Ullage　height　(the　distance　between　the　fuel　surface　and　the　pool　upper　rim)　is　one　of　the　most　important　and　widely　recognized　factors　that　affect　the　burning　rate　and　heat　transfer　of　pool　fires.　This　study　investigated　the　effects　of　ullage　height　on　the　burning　rate,　heat　feedback,　and　radiation　fraction　of　medium-scale　pool　fires.　Heptane　pool　fires　were　tested　with　a　diameter　(D)　of　30　cm　and　the　non-dimensional　ullage　height　(h/D,　h　is　the　ullage　height)　being　varied　from　0　to　1.48.　Results　show　that　the　non-dimensional　burning　rate　tends　to　decrease　exponentially　with　h/D.　It　has　been　proved　that　the　current　models　used　to　predict　the　burning　rate　of　pool　fires　are　not　applicable　to　those　medium-scale　pool　fires　that　are　affected　by　the　ullage　height.　The　radiative,　conductive,　and　convective　heat　feedback　rate　overall　decrease　with　the　ullage　height.　The　conductive　heat　feedback　fraction　weakly　depends　on　h/D.　The　radiative　heat　feedback　fraction　firstly　decreases　then　stabilizes　with　h/D,　while　the　convective　heat　feedback　fraction　shows　an　opposite　trend.　The　radiative　fractions　firstly　increase　then　decrease　with　h/D.　This　paper　presents　a　new　correlation　with　considering　the　ullage　height　and　the　mean　beam　length　within　the　pool　ullage.　The　universality　and　accuracy　of　the　proposed　model　were　verified　by　comparing　it　with　extensive　experimental　data,　where　D　varied　from　10　cm　to　35　cm,　and　h/D　varied　from　0　to　2.0.　©　2023　Elsevier　Masson　SAS