scholarly journals Heat Transfer Modeling of Oriented Sorghum Fibers Reinforced High-Density Polyethylene Film Composites during Hot-Pressing

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3631
Author(s):  
Chusheng Qi ◽  
Jinyue Wang ◽  
Vikram Yadama
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Core Temperature ◽  
Hot Pressing ◽  
High Density Polyethylene ◽  
High Density ◽  
Apparent Heat Capacity ◽  
Pressing Process ◽  
Mat Density ◽  
Film Composites

A one-dimensional heat transfer model was developed to simulate the heat transfer of oriented natural fiber reinforced thermoplastic composites during hot-pressing and provide guidance for determining appropriate hot-pressing parameters. The apparent heat capacity of thermoplastics due to the heat of fusion was included in the model, and the model was experimentally verified by monitoring the internal temperature during the hot-pressing process of oriented sorghum fiber reinforced high-density polyethylene (HDPE) film composites (OFPCs). The results showed that the apparent heat capacity of HDPE accurately described its heat fusion of melting and simplified the governing energy equations. The data predicted by the model were consistent with the experimental data. The thermal conduction efficiency increased with the mat density and HDPE content during hot-pressing, and a higher mat density resulted in a higher mat core temperature. The addition of HDPE delayed heat transfer, and the mat had a lower core temperature at a higher HDPE content after reaching the melting temperature of HDPE. Both the experimental and simulated data suggested that a higher temperature and/or a longer duration during the hot-pressing process should be used to fabricate OFPC as the HDPE content increases.

scholarly journals Environmentally-Friendly High-Density Polyethylene-Bonded Plywood Panels

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1166 ◽  
Author(s):  
Pavlo Bekhta ◽  
Ján Sedliačik
Keyword(s):  
Mechanical Properties ◽  
Hot Pressing ◽  
High Density Polyethylene ◽  
Phenol Formaldehyde ◽  
Urea Formaldehyde ◽  
Physical And Mechanical Properties ◽  
Core Layer ◽  
High Density ◽  
Pressing Pressure ◽  
Pressing Time

Thermoplastic films exhibit good potential to be used as adhesives for the production of veneer-based composites. This work presents the first effort to develop and evaluate composites based on alder veneers and high-density polyethylene (HDPE) film. The effects of hot-pressing temperature (140, 160, and 180 °C), hot-pressing pressure (0.8, 1.2, and 1.6 MPa), hot-pressing time (1, 2, 3, and 5 min), and type of adhesives on the physical and mechanical properties of alder plywood panels were investigated. The effects of these variables on the core-layer temperature during the hot pressing of multiplywood panels using various adhesives were also studied. Three types of adhesives were used: urea–formaldehyde (UF), phenol–formaldehyde (PF), and HDPE film. UF and PF adhesives were used for the comparison. The findings of this work indicate that formaldehyde-free HDPE film adhesive gave values of mechanical properties of alder plywood panels that are comparable to those obtained with traditional UF and PF adhesives, even though the adhesive dosage and pressing pressure were lower than when UF and PF adhesives were used. The obtained bonding strength values of HDPE-bonded alder plywood panels ranged from 0.74 to 2.38 MPa and met the European Standard EN 314-2 for Class 1 plywood. The optimum conditions for the bonding of HDPE plywood were 160 °C, 0.8 MPa, and 3 min.

Latent Thermal Storage Unit Using Form-Stable High Density Polyethylene; Part I: Performance of the Storage Unit

1986 ◽  
Vol 108 (4) ◽  
pp. 282-289 ◽  
Author(s):  
M. Kamimoto ◽  
Y. Abe ◽  
S. Sawata ◽  
T. Tani ◽  
T. Ozawa
Keyword(s):  
Heat Transfer ◽  
High Density Polyethylene ◽  
Direct Contact ◽  
Thermal Storage ◽  
High Density ◽  
Heat Transfer Fluid ◽  
Contact Heat ◽  
Storage Unit ◽  
Contact Heat Transfer ◽  
Solar Thermal Applications

A latent thermal storage unit of 30 kWh using form-stable high density polyethylene (HDPE) rods has been developed mainly for solar thermal applications, and heat transfer experiments have been carried out. A direct contact heat transfer technique between HDPE rods and ethylene glycol (EG: a heat transfer fluid) is adopted. Charge and discharge characteristics have been obtained for various thermal input/output and different initial temperature profiles in the storage unit. The direct contact heat transfer and a formation of a clear thermocline provide a good performance for all the cases. Discussions are given of thermal efficiency, storage density, and thermal insulation.

