scholarly journals Impact of Channel Geometries and Flow Patterns On Micro-Channel Heat Sink Performance

2019 ◽  
Vol 8 (11) ◽  
pp. 331-336
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Volume Ratio ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Micro Channel ◽  
Micro Channels ◽  
Extended Surface ◽  
Vapour Quality

Demand for greater capability of electronic devices in very small volume for compactness has affected huge augmentations in heat indulgence at all stages of device, electronic wrapping, test section and system. Latest cooling systems are hence needed to eliminate the released heat while maintaining compactness of the device. The micro-channel heat sink (MCHS) is ideal for this situation as it consists of channels of micron size which offers an extended surface area to volume ratio of approximately 15.294 m2 / m3 compared to 650 m2 / m3 for a typical heat compact exchanger. A comprehensive review has been done for consequence of heat flux (qo ), mass flux (G), vapour quality (x) and channel geometries at flow patterns and heat dissipation of MCHS. The study show that to increase the rate of heat transfer by using different channel geometries like converging-diverging, segmented etc. compared to conventional rectangular micro-channels has given better cooling effect The Flow patterns like bubbly, slug flow are associated with nucleate boiling dominated in low vapour quality and annular flow also given the significant effect on heat transfer in higher vapour quality region

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

Transport Phenomena in Two-Phase Micro-Channel Heat Sinks

2002 ◽  
Author(s):  
Weilin Qu ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Hydrodynamic Instability ◽  
Transport Phenomena ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Micro Channel ◽  
Two Phase ◽  
Convective Boiling ◽  
Micro Channels

The design and reliable operation of a two-phase micro-channel heat sink require a fundamental understanding of the complex transport phenomena associated with convective boiling in small, parallel coolant passages. This understanding is the primary goal of this paper. This goal is realized by exploring the following aspects of boiling in micro-channels: hydrodynamic instability, two-phase flow patterns, pressure drop, and convective boiling heat transfer. High-speed photographic methods were used to determine dominant flow patterns and explore as well as characterize hydrodynamic instabilities. Two types of dynamic instability were identified, a severe pressure drop oscillation and a mild parallel channel instability, and a simple method is recommended to completely suppress the former. Predictions of three popular two-phase pressure drop models and correlations were compared to micro-channel water data, and only a separated flow (Lockhart-Martinelli) correlation based on the assumption of laminar flow in both phases gave acceptable predictions. Several popular heat transfer correlations were also examined and deemed unsuitable for micro-channel heat sinks because all these correlations are based on turbulent flow assumptions, and do not capture the unique features of micro-channel flow such as abrupt transition to slug flow, hydrodynamic instability, and high droplet entrainment in the annular regime. These findings point to the need for further study of boiling behavior and new predictive tools specifically tailored to micro-channel heat sinks.

Effect of Flow Arrangements on Thermohydraulic Performance of a Microchannel Heat Sink

2009 ◽  
Author(s):  
Satbir S. Sehgal ◽  
Krishnan Murugesan ◽  
S. K. Mohapatra
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Experimental Studies ◽  
Heat Sinks ◽  
Heat Transfer Analysis ◽  
Maximum Temperature ◽  
Micro Channel ◽  
Flow Conditions ◽  
Micro Channels ◽  
Microchannel Heat Sinks

The advancements in fabricating and utilizing microchannel heat sinks (MCHS) for cooling of electronic devices during the last decade has not been matched by corresponding advances in our fundamental understanding of the unconventional micro fluidics. Many theoretical and experimental studies have been reported for the heat transfer analysis along the direction of flow within the microchannels, but to the best knowledge of the authors, the effect of the size of the inlet and outlet plenum and direction of the flow to the plenums was not studied exhaustively till date. The liquid is supplied to the microchannels via the inlet and outlet plenums and this can be achieved by many flow arrangements. Due to the small size of the channel dimensions, the entrance and exit conditions will significantly affect the heat transfer characteristics of the flow field in the channel. Instability effects at the entrance and exit regions of the micro-channel also need to be fully understood for efficient design of microchannel heat sinks. This paper presents an experimental study that has been conducted to explore the effect of entrance & exit conditions of the liquid flow within a copper micro-channel heat sink (MCHS). Three test pieces having inlet & outlet plenum dimensions of 8mm × 30mm, 10mm × 30 mm and 12 mm × 30 mm each with constant depth of 2.5 mm have been selected. Three different flow arrangements (U-Type, S-type and P-type) are studied for each test piece resulting in total nine flow arrangements. Each micro-channel heat sink contains an array of micro-channels in parallel having individual width of 330μm and channel depth of 2.5 mm. A comparison is made based on thermohydraulic performance of MCHS for different flow conditions at inlet and outlet plenums maintaining constant heat flux. Deionised water has been used in the experiments for the Reynolds number ranging from approximately 220 to 1100. The results are interpreted based on pressure drops and maximum temperature variations for these nine flow arrangements. Tests has been conducted to look for optimized dimensions and flow conditions at inlet and outlet plenums for the given fixed length of microchannels under same conjugate heat transfer conditions. Evaluations of experimental uncertainties have been meticulously made while selecting the instruments used in the experimental facility.

