[en] Highlights: • The features of a three-dimensional CLPHP charged with deionized water and surfactant are probed. • The effects of initial pressure and surfactant concentration on heat transfer performance are investigated. • Suitable combination of surfactant concentration and heat load can improve heat transfer performance. • Surfactant can improve the wettability of the tube wall and effectively prevent the occurrence of “dry-out”. -- Abstract: A three-dimensional closed-loop pulsating heat pipe (CLPHP) charged with deionized water and surfactant is numerically investigated in present work. The surfactant used in present work is hexadecyl trimethyl ammonium chloride (CTAC). The start-up performance and heat transfer characteristics of CLPHP with deionized water and surfactant are compared by changing the initial pressure (0.1 MPa, 0.07 MPa, 0.05 MPa) and input heat load (10 W, 20 W, 30 W, 40 W). It’s found that the performance of CLPHP is affected by the initial pressure, surfactant concentration and input heat load jointly. Under the condition of high initial pressure, the performance of CLPHP with surfactant is not as good as that with deionized water. However, under the condition of low initial pressure, especially at higher input heat load, the superiority of the surfactant begins to appear. Compared with the CLPHP with deionized water, the thermal resistance could be decreased by 4.78% when the initial pressure, the input heat load and the surfactant concentration is 0.05 MPa, 40 W and 50 ppm, respectively. It is also found that the CLPHP with 2000 ppm CTAC has a much lower heat transfer performance than that with deionized water under any conditions. Finally, surfactant can improve the wettability of the CLPHP wall, reduce the contact angle, and absolutely prevent the occurrence of “dry-out”.