Effect of Moisture on the Efficiency and Power Density of a Liquid Piston Air Compressor/Expander

2016 ◽  
Author(s):  
Anirudh Srivatsa ◽  
Perry Y. Li
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Power Density ◽  
Water Evaporation ◽  
Water Droplets ◽  
Flow Rates ◽  
Trade Off ◽  
Air Compressor ◽  
Apparent Heat Capacity ◽  
Effect Of Moisture

For a compressed air energy storage (CAES) system to be competitive for the electrical grid, the air compressor/expander must be capable of high pressure, efficient and power dense. However, there is a trade-off between efficiency and power density mediated by heat transfer, such that as the process time increases, efficiency increases at the expense of decreasing power. This trade-off can be mitigated in a liquid (water) piston air-compressor/expander with enhanced heat transfer. However, in the past, dry air has been assumed in the design and analysis of the compression/expansion process. This paper investigates the effect of moisture on the compression efficiency and power. Evaporation and condensation of water play contradictory roles — while evaporation absorbs latent heat enhancing cooling, the tiny water droplets that form as water condenses also increase the apparent heat capacity. To investigate the effect of moisture, a 0-D numerical model that takes into account the water evaporation/condensation and water droplets have been developed. Results show that inclusion of moisture improves the efficiency-power trade-off minimally at lower flow rates, high efficiency cases, and more significantly at higher flow rates, lower efficiency cases. The improvement is primarily attributed to the increase in apparent heat capacity due to the increased propensity of water to evaporate.

Biocompatibility of CaSiO3 /High-Density Polyethylene Composites Prepared by Hot-Pressing

2006 ◽  
Vol 309-311 ◽  
pp. 1161-1164 ◽  
Author(s):  
Miho Tanuma ◽  
Yoshikazu Kameshima ◽  
Akira Nakajima ◽  
Kiyoshi Okada ◽  
Shigeo Asai ◽  
...  
Keyword(s):  
Hot Pressing ◽  
High Density Polyethylene ◽  
Ceramic Powder ◽  
High Density ◽  
Apatite Formation ◽  
Composite Surface ◽  
Ceramic Particles ◽  
Fast Bone ◽  
The Matrix

We have reported that CaSiO3 ceramics show very fast bone-like apatite formation in simulated body fluid (SBF). However, CaSiO3 ceramics have disadvantages in their mechanical properties and shapability. It is therefore more effective to develop composites of CaSiO3 particles dispersed in a matrix of polymer or metal. Such composites are usually prepared by homogeneously blending the ceramic powder with the matrix component. This method is, however, ineffective for the preparation of biocompatible polymers or metals because only the surfaces containing accidentally-exposed ceramic particles play a role in generating apatite in SBF. It is therefore necessary to add a large volume of ceramic powder and also to abrade the surface to expose more of the ceramic particles. In this study, CaSiO3/high-density polyethylene (HDPE) composites were prepared by hot-pressing to introduce surface CaSiO3 particles and their biocompatibilities were evaluated under in vitro conditions using SBF. CaSiO3 powders were spread on a HDPE plate and hot-pressed at 140oC and 4.9-14.7 MPa for 2 min. The composite sample (about 10×10×1 mm3 in size) was immersed in 30ml SBF (sample/solution ratio of 2.5 g/l) at 36.5oC. After 14 days soaking, the apatite product particles covered most of the composite surface and formed apatite layers. Bone-like apatite particles were formed only on the surface regions containing exposed CaSiO3 particles but no apatite was formed on the CaSiO3 particles buried in the HDPE matrix. The results show that this surface deposition method is very effective in developing biocompatibility in the composites using very small amounts of CaSiO3 powder (about <1 %v) compared with results reported for hydroxyapatite and AW glass-ceramic powders (requiring about 40 %v). It is also found that the inhomogeneous state of the CaSiO3 particles in the surface of the present composites strongly influences their biocompatibility. It will be necessary to improve the homogeneity of CaSiO3 dispersion in the surface of the composites to achieve a more uniform surface apatite layer.

scholarly journals Identification of Phase Fraction–Temperature Curves from Heat Capacity Data for Numerical Modeling of Heat Transfer in Commercial Paraffin Waxes

