Experimental Investigation of Porous Micro Heat Sink for Electronics Cooling Application

2011 ◽  
Vol 204-210 ◽  
pp. 2023-2026
Author(s):  
Ka Lin Su ◽  
Jing Liu ◽  
Jun Rong ◽  
Jun Hua Wan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Load ◽  
High Heat ◽  
Heat Fluxes ◽  
Coolant Flow ◽  
Coolant Flow Rate

A novel porous micro heat sink system was presented for dissipating high heat fluxes of electronic device. The flow and heat transfer of porous micro heat sink was investigated by experiment at the condition of high heat fluxes, and the results showed that the heat load of up to 280W was removed by the heat sink, and the heater junction temperature was 63.8°C at the coolant flow rate of 5.1cm3/s. The whole heat transfer coefficient of heat sink increased with the increases of coolant flow rate and heat load, and the maximal heat transfer coefficient was 33kW(m2.°C)-1 in the experiment. The minimum value of 0.19°C/W for whole thermal resistance of heat sink was achieved at flow rate of 5.1cm3/s, and increasing of coolant flow rate and heat fluxes could decrease the thermal resistance.

Analytical Model Quantifying the Net Coolant Flow Rate to a Microstructured Copper Surface validated with Two-Phase PIV Measurements

2021 ◽  
Author(s):  
Matt Harrison ◽  
Joshua Gess
Keyword(s):  
Heat Transfer ◽  
Analytical Model ◽  
Flow Rate ◽  
Circular Disk ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Two Phase

Abstract Using Particle Image Velocimetry (PIV), the amount of fluid required to sustain nucleate boiling was quantified to a microstructured copper circular disk. Having prepared the disk with preferential nucleation sites, an analytical model of the net coolant flow rate requirements to a single site has been produced and validated against experimental data. The model assumes that there are three primary phenomena contributing to the coolant flow rate requirements at the boiling surface; radial growth of vapor throughout incipience to departure, bubble rise, and natural convection around the periphery. The total mass flowrate is the sum of these contributing portions. The model accurately predicts the quenching fluid flow rate at low and high heat fluxes with 4% and 30% error of the measured value respectively. For the microstructured surface examined in this study, coolant flow rate requirements ranged from 0.1 to 0.16 kg/sec for a range of heat fluxes from 5.5 to 11.0 W/cm2. Under subcooled conditions, the coolant flow rate requirements plummeted to a nearly negligible value due to domination of transient conduction as the primary heat transfer mechanism at the liquid/vapor/surface interface. PIV and the validated analytical model could be used as a test standard where the amount of coolant the surface needs in relation to its heat transfer coefficient or thermal resistance is a benchmark for the efficacy of a standard surface or boiling enhancement coating/surface structure.

Performance Investigation on Porous Micro Heat Sink for Cooling of High Power LEDs

2011 ◽  
Vol 204-210 ◽  
pp. 1481-1484
Author(s):  
Zhong Min Wan ◽  
Zheng Kai Tu ◽  
Jing Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Power ◽  
Heat Sink ◽  
Heated Surface ◽  
High Heat ◽  
Heat Fluxes ◽  
Local Thermal Equilibrium ◽  
Micro Pump

A novel porous micro heat sink system is presented for thermal management of high power LEDs, which has high heat transport capability. Numerical model for the micro heat sink is developed to describe liquid flow and heat transfer based on the local thermal equilibrium of porous media, and it is solved with SIMPLE algorithm. The numerical results show that the heated surface temperature of porous micro heat sink is low at high heat fluxes and is much less than the bearable temperature level of LED chips. The heat transfer coefficient of heat sink is very high, and increasing the liquid velocity can enhance the average heat transfer coefficient. The overall pressure loss of heat sink system increases with the increasing the inlet velocity, but the overall pressure drop is much less than the pumping pressure provided by micro pump.

Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

2008 ◽  
Author(s):  
Ayman Megahed ◽  
Ibrahim Hassan ◽  
Tariq Ahmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Microchannel Heat Sink

The present study focuses on the experimental investigation of boiling heat transfer characteristics and pressure drop in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 295 μm, width of 254 μm, and a length of 16 mm. Un-encapsulated Thermochromic liquid Crystals (TLC) are used in the present work to enable nonintrusive and high spatial resolution temperature measurements. This measuring technique is used to provide accurate full and local surface-temperature and heat transfer coefficient measurements. Experiments are carried out for mass velocities ranging between 290 to 457 kg/m2.s and heat fluxes from 6.04 to 13.06 W/cm2 using FC-72 as the working fluid. Experimental results show that the pressure drop increases as the exit quality and the flow rate increase. High values of heat transfer coefficient can be obtained at low exit quality (xe < 0.2). However, the heat transfer coefficient decreases sharply and remains almost constant as the quality increases for an exit quality higher than 0.2.

scholarly journals Deterioration in Heat Transfer to Fluids at Supercritical Pressure and High Heat Fluxes

1969 ◽  
Vol 91 (1) ◽  
pp. 27-36 ◽  
Author(s):  
B. S. Shiralkar ◽  
Peter Griffith
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Heat ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Bulk Temperature ◽  
Operating Pressure ◽  
The Heat Transfer Coefficient

At slightly supercritical pressure and in the neighborhood of the pseudocritical temperature (which corresponds to the peak in the specific heat at the operating pressure), the heat transfer coefficient between fluid and tube wall is strongly dependent on the heat flux. For large heat fluxes, a marked deterioration takes place in the heat transfer coefficient in the region where the bulk temperature is below the pseudocritical temperature and the wall temperature above the pseudocritical temperature. Equations have been developed to predict the deterioration in heat transfer at high heat fluxes and the results compared with previously available results for steam. Experiments have been performed with carbon dioxide for additional comparison. Limits of safe operation for a supercritical pressure heat exchanger in terms of the allowable heat flux for a particular flow rate have been determined theoretically and experimentally.

Effect of Rotation and Coolant Throughflow on the Heat Transfer and Temperature Field in an Enclosure

1976 ◽  
Vol 98 (3) ◽  
pp. 387-394 ◽  
Author(s):  
E. M. Sparrow ◽  
Leonardo Goldstein
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Flow Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Transfer Coefficients ◽  
Disk System ◽  
Heat Transfer Coefficients

Measurements were performed to determine the local heat transfer coefficients along the heated shroud of a shrouded parallel disk system. The temperature field within the enclosure formed by the shroud and the disks was also measured. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air was introduced into the enclosure through an aperture at the center of the stationary disk and exited through a slot at the rim of the rotating disk. The coolant entrance-exit arrangement differed from that of previous studies, with the additional difference that the incoming coolant stream was free of rotation. The coolant flow rate, the disk rotational speed, and the aspect ratio of the enclosure were varied during the experiments. The heat transfer coefficients were found to be increasingly insensitive to the absence or presence of rotation as the coolant flow rate increased. There was a general increase of the transfer coefficients with increasing coolant flow rate, especially for low rotational speeds. The temperature field in the enclosure differed markedly depending on the relative importance of rotation and of coolant throughflow. When the latter dominates, the temperature in the core is relatively uniform, but in the presence of strong rotation there are significant nonuniformities. A comparison was made between the present Nusselt number results and those of prior experiments characterized by different coolant entrance—exit arrangements. The positioning of the coolant exit slot relative to the direction of the boundary layer flow on the shroud emerged as an important factor in the comparison.

Heat Transfer for the Blade of a Cooled Stage and One-Half High-Pressure Turbine—Part II: Independent Influences of Vane Trailing Edge and Purge Cooling

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Flow Rate ◽  
Pressure Field ◽  
Its Region ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Trailing Edge

The independent influences of vane trailing edge and purge cooling are studied in detail for a one-and-one-half stage transonic high-pressure turbine operating at design-corrected conditions. This paper builds on the conclusions of Part I, which investigated the combined influence of all cooling circuits. Heat-flux measurements for the airfoil, platform, tip, and root of the turbine blade, as well as the shroud and the vane side of the purge cavity, are used to track the influence of cooling flow. By independently varying the coolant flow rate through the vane trailing edge or purge circuit, the region of influence of each circuit can be isolated. Vane trailing edge cooling is found to create the largest reductions in blade heat transfer. However, much of the coolant accumulates on the blade suction surface and little influence is observed for the pressure surface. In contrast, the purge cooling is able to cause small reductions in heat transfer on both the suction and pressure surfaces of the airfoil. Its region of influence is limited to near the hub, but given that the purge coolant mass flow rate is 1/8 that of the vane trailing edge, it is impressive that any impact is observed at all. The cooling contributions of these two circuits account for nearly all of the cooling reductions observed for all three circuits in Part I, indicating that the vane inner cooling circuit that feeds most of the vane film-cooling holes has little impact on the downstream blade heat transfer. Time-accurate pressure measurements provide further insight into the complex interactions in the purge region that govern purge coolant injection. While the pressures supplying the purge coolant and the overall coolant flow rate remain fairly constant, the interactions of the vane pressure field and the rotor pressure field create moving regions of high pressure and low pressure at the exit of the cavity. This results in pulsing regions of injection and ingestion.

