Experimental Study on Viscous Dissipaition of Polymer Melt in Micro-Channels

2010 ◽  
Vol 97-101 ◽  
pp. 2527-2532 ◽  
Author(s):  
Tong Min Yu ◽  
Hai Xin Bei ◽  
Ze Yu Yan ◽  
Bin Xu ◽  
Hua Xu ◽  
...  
Keyword(s):  
Shear Rate ◽  
Viscous Dissipation ◽  
Amorphous Polymer ◽  
Polymer Melt ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Micro Channel ◽  
Aspect Ratios ◽  
Micro Channels ◽  
Macro Scale

The polymer melts viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions. In this paper, the temperature rises due to viscous dissipation were investigated when amorphous polymer material, PMMA, flows through several micro-channels with the diameters of 350μm, 500μm and different aspect ratios. The results indicate that, temperature rises reduce with the increase of inlet temperature of melt and increase with increasing channel’s diameter and aspect ratio at the same shear rate. The outlet temperature rises due to viscous dissipation in all micro channels increase with the increase of shear rate. In addition, the outlet temperature rise grows faster with the decrease of micro-channel’s diameter. Therefore, viscous dissipation effect is significant and should not be neglected in micro channel.

Viscous Dissipation of Polymer Melt in Micro Channels and Macro Channels

2014 ◽  
Vol 609-610 ◽  
pp. 521-525
Author(s):  
Bin Xu ◽  
Xiao Yu An ◽  
Liang Chao Li ◽  
Guang Ming Li
Keyword(s):  
Shear Rate ◽  
Viscous Dissipation ◽  
Unit Length ◽  
Experimental Studies ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Scale ◽  
Micro Channels ◽  
Macro Scale ◽  
The Difference

Viscous dissipation is the key factor impacting flowing characteristics of polymer melt. In order to study the difference between micro scale and macro scale, experimental studies of viscous dissipation at various shear rate were investigated with several polymers, including PMMA and HDPE, at different temperature when melts flow through 1000μm,500μm,350μm diameter channels of identical aspects ratio in the paper. The results indicate that the temperature rises caused by viscous dissipation increase with increasing shear rate and the temperature rise for some shear rate decreases with increasing melts temperature. The temperature rises decrease significantly with the reduction of the characteristic size of micro channel at the same shear rate. However, the average temperature rises per unit length increase when the character size of channel decreases. This indicates the shear friction gradually increases with the decrease of channel characteristic size. Therefore polymer melt viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions.

Experimental Research on the Viscosity of Polymer Melts Filling through Micro Channels

2011 ◽  
Vol 314-316 ◽  
pp. 1346-1349
Author(s):  
Bin Xu ◽  
Yu Bin Lu ◽  
Guang Ming Li ◽  
Song Xue
Keyword(s):  
Shear Rate ◽  
Flow Model ◽  
Capillary Flow ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Channel ◽  
Test Results ◽  
Micro Channels ◽  
Rate Test ◽  
The Difference

Experimental observations indicate that the viscosity of polymer melt flowing through micro channel is altered with variation of characteristic size of micro channels. The explanation about the trend of various viscosity is inconsistent. In this paper, the micro channel dies of 1000μm ,500μm and 350μm diameter were developed and with several polymers, including PP , PS and HDPE, depending on the capillary flow model, the measurement experiments of polymer melt viscosity were investigated at various shear rate. Test results show that with micro-channel size decrease, the percentage reduction in viscosity increases and the difference of viscosities in different micro channels reduces with increasing shear rate.

