Two-dimensional simulation of airflow and thermal comfort in a room with open-window and indoor cooling systems

Abstract

This paper presents the two-dimensional numerical simulation results of the ventilation rates, indoor airflow fields and temperature distributions in an office room with open windows and auxiliary cooling devices. The standard k− ϵ turbulence model is used for flow pattern and temperature predictions. Possible comfort problems are analyzed in terms of the percentage of dissatisfied (PD) people due to draught, as well as vertical temperature difference. The simulation results show that open windows can give a high ventilation rate due to the stack effect alone, and that good thermal comfort can be achieved when the outdoor temperature is moderate. However, thermal comfort analysis in terms of vertical temperature stratification and the PD value shows that discomfort can arise due to draughts near the floor and the too-large vertical temperature gradient in the occupied zone when the outdoor temperature is too low, and that a cooling radiator located below the window presents the same problems. The results also indicate that a lightly cooled ceiling makes the air temperature more uniform in the room. It is also shown that both of the cooling systems, when combined with open windows, can have a good energy efficiency.