scholarly journals Design Optimization and Validation of Single-Phase Rectangular Micro Channels With Axial Non-Uniform Width

2010 ◽  
Author(s):  
Tijs Van Oevelen ◽  
Martine Baelmans
Keyword(s):  
Heat Transfer ◽  
Simple Model ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Single Phase ◽  
Analytical Models ◽  
Micro Channel ◽  
Hydraulic Behaviour ◽  
Developing Flow ◽  
Micro Channels

A simple model for the simulation of the hydraulic behaviour and heat transfer of a single micro channel is formulated, assessed and optimized. The model is based on a thermally developing flow regime. The results of the optimization show that a reduction of 7.8% in thermal resistance can be achieved using non-uniform channels instead of uniform channels. Furthermore, the assumptions of the simple model are validated by comparing the results with a more accurate, numerical model. It is shown that the simple model is sufficiently accurate to simulate the hydraulic and thermal behaviour of micro channels as such. However, the effective improvement of channel width optimization cannot accurately be determined by the analytical models.

scholarly journals Designing and Optimising the Parameters of Micro Channels

2020 ◽  
Vol 8 (2S12) ◽  
pp. 71-76
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Convective Heat Transfer Coefficient ◽  
Volume Flow ◽  
Micro Channel ◽  
Micro Channels ◽  
Good Agreement

This paper documents the optimization of different parameters of micro channel heat sink which enhance the heat transfer. The objective is to find the major thermal resistance in micro channel and its effect on other parameters. Water is used as a coolant and the initial values of convective heat transfer coefficient and volume flow rate are 30000 W/m2K and 1 lpm respectively. Different graph are plotted between pressure drop,heat transfer co-efficient, pressure drop,thermal resistance and flow rate to finally achieve the optimized valus of channel width and height, hydraulic diameter, thermal resistance and pressure drop. The result achieved are in good agreement with the previous researches.

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.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

2005 ◽  
Vol 128 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Transfer Model ◽  
Heat Sinks ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Developing Flow ◽  
Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

Coupled Heat Transfer and Hydraulic Modeling of an Experimental Printed Circuit Heat Exchanger Using Finite Element Methods

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Ian W. Jentz ◽  
Mark H. Anderson
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Exchanger ◽  
Hydraulic Modeling ◽  
Design Tool ◽  
Micro Channel ◽  
Printed Circuit ◽  
Coupled Heat Transfer ◽  
Computational Overhead ◽  
Micro Channels

Abstract The Homogenized Heat Exchanger Thermohydraulic (HHXT) modeling environment has been developed to provide thermodynamic modeling of printed circuit heat exchangers (PCHEs). This finite element approach solves solid conduction and fluid thermohydraulics simultaneously, without the need to mesh the minuscule micro-channels of a PCHE. The model handles PCHE features such as headers, solid side walls, and channel inlet and outlet regions, in addition to the micro-channel core. The HHXT model resolves PCHE thermohydraulics using simple model definitions and minimum computational overhead, making it an ideal design tool. This work introduces the thermohydraulic model at the core of HHXT. The homogenization approach used in the model occupies a medium between simplified linear analyses of heat transfer within a PCHE and the brute force of a fully resolved finite element, or computational fluid dynamics, model. An example problem modeling an experimental PCHE is presented. The ability of the HHXT model to simulate fluid flow through a directional varying micro-channel core of two heat-exchanging streams is demonstrated. The HHXT model is being distributed for free within the research community.

Conjugated Heat Transfer in 2-Dimensional Mini and Micro Channels: Influence of Axial Conduction in the Walls

2004 ◽  
Author(s):  
G. Maranzana ◽  
I. Perry ◽  
D. Maillet
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Reynolds Numbers ◽  
Analytical Models ◽  
Conductive Heat ◽  
Axial Conduction ◽  
Micro Channels ◽  
Small Reynolds Numbers ◽  
Conjugated Heat Transfer ◽  
Axial Heat

For small Reynolds numbers, conductive heat transfer in the wall of mini-micro channels can become quite multidimensional: the wall heat flux density does not stay uniform and heat transfer mainly occurs at the entrance of the channels. The use of a ID model to invert measurements designed for estimating the convective heat transfer coefficient can lead to misinterpretations such as a variation of the Nusselt number with the Reynolds number. Three analytical models of conjugated heat transfer in channels are proposed, and the potential inversion of measurements is considered. A non-dimensional number M quantifying the relative part of conductive axial heat transfer in walls is introduced.

