An experimental investigation is conducted to explore the heat-transport capability of pulsating heat pipes (PHP) working with functional thermal fluids (FS-39E microcapsule fluid and Al2O3 nano-fluid), by comparing them with pure water. The test tube is a four-turn pulsating heat pipe, made of a copper tube with an external diameter of 2.5 mm, and an inner diameter of 1.3 mm. The results show that the heat-transport capability of PHP can be enhanced by using FS-39E microcapsule fluid and Al2O3 nanofluid as working fluid under specific conditions. When using vertical bottom heat mode, FS-39E microcapsule fluid is the best working fluid and its best concentration is 1 wt%; when using horizontal heat mode, Al2O3 nano-fluid is the best working fluid and its best concentration is 0.1 wt%. (C) 2009 Elsevier Ltd. All rights reserved.