A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

2013 ◽  
Vol 33 (2) ◽  
pp. 95-110
Author(s):  
Mustafa Tutar ◽  
Ali Karakus
Keyword(s):  
Shear Rate ◽  
Phase Change ◽  
Viscous Dissipation ◽  
Polymer Melt ◽  
Viscous Heating ◽  
Transient Phase ◽  
Melt Flow ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Dependent Viscosity

Abstract The combined effects of solidification and viscous dissipation on the hydrodynamic and thermal behavior of polymer melt flow during the injection process in a straight plane channel of constant cross section are numerically studied by considering the shear-rate and temperature-dependent viscosity and transient-phase change behavior. A numerical finite volume method, in conjunction with a modified form of the Cross constitutive equation to account for shear rate, temperature-dependent viscosity changes and a slightly modified form of the method proposed by Voller and Prakash to account for solidification of the liquid phase, is used and a validation with an analytical solution is presented for viscous heating effects. The hydrodynamic and solidified layers growth under the influence of a transient phase-change process and viscous dissipation, are analyzed for a commercial polymer melt flow, polypropylene (PP) for different parametric conditions namely, inflow velocity, polymer injection (inflow) temperature, the channel wall temperature, and the channel height. The results demonstrate that the proposed numerical formulations, including conjugate effects of viscous heating and transient-solidification on the present thermal transport process, can provide an accurate and realistic representation of polymer melt flow behavior during the injection molding process in plane channels with less simplifying assumptions.

Viscous dissipation influencing viscosity of polymer melt in micro channels

2010 ◽  
Vol 24 (7) ◽  
pp. 1417-1423 ◽  
Author(s):  
Bin Xu ◽  
Minjie Wang ◽  
Tongmin Yu ◽  
Danyang Zhao
Keyword(s):  
Viscous Dissipation ◽  
Polymer Melt ◽  
Micro Channels

Energy Equation of Gas Flow With Low Velocity in a Micro-Channel

2014 ◽  
Author(s):  
Yutaka Asako
Keyword(s):  
Viscous Dissipation ◽  
Incompressible Flow ◽  
Gas Flow ◽  
Energy Equation ◽  
Outlet Temperature ◽  
Gas Temperature ◽  
Low Velocity ◽  
Dissipation Term ◽  
Pressure Term ◽  
Micro Channels

The energy equation for incompressible flow with the viscous dissipation term is often used for the governing equations of gas flow with low velocity in micro-channels. However, the results which are obtained by solving these equations do not satisfy the first law of the thermodynamics. In the case of ideal gas with low velocity, the inlet and the outlet temperatures of an adiabatic channel are the same based on the first law of the thermodynamics. However, the outlet temperature which is obtained by solving the energy equation for incompressible flow with the viscous dissipation term is higher than the inlet gas temperature, since the viscous dissipation term takes positive value. This inconsistency arose from wrong choice of the relation between the enthalpy and temperature that resulted in neglecting the substantial derivative of pressure term in the energy equation. In this paper the correct energy equation which includes the substantial derivative of pressure term is proposed. Some samples of physically consistent results which are obtained by solving the proposed energy equation are demonstrated.

Effects of Polymer Morphology on the Rheological Behavior of Melt Within Micro-Channels

2008 ◽  
Author(s):  
Shia-Chung Chen ◽  
Rean-Der Chien ◽  
Song-Wei Huang ◽  
Chun-Sheng Chen
Keyword(s):  
Rheological Behavior ◽  
Polymer Melt ◽  
Degree Of Crystallinity ◽  
Micro Channel ◽  
Melt Temperature ◽  
Channel Size ◽  
High Crystallinity ◽  
Micro Channels ◽  
Micro Molding ◽  
Low Crystallinity

