Theoretical (Ideal) Module Cooling and Module Cooling Effectiveness

2015 ◽  
Author(s):  
Michael J. Ellsworth ◽  
Levi A. Campbell
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Volumetric Flow Rate ◽  
Cooling Effectiveness ◽  
Minimum Heat ◽  
Internal Thermal Resistance ◽  
Theoretical Minimum ◽  
Processor Module ◽  
The Ideal

When contemplating processor module cooling, the notion of maximum cooling capability is not simple or straight forward to estimate. There are a multitude of variables and constraints to consider; some more rigid or fixed than others. This paper proposes a theoretical maximum cooling capability predicated on the treatment of the module heat sink or cold plate as a heat exchanger with infinite conductive and convective behavior. The resulting theoretical minimum heat sink thermal resistance is a function of the bulk thermal transport of the fluid dependent only on the fluid’s density, specific heat (at constant pressure) and volumetric flow rate. An ideal module internal thermal resistance will also be defined. The sum of the two resistances constitutes the theoretical minimum total module thermal resistance and defines the ideal thermal performance of the module. Finally, a module cooling effectiveness relating the actual module thermal performance to the ideal thermal performance will defined. Examples of both air and water cooled modules will be given with discussion on the relevance and utility of this methodology.

Understanding the Impact of Flow Bypass on the Thermal Performance of Air Cooled Heat Sinks

2014 ◽  
Author(s):  
Krishna Kota ◽  
Mohamed M. Awad
Keyword(s):  
Energy Conservation ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Laminar Regime ◽  
Flow Energy ◽  
Factor Α ◽  
The Impact ◽  
Fundamental Mass

In this effort, theoretical modeling was employed to understand the impact of flow bypass on the thermal performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink configuration and the bypass region were applied and a generic parameter, referred as the Flow Bypass Factor (α), was identified from the theoretical solution that mathematically captures the effect of flow bypass as a quantifiable parameter on the junction-to-ambient thermal resistance of the heat sink. From the results obtained, it was found that, at least in the laminar regime, the impact of flow bypass on performance can be neglected for cases when the bypass gap is typically less than 5% of the fin height, and is almost linear at high relative bypass gaps (i.e., usually for bypass gaps that are more than 10–15% of the fin height). It was also found that the heat sink thermal resistance is more sensitive to small bypass gaps and the effect of flow bypass decreases with increasing bypass gap.

Experimental Investigation on Thermal Performance of Heat Sink With Two Pairs of Embedded Heat Pipes

2007 ◽  
Author(s):  
Hsiang-Sheng Huang ◽  
Jung-Chang Wang ◽  
Sih-Li Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Heat Sink ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Total Heat ◽  
Heating Power ◽  
Total Heat Transfer

This article provides an experimental method to study the thermal performance of a heat sink with two pairs (outer and inner pair) of embedded heat pipes. The proposed method can determine the heat transfer rate of the heat pipes under various heating power of the heat source. A comprehensive thermal resistance network of the heat sink is also developed. The network estimates the thermal resistances of the heat sink by applying the thermal performance test result. The results show that the outer and inner pairs of heat pipes carries 21% and 27% of the total heat transfer rate respectively, while 52% of the heating power is dissipated from the base plate to the fins. The dominated thermal resistance of the heat sink is the base to heat pipes resistance which is strongly affected by the thermal performance of the heat pipes. The total thermal resistance of the heat sink shows the lowest value, 0.23°C/W, while the total heat transfer rate of the heat sink is 140W and the heat transfer rate of the outer and inner pairs of heat pipes is 30W and 38 W, respectively.

Numerical Prediction of Thermal Performance of Water Cooled Multi-Stack Microchannel Heat Sink with Counterflow Arrangement

2011 ◽  
Vol 8 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Pradeep Hegde ◽  
Mukesh Patil ◽  
K. N. Seetharamu
Keyword(s):  
Finite Element ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Element Model ◽  
Channel Length ◽  
Computational Time ◽  
Microchannel Heat Sink ◽  
Method Performance

Thermal performance of a water cooled multistack microchannel heat sink with counterflow arrangement has been analyzed using the finite element method. Performance parameters such as thermal resistance, pressure drop, and pumping power are computed for a typical counterflow heat sink with different number of stacks. The temperature distribution in a typical multistack counterflow microchannel heat sink is obtained for different numbers of stacks and plotted along the channel length. A parametric study involving the effects of number of stacks and channel aspect ratio on thermal resistance and pressure drop of the heat sink is done. The finite element model developed for the analysis is simple and consumes less computational time.

