Manifold Design for Micro-Channel Cooling With Uniform Flow Distribution

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Stephen A. Solovitz ◽  
Jeffrey Mainka
Keyword(s):  
Power Law ◽  
Cooling System ◽  
Heat Removal ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Electronic Systems ◽  
Pressure Drops ◽  
Developing Flow ◽  
Micro Channels ◽  
Uniform Flow Distribution

High-power electronic systems often require temperature uniformity for optimal performance. While many advanced cooling systems, such as micro-channels, result in significant heat removal, they are also susceptible to flow mal-distribution that can impact the local temperature variation on a device. By examining the pressure drops through each flow path in a multi-channel cooling system, an analytical model is predicted for the optimal manifold shape to produce uniform velocities. This is a simple power law, whose exponent depends on the flow regime in the manifold passages. The model is validated for laminar fully developed conditions using a series of computational simulations. With the power law design, the speeds in a parallel channel design are uniformly distributed at low Reynolds numbers, with a standard deviation of less than 3% of the overall mean channel speed. At higher Reynolds numbers, some mal-distribution is observed due to developing flow conditions, but it is not as significant as with typical untapered designs.

scholarly journals Influence of Hydrophobic Fin Configuration in Thermal System in Relation to Electronic Device Cooling Applications

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1631
Author(s):  
Shahzada Zaman Shuja ◽  
Bekir Sami Yilbas ◽  
Hussain Al-Qahtani
Keyword(s):  
Nusselt Number ◽  
Pressure Drop ◽  
Electronic Device ◽  
Cooling System ◽  
Flow Analysis ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Solution Domain ◽  
Uniform Flow Distribution ◽  
Temperature Parameter

In this study, heat and flow analysis of the cooling system incorporating fins with hydrophilic and hydrophobic wetting surfaces has been considered in relation to electronic cooling applications. Temperature and velocity fields in the solution domain are simulated for various fin numbers and sizes. A temperature parameter is introduced to assess the thermal performance of the system. Fin count is introduced to formulate the number of fins in the solution domain. The Nusselt number and pressure drop between the inlet and exit ports due to different fin configurations of the cooling system for various fin counts are presented. It is found that the temperature parameter attains high values for large sizes and small fin counts, which is more pronounced for low Reynolds numbers. Increasing number of fins results in almost uniform flow distribution among the fin, which is more pronounced for the hydrophobic fin configuration. The Nusselt number attains larger values for the hydrophilic fin configuration than that corresponding to the hydrophobic fin, and it attains a peak value for certain arrangement of fin count, which differs with the Reynolds number. The pressure drop between the inlet and exit ports reduces for hydrophobic fin; hence the slip velocity introduced for hydrophobic fin improves the pressure drop by 6% to 16% depending on the fin counts in the cooling system.

Analysis of non-uniform flow distribution in parallel micro-channels

2019 ◽  
Vol 33 (8) ◽  
pp. 3859-3864 ◽  
Author(s):  
Jungchul Kim ◽  
Jeong Heon Shin ◽  
Sangho Sohn ◽  
Seok Ho Yoon
Keyword(s):  
Flow Distribution ◽  
Uniform Flow ◽  
Micro Channels ◽  
Uniform Flow Distribution

scholarly journals Partial Redesign of an Accelerator Driven System Target for Optimizing the Heat Removal and Minimizing the Pressure Drops

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2090 ◽  
Author(s):  
Guglielmo Lomonaco ◽  
Giacomo Alessandroni ◽  
Walter Borreani
Keyword(s):  
Cooling System ◽  
Fluid Dynamic ◽  
Heat Removal ◽  
Dynamic Features ◽  
Pressure Drops ◽  
Driven System ◽  
Reference Design ◽  
Accelerator Driven Systems ◽  
Definition Of ◽  
Target Design

Accelerator Driven Systems (ADS) seem to be a good solution for safe nuclear waste transmutation. One of the most important challenges for this kind of machine is the target design, particularly for what concerning the target cooling system. In order to optimize this component a CFD-based approach has been chosen. After the definition of a reference design (Be target cooled by He), some parameters have been varied in order to optimize the thermal-fluid-dynamic features. The final optimized target design has an increased security margin for what regarding Be melting and reduces the maximum coolant velocity (and consequently even more the pressure drops).

