This　paper　proposed　a　more　advanced　moving-boundary　method　for　establishing　dynamic　mathematical　models　of　heat　exchangers　based　on　the　dynamic　characteristics　of　split　type　heat　pump　systems　with　low　charge.　On　the　basis　of　the　traditional　sub-model,　two　phase　model　(non-linear)　and　two　phase-liquid　model　have　been　added　for　the　condenser,　and　vapor　model　(linear)　and　vapor　model　(non-linear)　model　have　been　added　for　the　evaporator.　Based　on　the　characteristics　of　split　type　heat　pumps,　this　article　introduced　a　detailed　method　for　setting　initial　boundary　conditions　under　refrigeration　and　heating　conditions.　At　the　same　time,　this　article　proposed　more　rigorous　algorithm　for　model　switching　and　a　method　for　calculating　the　initial　phase　length,　which　will　improve　the　robustness　and　computational　speed　of　the　system　model.　The　model　proposed　of　a　split　heat　pump　achieves　dynamic　numerical　simulation　of　the　entire　process　from　start-up　to　stability.　In　addition,　the　system　model　was　validated　and　error　analysed　by　building　an　experimental　platform　and　conducting　data　analysis.　Finally,　the　dynamic　characteristics　of　fixed　frequency　start-up　operation　and　variable　frequency　start-up　operation　were　discussed.　©　2025　Elsevier　Ltd