Airflow Window Research Articles

Development and evaluation of a buoyancy-driven airflow window with multioperation modes

This study introduces a novel, cost-effective window-integrated passive system (WIPS) that enhances indoor air quality and maintains comfortable temperatures throughout both summer and winter. The WIPS utilizes buoyancy-driven air flow through dual air cavities that alternately preheat or cool the incoming air depending on the season. The system’s design was optimized for Seoul, Korea, through computational fluid dynamics (CFD) simulations using Fluent 2021 R2 software, which employed a Reynolds-Averaged Navier-Stokes (RANS) model with RNG κ-ε turbulence modeling. Key design adjustments included the use of glass and unplasticized polyvinyl chloride (UPVC) to minimize unintended airflow, as well as modifications to the geometry and size of the air cavities to maximize efficient air flow and thermal effectiveness. The optimized design demonstrated significant improvements in thermal performance, achieving a preheating effect up to 35 °C in winter and reducing indoor temperatures by 10 °C in summer. These results underline the potential of WIPS to provide a sustainable solution for building ventilation and climate control.

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Adaptation of electrochromic glass into an airflow window system and its performance evaluation

AbstractAirflow windows (AFWs) help to stabilize the thermal environment in the perimeter zone and also allows for switching between solar‐shielding and solar heat acquisition operations. This is based on the method of channelizing the air discharged from its cavity layer, either by using a total heat enthalpy exchanger and choosing to exchange heat or otherwise. It has a certain thickness owing to the blinds that are installed in its cavity layer. The purpose of this research is to develop a window system that uses electrochromic (EC) glass, instead of blinds, as a solar‐shielding device. This study also provides the specifications of the window system of reduced thickness. The performance of the window system is assessed by CFD analysis. The solar heat gain coefficient (SHGC) of the proposed window system is found to range from 0.083 to 0.268 and its solar radiation properties can be controlled in a flexible manner. These characteristics contribute to an improvement in the building environmental performance in the form of climate‐adaptive building shells (CABS) in places with four distinct seasons such as Japan that require solar‐shielding to reduce the cooling load in summer and solar heat gain to reduce the heating load in winter.

Study on summer thermal performance of a solar ventilated window integrated with thermoelectric air-cooling system

In this paper, a thermoelectric air-cooling system was used to cool down the airflow window glazing surfaces during summer in hot climates by which cooling load of the indoors and occupant’s thermal discomfort near the window reduce. The performance of the proposed system was modeled analytically, in which the models used were validated by the literature experiment results. To determine the thermoelectric system specifications, the three features of the system including the time working interval, the number of modules, and the degree of air temperature attenuation were investigated. The results show that using the thermoelectric air cooling system for the limited time interval within hours of peak cooling load can significantly reduce the energy consumption, while using the system for a longer time interval not only cannot decrease the energy consumption but also may increase. Besides, the results reveal that the thermoelectric system with 15 modules is required to be energy efficient. On the other hand, an increase in the number of modules more than 20 has no considerable effect on energy saving. Furthermore, the percentage of energy saving is 6.5% for 5 °C air cooling and reached a maximum of 7.1% for 7 °C air cooling, while for 10 °C, this value is zero. The mean reduction of the maximum interior glazing surface temperature is 5.9 and 7.4 °C for air cooling degrees of 5 and 10 °C.

Numerical investigation on the thermal performance of double glazing air flow window with integrated blinds

In this paper, double glazing air flow window with integrated blinds (IBAFW) numerically is investigated and the only winter indoor mode is considered for further assessments. To validate the CFD model, the results are compared with the experimental data found in the literature. For the thermal performance evaluation, total heat gain (qgain) which represents the heat gained by ventilation (qadv)and heat gained by the back glass (qbg) was considered. As a part of the study, effect of the structural parameters such as tilt angle of blinds, gap size and the areas of inlet and outlet vents on the thermal performance of IBAFW were studied. The results showed that by changing the blinds tilt angle from 30° to 60°, total heat gain increased approximately 132–146% in different solar radiation ranges. It is also concluded that increasing the gap size increased the total heat gain approximately 106%. However, the increase of outlet vent area effected reversely and resulted in decreasing the thermal efficiency by 127%.Additionally, thermal performance comparison between IBAFW and conventional solar ventilated window (SOLVENT) was carried out. The results showed that the IBAFW reveals approximately 330–580% higher thermal efficiency comparing to the SOLVENT systems.

