A Compact Integrated Thermosyphon Heat Sink for Power Electronics Cooling

2019 ◽  
Author(s):  
Ahmed Elkholy ◽  
Roger Kempers
Keyword(s):  
Natural Convection ◽  
Heat Sink ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Heat Sinks ◽  
Working Fluid ◽  
Convection Heat ◽  
Two Phase ◽  
Spreading Resistance

Abstract The trend in miniaturization of power electronic components requires the development of new robust and passive cooling methods to meet increased heat flux demands. Conventional heat sinks encounter inherent shortcomings due to heat spreading resistance of the heat sink baseplate particularly in natural convection heat sinks used to cool small localized heat sources. Heat pipes embedded within the base of heat sinks can be used to improve spreading performance but are limited by the ability to conduct heat into and out of the heat pipes. In the current study, a small, naturally aspirated two-phase thermosyphon heat sink was developed and characterized experimentally. The proposed architecture integrates all thermosyphon components into one compact device, where the evaporator, riser and the downcomer are incorporated at the heat sink base. The downcomer also serves as the condenser within the base of a vertical finned natural convection heat sink. The side-heated evaporator consists of an array mini-channels configuration which can operate in either pool boiling or flow boiling configuration, which allows the thermosyphon heat sink to operate in either reflux mode or looped mode, respectively. Experiments were carried out using HFE 7000 as the working fluid. The effect of the of input power on the thermal performance is examined for both modes for powers ranging from 10 to 80 W. Results demonstrate that this approach significantly reduces the spreading resistance resulting in a net improvement which can be traded-off for a decrease the overall size or weight of the heat sink.

Two-Phase Flow in Microchannels

2001 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Sink ◽  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Infrared Radiometry ◽  
Phase Water

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

Characteristics of Flow Boiling Oscillations in Silicon Microchannel Heat Sinks

2007 ◽  
Vol 129 (10) ◽  
pp. 1341-1351 ◽  
Author(s):  
R. Muwanga ◽  
I. Hassan ◽  
R. MacDonald
Keyword(s):  
Heat Sink ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Standard Heat ◽  
Flow Oscillations ◽  
Footprint Area

Flow boiling oscillation characteristics in two silicon microchannel heat sink configurations are presented. One is a standard heat sink with 45 straight parallel channels, whereas the second is similar except with cross-linked paths at three locations. Data are presented over a flow range of 20–50ml∕min(91–228kg∕(m2s)) using distilled water as the working fluid. The heat sinks have a footprint area of 3.5cm2 and contain 269μm wide by 283μm deep reactive ion etching channels. Flow oscillations are found to be similar in characteristic trends between the two configurations, showing a decreasing frequency with increasing heat flux. The oscillation amplitudes are relatively large and identical in frequency for the inlet temperature, outlet temperature, inlet pressure, and pressure drop. Oscillation properties for the standard heat sink at two different inlet temperatures and various flow rates are correlated for different heat fluxes. This work additionally presents a first glimpse of the cross-linked heat sink performance under flow boiling instability conditions.

Next Generation Devices for Electronic Cooling

2003 ◽  
Author(s):  
Ralph L. Webb
Keyword(s):  
Heat Sink ◽  
New Technology ◽  
Heat Removal ◽  
Cost Effective ◽  
Heat Sinks ◽  
Working Fluid ◽  
Two Phase ◽  
Conventional Technology ◽  
Removal Technology ◽  
R Value

Conventional technology to cool desktop computers and servers is that of the “direct heat removal” heat sink, which consists of a heat sink/fan mounted on the CPU. Although this is a very cost effective solution, it is nearing its end of life. This is because future higher power CPUs will require a lower R-value than can be provided by this technology, within current size and fan limits. This paper discusses new technology that uses “indirect heat removal” technology, which involves use of a single or two-phase working fluid to transfer heat from the hot source to an ambient heat sink. This technology will support greater heat rejection than is possible with the “direct heat removal” method. Further, it will allow use of higher performance air-cooled ambient heat sinks than are possible with the “direct heat removal” heat sink. A concern of the indirect heat removal technology is the possibility that it may be orientation sensitive. This paper identifies preferred options and discusses the degree to which they are (or or not) orientation sensitive. It should be possible to attain an R-value of 0.12K/W at the balance point on the fan curve.

Development and Experimental Validation of a Micro/Nano Thermal Ground Plane

2011 ◽  
Author(s):  
H. Peter J. de Bock ◽  
Shakti Chauhan ◽  
Pramod Chamarthy ◽  
Chris Eastman ◽  
Stanton Weaver ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Ground Plane ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Working Fluid ◽  
Heat Sources ◽  
Two Phase ◽  
Evaporation And Condensation ◽  
Two Phase Heat Transfer ◽  
Thermal Ground Plane

Heat pipes are commonly used in electronics cooling applications to spread heat from a concentrated heat source to a larger heat sink. Heat pipes work on the principles of two-phase heat transfer by evaporation and condensation of a working fluid. The amount of heat that can be transported is limited by the capillary and hydrostatic forces in the wicking structure of the device. Thermal ground planes are two-dimensional high conductivity heat pipes that can serve as thermal ground to which heat can be rejected by a multitude of heat sources. As hydrostatic forces are dependent on gravity, it is commonly known that heat pipe and thermal ground plane performance is orientation dependent. The effect of variation of gravity force on performance is discussed and the development of a miniaturized thermal ground plane for high g operation is described. In addition, experimental results are presented from zero to −10g acceleration. The study shows and discusses that minimal orientation or g-force dependence can be achieved if pore dimensions in the wicking structure can be designed at micro/nano-scale dimensions.