Thermal Performance Analysis of Hybrid Jet Impingement/Microchannel Cooling for Concentrated Photovoltaic (CPV) Cells

2016 ◽  
Author(s):  
Afzal Husain ◽  
Mohd Ariz ◽  
Nasser A. Al-Azri ◽  
Nabeel Z. H. Al-Rawahi ◽  
Mohd. Z. Ansari
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Constant Heat Flux ◽  
Pumping Power ◽  
High Concentration ◽  
Microchannel Cooling ◽  
Characteristic Relationship

The increase in the CPV temperature significantly reduces the efficiency of CPV system. To maintain the CPV temperature under a permissible limit and to utilize the unused heat from the CPVs, an efficient cooling and transportation of coolant is necessary in the system. The present study proposes a new design of hybrid jet impingements/microchannels heat sink with pillars for cooling densely packed PV cells under high concentration. A three-dimensional numerical model was constructed to investigate the thermal performance under steady state, incompressible and laminar flow. A constant heat flux was applied at the base of the substrate to imitate heated CPV surface. The effect of two dimensionless variables, i.e., ratios of standoff (distance from the nozzle exit to impingement surface) to jet diameter and jet pitch to jet diameter was investigated at several flow conditions. The performance of hybrid heat sink was investigated in terms of heat transfer coefficient, pressure-drop, overall thermal resistance and pumping power. The characteristic relationship between the overall thermal resistance and the pumping power was presented which showed an optimum design corresponding to S/Dj = 12 having lower overall thermal resistance and lower pumping power.

Fluid Flow and Heat Transfer Characteristics of a Centrifugal Heat Sink

2009 ◽  
Author(s):  
Juwan Kim ◽  
Sung Jin Kim
Keyword(s):  
Thermal Resistance ◽  
Flow Rate ◽  
Heat Sink ◽  
Volumetric Flow Rate ◽  
Design Principles ◽  
Constant Heat Flux ◽  
Centrifugal Fan ◽  
Flow And Heat Transfer ◽  
Relative Structure ◽  
Additional Space

A novel heat sink called a centrifugal heat sink is proposed. The principle of coolant pumping in the centrifugal heat sink is similar to a centrifugal fan. The blades of a fan are arranged to be placed between the fins of the heat sink. Due to the relative structure of the blades and the fins, additional space for the blades of the fan is no longer required for the centrifugal heat sink. Consequently, the centrifugal heat sink makes efficient use of its total amount of cooling space. The shape of the blades for coolant pumping is based on the design principles of centrifugal turbomachinery. Due to the design principles, it is possible to increase the volumetric flow rate of the air through the heat sink. By the rotary motion of the blades, the coolant in the heat sink passes through channels formed by the adjacent fins. In this paper, an experimental investigation is conducted to demonstrate the concept of the centrifugal heat sink. As the speed of the fan increases, the volumetric flow rate is shown to increase proportionally. Thermal performance of the centrifugal heat sink is evaluated in terms of the thermal resistance under the constant heat flux condition. As a result, the thermal resistance of the centrifugal heat sink is shown to decrease as the rotation speed of the centrifugal heat sink increases.

Thermal Performance Measurements of Thermal Interface Materials Using the Laser Flash Method

2007 ◽  
Author(s):  
Vinh Khuu ◽  
Michael Osterman ◽  
Avram Bar-Cohen ◽  
Michael Pecht
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Composite Structures ◽  
Laser Flash ◽  
Flash Method ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Layer Composite ◽  
Interface Materials

Thermal interface materials are used to reduce the interfacial thermal resistance between contacting surfaces inside electronic packages, such as at the die-heat sink or heat spreader-heat sink interfaces. In this study, the change in thermal performance was measured for elastomeric gap pads, gap fillers, and an adhesive throughout reliability tests. Three-layer composite structures were used to simulate loading conditions encountered by thermal interface materials in actual applications. The thermal resistance of the thermal interface material, including contact and bulk resistance, was calculated using the Lee algorithm, an iterative method that uses properties of the single layers and the 3-layer composite structures, measured using the laser flash method. Test samples were subjected to thermal cycling tests, which induced thermomechanical stresses due to the mismatch in the coefficients of thermal expansion of the dissimilar coupon materials. The thermal resistance measurements from the laser flash showed little change or slight improvement in the thermal performance over the course of temperature cycling. Scanning acoustic microscope images revealed delamination in one group of gap pad samples and cracking in the putty samples.

