For the flow pattern passing through CV1, inflow (unidirectional flow) from the outside of the compartment to its inside was observed under the condition with the smallest CV1 area (
Figure 5(a)). Under other conditions, bidirectional flow involving both outflow and inflow through the vent was observed. Similarly, for the flow pattern passing through CV2, inflow was observed under the condition with the smallest CV2 area (
Figure 5(e)), and bidirectional flow was mostly observed when the area was large. Hence, for CV1 and CV2, unidirectional inflow occurred when the area was small, and bidirectional flow occurred when the area was large. As A
1/A
2 ratio increased, the flow pattern changed from unidirectional inflow to bidirectional flow for CV1 and from bidirectional flow to unidirectional inflow for CV2.
Based on the results in
Figure 5, the vent flow patterns observed under the conditions of the numerical simulation in this study are summarized in
Figure 6. Under the numerical simulation conditions, three combinations of vent flow patterns were observed. They represented a case in which unidirectional inflow occurs at CV1 and bidirectional flow at CV2 (
Figure 6(a)), a case in which bidirectional flow occurs at CV1 and CV2 (
Figure 6(b)), and a case in which bidirectional flow occurs at CV1 and unidirectional inflow at CV2 (
Figure 6(c)). As shown in
Figure 6, bidirectional flow or unidirectional inflow occurs at each vent under the conditions of the numerical simulation, and unidirectional outflow from the inside of the compartment to its outside is not observed. A combination of outflow at CV1 and inflow at CV2 (
Figure 1(a)) was observed in the previous study [
9], but no such combination was observed in this study.
Based on the outflow and inflow mass flow rate measurement results for the vents shown in
Figure 5, the effect of the area ratio (A
1/A
2) between CV1 and CV2 on the outflow and inflow mass flow rates of the vents is illustrated in
Figure 7.
Figures 7(a) and
7(b) display the results for CV1 and CV2, respectively. Overall, the outflow and inflow mass flow rates through CV1 increased as the A
1/A
2 ratio increased (i.e., as the area of CV1 increased) (
Figure 7(a)), and those through CV2 increased as the A
1/A
2 ratio decreased (i.e., as the area of CV2 increased) (
Figure 7(b)). This implies that as the area of each vent increased, an increasing tendency of the outflow and inflow mass flow rates was observed. Meanwhile, when the A
1/A
2 ratio was 0.542, the outflow and inflow mass flow rates were found to be almost identical for both CV1 and CV2. For CV1 (
Figure 7(a)), the inflow mass flow rate was higher than the outflow mass flow rate when the A
1/A
2 ratio was lower than 0.542, but the outflow mass flow rate was higher than the inflow mass flow rate when A
1/A
2 ratio was higher than 0.542. Conversely, in the case of CV2 (
Figure 7(b)), the outflow mass flow rate was higher than the inflow mass flow rate when the A
1/A
2 ratio was lower than 0.542, but the inflow mass flow rate was higher than the outflow mass flow rate when the A
1/A
2 ratio was higher than 0.542.
Figures 7(c) and
7(d) show the effect of the A
1/A
2 ratio on the outflow and inflow mass flow rates of the vents, respectively. The outflow and inflow mass flow rates at CV1 were higher than those at CV2 when the A
1/A
2 ratio was high, whereas the outflow and inflow mass flow rates at CV2 were higher than those at CV1 when the A
1/A
2 ratio was low. Meanwhile, in the results of the previous study [
12] when A
1/A
2 ratio was 1 (the areas of CV1 and CV2 were identical), the outflow mass flow rate of CV1 was higher than that of CV2 (
Figure 7(c)), and the inflow mass flow rate of CV1 was lower than that of CV2 (
Figure 7(d)). Although CV1 and CV2 had the same area, their mass flow rates were not the same, indicating that the duct height of the ceiling vents affects the outflow and inflow mass flow rates [
12].