Experiments on critical heat flux (CHF) were conducted to clarify the enhancement effects of twisted tapes. The swirled tube is made of stainless steel (6mm in inside diameter, 0.25mm in thickness, and 100mm in heated length) and equipped with a twisted zirconia tape (about 1.2mm in thickness and 5.4mm in width). Twisted tape ratios y (value of tube inside diameter to complete 180 degree twists of tape insert) are about 2.7, 4.0, 9.0, and ∞. Swirl-flow CHF increased in proportion to the one-third power of (y-1) at small y or of the tangential velocity at the inner tube wall at large centrifugal force. An empirical CHF correlation for swirl flow was proposed by applying the tangential non dimensional centrifugal acceleration at the wall as a parameter. It was verified that this correlation gave accurate predictions at nearly atmospheric pressure.