Appendix I 
Page A I- 137 
4.2 Justification of Steady-State for Temperature and Air Velocity 
Field 
4.2.1 Definition of Steady -State 
In this project, steady-state is defined as when the fluctuation of mean air velocity and room 
temperature are less than 7 percent of the target value. The target value is the expected steady- 
state values over an extended period of time (in this case, mean values of over approximately 
two hours). For example, the target room temperature is 22.0 °C. Room temperatures within 
22.0±1.5 °C (71.6+2.7 °F) (1.5 °C is 7 percent of 22.0 °C) is considered steady-state. 
4.2.2 Justification 
Air velocity responses: 
Even at a very low air velocity, e.g., 0.05m/s (10 fpm), it only takes less than three minutes for a 
given air sample to travel from one location to any other location in the room and return. Thus, 
once the ventilation system is actuated and the door is closed, it is expected that a steady state- 
airflow field will be established within three minutes. To verify this assumption, air velocity 
fluctuations at one point (P s ) were measured. The point was near the end of traveling path of an 
air stream exiting from the exhaust: 0.61m (24”) above floor, 0.61m (24”) from west wall and 
1.22m (48”) from north wall. Figure 4.2.01 illustrates the air velocity fluctuations at this point 1, 
4, 7, and 10 minutes after the door was closed, respectively. 