A simulation study on the performance of double skin façade through experimental design methods and analysis of variance

Systematic studies of the thermal fluid dynamic behaviour of building envelope systems through experiment analyses is limited by the relevant amount of time and high costs necessary to carry out a relevant number of tests covering all the possible configurations. Building simulation can be used as a tool to support the design of the experiments, i.e. to test, in a parametric way, different configurations to highlight the main trends, and therefore select the most relevant cases to be tested experimentally. Such a preliminary activity to maximize the effectiveness of the experiments may relates to both parametric analysis of indoor/outdoor boundary conditions, as well as parametric analysis of building envelope configurations. In the framework of a research project on double skin facade (DSF) systems where experiments are planned on a full-scale prototype, a model of a DSF is realized in a whole building energy software tool, and used to carry out a preliminary sensitivity analysis, by means of orthogonal array method and analysis of variance. Simulations were carried out in EnergyPlus, using the Airflow window module, and under steady-state conditions, a series of variables (cavity depth, venetian blinds tilt angle, airflow rate) have been investigated to assess their impact on the heat extract through the ventilation air and the total heat transmission between the outdoor and indoor environment. The results show that the main driver in the performance of DSF considering net heat rate transfer is the irradiation impinging on the façade in terms of boundary conditions, and coherently, the shading device is the feature that most affects the performance of the system among the characteristics of a DSF.

Principles of energy conversion and noise characterization in air ventilation ducts exposed to solar radiation

The aim of this paper is to present a design tool with its guiding principles for energy conversion and noise characterization of an exterior rectangular duct often installed on building envelopes for pre-conditioning of fresh air. The energy conversion in an exterior rectangular duct is a function of solar irradiation, air gap width, mass flow rate and pressure, wall and air temperatures. A generalized two dimensional thermal analysis of an outdoor duct is presented by placement of surface and air nodes into two adjacent stacks of control volumes representing outer and inner walls of duct. A matrix solution procedure is adopted by constituting conjugate heat exchange of conduction, convection, radiation and ventilation heat transport. The rectangular duct model is built by a metallic exterior wall exposed to a steady heat flux generation due to solar heat gain and a well-insulated back panel as its counterpart wall. The model improves the results of traditional thermal models for the cases where: (i) there are sections of conjugate heat exchange; and (ii) stack effect due to thermal buoyancy necessitates 2-D nodal analysis for distant composite nodes. The design tool is supported with some numerical and experimental results of an airflow window with a photovoltaic (PV) solar wall installed in an outdoor test-room. Furthermore, some examples of noise characterization calculations are illustrated using devised noise measurement equations.

Modelling of an airflow window and numerical investigation of its thermal performances by comparison to conventional double and triple-glazed windows

