CFD Simulations of Wind Effect on Net Solar Heat Gain of South Walls with Internal Insulation

Computational fluid dynamics( CFD) techniques are used to investigate effects of both wind direction and wind speed on net solar heat gain of south wall with internal insulation in winter.Results show that wind effect has a significant influence on the net solar heat gain,where the impact of wind direction is stronger than that of wind speed. For regions in lower reaches of the Yangtze River,difference of their average net solar heat gains( NSHGS) is about 20% due to various wind speeds and wind directions.Buildings in districts with a dominant wind direction of north achieve the highest solar energy utilization.

Secondary solar heat gain modelling of spectral-selective glazing based on dynamic solar radiation spectrum

The secondary solar heat gain,defined as the heat flows from glazing to indoor environment through longwave radiation and convection,grows with the increasing of glazing absorption.With the rapid development and application of spectrally selective glazing,the secondary solar heat gain becomes the main way of glazing heat transfer and biggest proportion,and indicates it should not be simplified calculated conventionally.Therefore,a dynamic secondary solar heat gain model is developed with electrochromic glazing system in this study,taking into account with three key aspects,namely,optical model,heat transfer model,and outdoor radiation spectrum.Compared with the traditional K-Sc model,this new model is verified by on-site experimental measurements with dynamic outdoor spectrum and temperature.The verification results show that the root mean square errors of the interior and exterior glass surface temperature are 3.25°C and 3.33°C,respectively,and the relative error is less than 10.37%.The root mean square error of the secondary heat gain is 13.15 W/m2,and the dynamic maximum relative error is only 13.2%.The simulated and measured results have a good agreement.In addition,the new model is further extended to reveal the variation characteristics of secondary solar heat gain under different application conditions(including orientations,locations,EC film thicknesses and weather conditions).In summary,based on the outdoor spectrum and window spectral characteristics,the new model can accurately calculate the increasing secondary solar heat gain in real time,caused by spectrally selective windows,and will provide a computational basis for the evaluation and development of spectrally selective glazing materials.

Design and optimization of thermally responsive autonomous dynamic glazed attachment systems for building solar heat gain control

Windows,as transparent intermediaries between the indoors and outdoors,have a significant impact on building energy consumption and indoor visual and thermal comfort.With the recent development of dynamic window structures,especially various attachment technologies,the thermal,visual,and energy performances of windows have been significantly improved.In this research,a new dynamic transparent louver structure sandwiched within conventional double-pane windows is proposed,designed,optimized,and examined in terms of energy savings in different climates.The uniqueness of the proposed design is that it autonomously responds to the seasonal needs prompted by solar heat gain through the use of thermally deflected bimetallic elements.Moreover,by integrating spectral selective louvers into the system design,the dynamic structure enables strong solar infrared modulation with a little visible variation.The optical and thermal properties of the dynamic glazing structure support about 30%and 16%seasonal variations in solar heat gains and visible transmittance,respectively.Furthermore,the potential energy savings were explored via parametric energy simulations,which showed significant potential for heating and cooling energy savings.This proposed design demonstrates a simple smart dynamic glazing structure driven by seasonal temperature differences,with significant solar heat control capabilities and minor effects on the visible or visual quality of the glazing system.

A study on the comparative review of cool roof thermal performance in various regions

Energy demand is growing significantly worldwide to create thermal comfort in buildings.Air-conditioning is contributing to energy consumption at a massive scale in the residential and commercial sectors.The roof is one of the most critical components of the building envelopes,and it achieved maximum heat gain in summer,and it covered nearly 20-25%of overall urban surface areas.In this respect,cool roofs are considered one of the sustainable solutions to maintain thermal comfort in buildings.The results achieved from the literature review indicate that cool roof application reduced energy use in the buildings and a useful tool to mitigate Urban Heat Island(UHI)effect.This paper summarizes cool roof thermal performance with different types of surface coatings in different climatic zones for buildings with additional benefits,limitations,and recommendations for future research work.The results of this review can be helpful for engineers,researchers,dwellers,and architectures to have a good understanding of the benefits of cool roofs to mitigate energy consumption demand in dwelling in a sustainable,cost-effective,and energy-efficient way.The average energy-saving effect of the roof is expressed from 15%to 35.7%in different climatic zones(Temperate,Tropical,Composite,Hot and Warm-Humid)as per the literature survey results.Also,the average roof surface temperature reduction is possible from 1.4℃ to up to 4.7℃ using cool roof technology.

Distribution Characteristics of Transmitted Diffuse Solar Radiation on the Indoor Surface

The transparent envelope structure has huge energy-saving potential, which is the key point to reduce building energy consumption and improve the thermal building environment. The solar radiation transmitted through the transparent envelope structure(transmitted solar radiation) is reflected, scattered and absorbed by the indoor surface, which has a significant impact on the heat gain of the building. In this paper, firstly, the diffuse radiation received by different depths of various indoor surfaces is measured by experimental tests, and the distribution function of transmitted diffuse solar radiation(TDSR) on the indoor surface is established. Secondly, the diffuse solar radiation received by the indoor and outdoor surfaces in different seasons is continuously monitored;the variation of TDSR with time is analyzed, and the distribution function of TDSR on indoor surface with time is proposed. Finally, based on the temporal and spatial distribution characteristics of diffuse radiation under different weather conditions, the variation of TDSR with the weather is studied, and the distribution function of TDSR on the indoor surface with weather changes is established. The distribution function of the TDSR on the indoor surface under different depths, time and weather conditions obtained in this study can supplement and improve the theory of building heat gain and load, and help accurate simulation of building energy consumption.