipes, especially related to the fields of electronic cooling and energy. For example, several million heat pipes are now manufactured each month since all modern laptops use heat pipes for CPU cooling. Numerical modeling, analysis, and experimental simulation of heat pipes have also significantly progressed due to a much greater understanding of various physical phenomena in heat pipes, as well as advances in computational and experimental methodologies.

http://m.thermalfluidscentral.org/journals/index.php/Heat_Pipes/article/view/360/362

Heat pipes: review, opportunities and challenges

http://www.porousmedialab.by/seminar/pdf/07_Vasiliev_Miniature.pdf

Micro and miniature heat pipes – Electronic component coolers

Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface

Flat miniature heat pipes (FMHP's) are shown to be very promising in the cooling of electronic component systems. This investigation presents a detailed experimental and theoretical analysis on maximum heat transfer capabilities of two copper-water FMHP's with diagonal trapezoidal micro capillary grooves and one copper-water FMHP with axial rectangular micro capillary grooves. Maximum heat flux on the evaporator wall of the 120-mm long axial grooved heat pipe, with a vapor channel cross-sectional area of approximately 1.5 x 12 mm 2 and rectangular grooves of dimensions 0.20 mm wide by 0.42 mm deep, exceeded 90 W/cm 2 in the horizontal orientation and 150 W/cm 2 in the vertical orientation. Theoretical prediction of the capillary limitation in the horizontal orientation agreed reasonably well with the experimental data.

R. Hopkins

Papers

Flat Miniature Heat Pipes With Micro Capillary Grooves

Critical Heat Fluxes in Flat Miniature Heat Sinks With Micro Capillary Grooves