In this paper, we numerically investigate thermal characteristics and performances of a triple-glazed airflow window, by comparison to conventional double and triple-glazed ones. Numerical simulations were performed with a nodal model of the airflow window, which has been first validated from experiments.Both experimental and numerical results show that the air supply preheating through the airflow window is significant, ranging from approximately 10–20 °C without solar radiation and during sunny periods, respectively. In the first case, the energy gain comes from both solar radiation and heat loss recovery through the window, while only from heat loss recovery in the second one. Then, additional simulations have been performed in order to compare the airflow window to a conventional airflow ventilation system combined to conventional double and triple-glazed windows. Numerical results point out that, due to the entering fresh outdoor air, the airflow window causes a stronger cold wall effect. However, at the same time, it reduces cold draught risks (air supply preheating of about 10 °C) and heat losses too. Indeed, for the same reason, the outer face temperature of the airflow window glazing is low and subsequently external heat transfers by convection and radiation reduced.Results also show that, in comparison to conventional windows, energy needs to heat a room are lower if this one is equipped with an airflow window. The reduction approximately ranges from 5% for night-time to 90% for daylight conditions. The main reason is the significant reduction in energy needs to heat the fresh air entering the room, by 36% and 79%, respectively. For an entire day, we found that the energy balance sheet is approximately neutral for an airflow window (−70 Wh), while negative for conventional double and triple-glazed ones (−572 Wh and −653 Wh, respectively).Finally, we compare and discuss the airflow window performance in terms of thermal transmittances, Ug and Uw values, and solar heat gain coefficients, gg and gw values. Results obtained for the airflow window point out that Ug and Uw significantly decrease when the airflow rate increases, due to an increase in the air supply preheating, especially until 15 m3 h−1. Results also show that it outperforms the double-glazed window at any airflow rate and the triple-glazed one for airflow rates from just 3 m3 h−1. At the opposite, gg and gw increase with the airflow rate, especially until 15 m3 h−1 and the comparison points out that the airflow window outperforms both the double and triple-glazed ones at any airflow rate. As an example, for an airflow rate of 15 m3 h−1, that is for practical applications in residential or office buildings, the glazing solar heat gain coefficient of the airflow window is approximately 20 and 30% higher than double and triple-glazed ones, respectively.

Summer study on thermal performance of an exhausting airflow window in evaporatively-cooled buildings

By using exhaust mode ventilated windows in buildings cooled by evaporative cooler, the air flow channel of the window can play the role of natural relief air path. Thereby, the cooling potential of the relief air can be recovered and used to improve the thermal performance of the ventilated window. This paper investigates the thermal performance of an exhausting ventilated window in a typical evaporatively-cooled space. In this study, a zonal model has been used for simulation. The numerical approach was validated with reported experimental data and good agreement was shown. Results showed that the heat gain and the maximum daily temperature of the interior glass pane of the proposed ventilated window are less than those of the conventional double-glazed window. Providing natural relief through ventilated window can cause extra pressure drop and consequently reducing cooling capacity. This may also disturb the occupant's comfort due to noise issue. Hence, the impacts of window aspect ratio and thickness of the air flow channel have been investigated as effective factors on pressure drop and sound power level. Eventually, a step by step procedure has been proposed for determining the geometric parameters of the ventilated window for practical use in evaporatively-cooled buildings.

Acoustic Filters for Sensors and Transducers

The acoustic filter is used to filter unwanted frequencies of oscillations from a power system. It is a network with selective transmission for currents from a power system of varying frequency. The unwanted frequencies generated from a power system are removed by using an operational amplifier with different combination of filter arrangements. A new theory for noise protection and security from power systems is presented. The power systems are classified as per source signals of solar power, electric power, light power, sound power, heat power, fluid power and fire power. The acoustic filters as per source of noise signals are defined. The filters are differentiated as per source signal of unwanted frequencies from solar power, electric power, light power, sound power, heat power, fluid power and fire power. Some examples of noise filtering from power systems are illustrated: i) a vocal apparatus; ii) an airflow window with a photovoltaic solar wall; iii) a psychrometric air-conditioner; iv) a telephone line; v) a fire and smoke detection system; vi) sensors and transducers: energy balance for a human brain and vii) comfort and health. A slide rule for noise measurement is illustrated along with noise grades and flag colors under limiting conditions.

