Effect of Air Supply Temperature on the Performance of Displacement Ventilation (Part I) - Thermal Comfort

Abstract

The effect of the air supply temperature on the performance of a displacement ventilation (DV) system has been investigated. The study looks into the case of a typical office building in Hong Kong, under local thermal environment and airflow conditions. These are characterised by the high cooling load density, which commonly occurs in Hong Kong. The lower supply temperatures were found to result in higher draft effects, yet increasing temperatures leads to an increase in the predicted percentage of dissatisfied people (PPD). The DV system was found to provide acceptable thermal comfort at certain air supply temperatures. The levels of PPD could be marginal should the parameters of the system not be optimised.

Numerical optimisation of thermal comfort improvement for indoor environment with occupants and furniture

“…In the sofa layout , both two occupants are having uncomfortable conditions throughout the vertical level in the domain, due to significant air temperature increases by across the domain, compared with that of the volumetric fluid (air) temperature in two layouts and . The similar findings were previously reported by Lin et al [48]. It can be seen in the layout that there are large fluctuations in the PPD values for the occupant at two lower vertical levels ( , ) whilst at two higher vertical levels ( , ), its PPD predictions are aligned with that of the occupant This is probably due to the fact that there is no big difference between two occupants in the upper part of the domain in terms of air temperature and airflow velocity.…”

“…It can be seen that air temperature increases with the height and the formation of thermal plume from human bodies can be clearly observed. The trends of temperature elevation and thermal plume from the human body were observed previously in various studies [46][47][48]. While increasing the number of occupant from one to two (i.e.…”

“…In comparison, heat generation from a TV did not have important influence on the thermal comfort and heat transfer system. However, the number of occupant increase from one to two did increase air temperature in the fluid domain by , causing the PPD value increase by for which the occupants will normally feel uncomfortable in such a warm environment [48].…”

Numerical analysis to determine the performance of combined variable ceiling and floor-based air distribution systems in an office room

“…However, interest in floor-based air distribution system has been growing and is being considered as an alternative to enhance building energy saving and indoor environmental control. [6][7][8][9][10][11] The concept of floor-based air distribution system was first introduced in the early 1960s in the Federal Republic of Germany. 12 Floor-based air distribution system allows the conditioned air to mix with indoor air in a relatively short distance from the air inlet to the occupied zone.…”

The Energy Saving Potential and the Associated Thermal Comfort of Displacement Ventilation Systems Assisted by Personalised Ventilation

“…The task ventilation modules are known for providing better thermal comfort, better air quality and lower energy consumption [7][8][9][10][11][12].…”