Ali Beheshti

Performance evaluation of an attic radiant barrier system using three-dimensional transient finite element method

A three-dimensional transient finite element model was developed to evaluate the thermal performance of an attic radiant barrier system as an energy-efficient insulation technology. The finite element model simulates different heat transfer modes including convection, radiation, and conduction. Hourly experimental data collected in a housing complex in Zachary, LA, were used to validate the finite element analysis. Upon validation, the design variables and their influence on the performance of the radiant barrier insulation system were investigated. Among the different design variables, the presence of an air gap on both sides of the radiant barrier had a significant effect on the performance of the insulation system.

On the Contact of Curved Rough Surfaces: Contact Behavior and Predictive Formulas

The statistical microcontact models of Greenwood–Williamson (GW), Kogut–Etsion (KE), and Jackson–Green (JG) are employed along with the elastic bulk deformation of the contacting solids to predict the characteristics of rough elliptical point contact such as the pressure profile, real area of contact, and contact dimensions. In addition, the contribution of the bulk deformation and the asperity deformation to the total displacement is evaluated for different surface properties and loads. The approach involves solving the microcontact and separation equations simultaneously. Also presented are formulas that can be readily used for the prediction of the maximum contact pressure, contact dimensions, contact compliance, real area of contact, and pressure distribution.

Prediction of Crack Nucleation in Rough Line-Contact Fretting via Continuum Damage Mechanics Approach

The crack nucleation behavior of rough surfaces in line contact is investigated by means of a thermodynamically based continuum damage mechanics technique. The deterministic approach is employed to investigate the effect of roughness on the surface tractions and contact stresses. In order to treat the effect of high stress gradients, a special averaging technique, proposed previously for the case of smooth surface, is adopted in this study. The predictions of the crack nucleation life are compared with the relevant experimental data in the literature and indicate the validity of the analysis.

Quantification of Residential Energy Consumption Reduction Using Glass-Modified Asphalt Shingle

AbstractThe urban heat island (UHI) phenomenon is defined as the differences in temperatures between urban and rural areas caused by the thermal properties of urban materials, urban geometry, and air pollution. Rooftops are playing a vital role in urban sustainability efforts and mitigating the UHI effect. Continuing these efforts, a study was conducted to evaluate the effectiveness of using recycled broken and waste glass cullet in the production of asphalt shingles to mitigate heat island effects and reduce building energy consumption by increasing the reflectivity of the roof asphalt shingles. To achieve this objective, shingle samples were prepared with and without glass cullet and the Solar Reflectance Index (SRI) of the specimens was measured based on ASTM E1980-11. The SRI of the asphalt shingles prepared with glass cullet and a white pigment powder was found to be 30, whereas it was 0 for the asphalt shingles without glass cullet. A three-dimensional transient finite-element (FE) model was formula...

3D finite element modeling of recycled glass cullets in asphalt shingles

Recycled glass cullets in asphalt shingles may be utilized as a cool roof strategy to reduce the harmful effects of Urban Heat Island (UHI). A Three-Dimensional (3D) transient Finite Element (FE) model was developed and validated to quantify energy savings provided by the proposed recycling process under various climatic conditions. Simulations were carried out for three cities located in three climate regions in the United States representing different climatic conditions. The three cities representing each region were Kansas City (Missouri) for Zone 3, Charlotte (North Carolina) for Zone 4, and Miami (Florida) for Zone 5. Results for each of the climatic zones were quantified. Results showed that the annual energy savings ranged from

Asperity micro-contact models as applied to the deformation of rough line contact

35.37 in cold climatic regions to

An engineering approach for the prediction of wear in mixed lubricated contacts

92.58 in hot climates.