Advanced fiber-composite hybrids--A new structural material

Introduction of metal foil as part of matrix and fiber composite, or ""sandwich'', improves strength and stiffness for multidirectional loading, improves resistance to cyclic loading, and improves impact and erosion resistance of resultant fiber-composite hybrid structure

Boron/aluminum graphite/resin advanced fiber composite hybrids

Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements

Simulation and Measurement of Windows with Low Emissivity Coatings Used in Conjunction with Teflon Inner Glazings

Theoretical work has illustrated that highly infrared, transparent plastic films are well suited for use as intermediate glazings when used in conjunction with a low emissivity coating. Prototype glazing systems that incorporate low emissivity coatings and Teflon films were constructed. The thermal resistance of each of these prototypes was measured using the University of Waterloo Natural Convection Apparatus. Simulation of the glazing systems was carried out using a two-band glazing system thermal analysis program called VISION. Comparison between measurement and simulation showed good agreement. It can be concluded that highly infrared transparent intermediate glazings can be useful when high thermal resistance is desired and that the VISION glazing system analysis program is useful not only for parametric and sensitivity investigations but can also be used with confidence to estimate U-values of specific glazing systems.Renewable Energy Branch of the Department of Energy, Mines and Resource

A two-dimensional numerical model for natural convection in a vertical, rectangular window cavity

© 1994 ASHRAE (www.ashrae.org). Published in ASHRAE Transactions 1994, Vol. 100, Part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE`s prior written permissionIt is common for sealed glazing units to exhibit condensation problems when operated in cold climates. Condensation often forms along the perimeter of the exposed surface of the indoor glazing because of the thermal short circuit caused by the edge seal. Furthermore, condensation most readily forms along the bottom edge of the indoor glazing because of the combined effects of edge seal conduction and fill gas convection. A simple two-dimensional numerical control volume formulation is presented that can be used to model the natural convection of gas within a vertical, rectangular cavity. Details of a unique perturbation scheme used to generate secondary cells are also presented This model closely reproduces the average Nusselt number results of more complex numerical models. Average and local Nusselt numbers have also been compared with experimental results and close agreement has been demonstrated for conditions typical of window cavities.Energy efficiency technology division || CANMET || Department of Energy || Mines and Resources Canada || Natural Sciences and Engineering Research Council of Canad

Simulation And Measurement Of Windows With Metal Films Used In Conjunction With Teflon Inner Glazings

Previous work has shown that highly infrared transparent plastic films are well suited for use as inner glazings when used in conjunction with a low emissivity coating. Thermal resistance measurements of a set of glazing systems incorporating gold or copper coatings plus Teflon intermediate glazings are reported. The same glazing systems were simulated using a computer program called VISION. The agreement between the two sets of results was found to be very good.Renewable Energy Branch of the Department of Energy, Mines and Resource

Glazing System U-Value Measurement Using a Guarded Heater Plate Apparatus

© 1988. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Vol. 94, Part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.Precise heat transfer measurements have been carried out during the last 20 years using a guarded heater plate apparatus. This apparatus has been adapted and used over the last several years to perform U-value measurements on a variety of prototypical glazing systems. Results from two sets of measurements are presented. One set of results quantifies heat transfer across stagnant air layers containing an intermediate fluorinated ethylene-propylene (FEP) glazing and bounded by plates of various emissivities. The second set consists of values (i.e., glass-to-glass U-values) for a set of glazing systems that incorporate up to four glazings, one of two solar-control metal coatings and up to two intermediate glazings made of FEP film. In each case the measured results are compared to simulation. In the first study the discrepancy between measured and calculated heat transfer rates was less than 2% in all cases. In the second study the discrepancy was never greater than 8% and was less than 3% in the majority of cases. These results indicate that the test method used is well suited to the reliable measurement of glazing system U-value. It is a useful tool as a developmental test procedure for glazing system design because it can be carried out quickly and at low cost. The apparatus and procedure are described in detail.Renewable energy division || Solar energy development program || Department of energy, mines, and resources Canad

A Novel Furnace Design Utilizing a Low Temperature Plastic Condensing Heat Exchanger

The initial phase of a research and development program for the Consumers' Gas Co. and the Federal Department of Energy, Mines and Resources to design a condensing heat exchanger/gas fired residential air furnace has been com­pleted. Progress to date has resulted in a novel design utilizing a relatively low temperature plastic material for the last stage heat exchanger. To utilize this low temperature plastic, a method of reducing the temperature of the flue gas entering the final heat exchanger was devised using a unique flue gas recirculation process. Heat transfer calculations and pressure drop prediction methods have indicated that the design is sound and can easily be accommodated in a residential furnace with only moderate increase in cost and space requirements. The existing design is also well suited to incorporation as a retrofit package and this is also being pursued. Based on the calculated performance, a condensing heat exchanger was sized, fabricated and installed on a con­ventional 80,000 BTU/hr input gas fired residential fur­nace. The initial experimental tests have given very en­couraging results. Based on a final flue gas exit temp­erature of 85F with an excess air condition of 25%, these initial tests yielded a furnace efficiency of approximate­ly 97%. Although combustion air preheat has not been em­ployed in these initial tests, this feature is planned as part of the prototype design

Visible and near infrared observation on the Global Aerosol Backscatter Experiment (GLOBE)

The Global Aerosol Backscatter Experiment (GLOBE) was intended to provide data on prevailing values of atmospheric backscatter cross-section. The primary intent was predicting the performance of spaceborne lidar systems, most notably the Laser Atmospheric Wind Sounder (LAWS) for the Earth Observing System (EOS). The second and related goal was to understand the source and characteristics of atmospheric aerosol particles. From the GLOBE flights, extensive data was obtained on the structure of clouds and the marine planetary boundary layer. A notable result for all observations is the consistency of the large increases in the aerosol scattering ratio for the marine boundary layer. Other results are noted

Weak Localization Thickness Measurements of Si:P Delta-Layers

We report on our results for the characterization of Si:P delta-layers grown by low temperature molecular beam epitaxy. Our data shows that the effective thickness of a delta-layer can be obtained through a weak localization analysis of electrical transport measurements performed in perpendicular and parallel magnetic fields. An estimate of the diffusivity of phosphorous in silicon is obtained by applying this method to several samples annealed at 850 Celsius for intervals of zero to 15 minutes. With further refinements, this may prove to be the most precise method of measuring delta-layer widths developed to date, including that of Secondary Ion Mass Spectrometry analysis

A Study Of Pane Spacing In Glazing Systems

The selection of optimum pane spacing for glazing systems has been a topic of ongoing debate in the window manufacturing industry. Arguments are often based on speculation, intuition and results from tests not specifically designed to examine the effects of pane spacing. This study presents a set of measured centre-glass U-values taken from experiments where pane spacing was carefully varied while holding all remaining conditions unchanged. Heat flux measurements were made using a guarded heater plate apparatus. Glazing systems were all double glazed, air filled and tested in the vertical position. Measured centre-glass U-values were compared to calculated U-values. These calculations were performed using a version of the VISION glazing system thermal analysis program which was modified in order to model the guarded heater plate test conditions. VISION runs were also carried out in order to predict the optimum pane spacing as a function of variations in glazing system design, fill gas type, weather condition, and the number of panes incorporated in the glazing system. VISION results were combined with results of the window frame thermal analysis program, FRAME. FRAME was used to estimate the average edge-glass and frame U-values for several design options. The results of these calculations provide an estimate of the sensitivity of overall U-values to variations in pane spacing.Renewable Energy Branch of the Department of Energy Mines and Resources || Natural Sciences and Engineering Research Council of Canad