Coupled simulation of BES-CFD and performance assessment of energy recovery ventilation system for office model

Thermal comfort and indoor air quality as well as the energy efficiency have been recognized as essential parts of sustainable building assessment. This work aims to analyze the energy conservation of the heat recovery ventilator and to investigate the effect of the air supply arrangement. Three types of mixing ventilation are chosen for the analysis of coupling ANSYS/FLUENT （a computational fluid dynamics （CFD） program） with TRNSYS （a building energy simulation （BES） software）. The adoption of mutual complementary boundary conditions for CFD and BES provides more accurate and complete information of indoor air distribution and thermal performance in buildings. A typical office-space situated in a middle storey is chosen for the analysis. The office-space is equipped with air-conditioners on the ceiling. A heat recovery ventilation system directly supplies flesh air to the office space. Its thermal performance and indoor air distribution predicted by the coupled method are compared under three types of ventilation system. When the supply and return openings for ventilation are arranged on the ceiling, there is no critical difference between the predictions of the coupled method and BES on the energy consumption of HVAC because PID control is adopted for the supply air temperature of the occupied zone. On the other hand, approximately 21% discrepancy for the heat recovery estimation in the maximum between the simulated results of coupled method and BES-only can be obviously found in the floor air supply ventilation case. The discrepancy emphasizes the necessity of coupling CFD with BES when vertical air temperature gradient exists. Our future target is to estimate the optimum design of heat recovery ventilation system to control CO2 concentration by adjusting flow rate of flesh air.

The Impact of Occupant Behavior on Daylight Performance of an Office Room in a Tropical Climate

This work explores three patterns of occupants’ control of window blinds and the potential influence on daylight performance of an office room in a tropical climate. In this climate, windows are frequently obstructed by curtains to avoid glare, despite the daylighting and the exterior view. The consequences are obstructed outside view, poor daylight quality and dependency on artificial lighting. This paper assesses the impact on available daylight using parametric analysis based on daylighting dynamic computer simulations using Grasshopper and Daysim software, combining WWR （window-to-wall ratio） （40% and 80%）, SVF （sky view factor） （small and large） and occupant behavior （active, intermediate and passive users）. The user patterns are based in an office buildings survey that identifies preferences concerning daylight use and control of shading devices. The daylight performance criteria combine UDI （useful daylight illuminance） （500-5,000 lux） and illuminance uniformity distribution. Results confirm the impact of occupant behavior on daylighting performance. The optimum combination of external shading devices, high SVF and high window size results in a useful daylighting for 1/3 of the time for passive users and 2/3 for active users.

Perceived Indoor Discomfort, Performance and Productivity

Even all indoor environmental standards are met the users are usually not satisfied and perceived discomfort is occurred in the smart office buildings. The most frequently cause of discomfort in smart buildings is overrun of intelligence. There are physical and psychological factors that influenced building users＇ comfort. An indoor air quality seems to be one of the main problems of smart office buildings. In Slovakia the office buildings relating to indoor environment European standard are mostly evaluated as the non-low polluting buildings. The pollution from building as well as the pollution from occupancy and using was respected. The odor intensity and indoor air acceptability were assessed by a sensory panel. The concentrations of total volatile organic compounds and carbon dioxide were measured. The odors from building materials studied under different air change rate are presented in this paper. The case study of indoor air acceptability concerning to indoor odors under occupancy and its affect on perceived air quality influenced by air change rate are also presented in this paper.

Performance and Effectiveness of Portable Air Cleaners in an Office Room： An Experimental Study

Nowadays, many people work in an office environment. Air pollutants, including particles and gases, are generated by humans and by different devices that are used in offices. Pollutants can also enter an office room with the air supplied from outdoors. It has been established that air pollutants have adverse health effects on human body. Air cleaning devices are commonly marketed as being beneficial for the health by removing air pollutants and consequently improving indoor air quality. The performance of five air cleaning technologies was tested in order to determine the generation of ozone and particles in an office room. The particle removal effectiveness of the technologies was also determined in order to clarify their ability to remove UFPs （ultrafine particles） in the office room. The tested five air cleaning technologies are non-thermal plasma, corona discharge ionizer, portable air purifier, electrostatic fibrous filter and three-dimensional fibrous filter. The interior surfaces of the office room emit low levels of volatile organic compounds, since the office room has not been refurbished for about two decades. The results showed that the particle removal effectiveness of the technologies was ranged between 0.2 and 0.45 for the office room. The three technologies using/generating ozone significantly increased the ozone level in the office room. However, no increase of the UFP concentration was detected.

An Experimental and Numerical Analysis of Daylighting Performance for an Office Building

The urgency of increasing energy efficiency in new building design and retrofits has pushed lighting simulation to play a central role in sustainable lighting design. The shape of the building and its orientation, the reflectances of building surfaces and glazed areas are important parameters in the daylighting design of buildings. Glazing systems can cut energy consumption and associated pollution sources, reduce peak demand, enhance daylighting performance and improve occupant comfort. This paper presents the results of a numerical and experimental comparison between the performances of an office building with and without external sunscreens. The aim was to analyse the illuminance distribution and some investigations have also been made with regards to the effect on daylight in rooms when sunscreens are used. The experimental results were obtained using an office building scale model and sky simulator. The numerical results were obtained through radiance, the ray-tracing program, to accurately predict the light levels and produce photo realistic images of the architectural space in all sky conditions： Illuminance values were obtained respectively through reference point measurements. The daylighting performances of the office building model with and without the sunscreens have been compared and analysed.

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