Comparative studies on isothermal attachment ventilation based on vertical walls, square and circular columns

Abstract

Ventilation and air distribution methods play an important role in indoor air quality and thermal environments. Effective airflow distribution within indoor environments has always been a great cause of concern. Attachment ventilation has drawn considerable interest since it is more energy efficient and space saving than traditional mixing or displacement ventilation methods. As a newly developed and applied attachment ventilation method, vertical wall-based attachment ventilation (WAV) was first proposed in the 1990’s by the authors. Later, the concepts of square column-based attachment ventilation (SAV) and circular column-based attachment ventilation (CAV) were also presented to meet the needs of more industrial applications. In this paper, three attachment ventilation methods— i.e., WAV, SAV and CAV are compared based on experimental studies and numerical simulations. For the vertical attachment region, semi-theoretical equations characterizing the dimensionless centerline velocity of WAV, SAV and CAV are proposed. The velocity profiles of all three types of attachment ventilation methods are similar. Of the three attachment ventilation methods, for the same distance y* along the attached wall measured from the slot inlet, the dimensionless centerline velocity of WAV is the largest, while those of SAV and CAV remain almost identical. In the horizontal air reservoir region (air lake zone), the semi-theoretical equations to predict dimensionless centerline velocity also are presented. The results show that for the same distance x normal to the wall/column, the dimensionless centerline velocity of WAV is the largest, followed by SAV and CAV. Additionally, unified semi-theoretical equations are presented for predicting the jet centerline velocity decay of attachment ventilation, which is helpful for the design of air distribution systems in heating, ventilation and air conditioning (HVAC) engineering applications.