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.

Oscillatory Heat Transfer in a Pipe Subjected to a Laminar Reciprocating Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 592-597 ◽  
Author(s):  
T. S. Zhao ◽  
P. Cheng
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Nusselt Number ◽  
Numerical Study ◽  
Temperature Cycle ◽  
Uniform Heat Flux ◽  
Fluid Temperature ◽  
Cycle Space ◽  
Reciprocating Flow

An experimental and numerical study has been carried out for laminar forced convection in a long pipe heated by uniform heat flux and subjected to a reciprocating flow of air. Transient fluid temperature variations in the two mixing chambers connected to both ends of the heated section were measured. These measurements were used as the thermal boundary conditions for the numerical simulation of the hydrodynamically and thermally developing reciprocating flow in the heated pipe. The coupled governing equations for time-dependent convective heat transfer in the fluid flow and conduction in the wall of the heated tube were solved numerically. The numerical results for time-resolved centerline fuid temperature, cycle-averaged wall temperature, and the space-cycle averaged Nusselt number are shown to be in good agreement with the experimental data. Based on the experimental data, a correlation equation is obtained for the cycle-space averaged Nusselt number in terms of appropriate dimensionless parameters for a laminar reciprocating flow of air in a long pipe with constant heat flux.

Validation of Film Evaporation Model in GASFLOW-MPI

2018 ◽  
Author(s):  
Li Yabing ◽  
Zhang Han ◽  
Xiao Jianjun
Keyword(s):  
Experimental Data ◽  
Wall Temperature ◽  
Cooling System ◽  
Numerical Study ◽  
Thermal Power ◽  
Heat Removal ◽  
Air Velocity ◽  
Evaporation Model ◽  
Film Evaporation ◽  
Test Region

A dynamic film model is developed in the parallel CFD code GASFLOW-MPI for passive containment cooling system (PCCS) utilized in nuclear power plant like AP1000 and CAP1400. GASFLOW-MPI is a widely validated parallel CDF code and has been applied to containment thermal hydraulics safety analysis for different types of reactors. The essential issue for PCCS is the heat removal capability. Research shows that film evaporation contributes most to the heat removal capability for PCCS. In this study, the film evaporation model is validated with separate effect test conducted on the EFFE facility by Pisa University. The test region is a rectangle gap with 0.1m width, 2m length, and 0.6m depth. The water film flowing from the top of the gap is heated by a heating plate with constant temperature and cooled by countercurrent air flow at the same time. The test region model is built and analyzed, through which the total thermal power and evaporation rate are obtained to compare with experimental data. Numerical result shows good agreement with the experimental data. Besides, the influence of air velocity, wall temperature and gap widths are discussed in our study. Result shows that, the film evaporation has a positive correlation with air velocity, wall temperature and gap width. This study can be fundamental for our further numerical study on PCCS.

scholarly journals Temperature and Velocity Effects on Mass and Momentum Transport in Spacer-Filled Channels for Reverse Electrodialysis: A Numerical Study

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2028 ◽  
Author(s):  
Zohreh Jalili ◽  
Jon Pharoah ◽  
Odne Stokke Burheim ◽  
Kristian Einarsrud
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Concentration Polarization ◽  
Numerical Study ◽  
Membrane Surface ◽  
Lower Pressure ◽  
Low Flow ◽  
Fluid Temperature ◽  
Reverse Electrodialysis ◽  
Flow Velocities

Concentration polarization is one of the main challenges of membrane-based processes such as power generation by reverse electrodialysis. Spacers in the compartments can enhance mass transfer by reducing concentration polarization. Active spacers increase the available membrane surface area, thus avoiding the shadow effect introduced by inactive spacers. Optimizing the spacer-filled channels is crucial for improving mass transfer while maintaining reasonable pressure losses. The main objective of this work was to develop a numerical model based upon the Navier–Stokes and Nernst–Planck equations in OpenFOAM, for detailed investigation of mass transfer efficiency and pressure drop. The model is utilized in different spacer-filled geometries for varying Reynolds numbers, spacer conductivity and fluid temperature. Triangular corrugations are found to be the optimum geometry, particularly at low flow velocities. Cylindrical corrugations are better at high flow velocities due to lower pressure drop. Enhanced mass transfer and lower pressure drop by elevating temperature is demonstrated.

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.

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.

Laminar Fluid Flow in a Planar 90 Degree Bifurcation With and Without a Protruding Branching Duct

1996 ◽  
Vol 118 (1) ◽  
pp. 81-84 ◽  
Author(s):  
T. G. Travers ◽  
W. M. Worek
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Fluid Flow ◽  
Velocity Field ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Flow Field ◽  
Numerical Study ◽  
Main Duct

The laminar flow field in a planar, ninety degree bifurcation is examined. This numerical study uses the computational-fluid-dynamics software Fluent Version 4.11. First, the velocity field in a bifurcation without a protruding branching duct is modeled, and the results are successfully compared to experimental data. Next, the flow field is studied in bifurcations that have branching ducts that protrude into the main duct. The velocity field and pressure drop are documented, and are found to be strongly influenced by the extent of the branching duct protrusion.