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.

S-Shaped Pin-Fins for Enhancement of Overall Performance of the Pin-Fin Heat Sink

2010 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Uniform Heat Flux ◽  
Pumping Power ◽  
Pin Fin ◽  
Pin Fins ◽  
Overall Performance

In this paper the authors are studying the effect of introducing S-shaped pin-fin structures in a micro pin-fin heat sink to enhance the overall thermal performance of the heat sinks. For the purpose of evaluating the overall thermal performance of the heat sink a figure of merit (FOM) term comprising both thermal resistance and pumping power is introduced in this paper. An optimization study of the overall performance based on the pitch distance of the pin-fin structures both in the axial and the transverse direction, and based on the curvature at the ends of S-shape fins is also carried out in this paper. The value of the Reynolds number of liquid flow at the entrance of the heat sink is kept constant for the optimization purpose and the study is carried out over a range of Reynolds number from 50 to 500. All the optimization processes are carried out using computational fluid dynamics software CoventorWARE™. The models generated for the study consists of two sections, the substrate (silicon) and the fluid (water at 278K). The pin fins are 150 micrometers tall and the total structure is 500 micrometer thick and a uniform heat flux of 500KW is applied to the base of the model. The non dimensional thermal resistance and nondimensional pumping power calculated from the results is used in determining the FOM term. The study proved the superiority of the S-shaped pin-fin heat sinks over the conventional pin-fin heat sinks in terms of both FOM and flow distribution. S-shaped pin-fins with pointed tips provided the best performance compared to pin-fins with straight and circular tips.

Analysis of Liquid-Cooled Heat Sink Used for Power Electronics Cooling

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Hemin Hu ◽  
Jiahui Zhang ◽  
Xiaoze Du ◽  
Lijun Yang
Keyword(s):  
Power Electronics ◽  
Hydraulic Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Rectangular Channel ◽  
Geometry Optimization ◽  
Electronics Cooling ◽  
Volumetric Flow Rate ◽  
Cold Plate ◽  
Channel Density

Liquid-cooled heat sink (cold plate) used for power electronics cooling is numerically studied. Thermal performance and hydraulic resistance are analyzed, with emphasis on geometric construction of cooling channels. Two heat transfer enhancing channel shapes are investigated, such as alternating elliptical channel and alternating rectangular channel (AR-C). Their performances are compared with that of three traditional straight channel shapes, as straight circular channel, straight elliptical channel, and straight rectangular channel. A heat sink with uniform and discrete heat sources is studied. Thermal and hydraulic characteristics in the heat sink are simulated using computational fluid dynamics approach, with water as coolant. The results show that the AR-C has the highest thermal performance with a little penalty on pressure drop, considering fixed channel hydraulic diameter and coolant volumetric flow rate. Geometry optimization is investigated for the AR-C, as well as the effect of channel density. It is found that higher channel density can improve both thermal performance and hydraulic resistance. It is concluded that alternating channel can improve cold plate performance and should be taken into application to power electronics cooling.

scholarly journals Optimization of the thermal performance of multi-layer silicon microchannel heat sinks

2016 ◽  
Vol 20 (6) ◽  
pp. 2001-2013 ◽  
Author(s):  
Shanglong Xu ◽  
Yihao Wu ◽  
Qiyu Cai ◽  
Lili Yang ◽  
Yue Li
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Optimization Design ◽  
Heat Sinks ◽  
Structural Parameter ◽  
Microchannel Heat Sink ◽  
Total Thermal Resistance ◽  
Sqp Method ◽  
Resistance Network Model

The objective is to optimize the configuration sizes and thermal performance of a multilayer silicon microchannel heat sink by the thermal resistance network model. The effect of structural parameter on the thermal resistance is analyzed by numercal simulation. Taking the thermal resistance as an objective function, a nonlinear and multi-constrained optimization model are proposed for the silicon microchannel heat sink in electronic chips cooling. The sequential quadratic programming (SQP) method is used to do the optimization design of the configuration sizes of the microchannel. For the heat sink with the size of 20mm?20mm and the power of 400 W, the optimized microchannel number, layer, height and width are 40 and 2, 2.2mm and 0.2mm, respectively, and its corresponding total thermal resistance for whole microchannel heat sink is 0.0424 K/W.

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