An　experimental　study　on　a　pump-driven　loop　heat　pipe　(PLHP)　charged　with　R22　for　cooling　a　data　center　is　reported　in　this　paper.　The　PLHP　had　five　tube-fin　heat　exchangers　as　evaporators　and　three　tube-fin　heat　exchangers　as　condensers,　a　liquid　reservoir,　and　a　canned　motor　pump.　The　coefficient　of　performance　of　the　unit　was　3.75　when　the　indoor-outdoor　temperature　difference　was　10　degrees　C,　then　increased　to　9.37　when　the　temperature　difference　was　25　degrees　C.　The　mass　flow　rates　of　R22　increased　from　200　to　1,100　kg=　h　with　one　evaporator　and　one　condenser　of　the　PLHP,　and　the　heat　transfer　rates　first　increased　and　then　decreased.　When　the　vapor　quality　of　R22　at　the　evaporator　outlet　was　between　0.3　and　0.6,　the　mass　flow　rate　affected　the　heat　transfer　rate　slightly.　As　the　increase　of　mass　flow　rate　in　the　PLHP,　the　temperature　difference　between　the　evaporator　inlet　and　outlet,　and　the　sensible　heat　ratio　were　both　rising.　When　the　mass　flow　rate　was　about　1,400　kg/h　and　the　indoor-outdoor　temperature　difference　increased　from　10　to　30　degrees　C,　the　relationship　between　the　heat　transfer　rate　and　the　temperature　difference　was　(C)　2014　American　Society　of　Civil　Engineers.