The　low　thermal　conductivity　of　phase-change　materials　(PCMs)　limits　the　widespread　use　of　phase-change　thermal-storage　units　(TSUs).　This　problem　can　be　solved　by　expanding　the　heat-exchange　area　(HEA)　in　the　PCM　side.　Related　studies　have　shown　that　expanding　HEA　can　greatly　increase　the　heat-transfer　rate　of　TSU.　However,　few　studies　have　been　able　to　increase　the　compactness　factor　(CF)　of　TSUs　while　expanding　the　HEA　of　the　PCM　side　to　become　sufficiently　large.　In　this　work,　a　multichannel　flat-tube　phase-change　TSU　was　constructed　based　on　the　CF　and　ratio　of　HEA　to　PCM　volume　(delta).　The　developed　TSU　uses　a　multichannel　flat　tube　as　the　heat-exchange　element,　water　as　the　heat-transfer　flow　(HTF),　and　lauric　acid　as　the　PCM.　The　delta　and　CF　of　the　multichannel　flat　tube　TSU　are　238.91/m　and　82%,　respectively.　The　temperature　distribution,　power,　and　average　effectiveness　of　the　TSU　at　different　HTF-injection　modes,　inlet　temperatures,　and　mass-flow　rates　are　studied　experimentally.　Results　show　that　the　multichannel　flat　tube　exhibits　excellent　heat-transfer　performance,　and　the　convective　heat-transfer　coefficient　under　experimental　conditions　reaches　515　W/(m(2).k)　or　more.　The　maximum　effectiveness　during　charge　and　discharge　is　0.235　and　0.232,　respectively.　Moreover,　the　corresponding　pressure　loss　and　heat-transfer　temperature　difference　between　the　inlet　temperature　and　melting　point　of　PCM　are　3986　Pa　and　22　degrees　C,　respectively.　Results　also　show　that　delta　and　CF　are　parameters　that　need　to　be　fully　considered　when　designing　a　practical　TSU.