An improved multi-point source radiant heat transfer model for asymmetric multiple pool fire scenarios

An accidental fire in chemical fuel storage areas can trigger a catastrophic domino effect due to intense radiative heat transfer. Understanding the radiative heat transfer mechanisms of pool fires and developing the predictive model are vital for improving thermal energy management and fire prevention in the chemical industry. To mimic the related asymmetric pool fire scenarios, the multiple square heptane pools with the length of d = 15 cm were used as fire sources. Variations were introduced in terms of pool edge spacing p (0-0.6 m), fire source numbers n (1-4), and different layout patterns were considered, including linear and square arrangements. Radiative heat flux was measured horizontally and vertically. The results showed that, under the coupled effects of air entrainment and thermal feedback, the radiative heat flux exhibited an initial increase followed by a subsequent decrease as p decreased. When 0.5 <= p/d <= 1, the radiative heat flux reached its maximum value, denoted as q(rmax)". q(rmax)" was positively correlated with the fire source numbers. With a fixed fire source number, the linear layout yielded a relatively larger q(rmax)" than the square layout. The radiation received by a target primarily depends on the flame temperature and view factor. The radiative effect of the intermittent zone was neglected, as the flame temperature gradually decreased with height. In the continuous zone, the uniform flame temperature allowed targets with high view factors to receive strong radiative heat flux. Consequently, the horizontal radiometers received more radiative heat flux than the vertical ones. Specifically, compared to other positions, locations closer to the continuous zone exhibited larger view factors, resulting in higher radiative values. At large spacings, the lowest point received more radiation than the highest point. As spacing decreased, restricted air entrainment caused the continuous flame height to rise, causing a reversal in the radiation trend. Furthermore, an improved multi-point source radiant heat transfer model (IMSM) was developed to forecast external radiation in scenarios involving multiple fires with asymmetrical configurations. The model determines the ratio of point sources between the continuous zone and the intermittent zone as k = b:1 (where b is an integer), based on the proportional relationship H-c: H = a (0 < a < 1) between the continuous flame height H-c and the average flame height H, while b approximate to a/(1-a). By incorporating flame morphology assumptions, the continuous zone and intermittent zone flame volume fractions are defined as 3H(c)/(2H(c) + H) and (H-H-c)/(2H(c) + H), respectively. The weight of point source for each zone is derived as the ratio of its volume fraction to the number of point sources in that zone. By adopting this method, the minimum total number of point sources N = k + 1 ensures computational efficiency while maintaining high predictive accuracy. Through extensive comparative data validation, the applicability of the model has been further extended to scenarios including single fire sources, linear multi-fire source arrays, square multi-fire source configurations, both gaseous and liquid fuels, pool length scales ranging from 4.6 cm to 100 cm, and pool fire burning under weak wind speed environments (<= 0.5 m/s).