Effect of Manifold Design on Flow Distribution in Parallel Micro-Channels

2003 ◽  
Author(s):  
Ralph L. Webb
Keyword(s):  
Flow Distribution ◽  
Reynolds Numbers ◽  
Published Data ◽  
Micro Electro Mechanical Systems ◽  
Micro Channels ◽  
Significant Disagreement ◽  
Manufacturing Tolerances ◽  
Header Design ◽  
Laminar And Turbulent Regimes ◽  
Good Agreement

Gas or liquid flow in multiple, parallel micro-channels is of interest for Micro-Electro-Mechanical Systems (MEMS) cooling applications. The published data for friction in 10-to-400μm hydraulic diameter, single micro-channels show good agreement with the conventional equations in the laminar and turbulent regimes. However, investigators of flow in multiple, parallel micro-channels in the same range of channel sizes report significantly different results. They report significant disagreement with the conventional equations and argue that transition occurs at Reynolds numbers as small as 200, dependent on the channel shape. This paper proposes that the apparent discrepancies of friction in multiple micro-channels can be attributed to flow mal-distribution. Flow mal-distribution is expected in multi-channels, because of manufacturing tolerances and poor manifold design. It can be minimized by proper header design and better manufacturing tolerances.

Analysis of Parallel Microchannels for Flow Control and Hot Spot Cooling

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Stephen A. Solovitz
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Hot Spots ◽  
Hot Spot ◽  
Electronics Cooling ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Cooling Devices ◽  
Parallel Microchannels

Microchannel heat transfer is commonly applied in the thermal management of high-power electronics. Most designs involve a series of parallel microchannels, which are typically analyzed by assuming a uniform flow distribution. However, many devices have a nonuniform thermal distribution, with hot spots producing much higher heat fluxes and temperatures than the baseline. Although solutions have been developed to improve local heat transfer, these are advanced methods using embedded cooling devices. As an alternative, a passive solution is developed here using analytical methods to optimize the channel geometry for a desired, nonuniform flow distribution. This results in a simple power law for the passage diameter, which may be useful for many microfluidic systems, including electronics cooling devices. Computational simulations are then applied to demonstrate the effectiveness of the power law for laminar conditions. At low Reynolds numbers, the flow distribution can be controlled to good accuracy, matching the desired distribution to within less than 1%. Further simulations consider the control of hot spots in laminar developing flow. Under these circumstances, temperatures can be made uniform to within 2 °C over a range of Reynolds numbers (60 to 300), demonstrating the capability of this power law solution.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2012 ◽  
Author(s):  
Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a ‘U’ type parallel micro-channel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a Response surface based surrogate approximation (RSA) and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 5, Ac/Ap = 0.12, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

Uniform Flow Control for a Multipassage Microfluidic Sensor

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Stephen A. Solovitz ◽  
Jiheng Zhao ◽  
Wei Xue ◽  
Jie Xu
Keyword(s):  
Standard Deviation ◽  
Power Law ◽  
Electronics Cooling ◽  
Flow Distribution ◽  
Uniform Flow ◽  
Individual Agent ◽  
Microparticle Image Velocimetry ◽  
Uniform Flow Distribution ◽  
Channel Space ◽  
Parallel Microchannels

Microfluidic sensors have been very effective for rapid, portable bioanalysis, such as in determining the pH of a sample. By simultaneously detecting multiple chemicals, the overall measurement performance can be greatly improved. One such method involves a series of parallel microchannels, each of which measures one individual agent. For unbiased readings, the flow rate in each channel should be approximately the same. In addition, the system needs a compact volume which reduces both the wasted channel space and the overall device cost. To achieve these conditions, a manifold was designed using a tapered power law, based on a concept derived for electronics cooling systems. This manifold features a single feed passage of varying diameter, eliminating the excess volume from multiple branch steps. The design was simulated using computational fluid dynamics (CFD), which demonstrated uniform flow performance within 2.5% standard deviation. The design was further examined with microparticle image velocimetry (PIV), and the experimental flow rates were also uniform with approximately 10% standard deviation. Hence, the tapered power law can provide a uniform flow distribution in a compact package, as is needed in both this microfluidic sensor and in electronics cooling applications.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
V. Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However, in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a “U” type parallel microchannel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a response surface based surrogate approximation and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 7, Ac/Ap = 0.69, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

