P J Sebastian

Bio: P J Sebastian is an academic researcher. The author has contributed to research in topics: Transmittance & Thin film. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Solar control characteristics of Cu2Se coatings

Abstract: Solar control coatings required for architectural glazing applications in tropical locations warrant much attention due to their vital role in energy conservation. The solar control properties of Cu2Se thin film coatings were investigated and the results are presented. It was observed that Cu2Se coatings have moderate optical transmittance and low reflectance in the visible region and high reflectance and low transmittance in the IR region. These characteristics are useful for the above purpose. The evaluation of their solar control parameters in the visible and IR region showed that they exhibit superior solar control characteristics in certain respects over the metallic and PbS coatings and have comparable characteristics with CuxS films.

Two-dimensional model for the double glass naturally ventilated window

Abstract: This paper presents a mathematical model and the results of numerical simulations of a double sheet ventilated glass window. The incident solar radiation heats up the air between the glass sheets creating buoyancy forces that induces upward flow of air. The two-dimensional transient model is formulated based upon the fundamental equations of mass conservation, momentum and energy, the associated constant and time varying boundary conditions and is solved by finite difference approach and the ADI (alternating direction implicit) scheme. The numerical grid and the time increment were optimized and the numerical results were validated against available data. Results of the temperature field along and across the channel are obtained for different spacing between the glass sheets and incident radiation conditions. The effects on the solar heat gain coefficient and the shading coefficient were also presented and discussed.

Modeling and simulation of a simple glass window

Abstract: This paper presents a mathematical model with numerical simulations of the heat transfer across a simple glass window. The model is two-dimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet. Variable incident solar radiation and external ambient temperature are considered in the numerical simulations. The governing equations and the associated boundary conditions are discretized by the finite difference approach and the ADI scheme. Numerical simulations are realized for the cases of clear and absorbing glass to show the effect of the glass thickness on the total heat gain, the solar heat gain and the shading coefficient.

Simplified model for a ventilated glass window under forced air flow conditions

Abstract: This paper presents a study on a ventilated window composed of two glass sheets separated by a spacing through which air is forced to flow. The proposed model is one dimensional and unsteady based upon global energy balance over the glass sheets and the flowing fluid. The external glass sheet of the cavity is subjected to variable heat flow due to the solar radiation as well as variable external ambient temperature. The exchange of radiation energy (infrared radiation) between the glass sheets is also included in the formulation. Effects of the spacing between the glass sheets, variation of the forced mass flow rate on the total heat gain and the shading coefficients are investigated. The results show that the effect of the increase of the mass flow rate is found to reduce the mean solar heat gain and the shading coefficients while the increase of the fluid entry temperature is found to deteriorate the window thermal performance.

Deposition of nanocrystal thin films of Cu2Se and their optical and electrical characterization

Abstract: Cu2Se nanocrystal (NC) films of different nanocrystal sizes were synthesized using vacuum deposition technique. The structure of the films was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and High Resolution Transmission Electron Microscopy (HRTEM) analyses. Band gaps of the films were found to decrease with increase in grain size. Analysis of the Raman spectra of the Cu2Se NC films showed that the exciton-phonon coupling in the films could be tuned by varying the grain size. DC conductivity of the films was found to increase and the activation energy for conduction to decrease with increase in the grain size of the samples. The grain size dependent conductivity along with the optical properties of the Cu2Se NC films may find practical applications such as window material for solar cells.

Ventilated double glass window with reflective film: Modeling and assessment of performance

Abstract: In the present study, the thermal behavior of a ventilated double glass window with a solar reflective film is numerically investigated and validated against results available in the literature. The objectives of the study are to develop a validated robust thermal model for the ventilated double glass window, make it versatile so that it can incorporate different inserts (such as reflective and absorptive films, etc.), different glass sheets and different fluids and can be integrated with other available design tools. The proposed ventilated double window is composed of two glass sheets separated by a gap forming a channel having a solar reflective film on the internal surface of outer glass sheet. The model is based on the equations of mass, momentum and the energy conservation equations in steady state. Boussinesq approximation is used to evaluate buoyancy term. The discretization of conservative equations is done using the finite volume method. A numerical code is developed and validated against available experimental and numerical results. Thermal performance of the ventilated double glass window is assessed under different conditions and the results show that in order to reduce the heat gain in the internal ambient, the optimum spacing between the glass sheets should be at least 2.5 cm. The solar reflective film in a ventilated double glass window can reduce the penetrating solar energy by about 64.7% in comparison with a traditional double glass window.