Micro molding has shown great commercial potential in recent years and determination of the rheological behavior of the polymer melt within micro structured geometry is vital for accurate simulation modeling of micro molding. The lack of commercial equipment is one of main hurdles in the investigation of micro melt rheology. In this study, a melt viscosity measurement system for low and high density polyethylene polymer melt flowing through micro-channels was established using a micro channel mold operated at a mold temperature as high as the melt temperature. For measured pressure drop and volumetric flow rate, capillary flow model was used for the calculation of viscosity utilizing Rabinowitsch correction. The calculated results of low crystallinity LDPE resin were also compared with those of high crystallinity HDPE resin to discuss the effect of degree of crystallinity on the viscosity characteristics of polymer within micro-channels. It was found that the measured LDPE and HDPE viscosity values in the test ranges are significantly lower (about 40∼56% and 22∼29% for LDPE and HDPE, respectively, flowing through a channel size of 150μm) than those obtained with a traditional capillary rheometer. Meanwhile, the percentage reduction in the viscosity value and the ratio of slip velocity relative to mean velocity all increase with decreasing micro-channel size. In the present study we emphasize that the rheological behavior of the high crystallinity HDPE and low crystallinity LDPE resins in microscopic scale are all different from that of macroscopic scale but HDPE displays a less significant lower. The reason can be attributed to for LDPE resin within the micro-channel can create the higher extra bonding force between the bulk chains than HDPE resin. Thus, it will have the lower adhesive force between the bulk chains with the micro-channel wall, resulting in higher degree of wall slip.

Design of a Ceramic Heat Exchanger for Sulfuric Acid Decomposition

2006 ◽  
Author(s):  
Merrill A. Wilson ◽  
Charles Lewinsohn ◽  
James Cutts ◽  
Valery Ponyavin
Keyword(s):  
Heat Transfer ◽  
Sulfuric Acid ◽  
High Temperature ◽  
Heat Exchanger ◽  
Ceramic Materials ◽  
Compact Heat Exchanger ◽  
Micro Channel ◽  
Micro Channels ◽  
Macro Scale ◽  
Chemical Cycle

It has been proposed that compact ceramic heat exchangers can be used for high temperature, corrosive applications. This paper discusses the design development of a micro-channel heat exchanger for the decomposition of sulfuric acid as part of the hydrogen producing sulfur iodine thermo-chemical cycle. Corrosion studies of candidate materials indicate that ceramic materials have superior corrosion and creep resistance under these high temperature, high acid concentration environments. This compact heat exchanger utilizes micro-channels to enhance the heat transfer while maintaining low pressure drops within the system. Through modular stacking of these micro-channel networks, a "shell and plate" configuration enables the processing of commercial-scale processes. The ceramic materials provide for long-life applications. The design of the micro-channel features captures the enhanced heat transfer characteristics at the micro-scale; the modular assembly permits the integration into macro-scale processes. As a case study, the thermal performance and the economics were investigated to determine the feasibility of this compact heat exchanger for the hydrogen producing sulfur iodine thermo-chemical cycle. The results of this design effort with its associated performance goals and development status will be reported.

Rheological Behavior of Polymethyl Methacrylate (PMMA) Filling through Micro Channels

2011 ◽  
Vol 189-193 ◽  
pp. 451-454 ◽  
Author(s):  
Bin Xu ◽  
Yu Bin Lu ◽  
Guang Ming Li ◽  
Song Xue ◽  
Bei Ping Xiang
Keyword(s):  
Polymethyl Methacrylate ◽  
Rheological Behavior ◽  
Capillary Flow ◽  
Rapid Development ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Channel ◽  
Channel Characteristic ◽  
Micro Channels ◽  
The Difference

With the rapid development of micro injection molding, the determination of melt rheological behavior within micro mold cavity is very important for the accurate simulation modeling. Yet several investigations show the viscosity of melt decreases with the reduction of micro channel characteristic size, but there has been no sufficient experimental data for the conclusion. In this paper, depending on the capillary flow model, the measurement experiments of polymer melt viscosity were investigated when Polymethyl Methacrylate (PMMA) was extruded through the micro channel dies of 1000μm ,500μm and 350μm diameter. Test results show that, as micro-channel size decreases, the viscosity increases and the difference of viscosities in different micro channels reduces with increasing shear rate. This indicates microscopic scale melt rheological behavior of PMMA is different from that of other materials.

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.

Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle

2009 ◽  
Author(s):  
V. G. Razumovskiy ◽  
Eu. N. Pis’mennyy ◽  
A. Eu. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Water ◽  
Annular Channel ◽  
Heat Fluxes ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Temperature Regimes ◽  
Outside Diameter

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.

Sign in / Sign up

Export Citation Format

Share Document