The　impacts　of　cross　wind　and　ullage　height　(distance　between　the　fuel　surface　and　the　pool＇s　upper　edge,　h)　on　the　burning　rate　of　medium-scale　heptane　pool　fires　were　studied.　Using　a　series　of　30　cm　diameter　fuel　pools,　the　study　covered　crosswind　speeds　(u)　from　0　to　5　m/s　and　dimensionless　ullage　heights　(h/D)　from　0　to　1.48.　It　was　found　that　the　overall　burning　rate　decreased　with　increasing　ullage　height.　Comparing　the　experimental　mass　flux　with　prior　model　predictions,　classical　models　were　accurate　only　when　ullage　height　was　low　(h/D　≤　0.35),　with　deviation　increasing　as　ullage　height　rose.　The　simulation　revealed　the　formation　of　a　strong　clockwise　recirculating　vortex　inside　the　cavity,　with　the　flame　body　positioned　inside　the　pool.　Changes　in　ullage　height　and　crosswind　speed　influenced　the　recirculation　flow　velocity　(uc),　affecting　fuel　vapor-air　mixing,　boundary　layer　development　over　the　fuel　surface,　and　heat/mass　transfer　between　the　plume　and　fuel　body,　leading　to　a　higher　burning　rate.　A　new　mass　flux　model　based　on　momentum　conservation　within　the　pool　was　developed,　addressing　the　limitations　of　classical　models　at　high　ullage　heights　and　providing　a　valuable　tool　for　energy　safety　and　emergency　planning.　©　2025　Elsevier　Ltd