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5149 ◽  
Author(s):  
Tilman Barz ◽  
Johannes Krämer ◽  
Johann Emhofer
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Numerical Solutions ◽  
Spline Approximation ◽  
Heat Capacity Data ◽  
Phase Fraction ◽  
Supplementary Information ◽  
Scanning Calorimetry ◽  
Apparent Heat Capacity ◽  
Capacity Data

The area-proportional baseline method generates phase fraction–temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach for the numerical solution of heat transfer problems. However, the curves are non-smooth, discrete signals. They are affected by noise in the heat capacity data and should not be used as input to continuous simulation models. This contribution proposes an alternative method based on spline approximation for the generation of consistent and smooth phase fraction–temperature, apparent heat capacity–temperature and enthalpy–temperature curves. Applications are presented for two commercial paraffins from Rubitherm GmbH considering heat capacity data from Differential Scanning Calorimetry and 3-layer-calorimetry. Apparent heat capacity models are validated for melting experiments using a compact heat exchanger. The best fitting models and the most efficient numerical solutions are obtained for heat capacity data from 3-layer-calorimetry using the proposed spline approximation method. Because of these promising results, the method is applied to melting data of all 44 Rubitherm paraffins. The computer code of the corresponding phase transition models is provided in the Supplementary Information.

Latent Thermal Storage Unit Using Form-Stable High Density Polyethylene; Part II: Numerical Analysis of Heat Transfer

1986 ◽  
Vol 108 (4) ◽  
pp. 290-297 ◽  
Author(s):  
M. Kamimoto ◽  
Y. Abe ◽  
K. Kanari ◽  
Y. Takahashi ◽  
T. Tani ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Numerical Analysis ◽  
High Density Polyethylene ◽  
Thermal Storage ◽  
High Density ◽  
Storage Unit ◽  
Discharge Characteristics ◽  
One Dimensional ◽  
Finite Difference Equations

Heat transfer in the latent thermal storage unit using form-stable high density polyethylene rods has been numerically analyzed. The analysis is based on simple explicit one-dimensional finite difference equations. The calculation can well simulate both the charge and discharge characteristics of the prototype storage unit developed by the present authors. The computer simulation has been used also to speculate the performance of the storage unit under various conditions. Effects of several parameters on the discharge characteristics have been quantitatively made clear.

scholarly journals Effect of face-layer moisture content and face–core–face ratio of mats on the temperature and vapor pressure behavior during hot-pressing of wood-based panel manufacturing

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Kazushige Murayama ◽  
Kensuke Kukita ◽  
Hikaru Kobori ◽  
Yoichi Kojima ◽  
Shigehiko Suzuki ◽  
...  
Keyword(s):  
Moisture Content ◽  
Vapor Pressure ◽  
Core Temperature ◽  
Hot Pressing ◽  
Raw Materials ◽  
Face Layer ◽  
Pressure Behavior ◽  
Antoine Equation ◽  
Pressing Process ◽  
The Face

AbstractWood-based panels are made by consolidating mats of resinous wooden raw materials under a hot-pressing process. This study investigates the effect of face-layer moisture content (MC) and face–core–face (FCF) ratio of mats on the temperature and vapor pressure behavior during the hot-pressing process. Raising the face-layer MC and lowering the face-layer thickness was expected to reduce the time of reaching 100 °C in the hot-pressing process. When the temperature rise was limited or the core temperature decreased after reaching 100 °C (defined as plateau in this study), the mats with 25% and 30% face-layer MC with 1:2:1 FCF ratio reached the highest plateau core temperature, but required a longer time to complete the plateau. The relationship between core plateau temperature and maximum core vapor pressure was well described by the Antoine equation, which empirically models the vapor pressure as a function of temperature. The Antoine equation held across both face-layer MC series (varying face-layer MC at constant FCF ratio) and FCF series (varying FCF ratio at constant face-layer MC). The mat with 20% face-layer MC and 1:2:1 FCF ratio reached 180 °C within the shortest time, regardless of the evaluation conditions.

Biocompatibility of CaSiO3 /High-Density Polyethylene Composites Prepared by Hot-Pressing

2006 ◽  
pp. 1161-1164
Author(s):  
Miho Tanuma ◽  
Yoshikazu Kameshima ◽  
Akira Nakajima ◽  
Kiyoshi Okada ◽  
Shigeo Asai ◽  
...  
Keyword(s):  
Hot Pressing ◽  
High Density Polyethylene ◽  
High Density ◽  
Polyethylene Composites
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