Thermal Management of Time-Varying High Heat Flux Electronic Devices

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
T. David ◽  
D. Mendler ◽  
A. Mosyak ◽  
A. Bar-Cohen ◽  
G. Hetsroni
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Fluxes ◽  
Vapor Quality ◽  
Flow Loop ◽  
Pin Fin ◽  
The Heat Transfer Coefficient

The thermal characteristics of a laboratory pin-fin microchannel heat sink were empirically obtained for heat flux, q″, in the range of 30–170 W/cm2, mass flux, m, in the range of 230–380 kg/m2 s, and an exit vapor quality, xout, from 0.2 to 0.75. Refrigerant R 134a (HFC-134a) was chosen as the working fluid. The heat sink was a pin-fin microchannel module installed in open flow loop. Deviation from the measured average temperatures was 1.5 °C at q = 30 W/cm2, and 2.0 °C at q = 170 W/cm2. These results indicate that use of pin-fin microchannel heat sink enables keeping an electronic device near uniform temperature under steady state and transient conditions. The heat transfer coefficient varied significantly with refrigerant quality and showed a peak at an exit vapor quality of 0.55 in all the experiments. At relatively low heat fluxes and vapor qualities, the heat transfer coefficient increased with vapor quality. At high heat fluxes and vapor qualities, the heat transfer coefficient decreased with vapor quality. A noteworthy feature of the present data is the larger magnitude of the transient heat transfer coefficients compared to values obtained under steady state conditions. The results of transient boiling were compared with those for steady state conditions. In contrast to the more common techniques, the low cost technique, based on open flow loop was developed to promote cooling using micropin fin sinks. Results of this experimental study may be used for designing the cooling high power laser and rocket-born electronic devices.

scholarly journals Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

2021 ◽  
pp. 199-199
Author(s):  
Lakshmi Reddy ◽  
Srinivasa Bayyapureddy Reddy ◽  
Kakumani Govindarajulu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Tilt Angle ◽  
Heat Load ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

Convection Calibration of Schmidt–Boelter Heat Flux Gauges in Stagnation and Shear Air Flow

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
A. Gifford ◽  
A. Hoffie ◽  
T. Diller ◽  
S. Huxtable
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Shear Flow ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Nonlinear Dependence ◽  
Stagnation Flow ◽  
Internal Thermal Resistance

Experiments were performed to characterize the performance of Schmidt–Boelter heat flux gauges in stagnation and shear convective air flows. The gauges were of a standard design (25.4 mm and 38 mm in diameter), using a copper heat sink with water cooling channels around the active sensing element. A simple model of the gauges using an internal thermal resistance between the sensor surface and the heat sink is used to interpret the results. The model predicts a nonlinear dependence of the gauge sensitivity as a function of the heat transfer coefficient. Experimental calibration systems were developed to simultaneously measure the heat flux gauge response relative to a secondary standard under the same flow and thermal conditions. The measured gauge sensitivities in the stagnation flow matched the model, and were used to estimate the value of the internal thermal resistance for each of the four gauges tested. For shear flow, the effect of the varying gauge surface temperature on the boundary layer was included. The results matched the model with a constant factor of 15–25% lower effective heat transfer coefficient. When the gauge was water cooled, the effect of the internal thermal resistance of the gauge was markedly different for the two flow conditions. In the stagnation flow, the internal resistance further decreased the apparent gauge sensitivity. Conversely, in shear flow, the resistance was effectively offset by the cooler heat sink of the gauge, and the resulting sensitivities were nearly the same as, or larger than, for radiation.

Multi-Objective Optimization Design of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

2013 ◽  
Vol 709 ◽  
pp. 286-291 ◽  
Author(s):  
Li Feng Wang ◽  
Bao Dong Shao ◽  
He Ming Cheng
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Optimization Design ◽  
High Heat ◽  
Micro Channel ◽  
Compact Structure ◽  
Total Thermal Resistance ◽  
High Heat Transfer

The purpose of this paper is to optimize the structural sizes of multi-layer rectangle micro-channel heat sink, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 21 and 7, the width of optimized micro-channel Wc and fin Wf are 340 and 130μm, the height of optimized micro-channel Hc is 415μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.3354 °C/W. The corresponding pressure drop is about 1.3377 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

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