Application of Dynamic Insulation Technique to Airflow Window System

It is necessary to improve solar blocking performance and reduce solar heat gain coefficient (SHGC) of openings in office buildings in order to reduce the cooling loads. Airflow windows are often practiced in Japan’s office buildings. In this research, we apply a Dynamic Insulation (DI) technique into an airflow window system to improve the solar blocking performance. Computational fluid dynamics (CFD) analyses have been used to measure the thermal performance of the numerical opening model. In the case of using a conventional airflow window model, the inner-surface temperature of the inner glass is 29.4℃. In case the DI technique is applied, it is 27.0℃. The declination of the inner-surface temperature of the window improves the radiant environment in the building perimeter space. Moreover, the heat flux into the room is decreased due to the decline in the temperature difference between indoor temperature and the inner glass surface temperature.

非住宅建築物を対象とした先導的省エネルギー技術の評価方法に関する研究 （その9）エアフロー型窓を対象としたCFD解析

非住宅建築物を対象とした先導的省エネルギー技術の評価方法に関する研究 （その9）エアフロー型窓を対象としたCFD解析

空気流通窓システムのある室内熱・湿気環境評価に関する研究 : 評価法と実測による検証

空気流通窓システムのある室内熱・湿気環境評価に関する研究 : 評価法と実測による検証

Integrated Model for Shading and Airflow Window in BSk

Shading devices were investigated as a means to improve the energy performance of airflow windows in semi-arid climates (BSk), where ventilation is important for indoor comfort. According to previous research, louvers can improve energy efficiency. We have simulated an airflow window with integrated shading in the city of Yazd, Iran. Results obtained with EnergyPlus show that in comparison with common and double-glazed windows, airflow windows are more energy efficient. A network model was developed to take into account heat transfer in the integrated airflow window system.

B-11 プッシュプル型ペリメータ熱処理システムに関する実験的研究 : その1 水平ブラインドとロールスクリーンの揺れについて

B-11 プッシュプル型ペリメータ熱処理システムに関する実験的研究 : その1 水平ブラインドとロールスクリーンの揺れについて

C-31 事務室に設置した簡易型空気流通窓の熱的特性について : その3 冬季の実測結果

C-31 事務室に設置した簡易型空気流通窓の熱的特性について : その3 冬季の実測結果

B-33 高性能 Low-εガラスを外ガラスに用いたエアフローウィンドウシステムの性能評価 : (第1報) 模擬日射装置をもつ実験室による熱的性能評価

B-33 高性能 Low-εガラスを外ガラスに用いたエアフローウィンドウシステムの性能評価 : (第1報) 模擬日射装置をもつ実験室による熱的性能評価

Study of the Airflow Window

Multiple-skin facades are popular in the construction of fully-glazed buildings since they have the potential to reduce the heating and cooling load of the building. To make optimal use of multiple-skin facades, their performance needs to be calculated during the design phase.The study of the flow in such a façade is the purpose of this study.

Experimental Study on Opening or Closing Performance of Ventilated Double-Skin Facade on the Airflow Window in Winter

An actual office building with ventilated double-skin facade (VDSF) in cold region has been studied for researching the opening or closing performance of VDSF on the airflow window in winter. In the daytime of winter, airflow window of external facade should be closed, and airflow window of internal facade should be open, according to which the indoor temperature can be kept at a comfortable level effectively, and the purpose of reducing the indoor thermal load and the building energy consumption of air conditioning can be reached. The research also provides the best time of the airflow window of internal facade to open and close. If one directly applies the analysis of experimental results to guide the construction of VDSF and other energy-saving design of buildings, it can provide a reliable reference for similar projects.

A study of the effectiveness of different control strategies in double skin facades in warm and humid climates

Thermal building simulations were linked to nodal airflow network simulations for a detailed ventilated facade calculation of performance.The validated simulation model can be used to optimize airflow window design in respect to reducing the solar heat gains during the summer period by controlling the exhaust airflow. This may result in significant energy savings and a reduction in systems cooling size. This work evaluates different control strategies of internally ventilated facade designs in respect to energy consumption savings. It further proposes a new type of airflow window to control the exhaust airflow that can help to reduce cooling load of an office up to almost 40%. An important factor was the development of a climate sensitive regulator that helps to take advantage of the hot and humid climate.