Heat　pipes　with　plate　fins,　which　are　a　simple　and　effective　technique　for　heat　transfer　enhancement,　are　extremely　important　for　latent　heat　storage.　However,　the　effect　of　fin　geometry　on　the　solid‒liquid　phase　transition　is　not　fully　understood,　and　correlations　for　describing　the　melting　heat　transfer　process　are　rarely　proposed.　Here,　experiments　and　numerical　simulations　were　conducted　on　a　reduced-scale　model　of　a　latent　heat　storage　unit　that　used　flat　heat　pipes　and　plate　fins　for　charging.　The　evolution　of　the　temperature　pattern　and　solid‒liquid　interface　of　the　phase　change　material　during　melting　and　the　performance　of　the　flat　heat　pipe　with　and　without　fins　were　experimentally　investigated　in　terms　of　heat　transfer　enhancement.　Then,　the　latent　heat　storage　unit　was　numerically　simulated　based　on　the　enthalpy‒porosity　model　and　the　effective　thermal　conductivity　method.　The　effects　of　the　fin　structure　parameters　and　the　input　heat　on　the　melting　heat　transfer　mechanism　of　the　phase　change　material　were　also　studied.　Finally,　the　overall　results　were　generalized　via　multivariate　nonlinear　fitting,　and　the　correlations　of　melting　and　heat　transfer　of　the　phase　change　material　with　plate　fins　were　obtained.　This　research　contributes　to　the　study　of　latent　heat　storage　by　establishing　the　correlations　of　the　melting　process　and　heat　transfer　in　confined　spaces　of　plate　fins　using　the　Rayleigh　number,　Fourier　number,　Stefan　number,　fin　length‒width　ratio,　height‒width　ratio,　and　filling　ratio　of　the　fin.　©　2023　Elsevier　Ltd