Heat Transfer Experiments of Ethylene Glycol-Water Mixture in Multi-Port Serpentine Meso-Channel Heat Exchanger Slab

2010 ◽  
Author(s):  
Mesbah G. Khan ◽  
Amir Fartaj
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Ethylene Glycol ◽  
Test Fluid ◽  
Water Mixture ◽  
Micro Channel ◽  
Working Fluids ◽  
Micro Channels

In past few years, narrow diameter flow passages (≤3 mm) have attracted huge research attentions due to their several advantageous features over conventional tubes (≥6 mm) especially from the view points of higher heat transfer, lesser weight, and smaller device size. Several classifications of narrow channels, based on sizes, are proposed in the open literature from mini to meso and micro (3 mm to 100 μm). The meso- and micro-channels have not yet entered into the HVAC and automotive heat exchanger industries to the expected potentials to take the above-mentioned advantages. The reasons may be the limited availability of experimental data on pressure drop and heat transfer and the lack of consolidated design correlations as compared to what is established for compact heat exchangers. While a number of studies available on standalone single straight channels, works on multi-channel slab similar to those used as typical thermal heat exchanger core elements are inadequate, especially the research on multichannel serpentine slab are limited in the open literature. The 50% ethylene glycol and water mixture is widely used in heat exchanger industry as a heat transfer fluid. Studies of pressure drop and heat transfer on this commercially important fluid using narrow tube multi-channel slab is scarce and the availability of experimental data is rare in the open literature. Conducting research on various shapes of meso- and micro-channel heat exchanger cores using a variety working fluids are a definite needs as recommended and consistently urged in ongoing research publications in this promising area. Under present long-term project, an automated dynamic single-phase experimental infrastructure has been developed to carryout the fluid flow and heat transfer research in meso- and micro-channel test specimens and prototype microchannel heat exchanger using a variety of working fluids in air-to-liquid crossflow orientation. In the series, experiments have been conducted on 50% ethylene glycol and water solution in a serpentine meso-channel slab having 68 individual channels of 1 mm hydraulic diameter to obtain the heat transfer data and the general pressure drop nature of the test fluid. Current paper presents the heat transfer characteristics of ethylene glycol-water mixture and the Reynolds number effects on pressure drop, heat transfer rate, test specimen NTU and effectiveness, overall thermal resistance, and the Nusselt number.

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.

A Review of Prediction Methods for Two-Phase Pressure Loss in Mini/Micro-Channels

2016 ◽  
Vol 24 (01) ◽  
pp. 1630002 ◽  
Author(s):  
Jung Hoon Yun ◽  
Ji Hwan Jeong
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Separated Flow ◽  
Empirical Correlations ◽  
Two Phase ◽  
Flow Models ◽  
Micro Channels ◽  
Extensive Experimental Data ◽  
Phase Pressure

Previous methods and correlations for predicting two-phase frictional pressure loss in mini/micro-channels are reviewed and compared. The empirical correlations are classified into four groups of modeling approaches: Homogeneous equilibrium models (HEMs), separated flow models (SFMs), direct empirical correlations, and flow pattern specific correlations. In order to examine the characteristics of the predictive methods for two-phase pressure loss in mini-channels and to assess the accuracy of the previous models and correlations, extensive experimental data and correlations that are available in the open literature are collected. The 1175 and 1304 experimental data for the two-phase pressure drop for condensing and boiling flows, respectively, are gathered from 15 papers and reports. The results present that the size of the channel significantly influences the pressure drop. The comparison demonstrates that Cicchitti et al.’s two-phase viscosity model is recommended for predicting two-phase pressure loss when the HEM is used. In general, the SFM with the two-phase multipliers of Muller–Steinhagen and Heck and Kim and Mudawar outperforms others for channel diameters of less than 3[Formula: see text]mm.

Numerical Study of Pulsating Flow Frequency and Heat Transfer in Porous Channel Heat Sink

2013 ◽  
Vol 455 ◽  
pp. 470-473
Author(s):  
Chao Wang ◽  
Shang Long Xu ◽  
Yun Chuan Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Numerical Study ◽  
Porous Channel ◽  
Channel Network ◽  
Temperature Distributions ◽  
Constant Wall Heat Flux ◽  
Flow Through

A study has been conducted on the heat transfer of various oscillatory frequencies of pulsation flow through a porous channel network subjected to a constant wall heat flux. The surface temperature distributions, pressure drop, unit thermal resistance and local Nusselt number for different oscillatory frequencies were mainly investigated.

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