High-Flux Thermal Management With Supercritical Fluids

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Brian M. Fronk ◽  
Alexander S. Rattner
Keyword(s):  
Heat Flux ◽  
Thermal Management ◽  
Heat Sink ◽  
Electronics Cooling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Management Approach ◽  
High Heat Flux ◽  
Two Phase ◽  
Pump Design

A novel thermal management approach is explored, which uses supercritical carbon dioxide (sCO2) as a working fluid to manage extreme heat fluxes in electronics cooling applications. In the pseudocritical region, sCO2 has extremely high volumetric thermal capacity, which can enable operation with low pumping requirements, and without the potential for two-phase critical heat flux (CHF) and flow instabilities. A model of a representative microchannel heat sink is evaluated with single-phase liquid water and FC-72, two-phase boiling R-134a, and sCO2. For a fixed pumping power, sCO2 is found to yield lower heat-sink wall temperatures than liquid coolants. Practical engineering challenges for supercritical thermal management systems are discussed, including the limits of predictive heat transfer models, narrow operating temperature ranges, high working pressures, and pump design criteria. Based on these findings, sCO2 is a promising candidate working fluid for cooling high heat flux electronics, but additional thermal transport research and engineering are needed before practical systems can be realized.

Multiple Fan-Heat Sink Cooling System With Enhanced Evaporator Base: Design, Modeling, and Experiment

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Pablo D. Quinones ◽  
Lawrence S. Mok
Keyword(s):  
Heat Sink ◽  
Cooling System ◽  
Heat Pipes ◽  
High Conductivity ◽  
Heat Sinks ◽  
Copper Block ◽  
Cooling Device ◽  
Element Analysis ◽  
Spreading Resistance ◽  
Semiconductor Chip

A cooling device using stacked centrifugal fans and circular heat sinks was designed for cooling a semiconductor chip with a heat flux near 125 W/cm2. In this device, heat is conducted from the chip to a copper heat distribution block and then distributed to multiple heat sinks via four heat pipes. The copper block with embedded heat pipes or evaporator block was optimized using finite element analysis, and several cases were validated with experimental data. The experiments showed great benefits by having a second fan/heat sink in the device. The copper block by itself was found to contribute more than half of the overall thermal resistance of the cooling device. The thermal spreading resistance of the block can be reduced by about 70% if a piece of high-conductivity material, such as a diamond-copper composite, is inserted into its base. The thermal spreading resistance is generally lower when the thickness of the high-conductivity base piece increases. However, the analysis shows that the benefit of using a high-conductivity base tapers off as the thickness of the base piece nears the diameter of the heat pipes (δ∗=1) and weakly worsens after (δ∗>1). The base will also not have a benefit when the size of the chip approaches that of the copper block (A∗=1).

Integrate Monolithic Nanostructures in Microchannels to Enhance Flow Boiling Heat Transfer of HFE-7000

2015 ◽  
Author(s):  
Fanghao Yang ◽  
Xiaochuan Li ◽  
Wenming Li ◽  
Chen Li
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Dielectric Fluids ◽  
Flow Boiling Heat Transfer ◽  
Two Phase Heat Transfer

Two-phase microchannel heat sink is promising in cooling high power electronics with dielectric fluids. Compared to water, dielectric fluids can assure system safety in case of working fluid leakage. However, two-phase heat transfer of these hydrofluorocarbon refrigerants is restricted by their relatively low thermal conductivities and low latent heats. Numerous nanoscale/submicron structures have been developed to enhance the single and two-phase heat transfer in microchannels; but these techniques usually require nanoparticle seeds in multi-step wet processes or nanolithography to integrate these nanostructures. Therefore, most of these techniques were time-consuming and costly. In this study, we present a plasma etching method using a modified Bosch process to create silicon tips with nanoscale scallops in microchannels. This is a rapid and cost-effective method to integrate large density of nucleation sites without involving nanolithography method or using nanoparticle seeds. Then, these silicon tip arrays were aligned with side walls of microchannels. As a result, flow boiling heat transfer of a dielectric refrigerant, HFE-7000, is substantially enhanced in a microchannel heat sink (five parallel channels: 10 mm L × 220 μm W × 250 μm H). Compared to plain-wall microchannels, the average junction temperature can be reduced up to 10 °C at a heat flux of 55 W/cm2 and the equivalent thermal resistance of microchannel heat sink is reduced up to 31% at a mass flux of 1018 kg/m2·s.

Experimental Study of Linear and Radial Two-Phase Heat Transport Devices Driven by Electrohydrodynamic Conduction Pumping

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Source ◽  
Capillary Pressure ◽  
Heat Transport ◽  
Radial Direction ◽  
Heat Pipes ◽  
Working Fluid ◽  
Phase Flow ◽  
Transport Capacity ◽  
Two Phase ◽  
Capillary Phenomenon

Heat pipes are well known as simple and effective heat transport devices, utilizing two-phase flow and the capillary phenomenon to remove heat. However, the generation of capillary pressure requires a wicking structure and the overall heat transport capacity of the heat pipe is generally limited by the amount of capillary pressure generation that the wicking structure can achieve. Therefore, to increase the heat transport capacity, the capillary phenomenon must be either augmented or replaced by some other pumping technique. Electrohydrodynamic (EHD) conduction pumping can be readily used to pump a thin film of a dielectric liquid along a surface, using electrodes that are embedded into the surface. In this study, two two-phase heat transport devices are created. The first device transports the heat in a linear direction. The second device transports the heat in a radial direction from a central heat source. The radial pumping configuration provides several advantages. Most notably, the heat source is wetted with fresh liquid from all directions, thereby reducing the amount of distance that must be travelled by the working fluid. The power required to operate the EHD conduction pumps is a trivial amount relative to the heat that is transported.

Sign in / Sign up

Export Citation Format

Share Document