NUMERICAL STUDY OF THE EFFECT OF AREA OF MANIFOLD AND INLET/OUTLET FLOW ARRANGEMENT 0N FLOW DISTRIBUTION IN PARALLEL RECTANGULAR MICROCHANNEL COOLING SYSTEM

2017 ◽  
Vol 79 (7-3) ◽  
Author(s):  
Amirah M. Sahar ◽  
A. I. M. Shaiful
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Cooling System ◽  
Numerical Study ◽  
Flow Distribution ◽  
Fluid Temperature ◽  
Rectangular Microchannel ◽  
Temperature Distributions ◽  
Micro Channels ◽  
Parallel Microchannels

Parallel microchannels have been widely used in cooling of compact electronic equipment due to large contact area with liquid and availability of large mass of fluid to carry away heat. However, understanding of flow distribution for microchannel parallel system is still unclear and there still lack of studies give a clear pictures to understand the complex flow features which cause the flow maldistribution. Generally, the geometrical structure of the manifold and micro channels play an important role in flow distribution between micro channels, which might affects the heat and mass transfer efficiency, even the performance of micro exchangers. A practical design of exchanger basically involves the selection of an optimized solution, keeping an optimal balance between gain in heat transfer and pressure drop penalty. A parallel microchannels configurations consisting inlet and outlet rectangular manifold were simulated to study flow distribution among the channels were investigated numerically by using Ansys Fluent 14.5. The numerical results was validated using existing experimental data and showed a similar trend with values 1% higher than experimental data. The influence of inlet/outlet manifold area and inlet/outlet arrangement on flow distribution in channels were carried out in this study. Based on the predicted flow non-uniformity value, 𝜙, Z- type flow arrangement exhibits higher value of 𝜙, which is 8%, followed by U-type, 2.6% and the I-type, 2.49%. Thus, a better uniformity of velocity and temperature distributions can be achieved in I-shape flow arrangement. The behavior of the flow distributions inside channels is due to the vortices that occurred at manifold. Besides comparing the pressure drop for case 1(D1) and case 2(D2), it is worth to mention that, as the area of inlet and outlet manifold decrease by 50%, the pressure drop is increasing about 5%. However, the inlet/outlet area of manifold on velocity and fluid temperature distributions was insignificant.

Experimental Investigation of Manifold Induced Flow Maldistribution in U-and Z-Turn Flow Configurations

2011 ◽  
Vol 110-116 ◽  
pp. 4677-4683 ◽  
Author(s):  
Sachin B. Ingle ◽  
R.S. Maurya
Keyword(s):  
Experimental Study ◽  
Pipe Flow ◽  
Flow Distribution ◽  
Peripheral Region ◽  
Pressure Drops ◽  
Uniform Flow Distribution ◽  
Channel Velocity ◽  
Induced Flow ◽  
Flow Configurations ◽  
Flow Maldistribution

In many process equipments and mechanical system where a flow needs to be distributed among several outlets, the design is generally based on the assumption that the fluid is uniformly divided among them but practically in never happens. A non-uniform flow distribution imposes a serious design limitation in terms of rise in pressure drops and decrease in thermal performance of the system. Reynolds number being a characterizing parameter of pipe flow is expected to play a significant role in flow maldistribution pattern also. This paper present an experimental study performed on multi channel U-and Z-turn flow configurations where the flow is varied in the practical range of 20000 < Re < 35000. Result shows the presence of maldistribution. It is found that the Re plays an important role in characterizing the flow in terms of channel velocity, axial velocity in header and flow distribution pattern in a specific channel. Maldistribution effect is found to be dominant in the central region in U-turn flow and peripheral region in Z-turn configurations.

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