scholarly journals Evaluation and Optimization of a Cross-Rib Micro-Channel Heat Sink

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 132
Author(s):  
Haiying Chen ◽  
Chuan Chen ◽  
Yunyan Zhou ◽  
Chenglin Yang ◽  
Gang Song ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Junction Temperature ◽  
Micro Channel ◽  
Test Chip ◽  
Thermal Test ◽  
Micro Channels ◽  
The Cross

This article presents a novel cross-rib micro-channel (MC-CR) heat sink to make fluid self-rotate. For a thermal test chip (TTC) with 100 w/cm2, the cross-ribs micro-channel were compared with the rectangular (MC-R) and horizontal rib micro-channel (MC-HR) heat sinks. The results show that, with the cross-rib micro-channel, the junction temperature of the thermal test chip was 336.49 K, and the pressure drop was 22 kPa. Compared with the rectangular and horizontal ribs heat sink, the cross-rib micro-channel had improvements of 28.6% and 14.3% in cooling capability, but the pressure drop increased by 10.7-fold and 5.5-fold, respectively. Then, the effects of the aspect ratio (λ) of micro-channel in different flow rates were studied. It was found that the aspect ratio and cooling performance were non-linear. To reduce the pressure drop, the inclination (α) and spacing (S) of the cross-ribs were optimized. When α = 30°, S = 0.1 mm, and λ = 4, the pressure drop was reduced from 22 kPa to 4.5 kPa. In addition, the heat dissipation performance of the rectangular, staggered fin (MC-SF), staggered rib (MC-SR) and cross-rib micro-channels were analyzed in the condition of the same pressure drop, MC-CR still has superior heat dissipation performance.

A NOVEL INVESTIGATION OF HEAT TRANSFER CHARACTERISTICS IN HYBRID MICRO-CHANNEL HEAT SINK STRUCTURE: OPPOSITION-BASED ANTLION OPTIMIZATION

2019 ◽  
Vol 27 (05) ◽  
pp. 1950143 ◽  
Author(s):  
R. DEENA ◽  
G. SAI SUNDARA KRISHNAN
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Volume Ratio ◽  
Geometrical Parameters ◽  
Micro Channel ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Antlion Optimization ◽  
Energy Equations

Micro-channel heat sinks have been demonstrated to disperse heat at an extremely higher rate than the traditional devices because of huge heat transfer surface-to-volume ratio. This paper proposed to study the hydrothermal performance of hybrid combination of micro-channel heat sink (HMCHS) with secondary oblique channels in alternating directions and rectangular ribs. To enhance the heat transfer characteristics of the proposed hybrid model, we optimize three geometrical parameters such as secondary channel width, relative rib width and angle between the secondary channels. Primarily, numerical modeling is used to find the ranges of parameters by way of using the continuity, momentum and energy equations. Then the proposed model utilizes opposition-based antlion optimization (OALO) algorithm for selecting the optimal ranges of geometrical parameters to improve the system model. The optimal range will enhance the heat transfer characteristics of micro-channel and reduce the pressure drop when compared to the ones in the existing literature. Further, as a result of higher pressure drop, the micro-channel heat sink with secondary channels and ribs continuously loses its favorable position as an effective heat transfer enhancement technique at higher Reynolds number.

Transport Phenomena in Two-Phase Micro-Channel Heat Sinks

2004 ◽  
Vol 126 (2) ◽  
pp. 213-224 ◽  
Author(s):  
Weilin Qu ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Hydrodynamic Instability ◽  
Transport Phenomena ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Micro Channel ◽  
Two Phase ◽  
Convective Boiling ◽  
Micro Channels