Numerical Analysis on Flow Characteristics of Anti-Gravity Flow

2011 ◽  
Author(s):  
Yan Li ◽  
Shuchao Zhang ◽  
Ning Mei
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Flow Characteristics ◽  
Gravity Flow ◽  
Radius Of Curvature ◽  
Micro Channel ◽  
Subcooled Boiling ◽  
Evaporation Heat ◽  
Micro Channels

Fluid flow phenomena in micro channels received wide attention due to its high heat transfer coefficient. As a new technique in the field of micro channel phase-change heat transfer, anti-gravity flow can drive fluid flow by capillary force and create enhanced evaporation heat transfer conditions by promoting the formation of an extended meniscus in the three-phase contact-line region. Resulting from the circumferential discrepancy of degree of superheat, the radius of curvature of intrinsic meniscus decreases rapidly as liquid rising up, leading to the formation of capillary pressure gradient. With the increase of heat flux, subcooled boiling occurs and micro-bubble appears at the bottom of the fluted tube. Under the action of buoyancy and drag force, the bubble rises along the channel and at the same time grows continually for the presence of superheat until its break. This paper focuses on the numerical study of flow characteristics of anti-gravity flow in the micro channel and the influence of bubble under the subcooled boiling circumstance. The results shows that bubble plays a positive role in the formation of anti-gravity flow and the analytical expressions are presented for the rising velocity of liquid, the contact angle and the curvature of the intrinsic meniscus, which are all influenced by heat flux, superheat temperature and the geometric parameters of the channel.

Application of Micro-Channel Fin for Cold Plate of Liquid Cooling System and Vapor Chamber

2009 ◽  
Author(s):  
Koichi Mashiko ◽  
Masataka Mochizuki ◽  
Yuji Saito ◽  
Yasuhiro Horiuchi ◽  
Thang Nguyen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Cooling System ◽  
Cold Plate ◽  
Micro Channel ◽  
Vapor Chamber ◽  
Liquid Cooling ◽  
Liquid Cooling System ◽  
Heat Spreading

Recently energy saving is most important concept for all electric products and production. Especially, in Data-Center cooling system, power consumption of current air cooling system is increasing. For not only improving thermal performance but also reducing electric power consumption of this system, liquid cooling system has been developed. This paper reports the development of cold plate technology and vapor chamber application by using micro-channel fin. In case of cold plate application, micro-channel fin technology is good for compact space design, high thermal performance, and easy for design and simulation. Another application is the evaporating surface for vapor chamber. The well-known devices for effective heat transfer or heat spreading with the lowest thermal resistance are heat pipes and vapor chamber, which are two-phase heat transfer devices with excellent heat spreading and heat transfer characteristics. Normally, vapor chamber is composed of sintered power wick. Vapor chamber container is mechanically supported by stamped pedestal or wick column or solid column, but the mechanical strength is not enough strong. So far, the application is limited in the area of low strength assembly. Sometime the mechanical supporting frame is design for preventing deformation. In this paper, the testing result of sample is described that thermal resistance between the heat source and the ambient can be improved approximately 0.1°C/W by using the micro-channel vapor chamber. Additionally, authors presented case designs using vapor chamber for cooling computer processors, and proposed ideas of using micro-channel vapor chamber for heat spreading to replace the traditional metal plate heat spreader.

Thermally Developing Single-Phase Flows in Microtubes

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Mehmed Rafet Özdemir ◽  
Ali Koşar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Single Phase ◽  
High Mass ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Friction Factors ◽  
Developing Flow ◽  
Theoretical Predictions

The pressure drop and heat transfer due to the flow of de-ionized water at high mass fluxes in microtubes of ∼ 254 μm and ∼ 685 μm inner diameters is investigated in the laminar, transition and the turbulent flow regimes. The flow is hydrodynamically fully developed and thermally developing. The experimental friction factors and heat transfer coefficients are respectively predicted to within ±20% and ±30% by existing open literature correlations. Higher single phase heat transfer coefficients were obtained with increasing mass fluxes, which is motivating to operate at high mass fluxes and under thermally developing flow conditions. The transition to turbulent flow and friction factors for both laminar and turbulent conditions were found to be in agreement with existing theory. A reasonable agreement was present between experimental results and theoretical predictions recommended for convective heat transfer in thermally developing flows.

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