Effects of Duct Height and Fire Location on Fire Phenomena of Enclosure with Two Horizontal Vents Installed on Ceiling

Abstract

The effects of duct height (DH) and fire location (FL) in an enclosure on the mass flow rate and flow pattern of horizontal vent (HV) flow and temperature distribution in the enclosure were investigated through numerical simulations under the condition that two HVs were installed on the ceiling of the enclosure. To evaluate the effect of DH, DHs of HV1 were set to 0.19 m (HV1_DH0.19) and 0.05 m (HV1_DH0.05) under the condition that DH of HV2 was 0.05 m (HV2_DH0.05). The effect of FL was evaluated in three cases where the fire sources were located in the center of the floor (F LC), below HV1 (F L1), and below HV2 (F L2). With respect to the DH effect, the total mass flow rate of the vent flow was slightly higher and temperature was slightly lower in the case of HV1_DH0.19 than that in the case of HV1_DH0.05. However, considering the error bars, the effect of DH in this numerical simulation condition was considered to be insignificant. Furthermore, bidirectional flow patterns appeared in HV1 and HV2 in both DH conditions. Meanwhile, with respect to the FL effect, a bidirectional flow dominated by the mass flow rate of outflow occurred in the HV where the fire source was located, and a unidirectional inflow dominated by the mass flow rate of inflow occurred in the HV where the fire source was not located. The total mass flow rates of FL1 and FL2 conditions were similar, which were higher than those of FLC condition. The temperature was higher in FLC than those in FL1 and FL2. This was due to the small mass flow rate through the HV in the FLC. Meanwhile, an increasing trend of the temperature with the rising measurement height from the floor was observed at most of the temperature measurement points. However, when the fire source was located below HV1 and HV2, as the height from the floor increased, the temperature decreased and the overall temperature was low at the temperature measurement points below the vent where the fire source was not located. This trend was attributed to the occurrence of a strong unidirectional inflow wherein a large volume of low-temperature air flowed into the enclosure from the HV where the fire source was not located.

Effect of Vent Area Ratio on Vent Flow Characteristics and Temperature D istribution in a C ompartment F ire with T wo Ceiling Vents

“…The compartment measured 1.36 m in width, 1.5 m in depth, and 1.1 m in height, and it featured two ceiling vents. In accordance with the previous study [12], two vents with different heights were set. As depicted in Figure 2, the height of Ceiling Vent 1 (CV1) is higher than that of Ceiling Vent 2 (CV2), and each ceiling vent is designed as a square.…”

“…In this study, a scaled model was developed to facilitate experimentation for validating numerical simulation results. Specifically, the research was based on the numerical simulation geometry and conditions used in the previous study [12]. Figure 2 presents a schematic of the numerical simulation employed in this study.…”

“…However, in the study conducted by Epstein [9], the flow through horizontal vents was determined only by the density difference under non-fire condition. Recently, Park and Lee [12] investigated the effects of the duct heights of horizontal vents and the position of the fire source on the flow patterns and mass flow rates of the vents as well as temperature distribution in a compartment during a fire in the compartment with two ceiling vents through numerical simulations. In the study of Park and Lee [12], however, the two vents had the same size (5% of the floor area), and research was not conducted on the cases where they had different areas.…”

“…Recently, Park and Lee [12] investigated the effects of the duct heights of horizontal vents and the position of the fire source on the flow patterns and mass flow rates of the vents as well as temperature distribution in a compartment during a fire in the compartment with two ceiling vents through numerical simulations. In the study of Park and Lee [12], however, the two vents had the same size (5% of the floor area), and research was not conducted on the cases where they had different areas. In this study, the effect of vent area ratio on vent flow characteristics and temperature distribution was examined for a compartment fire with two ceiling vents using numerical simulation.…”

“…In this study, the effect of vent area ratio on vent flow characteristics and temperature distribution was examined for a compartment fire with two ceiling vents using numerical simulation. Based on a previous study [12] conducted under the condition of equal vent areas, this study involved varying the areas of the ceiling vents. The mass flow rate of the vent flow, its patterns, and temperature distribution measured below the vents were reported for five vent area ratios, and the relationship between vent flow characteristics and temperature distribution was analyzed.…”