DAYLIGHT GLARE PROBABILITY PREDICTION FOR AN OFFICE ROOM

Glare assessments are currently made from High Dynamic Range (HDR) images taken from the Point Of View (POV) and viewing direction of a user. This paper analyses the feasibility to estimate the Daylight Glare Probability (DGP) at the user-level based on machine-learning techniques, sun position and a downward-pointing camera sensor mounted at the ceiling of a simulated office environment. Three different office cases have been considered: an empty room, an empty room with venetian blinds and a furnished room without venetian blinds. The influence of the sun direction has been considered as a parameter to predict the observer DGP. Subsequently, the best parameters have been selected to build a black box model using Artificial Intelligence (AI). Results show that, by using the DGP of the ceiling camera and the sun position, it is possible to accurately predict the DGP for an observer’s POV.

Comfort and efficiency-based improvements to the control of residential Venetian blinds

This study focuses on the control of movable Venetian blinds. Multiple improvements to an existing on/off open-loop control strategy in a case-study apartment have been simulated in TRNSYS 18, thanks to the detailed optical and thermal modelling allowed by the Bidirectional Scattering Distribution Function (BSDF) used as input to the Type56_CFS. The control strategy improvements include the combination of rule-based, closed-loop and discrete state control, in addition to four control strategy activation methods (three use a schedule, and one measures the external temperature). Simulated control inputs include internal temperature, external temperature and vertical irradiance. The results show reductions in overheating, achieved without completely blocking natural illumination or compromising heating demand. While on/off control in winter often leads to increased heating energy consumption, the space sees regular overheating when on/off control is inactive over winter. Conversely, discrete state control is able to more precisely control solar gains in winter to maintain an adequate temperature without utilising the heating system, all the while allowing some level of natural illumination. Ultimately, it is concluded that the choice of the control strategy depends on which objective (minimisation of heating energy consumption, maximisation of daylight harvesting, reduction of overheating risk, etc.) is prioritised.

Irregular Light Scattering Properties of Fenestration for Comfortable and Energy-Efficient Buildings

The irregular reflection and transmission properties of innovative fenestration allow the redirection, selectively admittance, or blocking of solar irradiation based on its incident direction. Compared to systems that implement adaptivity by mechanical transformations, such tailored light scattering reduces the complexity of installation, operation, and maintenance as well as the impact on outward view and the aesthetical appearance of buildings. Examples of such fenestration techniques (e.g., light redirecting films and Venetian blinds featuring irregular reflection properties) are presented with their gonio-photometrically measured scattering properties. Techniques to model optically complex fenestration to support product development and planning are presented. Effects on daylight availability, glare, and solar gains are demonstrated. Preliminary results indicate the potential to control and modulate rather than to block irradiation through the design of buildings aiming at high comfort and energy efficiency.

A simplified model of the thermal interaction of a Venetian blind located on the indoor glazing surface of a window

A simplified model was developed to predict the radiative and convective heat transfer in complex fenestration systems, including the effect of solar radiation. The focus of the current work was on Venetian blinds mounted adjacent to the indoor window surface. From the perspective of convection, the model used a convective flat plate flow between the blind and ambient surroundings and a convective channel flow between the window and blinds. It was necessary to develop new empirical correlations to predict the average channel Nusslet numbers of the hot and cold walls separately. Therefore, a CFG study of free convection in an asymmetrically heated channel was performed. Then, the new empirical correlations were used to develop a simplified one-dimensional model of the heat transfer in the system. The radiative heat exchange between the blind, window and room was calculated using a four surface grey-diffuse model. Sample predicted results were compared with existing experimental and numerical data from the literature.

A simplified model of the thermal interaction of a Venetian blind located on the indoor glazing surface of a window

A simplified model was developed to predict the radiative and convective heat transfer in complex fenestration systems, including the effect of solar radiation. The focus of the current work was on Venetian blinds mounted adjacent to the indoor window surface. From the perspective of convection, the model used a convective flat plate flow between the blind and ambient surroundings and a convective channel flow between the window and blinds. It was necessary to develop new empirical correlations to predict the average channel Nusslet numbers of the hot and cold walls separately. Therefore, a CFG study of free convection in an asymmetrically heated channel was performed. Then, the new empirical correlations were used to develop a simplified one-dimensional model of the heat transfer in the system. The radiative heat exchange between the blind, window and room was calculated using a four surface grey-diffuse model. Sample predicted results were compared with existing experimental and numerical data from the literature.