The design and reliable operation of a two-phase micro-channel heat sink require a fundamental understanding of the complex transport phenomena associated with convective boiling in small, parallel coolant passages. This understanding is the primary goal of this paper. This goal is realized by exploring the following aspects of boiling in micro-channels: hydrodynamic instability, two-phase flow patterns, pressure drop, and convective boiling heat transfer. High-speed photographic methods were used to determine dominant flow patterns and explore as well as characterize hydrodynamic instabilities. Two types of dynamic instability were identified, a severe pressure drop oscillation and a mild parallel channel instability, and a simple method is recommended to completely suppress the former. Predictions of three popular two-phase pressure drop models and correlations were compared to micro-channel water data, and only a separated flow (Lockhart-Martinelli) correlation based on the assumption of laminar flow in both phases gave acceptable predictions. Several popular heat transfer correlations were also examined and deemed unsuitable for micro-channel heat sinks because all these correlations are based on turbulent flow assumptions, and do not capture the unique features of micro-channel flow such as abrupt transition to slug flow, hydrodynamic instability, and high droplet entrainment in the annular regime. These findings point to the need for further study of boiling behavior and new predictive tools specifically tailored to micro-channel heat sinks.

scholarly journals Effect of Taper Manifolds with Different Slopes in Microchannel Heat Sink

2019 ◽  
Vol 8 (12) ◽  
pp. 3988-3992
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Sink ◽  
Microchannel Heat Sink ◽  
Micro Channel ◽  
Flow And Heat Transfer ◽  
Micro Channels ◽  
Upward Direction ◽  
Degree Slope

In this analysis, the liquid flow and heat transfer in micro channel heat sink (MCHS) to find the pressure drop are experimentally investigated by three degree slope in manifolds in addition to the arrangement of micro channels. This experimental analysis is executed with respect to the Nusselt Number and Heat transfer characteristics for three manifolds with different arrangement. We are working on this experiment at three different arrangement manifolds: Arrangement (A) is the three-degree slope in manifolds downward and upward, Arrangement (B) is the three-degree slope in manifolds upward and downward and Arrangement (C) is the three-degree slope in upward direction of the manifolds are selected. In this investigation we are using the Reynolds number ranging from 705-1411 for micro channel heat sink. The Arrangement (A) is the greater heat transfer coefficient within the increase Nusselt number and velocity and low pressure drop in comparison to Arrangement (B) and (C) type manifolds

scholarly journals Heat Dissipation Performance of Micro-channel Heat Sink with Various Protrusion Designs

2021 ◽  
Vol 20 ◽  
pp. 240-249
Author(s):  
Siyuan Bai ◽  
Khalil Guy ◽  
Yuxiang Jia ◽  
Weiyi Li ◽  
Qingxia Li ◽  
...  
Keyword(s):  
Porous Medium ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Volume Averaging ◽  
Micro Channel ◽  
Partial Differential ◽  
Micro Channels ◽  
Pin Fins

This research will focus on studying the effect of aperture size and shape of the micro-channel heat sink on heat dissipation performance for chip cooling. The micro-channel heat sink is considered to be a porous medium with fluid subject inter-facial convection. Derivation based on energy equation gives a set of governing partial differential equations describing the heat transfer through the micro-channels. Numerical simulation, including steady-state thermal analysis based on CFD software, is used to create a finite element solver to tackle the derived partial differential equations with properly defined boundary conditions related to temperature. After simulating three types of heat sinks with various protrusion designs including micro-channels fins, curly micro-channels fins, and Micro-pin fins, the result shows that the heat sink with the maximum contact area per unit volume will have the best heat dissipation performance, we will interpret the result by using the volume averaging theorem on the porous medium model of the heat sink.

Experimental studies on micro-channel heat sink with different heat transfer fluid

2021 ◽  
Author(s):  
M. P. Dhanishk ◽  
P. Selvakumar ◽  
V. Ashwin ◽  
P. N. ArunKumar
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Experimental Studies ◽  
Heat Transfer Fluid ◽  
Micro Channel

Enhancement of Heat Transfer of Rectangular Saw Tooth Shaped Micro Channel Heat Sink with Water Nano Fluid/Aluminium Oxide

2015 ◽  
Vol 813-814 ◽  
pp. 685-689
Author(s):  
M. Vijay Anand Marimuthu ◽  
B. Venkatraman ◽  
S. Kandhasamy
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Sink ◽  
Micro Channel ◽  
Performance Curve ◽  
Theoretical Level ◽  
Enhancement Of Heat Transfer ◽  
Nano Fluid

This paper investigates the performance and characteristics of saw tooth shape micro channel in the theoretical level. If the conduct area of the nano fluid increases the heat transfer also increases. The performance curve has drawn Reynolds number against nusselt number, heat transfer co efficient. Pressure drop plays an important role in this device. If pressure drop is high the heat transfer increases. The result in this experiment shows clearly that the heat transfer is optimized.

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