Phase　change　thermal　storage　units　(TSUs)　that　use　air　as　heat　transfer　fluid　(HTF)　are　in　huge　demand　in　the　fields　of　building　heating,　solar　energy　utilization,　and　flue　gas　heat　recovery.　Researchers　have　developed　various　air-based　TSUs　and　used　different　methods　to　optimize　their　structure.　In　the　current　study,　the　structural　parameters　of　a　novel　TSU　with　air　as　the　HTF　are　optimized　using　a　comprehensive　method　that　combines　overall　thermal　resistance　analysis　and　numerical　simulation.　The　influence　of　different　HTF　injection　methods　on　the　natural　convection　of　a　phase　change　material　(PCM)　and　the　effects　of　different　structural　parameters　on　the　TSU＇s　charge　performance　were　investigated.　Results　indicated　that　the　heat　transfer　thermal　resistance　of　the　developed　TSU　is　mostly　concentrated　in　the　PCM　side.　When　the　depth　direction　of　the　flat　tube　was　perpendicular　to　the　direction　of　gravity　and　the　HTF　adopted　side　injection,　the　phase　change　completion　time　was　shortened　by　20.59%　compared　with　that　in　the　original　TSU.　Thermal　resistance　balance　was　achieved　in　the　air　and　PCM　sides　when　the　rib　height,　pitch,　and　thickness　of　the　flat　tube　were　0.03,　0.0232,　and　0.00025　m,　respectively.　At　this　moment,　the　compact　factor　and　effectiveness　of　the　novel　TSU　were　1.63　times　and　10.52%　higher　than　those　of　the　original　TSU,　respectively.