Deionized　water　was　used　as　the　working　fluid,　the　heat　transfer　performance　of　the　phase　change　chamber　with　rectangular　grooves　was　studied,　and　the　observed　experimental　phenomena　were　analyzed　by　visualization.　The　experimental　results　show　that　there　is　a　clear　interaction　between　boiling　and　condensation　processes　inside　the　phase　change　chamber.　The　heat　transfer　performance　of　the　phase　change　chamber　is　the　best　when　the　working　fluid　filling　ratio　is　11.4%,　because　the　condensation　heat　transfer　is　enhanced.　As　the　input　power　increases,　the　interaction　between　the　boiling　and　condensation　processes　increases,　and　the　heat　transfer　coefficients　of　the　boiling　and　condensation　increase.　The　heat　transfer　resistance　of　the　phase　change　chamber　is　mainly　concentrated　on　the　condensation　surface.　Under　the　optimum　filling　ratio,　the　condensation　surface　thermal　resistance　accounts　for　nearly　70%　of　the　total　thermal　resistance.　©　2020,　Science　Press.　All　right　reserved.