Numerical Investigation of the Effects of Window Height and Gas Thickness on Heat Transfer and Gas Flow in Double Pane Windows

Double pane window is an effective way to reduce the heat loss from windows in buildings. There are many studies on the thermal performance of these window applications for different parameters such as optimum gap width, suitable filling fluid and different applications such as film coatings on panes to obtain different surface emissivity values or placing venetian blinds inside the gap, etc. These investigations are mostly based on the laminar flow assumption inside the gas gap between the two panes for the same window height. In this research, effect of the window height and gap width on the gas flow in the gap and heat transfer over double pane for three cities of Turkey representing different climates were numerically investigated with turbulent flow and ideal gas assumptions inside the gap for air and argon. In the calculations, natural convection for pane surface facing indoors and forced convection for pane surface facing outdoors was assumed as boundary condition. The numerical results shown that also the window height such as gap width has an effect on the heat transfer and gas flow of the double pane window. Thereby, the window height should be taken into consideration for determining the optimum gap width in the double pane window applications.

ANALISIS PENGARUH TIPE INTERNAL SHADING SEBAGAI STRATEGI PENDINGINAN PASIF PADA BANGUNAN

Abstrak: Strategi pendinginan pasif pada bangunan menjadi salah satu alternatif dalam memperoleh kenyamanan termal dengan meminimalkan konsumsi energi pendinginan bangunan. Posisi Indonesia yang dilewati oleh garis khatulistiwa mengakibatkan terjadinya penyinaran matahari sepanjang tahun. Hal ini memerlukan sebuah perlakuan khusus terhadap bukaan pada fasad bangunan. Penelitian ini bertujuan untuk menganalisis dan melihat pengaruh tipe internal shading pada interior bangunan terhadap variabel solar gain bangunan. penggunaan tipe shading berupa venetian blind, roller shades dan drapes akan diaplikasikan pada bangunan. hasil dari penelitian ini didapatkan bahwa penggunaan roller shades mampu menurunkan level solar gain sebesar 55 persen. Sedangkan penggunaan venetian blinds dan drapes memberikan hasil penurunan sebesar 31 persen dan 25 persen. Dari penelitian ini dapat disimpulkan bahwa penggunaan roller shades memberikan hasil yang cukup efektif dalam menurunkan solar gain pada bangunan.Kata-kata kunci: pendinginan pasif, internal shading, solar gainAbstract: Passive cooling strategy in buildings is an alternative in obtaining thermal comfort by minimizing building cooling energy consumption. The position of Indonesia, which is crossed by the equator, results in solar radiation throughout the year. This requires a special treatment of openings in the facade of the building. This study aims to analyze and see the effect of the type of internal shading on the interior of the building on the variable solar gain of the building. the use of shading types in the form of venetian blinds, roller shades and drapes will be applied to the building. the results of this study found that the use of roller shades was able to reduce the level of solar gain by 55 percent. Meanwhile, the use of venetian blinds and drapes resulted in a decrease of 31 percent and 25 percent, respectively. From this research, it can be concluded that the use of roller shades gives quite effective results in reducing solar gain in buildings.Keywords: passive cooling, internal shading, solar gain

Development of a Double Skin Facade System Applied in a Virtual Occupied Chamber

In this study a system constituted by seven double skin facades (DSF), three equipped with venetian blinds and four not equipped with venetian blinds, applied in a virtual chamber, is developed. The project will be carried out in winter conditions, using a numerical model, in transient conditions, and based on energy and mass balance linear integral equations. The energy balance linear integral equations are used to calculate the air temperature inside the DSF and the virtual chamber, the temperature on the venetian blind, the temperature on the inner and outer glass, and the temperature distribution in the surrounding structure of the DSF and virtual chamber. These equations consider the convection, conduction, and radiation phenomena. The heat transfer by convection is calculated by natural, forced, and mixed convection, with dimensionless coefficients. In the radiative exchanges, the incident solar radiation, the absorbed solar radiation, and the transmitted solar radiation are considered. The mass balance linear integral equations are used to calculate the water mass concentration and the contaminants mass concentration. These equations consider the convection and the diffusion phenomena. In this numerical work seven cases studies and three occupation levels are simulated. In each case the influence of the ventilation airflow and the occupation level is analyzed. The total number of thermal and indoor air quality uncomfortable hours are used to evaluate the DSF performance. In accordance with the obtained results, in general, the indoor air quality is acceptable; however, when the number of occupants in the virtual chamber increases, the Predicted Mean Vote index value increases. When the airflow rate increases the total of Uncomfortable Hours decreases and, after a certain value of the airflow rate, it increases. The airflow rate associated with the minimum value of total Uncomfortable Hours increases when the number of occupants increases. The energy production decreases when the airflow increases and the production of energy is higher in DSF with venetian blinds system than in DSF without venetian blinds system.