The Effect of Uncaria gambir on Optical Properties and Thermal Stability of CNF/PVA Biocomposite Films

Cellulose-based film has gained popularity as an alternative to synthetic polymers due to its outstanding properties.Among all types of cellulose materials available,cellulose nanofiber(CNF)has great potential to be utilized in a diverse range of applications,including as a film material.In this study,CNF biocomposite film was prepared by using polyvinyl alcohol(PVA)as a matrix and Uncaria gambir extract as a filler.This study aims to investigate the effect of Uncaria gambir extract on the optical properties and thermal stability of the produced film.The formation of the CNF biocomposite films was confirmed using Fourier Transform Infrared Spectroscopy,their transmittance characteristics were measured using UV-Vis spectroscopy and a transmittance meter,while their reflectance was determined using a reflectance meter.The results revealed that the addition of Uncaria gambir extract to the CNF biocomposite film improved its UV-shielding properties,as indicated by the lower percentage of transmittance in the visible region,10%–70%.In addition,its reflectance increased to 10.6%compared to the CNF film without the addition of Uncaria gambir extract.Furthermore,the thermal stability of the CNF biocomposite film with the addition of Uncaria gambir extract improved to around 400℃–500℃.In conclusion,the results showed that CNF biocomposite film prepared by adding Uncaria gambir extract can be a promising candidate for optical and thermal management materials.

Numerical analysis of horizontal temperature distribution in large buildings by thermo-aeraulic zonal approach

The commercial and public services sectors including shopping centers,worship buildings,theatres,and other types,account for more than 20%of the electricity consumption in the world.These building typologies are characterized by large spaces and high and temporary occupation.Besides,the horizontal temperature distribution in these buildings becomes one of the important parameters on occupant's comfort and energy efficiency.In the present study,a thermo-aeraulic zonal model using TRNSYS and CONTAM simulation tools is developed to analyze the spatial temperature distribution in a large building.Parametric studies relating to mesh discretization of building volume are performed to optimize the computational time and convergence.Extensive computational simulation is carried out to analyze the impact of building height,internal loads,natural ventilation and climatic conditions on the spatial temperature distribution,building energy performance,and thermal comfort.The developed simulation model in this study is effective to predict the horizontal temperature distribution with reasonable computation time compared to CFD simulations.The results show that the internal heat gains lead to an increase in the horizontal temperature gradient which should not be negligible especially in the case of large buildings.On the other side,natural night ventilation can reduce the peak tempearture in building by 3℃ for normal occupation building with limited internal gains.Furthermore,good spatial temperature distribution can decrease annual building energy needs about 32%.It can be helpful for architects and building developers to make an optimal choice regarding to building envelope and HVAC design.