Abstract
The present study aims to evaluate whether downdraft can be prevented by applying a radiant floor heating system in glass curtain wall buildings. A radiant floor heating system does not directly supply heat to cold air, but does so via heat exchange with a cold airflow. Assessing whether a downdraft is prevented is, thus, necessary. For this assessment, a radiant floor heating system was applied to perimeter zones with different window types modeled using a computational fluid dynamics (CFD) simulation. The relationship between the radiant floor heating system and the windows was examined via an assessment of the resulting downdraft by considering the radiant heat exchange effect between the window and the floor. The assessment was conducted by utilizing a CFD simulation. The simulation results show that the temperature difference between the air supplied through the radiant floor heating system and the air descending along the cold surface of the window increased when the radiant floor heating system was applied to a narrow area with a high temperature. Furthermore, the airflow velocity increased with the heat exchange. The airflow re-entered the window side, and the downdraft in the occupied area exceeded the strict value specified by the standards. Conversely, if heat were applied according to the indoor thermal output by widening the radiant heat area of the radiant floor heating system, a downdraft could occur as a result of a blocking failure prior to the influx of the cold air into the occupied area caused by low surface temperatures. Therefore, applying a radiant floor heating system is advantageous in a perimeter zone without causing airflow inducement at the window side with acceptable surface temperatures.
Highlights
The control of thermal comfort in indoor building environments has become increasingly important as people look for ways to improve their quality of life
This study aims to evaluate whether a downdraft can be prevented by an radiantoffloor heating systems (RFHS) in glass curtain wall buildings, such as office buildings, restaurants, and atrium spaces etc
In a window equipped with a general level of thermal performance, This study assessment on glass curtain buildings with to partially an RFHS aaisdowndraft advantageous to prevent downdraft occurrences
Summary
The control of thermal comfort in indoor building environments has become increasingly important as people look for ways to improve their quality of life. Radiant heating systems are advantageous in terms of thermal comfort because this system can set the air temperature to be a little low while maintaining comfort conditions through the radiation heat exchange between the occupants and the radiation surface [2]. The radiant heat transfer of a radiant heating system covers 50% of heat exchange within a conditioned space [3], it has an advantage of the temperature being uniformly supplied and maintained. If the airflow thereby generated directly touches an occupant, the occupant may feel a chill or discomfort due to the localized cooling effect resulting from a loss of heat. This phenomenon is generally defined as a downdraft. Downdraft was defined as “an unwanted local cooling of the human body caused by air movement” in Fanger [12], ASHRAE [13] and ISO [14]
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